FOUNDATION PROGRAMME OFP 012 Geography

THE OPEN UNIVERSITY OF TANZANIA

Institute of Continuing Education

FOUNDATION PROGRAMME

Published by: The Open University of Tanzania Kawawa Road, P. O. Box 23409, Dar es Salaam. TANZANIA www.out.ac.tz

ISBN 978 9987 00 252 8

Contents

GENERAL INTRODUCTION ...... 6

PART 1 EARTH’S STRUCTURE AND MATERIALS OF EARTH Lecture 1: The Meaning and Branches of Geography ...... 8 1.1 Introduction ...... 8 1.2 Geography: An Overview ...... 8 Lecture 2: Structure of Earth ...... 12 2.1 Introduction ...... 12 2.2 The Structure of Earth ...... 13 Lecture 3: Origin of Earth ...... 16 3.1 Continental Drifting Theory ...... 16 3.2 The Plate Tectonic Theory ...... 16 3.3 Movement of Plates and Resulting Landforms ...... 17 Lecture 4: Classification of Rocks ...... 21 4.1 Introduction ...... 21 4. 2 Types of Rocks ...... 21 4.3 Rock cycle ...... 22

PART 2 EARTH’S MOVEMENT AND INTERNAL GEOMOPHIC PROCESSES Lecture 5: Internal Geomorphic Processes: Volcanicanism and Landforms ...... 26 5.1 Introduction ...... 26 5.2 Earth Movements ...... 26 5.3 Effects of Tension and Compression Forces ...... 28 5.4 Volcanic Activity ...... 29 5.5 Lifecycle of a Volcano ...... 32 5.6 Importance of Volcanic Activity to Man...... 32 5.7 Volcanic Activity as a Hazard ...... 33

PART 3 EXTERNAL GEOMORPHIC PROCESSES Lecture 6: External Geomorphic Processes Weathering and Mass Movement ...... 36 6.1 Introduction ...... 36 6.2 Weathering ...... 36 6.3 Factors Affecting the Type and Rate of Weathering...... 40 6.4 Mass Movement...... 40 Lecture 7: River Action and Landforms Produced ...... 44 7.1 Introduction ...... 44 7.2 Erosion and Deposition by Running Water ...... 44 7.3 Factors Which Reduce Energy of a River ...... 45 7.4 Features Produced in the Upper Course of River Valley ...... 46

7.5 Features Produced in the Middle Course of a River Valley ...... 47 7.6 Features of a Lower Course of a River Valley ...... 49 7.7 Types of delta ...... 50 Lecture 8: Erosion and Deposition by Action of Waves ...... 54 8.1 Introduction ...... 54 8.2 Features Produced by Wave Erosion ...... 55 8.3 Features Produced by Wave Deposition ...... 56 Lecture 9: Erosion and Deposition by Wind Action ...... 59 9.1 Introduction ...... 59 9.2 Processes of Wind Erosion ...... 59 9. 3 Wind Erosional Landforms ...... 60 9.4 Features Produced by Wind Deposition ...... 62 9.5 Types of Desert ...... 64 Lecture 10: Glacial Erosional and Depositional landforms ...... 66 10.1 Glacial Types and Processes...... 66 10.2 Glacial Erosional Landforms ...... 66 10.3 Glacial Depositional Landforms ...... 68 Lecture 11: The Study of Soil ...... 72 11.1 Introduction ...... 72 11.2 Soil Profile ...... 73 11.3 Constitutes of Soil ...... 74 11.4 Factors for Soil Formation ...... 75 11.5 Physical Characteristics of Soil ...... 76 11.6 Soil Fertility ...... 78 11.7 Soil Erosion, Conservation and Sustainability ...... 78

PART 4 HUMAN GEOGRAPHY Lecture 12: Constituents of Human Geography ...... 83 12.1 Introduction ...... 83 12.2 Main Concerns of Human Geography ...... 83 12.3 People and Environment ...... 85 12.4 Major Environmental Problems in Tanzania ...... 85 12.5 Human Impacts on the Environment...... 88 Lecture 13: Population and Development...... 90 13.1 Introduction ...... 90 13.2 Population Terms ...... 90 13.3 Population Distribution ...... 93 13.4 Population Density ...... 93 13.5 Overpopulation ...... 94 13.6 Population Controls ...... 94 13.7 Population Migration ...... 95 13.8 Factors for Migration ...... 95 13.9 Consequences of Migration in Area of Origin and Area of Destination ...... 97

PART 5 ENVIRONMENT AND EXPLOITATION OF NATURAL RESOURCES Lecture 14: Exploitation of Natural Resources: Agriculture ...... 100 14.1 Introduction ...... 100 14.2 Subsistence Agriculture...... 100 14.3 Agriculture Organisation in China ...... 101 14.4 Commercial Agriculture ...... 102 14.5 Agriculture in Tanzania ...... 103 14.6 Efforts in Improvement of the Agricultural Sector in Tanzania ...... 104 Lecture 15: Exploitation of Natural Resources: Mining ...... 107 15.2 Classification of Natural Resources ...... 107 15.3 Mining Industry...... 108 15.4 Mining in Tanzania ...... 108 15.5 Problems Associated with Mining in Tanzania ...... 110 Lecture 16: Exploitation of Natural Resources: Fishing ...... 112 16.1 Introduction ...... 112 16.2 Fishing in Tanzania ...... 112 16.3 Problems of Fishing in Tanzania ...... 113 Lecture 17: Exploitation of Natural Resources: Forestry ...... 115 17.1 Introduction ...... 115 17.2 Problems Associated with Forestry in Tanzania ...... 115 17.3 Causes for Deforestation ...... 116 Lecture 18: Exploitation of Ntural Resources: Tourism ...... 118 18.1 Introduction ...... 118 18.2 Tourism in Tanzania ...... 118 18.3 Community Participation in Tourism ...... 119 18.4 Tourism Limitations ...... 119

PART 6 PRACTICAL GEOGRAPHY Lecture 19: Application of Statistical Data in Geography ...... 123 19.1 Introduction ...... 123 19.2 Sources and Types of Geographical Data ...... 123 19.3 Summarising Data ...... 124 Lecture 20: Statistical Maps and Graphs ...... 128 20.1 Introduction...... 128 20.2 Statistcal Maps ...... 129 20.3 Statistical Graphs ...... 132 Lecture 21: Topographical Map Interpretation ...... 141 21.1 Introduction ...... 141 21.2 Topographical Map ...... 141 21.3 Map Scale ...... 142 21.4 Types of Maps by Scale ...... 143 21.5 Relief Features on a Map...... 148

General Introduction

This course examines the physical and human factors that contribute to and produce the variable character of the earth's surface. It deals with earth’s landscapes, human activities and the environment. It is a unique discipline in bridging social sSciences with the natural sciences. In human geography students will learn about culture, societies and their economies while in physical geography they will explore about physical landscapes and the environment. The course include practical part of geography in which learners will be equipped with knowledge and skills related to statistical presentation of geographical information as well as photographical and topographical interpretation of geographical information.

Objectives It is expected that at the end of this course you will be able to: 1. Explain the natural environments and the pressure they face. 2. Describe the earth movement and internal geomorphic processes. 3. Describe the external geomorphic processes 4. Assess how individual and societal actions contributing to change of environment. 5. Explain the exploitation of natural resources and its impact on the environment. 6. Read and interpret geographical information on Topographical Maps and Photographs.

PART 1 Earth’ Structure and Materials of Earth

Lecture 1 The Meaning and Branches of Geography

1.1 Introduction This lecture describes and explains to you the meaning of geography and its main branches. Despite being an interdisciplinary subject, the uniqueness of geography is portrayed by its role of showing spatial relationships, variations, patterns and process changes through time. The spatial aspect of the subject is emphasised by the use of maps and three-dimensional models. Some of these changes take place very slowly as in the case of rock weathering while other changes take place rapidly such as mass movements and volcanic eruptions. Another aspect of geographic studies is the focus on interactions between the natural environment and human activities. This course covers both physical and human geography because the two interact continuously. People are affected by natural events but people are also a very prominent factor in changing the natural environment. Human beings can bring changes in relatively a short time for example, when they construct new roads. This lecture provides an introduction to what is actually contained in geography and it is intended to help you develop awareness of the processes around you and outside your environment, so that you are able to observe, record and interpret phenomena as geographers.

Learning Objectives At the end of this lecture, you will be able to:  Define geography and differentiate it from other subjects;

 Explain the various spatial interactions and their resultants;

 Identify the main branches of geography;

 Describe the importance of rays of the sun in the formation of global patterns of temperature.

1.2 Geography: An Overview Geography has been defined by Bowen, et al. (2001) as ‘the study of the physical and human features of the earths surfaces especially their patterns and variation in distribution and of the interrelationships between them in the past or present’. Many patterns of distribution of observable facts are revealed in the human use of the environment. Therefore, geography as a discipline studies the human environment relationships and the way societies are influenced by their culture in organising their activities on the earth’s surface. Consequently, although there are many definitions of geography, its precise definition should include reference to the earth’s surface. Geography is an enlightening subject in many fields. It provides information in solving many economic, social, political, as well as environmental problems. Nevertheless, it differs from other subjects in that it is a spatial subject. Geographers investigate, describe, explain and analyse patterns and processes in space;

on or near the Earth’s surface. Geographers study spatial associations between features of the Earth’s surface such as the association between climate and vegetation, soils on one hand, and landscape features on the other. For that reason, the concept of environment is used widely in the study of geography. An environment is a set of surrounding conditions in which organisms live. These organisms include humans (Bradshaw and Weaver, 1995:4). The earth is our home and therefore it is important for us to understand how the earth’s environment works and how human activities can be performed in harmony with them. We can recognise a number of major global natural environments such as the tropical rainforests and the monsoon forests. There are also spatial interactions between climate, vegetation and soils. Each of these three elements in the system affects the others and this is basic to the concept of ecosystems. Climate is the main determining factor for the type of natural vegetation cover and the major influence on soil type. It also affects the speed of growth of that type of natural vegetation cover. Furthermore, climate affects the speed and type of weathering of the parent rock. Notwithstanding the above, climate itself is controlled by latitude and the amount of solar radiation. These two are responsible for the global pattern of temperature making climate the dominant factor within these associations of climate, vegetation and soils. Temperature is what starts many changes below and on the earth’s surface. Spatial patterns and processes on or close to the Earth’s surface – whether physical or human made, undergo changes overtime. Some changes are rapid such as volcanic eruptions while others take place slowly as in the case of rock weathering. We need to bear in mind that even if the process is a slow one, the change can be significant in the long run. For instance, human process of migration within regions can be a slow one but gradually, it can cause the region of destination to be overpopulated while the area of origin can undergo unplanned population decline. Geography as an interdisciplinary subject has long been divided into two main branches Physical and human geography which is further subdivided into small, more specialised branches as will be discussed. In addition to these, we also have another relatively new branch – Geographic Techniques and Geographical Information Systems (GIS). This branch deals with statistics and computer applications in geography.

Physical Geography This branch of geography is concerned with the study over time, of the characteristics, processes and distribution of the natural phenomena in space accessible to human beings and their instruments – the atmosphere, biosphere, hydrosphere and the lithosphere (Clark, 1990:239). Physical geography attempts to explain why certain features are found in some places and absent in others. It also provides reasons for changes of physical features over time and interactions between humans and the environment. The branch includes two main areas namely, geomorphology and climatology. Another added branch of geography is called Biogeography. 1. Geomorphology: It is the study of landforms, particularly their origins and development of the processes responsible for the formation of the surface forms of the earth (geo means earth and morphology refers to shape). 2. Climatology: It is the study of the characteristics and distribution of the world’s types of climate and of the atmospheric processes responsible for them. It also describes and explains climates and the role they play in the natural environment, particularly in soil formation and determination of the vegetation cover. 3. Biogeography: It is an added branch of geography that deals with the study of organic life and soils and the processes forming them. It is the study of spatial distribution of plants and animals (excluding human beings) and the processes that produce the patterns of distribution and of the interrelationships of plants and animals with their environment over time. Its branches are phyto geography that concentrates on plants and zoogeography that deals with animals (Ibid, p 38). Another branch of physical geography is soil geography. The study of soil is referred to as pedology. 9

Human Geography It is that branch of geography concerned with the study and features and phenomena in the space accessible to human beings which relate directly to or are due to people as individuals or in groups; their past or present activities and organisation. It concentrates on the interrelationship of people in space, with their physical environment and with their social environment, covering spatial and temporal distribution, the organisation of society and social processes on a local to global scale (Ibid, p 150). Human geography has many subdivisions, but only four are given below. Economic Geography: Deals with the interaction of geographical and economical conditions, with the production, spatial distribution, exchange and consumption of wealth and with the study of the economic factors affecting the actual differentiation of the earth’s surface (Clark, 1990:100). In other words, it concentrates on activities which create employment and generate income, their distribution and processes responsible for them. Political Geography: This is the study of the influence of governments upon people, processes and activities and the ways in which they change both spatially and temporarily. Population Geography: This is the study of demographic characteristics such as fertility, mortality and migration change and structure of their spatial and temporal variations. Urban Geography: This is the study of relatively densely built up areas where the majority of the economically occupied inhabitants are engaged in activities mainly concerned with secondary, tertiary and quaternary industries in towns or cities. It is the study of morphology, growth, functions and change of such urban settlements (Clark, 1990:344). Other branches of human geography are historical, medical and behavioural geography.

Activity 1.1 ? Throw light on the urban and economic geography of Tanzania.

Summary Geography is the study of physical and human related features of the earths surface particularly their patterns and variation in distribution over time. The study of Spatial associations of phenomena on the earth’s surface gives geography its distinct character. Knowledge of spatial interactions between climate, vegetation and soils is basic to the understanding of many events that take place beneath as well as on the surface of the earth. Even abstract events such as processes of migration are in one way or another related to interactions of those three factors. Thus, geographical analysis of phenomena looks at interactions between both physical and human environments. Physical geography is at large the study of earth’s environments, the interactions among them and changes in their conditions over time. Physical geographers also study how earth’s environments affect and are affected by human activities. Geographers collect data which help them to describe, explain, predict processes, which can take place in the earth’s environment. Maps are very essential for geographers as a tool for locating places and representing the earth’s features. Geography is an interdisciplinary subject. It is closely related to other subjects. For example, geomorphology is related to geology while remote sensing, statistics and quantitative methods in geography are studied in engineering. Geographers test ideas about the natural environment by gathering data at different scales and analysing them just as scientists analyse samples in laboratories.

Maps are also very useful to geographers in presenting and summarising data. Other subjects use maps too. Therefore, knowledge of map making and interpretation is crucial.

Exercise 1. Define geography. How does geography differ from other disciplines? 2. Write short notes on each of the following branches of geography: Physical geography, human geography, economic geography, political geography and population geography. 3. Why is knowledge of spatial interactions between climate, vegetation and soils important for a geographer? 4. Provide concrete examples of both rapid and slow spatial changes on the surface of the Earth.

References 1. Bowen, A and John Pallister, (2001), A2 Geography, Heinemann Educational Publishers. Oxford. 2. Clark, Audrey, (1990), Dictionary of Geography. Geographical Publications Ltd, London. 3. Bradshaw, M. and Ruth Weaver (1995), Foundations of Physical Geography, W. W. C. Brown Communications, Inc, Chicago.

Lecture 2 Structure of Earth

2.1 Introduction

This lecture attempts to explain the origin and processes that take place at the plate margins and the resulting features. It also explains the validity of the theory of continental drifting based on archaeological evidences and the theory of plate tectonics. This understanding is expected to help appreciate the environment surrounding us. We are already aware of the fact that the study of physical geography is based on the relationships between Earth’s environments, interactions among them and changes in their condition over time (Bradshaw and Weaver, (1995:10). The Earth can be divided into four interacting environments namely: the atmosphere-ocean environment, solid-earth environment, surface-relief environment and the living- organism environment. The surface relief environment results from the interaction between the atmosphere-ocean environment and the solid-earth environment while plants and animals result from the living-organism environment. This interaction is responsible for the formation and degradation of landforms. The occurrence of earthquakes and volcanic eruptions imply that the interior of the earth is not stable. These events provide clues to the nature of processes taking place in the interior of the Earth. Some of the clues reveal that there are internal movements and that the interior is very hot such that it causes melting of rocks. One of the most satisfying explanation of internal processes and the occurrence of earth quakes is best explained by the theory of plate tectonics. The basic idea which the theory attempts to explain is that the earth’s outermost part; the lithosphere which actually forms the Earth’s crust consists of large and fairly stable slabs of solid and relatively rigid rock called plates (Bolt, 1988:4). Each plate extends to about 80km in depth and moves horizontally relative to adjacent plates floating on softer rocks which form a semi-liquid zone, known as the asthenosphere. The continental and oceanic plates can converge towards each other to form destructive margins or diverge from each other to form constructive margins. Where transform faults develop, the margins become conservative and no outstanding landforms are produced except for earthquakes. The destructive and constructive zones are associated with the formation of landforms such as volcanic and fold mountains, trenches and rift valleys.

Learning Objectives At the end of this lecture, you will be able to:

 Name and describe the concentric zones of the earth, their physical and chemical characteristics;

 Describe the concepts of plate tectonic theory and continental drifting;

 Critically, explain processes at the destructive and constructive plate margins;

 Name and describe the main types of rocks, indicating the main characteristics of each.

2.2 The Structure of Earth The earth is made up of three main parts namely, the core (barysphere), the mantle (mesosphere), and the crust (lithosphere) (see figure 2.1). Part of the earth’s surface is the atmosphere which is composed of a mixture of gases and this forms a cover around the earth. The instability in the earth’s interior and its resulting features are well explained by the theory of plate tectonics. A theory is a presumption which attempts to explain reality.

The Crust The earth’s crust is the outside layer of the earth. It is thickest at the continents at about 40 Km (up to 70 Km) deep. It is thinnest under the oceans at about 10 Km deep. •Crust is very thin (only 1% of earth’s mass) and was formed when light elements “floated” to the surface and cooled. The crust is not one continuous piece like an orange peel to an orange. Instead it is made of separate pieces like a puzzle. These pieces are called plates. As you go deeper in the crust it gets warmer. Directly under the crust is a hot layer called the mantle. The crust and upper part of the mantle together form a layer called the lithosphere..Lithosphere is made of solid but moving masses of rock called lithospheric plates. Each plate is 65-100 km thick 12 major plates and several minor ones cover the surface of the earth. Plates may contain continental crust, oceanic crust, or both. Continents made of granite, an igneous rock. Oceanic crust made of basalt, also igneous but denser

The Mantle The mantle is the Earth’s thickest layer. Earth is the only planet in our solar system with a continually active mantle. The mantle is the mostly-solid bulk of Earth’s interior. The mantle lies between Earth’s dense, super-heated core and its thin outer layer, the crust. The upper mantle extends from the crust to a depth of about 410 kilometers (255 miles). The upper mantle is mostly solid, but its more malleable regions contribute to tectonic activity. The top part is a solid and is joined with the crust and called the lithosphere. The lithosphere floats on top of the asthenosphere. The asthenosphere is a plastic like solid that can flow like a liquid because it is under pressure. When it heats up at the bottom it becomes less dense and rises towards the top where it cools, shrinks, and sinks back down. The lower mantle extends from about 660 kilometers (410 miles) to about 2,700 kilometers (1,678 miles) beneath Earth’s surface. The lower mantle is hotter and denser than the upper mantle and transition zone

The Core Earth’s core is the very hot, very dense center of our planet. The ball-shaped core lies beneath the cool, brittle crust and the mostly-solid mantle. The core is found about 2,900 kilometers (1,802 miles) below Earth’s surface, and has a radius of about 3,485 kilometers (2,165 miles). It is divided into two parts namely outer core and inner core. Unlike the mineral-rich crust and mantle, the core is made almost entirely of metals pecifically, irons and nickel. Another key element in Earth’s core is sulfur in fact 90% of the sulfur on Earth is found in the core.

Outer Core The outer core, about 2,200 kilometers (1,367 miles) thick, is mostly composed of liquid iron and nickel. The NiFe alloy of the outer core is very hot, between 4,500° and 5,500° Celsius (8,132° and 9,932° Fahrenheit). The liquid metal of the outer core has very low viscosity, meaning it is easily deformed and malleable. It is the site of violent convection. The churning metal of the outer core creates and sustains Earth’s magnetic field. Temperatures in the outer core range from 4,000°C to 5,000 °C. The outer core is molten Iron (Fe) and Nickel (Ni). The spinning currents of liquid Iron (Fe) in the outer core are what cause Earth’s magnetic field which protects Earth from Solar winds stripping away the atmosphere.

Inner Core The inner core is a hot, dense ball of (mostly) iron. It has a radius of about 1,220 kilometers (758 miles). Temperature in the inner core is about 5,200° Celsius (9,392° Fahrenheit). The pressure is nearly 3.6 million atmospheres. The temperature of the inner core is far above the melting point of iron. However, unlike the outer core, the inner core is not liquid or even molten. The inner core’s intense pressure—the entire rest of the planet and its atmosphere—prevents the iron from melting. The pressure and density are simply too great for the iron atoms to move into a liquid state. Because of this unusual set of circumstances, some geophysicists prefer to interpret the inner core not as a solid, but as plasma behaving as a solid. The liquid outer core separates the inner core from the rest of the Earth, and as a result, the inner core rotates a little differently than the rest of the planet. It rotates eastward, like the surface, but it’s a little faster, making an extra rotation about every 1,000 years.

Lecture 3 Origin of Earth

3.1 Continental Drifting Theory The theory of Continental Drifting was founded by the German geologist, Alfred Wegna in 1912; he said that the present continents originated from one Super continent, surrounded by Single Ocean called Tethys. As the time go on Pangea divided into two parts: The northern part of Pangea is called Laurasia and the southern part– Gondwanaland. Laurasia and Gondwanaland continues to drift apart until we get the present continents It is believed that Africa developed from Gondwanaland, and the breaking began in the Cretaceous era (Refer to figure 2.5)

Evidence of Continental Drifting  Similarity of the coastlines: Western coast of Africa and the eastern coast of South America, western coast of Europe and the eastern coast of North America seem to fit together like a puzzle.  Fossil records are similar on separate landmasses: Mosasaurs – It was a small reptile that lived 270 million yrs. ago that lived in shallow, fresh water, inland seas. Its fossilized remains were found in eastern South America and also in Western Africa.  Geologic Evidence Similarities: The age and type of rocks are similar in the coastal regions: Rock samples taken from along the coastline of Africa are similar in age and type to the samples taken from South America „ Old mountain chains (more than 200 myo) are similar in age and structure: The age and structure of the Appalachians (in the Eastern U.S.) is similar to mountains in Greenland and Northern Europe Rocks in the Appalachians of North America and the Caledonians of Britain and Norway are very similar (folded mtns.) and are also similar in age. When we fit Europe and North America together, we find that The Appalachians and Caledonides form a single mountain chain.  Climatic Change Similarities: Evidence of glaciers found on separate landmasses of debris from glaciers rocks that have been carried great distances are found o Scarring is found in the rock layers. Evidence of tropical swamps on separate landmasses of Seams of coal are found in the United States and in Europe appear to connect o Seams of coal found in Antarctica (coal is made from ancient swamp material.

3.2 The Plate Tectonic Theory The theory states that, the earth’s crust consists of several large and some small, rigid, irregularly–shaped plates which carry the continents and the ocean floor and float on the asthenosphere, moving laterally, very slowly. Our knowledge of the earth’s interior helps us to understand the origin of features found into as well as those found on the surface of the earth. Large areas of the outer crushed layer of the earth are made of basaltic rocks (rich in basalt) very similar to sima (silica and magnesium). Recently, large areas of newly formed basaltic rocks which form the ocean floor in mid Atlantic Ocean and Indian Ocean have been discovered. These basaltic rocks are believed to have originated from the earth’s mantle, close to the mid-oceanic ridges, and have pushed outwards away from them. These discoveries are an indication that the earths crust is unstable and consist of a series of plates, which are slowly being pushed apart, away from the zone where they are formed.

The sialic rocks, which form the continents, are chiefly made up of silica and alumina minerals. These are carried on the slowly moving plates. Arbar, et al, (2000:25) attributes movements of plates to convection movements in the asthenosphere. The lithosphere (solid rock), which includes the crust, is very hot with an average temperature of about 1300° Celsius at a depth of 80 km. The inner core is also a solid rock with average temperature above 5000° Celsius. In between the lithosphere and the mantle is the asthenosphere, which is partly melted. The difference in the temperature of the two layers of solid rock is what sets up convection movements. How all this happens is explained bellow.

Close to the earth’s surface, the upward movements in the asthenoshere spread out horizontally. These lateral movements cause the crust to split. This in turn makes the vast continental plates move slowly. In some places, they are pulled apart, in others pushed together and sometimes they slide sideways. Where plates separate, plates break apart, forming rift valley faults and Block Mountains as in the case of the African Rift valley. Further movement is responsible for sea floor spreading.

3.3 Movement of Plates and Resulting Landforms Convection currents in the asthenosphere rises, separates and forms a mid ocean rift. The convection current sinks again where the oceanic plate meets the continental plate. At the edge of plates, adjoining plates come in contact thereby causing friction which result into large deforming (or tectonic) forces that operate on the rocks causing physical and chemical changes in them. This implies that geological structure of rocks is most affected at the plate margins. At the edges of a plate, the crust is weak and molten rocks try to force their way to the surface. Movements of the plate edges are felt as earthquakes. The theory of Plate tectonics thus helps us understand the origin of earthquakes and volcanoes as well as their associations. The movement and collision of the plates is referred to as plate tectonics. Destructive plate margins are also areas of intense seismic activity. In some places, the continental and oceanic plates meet each other at an oblique angle such that they avoid collision and subduction cannot occur. When this happens, the plates jerk forward and move again. Each horizontal change can cause earthquakes along a destructive plate margin. Consequently, earthquakes are also associated with subduction regions (where plates sink).

Source: http://www.bennett.karoo.net/topics/platetec.html Figure 2.2: The Boundaries of the Main Tectonic Plates

When an oceanic plate and a continental plate move towards each other, the edge of the oceanic plate is drawn underneath the edge of the continental plate. As it sinks, it carries some of the solid rocks downwards into the asthenosphere where they melt and finally get absorbed into the mantle. The region where the rocks from the edge of the ocean plate are carried down is known as the subduction zone. Active zones of subduction occur off the coasts of Japan, California and the West coast of South Africa (Burnett, 1990: 15). In zones of subduction, the edge of the oceanic plate is bent down into the mantle when the continental plate pushes up over it. This causes a trench to be formed, such as the Java Trench. Gradually, sediments from the continent fill up the trench, but because the plate continues to approach, the sediments are crushed and folded. These may give rise to a range of fold mountains or a chain of islands (Figure 2.2, 2.3). For example, when the Indian plate met the Asian plate, it pushed and folded the sediments up to make the Himalayan Mountains.

Source:http://legacy.hopkinsville.kctcs.edu/sitecore/instructors/Jason- Arnold/VLI/Module%203/Module3Evolution/Module3Evolution11.html

(A mid-oceanic ridge forms when two oceanic plates move apart; a trench and related fold mountains form when an oceanic plate and a continental plate collide) Figure 3. 1: Movement of Plates and Related Features

When molten rock (the magma) swells up from the mantle to fill the oceanic trench, the magma slowly cools and forms a new crust. Often, violent volcanic activity takes place as the magma continues to fill the trench and gradually forms mountain ridges. The mid-Atlantic ridge is being formed in this way. Melted rocks from the asthenosphere continually rise at the mid-ocean ridges, spreading out and hardening to form new ocean floor on either side of the ridge. This is what is referred to as seafloor spreading. Plates move at a uniform speed, getting older as they move further away from the ridges. It is for this reason that, mid-oceanic ridges are called spreading zones. This principle helps to explain the theory of continental drift. The subduction region is also called a constructive region because molten magma rises from the mantle and reaches the surface as basalt, which adds new crystal material on the Earth’s surface. At the zone of construction, plates are being pulled apart by diverging convection currents in upper mantle. When two plates move in different directions, tension builds up and fractures are created. It is through these that magma being forced up by convection currents, reaches the surface as lava (newest rock). When volcanic rocks reach the surface they make volcanic islands. Constructive margins are located in the Mid–Atlantic, eastern Pacific and central Indian Ocean. The diverging plates cause rifting as the solid basalt splits and fractures into many parallel cracks, which run along the top of the ridge. Magma from the mantle is forced into the cracks as they develop and solidifies to form intrusive features of volcanism.

Rifting at the constructive margins causes earthquakes and rift valleys. Ocean ridges and volcanoes also form at these margins as in the case of the East African Rift Valley which holds lakes Tanganyika (5000m deep), Lake Nyasa and Lake Rudolf but associated with volcanoes such as Mount, Kenya, Mount Meru and Kilimanjaro, the highest Mountain in Africa. The association between plate boundaries, volcanoes activity and earthquake zones is well illustrated in figure 2.4.

Source: http://sofiascienceblog7thgrade.blogspot.in/ Figure 3.2: Plate Boundaries, Volcanic Activity and Earthquake Zones

Take Note A mid-oceanic ridge forms when two oceanic plates move apart. A trench and related fold mountains form when an oceanic plate and a continental plate collide. The heavier oceanic crust sinks or sub ducts below the lighter continental crust. When the continental plates collide, the edges are not bent down into the mantle. Instead, they crumple and fold into mountain ranges due to compression.

Summary The earth is made of three main parts, the core, the mantle and the crust. The crust consists of plates. These are continental and oceanic plates, which are slowly moving laterally. Some are converging while others are diverging. When a continental plate and an oceanic plate move towards each other (converge), a trench or deep is formed. Fold Mountains and volcanic activity may also take place at the convergence zone. Usually a fold mountain range forms when two continental plates converge while a trench may form when two plates diverge. If this takes place on the ocean floor, lava pours out to produce oceanic ridges. These movements of plates cause crevices to form into the crust through which magma oozes out. They are

therefore responsible for volcanic eruptions and earthquakes. When the plates move apart beneath a continent, then a rift valley may form. Horizontal movements are responsible for continental drifting. The rocks that compose the crust are classified into three groups: igneous, sedimentary and metamorphic. Any rock can be changed into a metamorphic rock if exposed to prolonged heat and pressure. Rocks can also be classified according to age. They are given names according to the period during which they were formed. The bedrock of Africa is very old and belongs to the Precambrian rocks. Fold Mountains belong to the Mesozoic rocks while the volcanic rocks of East Africa belong to the Cainozoic rocks.

Exercise 1. State Theory of Continenal Drifting Theory 2. Give evidence of Continental Drifting Theory 3. What are the weaknesses of Continental Drifting Theory? 4. Give statement of Plate Tectonic Theory. 5. With concrete examples discuss types of plate margins and features formed.

Lecture 4 Classification of Rocks

4.1 Introduction Apart from internal processes, which take place in the interior of the Earth, there are others that take place on the surface of the Earth’s surface. Thus, the surface of the Earth is continuously changing its form and the rocks that make up the surface. Three kinds of rocks can be identified based on their mode of formation namely, Igneous, Sedimentary, and Metamorphic.

4. 2 Types of Rocks Rock is a naturally formed aggregate of mineral matter constituting a significant part of earth’s crust. Igneous Rocks The term igneous comes from the Latin word Ignis which means fire. Igneous rocks are produced from heated rock, but most igneous rocks are produced. deep underground and they are of two main types; namely Plutonic and Volcanic. Plutonic rocks are formed when the magma does not reach the surface. It solidifies deep in the crust producing a variety of geologic structures such as batholiths and dykes which are exposed on the surface by prolonged action of erosion. Plutonic rocks are also called intrusive igneous rocks. Volcanic rocks which are poured on the Earth’s surface are called lava. The lava that reaches the Earth's surface through volcanoes or through great fissures hardens and become igneous rock. These are also called extrusive igneous rocks. Some of the more common types of extrusive igneous rocks are lava rocks, cinders, pumice, and volcanic ash and dust. The nature of cooling of the magma determines the characteristics of the rocks formed. When molten rock from the asthenosphere, cools and solidifies deep beneath the surface of the Earth they form crystals on cooling and the rocks are called crystalline rocks. If the molten rock cools very slowly underneath, the large crystals have time to grow such as those of granite rock. On the other hand, if magma cools quickly on the earth’s surface the crystals are too small to be seen, such as those of basalt.

Sedimentary Rocks Most sedimentary rocks are formed from sediments deposited either by water, wind or by ice. The particles accumulate in layers or strata and with time they are hardened by compression and turned into rock. These are also called stratified rocks. Some particles accumulate in lakes and seas such as sandstone, which comes from other rocks that are broken down by weathering and erosion. Other sedimentary rocks come from the remains of animals and plants. Chalk and other limestone are made of the shells and bodies of sea creatures. Coal forms from the remains of tree

Three types of sedimentary rocks are recognized: (a) Mechanically formed sedimentary rocks: are deposited by water, ice, or wind. They include clays, gravels, and alluviums (deposited by water), moraines, boulder clay, boulder clay and gravels (deposited by ice), and loess (deposited by wind).

(b) Organically formed: are formed from plants (peat, coal and lignite) and animals (chalk and coral). (c) Chemically formed: These include potash, gypsum, nitrates, certain types of limestone and rock salt.

Metamorphic Rocks Solid rock can be changed into a new rock by stresses that cause an increase in heat and pressure. There are 3 main agents that cause metamorphism through increase in temperature, pressure, and chemical changes. Temperature increases can be caused by layers of sediments being buried deeper and deeper under the surface of the earth. As we descend into the earth the temperature increases about 25 degrees Celsius for every kilometre that we descend. The deeper the layers are buried the hotter the temperatures become. The great weight of these layers also causes an increase in pressure, which in turn, causes an increase in temperature which in turn brings chemical changes.

The descending rock layers at subduction zones cause metamorphism in two ways; the plates sliding past each other causes the rocks coming in contact with the descending rocks to change. Some of the descending rock melts because of this friction. When rock melts it is then considered igneous not metamorphic, but the rock next to the melted rock can be changed by the heat and become a metamorphic rock. Refer to figure 2.6 for the rock cycle.

Factors that cause chemical changes contribute to the formation of metamorphic rocks. Very hot fluids and vapors can, because of extreme pressures, fill the pores of existing rocks. These fluids and vapors can cause chemical reactions to take place that over time can change the chemical makeup of the parent rock. Metamorphism can be immediate as in the shearing of rocks at plate boundaries or can take millions of years as in the slow cooling of magma buried deep under the surface of the Earth.

4.3 Rock cycle Rock cycle - an idealized cycle of processes underwent by rocks in the earth's crust, involving igneous intrusion, uplift, erosion, transportation, deposition as sedimentary rock, metamorphism, remelting, and further igneous intrusion.

Igneous Rock Deep in the earth's crust there are places where the rock has melted into magma which is a mixture of crystals and liquid rock. Sometimes the magma erupts out of the earth through a volcano and then it is called lava. When the lava cools and hardens on the earth's surface, it is called volcanic igneous rock. If the magma cools and hardens under the ground, it is called plutonic igneous rock.

Sedimentary Rock Wind and water cause erosion, breaking off pieces of rock and carrying them from one place to another. Gradually these pieces along with sand, pebbles, shells and plant matter gather into layers called sediment. Over a long period of time the sediment hardens into rock. That is how sedimentary rock is formed. Most of the rock on the earth's surface is sedimentary.

Metamorphic Rock Just as cookie dough changes as it is baked, rock changes as it is heated, squeezed or both. Rocks deep within the earth are put through intense heat and pressure. In time, these forces change sedimentary or igneous rock into another type of rock called metamorphic rock

Source: http://volcano.und.edu/vwlessons/lessons/metrocks. Accessed on 12 04. 2007 Figure 4.1: The Rock Cycle

Take Note Rock that moves into the crust towards the surface is called magma. If it reaches the surface it is called lava. Igneous rocks occur in layers and do not contain remains of plants and animals.

All sedimentary rocks are non-crystalline and many contain fossils. Three types of sedimentary rocks are recognised:  Mechanically-Formed Sedimentary Rocks: They are deposited by water, ice, or wind. They include clays, gravels, and alluviums (deposited by water), moraines, boulder clay, boulder clay and gravels (deposited by ice), and loess (deposited by wind).  Organically Formed: They are formed from plants (peat, coal and lignite) and animals (chalk and coral).

 Chemically Formed: These include potash, gypsum, nitrates, certain types of limestone and rock salt.

Activity 4.1 ? Find out some places where igneous rocks in Tanzania are found.

Summary The rocks that compose the crust are classified into three groups: igneous, sedimentary and metamorphic. Any rock can be changed into a metamorphic rock if exposed to prolonged heat and pressure. Rocks can also be classified according to age. They are given names according to the period during which they were formed. The bedrock of Africa is very old and belongs to the Precambrian rocks. Fold Mountains belong to the Mesozoic rocks while the volcanic rocks of East Africa belong to the Cainozoic rocks.

Exercise 1. Name and explain the main characteristics of the concentric zones of the Earth. 2. Explain the concept of the theory of plate tectonics. 3. What do you understand about the theory of continental drifting? 4. Give an analytical explanation of processes which take place at the plate margins. 5. Explain the formation of three main groups of rocks and distinguish their main characteristics. 6. (a) Explain how and why fold mountain ranges are formed along destructive plate margins. (b) Why are ocean ridges associated with constructive margins and ocean trenches with destructive margins?

References 1. Arber, Nicola, Sue Lomas, Garrett Nagle, Linda Thomson and Paul Thomson (2000), A2 Geography: Heinemann Educational Publishers, Oxford. 2. Bolt, B.A (1988), Earthquakes, W.H. Freeman and Company, New York. 3. Bowen, Ann and John Pallister (2001), A2 Geography: Heinemann Educational Publishers, Oxford. 4. Bradshaw, M. and Ruth Weaver (1995), Foundations of Physical Geography, Ww. C. Brown Communications, Inc, Chicago. 5. Bunnett, R. B (1990), Physical Geography in Diagrams for Africa (8th edition). Longman Group Ltd, Hong Kong. 6. Clark, Audrey (1990), Geography Dictionary, Geographical Publishers Ltd. 7. Lines, C; Laurie Bowlwell and Anne Fielding Smith (1996), A Level Geography. Letts Educational, London.

PART 2 Earth’s Movement and Internal Geomophic Processes

Lecture 5 Internal Geomorphic Processes: Volcanicanism and Landforms

5.1 Introduction Internal geomorphic processes are produced by internal forces, which operate within the crust. These forces can be divided into two, earth’s movements and volcanic eruptions. Earth’s movements operate either vertically or horizontally. Vertical movements are up and down. Both movements cause the crustal rocks to fault to form plateaus, block mountains, basins and sometimes escarpments. Horizontal forces cause sideways movements, which render the crustal rocks to fold, thus forming fold mountains, rift valleys and at times block mountains. Such movements take place slowly. When the magma solidifies in the crust, internal features such as dykes, sills, batholiths and lacoliths are formed. When the lavas reach the surface, they produce external features such as lava flows, lava plateaus, geysers and volcanic cones. These movements are often rapid. In this lecture, you will learn how internal forces in the form of crustal movements give rise to the formation of various landforms that are embedded into the Earth’s crust as well as those that are produced on the surface of the earth.

Learning Objectives At the end of this lecture, you will be able to:

 Identify major characteristics of lateral and vertical forces;

 Explain causes of vertical and horizontal forces in order to balance the forces within the earth’s crust;  Explain the formation of landforms e.g. fold, block and volcanic mountains, ridges faults and rift valleys;

 Account for the significance of landforms resulting from internal forces;

 Determine the origin of earthquakes and their impact on the earth’s surface;  Distinguish various types of volcanoes;

 Describe main landforms resulting from volcanic processes. 5.2 Earth Movements An earth movement is a movement of the earth’s crust arising from disturbances in the earth’s interior including both the slow and sudden movements (Clark: 1990 p.98). Major geographical features such as mountains, plateaus and plains have been formed by both lateral and vertical earth movements.

Earth movements cause sedimentary rocks to be displaced; the rocks are tilted or inclined. These movements also cause sedimentary rocks to fold and fault. Lateral forces of compression cause folding while either lateral or vertical forces of tension or compression cause faulting depending on the nature of the rocks being acted upon.

Formation of Folds When compression forces act in an area of sedimentary rocks, rock layers are forced to bend up and down. The upper part is called an upfold or anticline while those which bend down form a downfold or syncline. The sides of a fold are called limbs. If compression continues, a simple fold can be changed into an asymmetrical fold where one limb is steeper than the other. Further compression can lead into an over-fold and finally an over-thrust as shown in Figure 3.1.

Source: 3dparks.wr.usgs.gov Figure 5.1: The Formation of Various Types of Folds

Formation of Faults A fault is a fracture or break in a series of rocks along which there has been vertical or lateral movement or both as a result of excessive strain. Tension forces (forces that act away from each other) cause normal faults while compression forces cause reverse faults. In addition, lateral movements may produce tear faults. Escarpments (fault scarps) develop if upward or downward movements of adjoining crust parts accompany faulting. Normal faults are those in which the rocks on one side have slipped down relative to the other whereas reverse faults are those where rocks have been pushed up. Overthrust faults develop where the plane is near the horizontal.

5.3 Effects of Tension and Compression Forces Formation of features as a result of tension and or compression is well elaborated by Bunnett (1990). He submitted that the rocks of the crust are subject to tension and compression when vertical or lateral earth movements take place. When one part of the crust is compressed, another part is stretched thus creating tension. It is when rocks are under tension that they usually fault. When they are under compression they may either fold or fault depending on their capacity to withstand stress. Weak rocks tend to fault whereas flexible ones fold. It is quite rare for faults to occur singly. More often they occur in series.

Source: http://earthquake.usgs.gov/regional/nca/haywardfault/symbols/ Figure 5.2: Faults and their Related Features

Earthquakes An earthquake is a sudden shaking of the ground or vibrations in the earth’s crust caused by deep-seated disturbances which produce a series of elastic shock waves spreading out from the epicentre. An earthquake usually originates from sudden adjustments in the crust of the earth, particularly by movement along faults or as a result of volcanic activity. Where there are no volcanoes to act as safety outlets, most several earthquakes are associated with fault lines (Clark, 1990:98). Thus, movement of plates largely causes earthquakes. Many earthquakes occur where immense stresses build up either where crustal plates collide along destructive margins, or where plates grind past each other along conservative margins. When two plates are subducted into the ocean trench, the tremendous friction arising from the rocks that are forced against other rocks generates earthquake shocks. Therefore, the subduction zone is the region of a series of foci from which earthquakes originate. Constructive margins also generate earthquakes because of the stress and tension which build up in the crustal material when two plates move apart. However, the scale and intensity of the movement are lower than at the destructive margins. Close observation from the map indicates that majority of earthquakes occur in narrow belts which mark the boundaries of tectonic plates. Shortly, the main regions where they occur are:

 The mid-ocean ridges  The oceanic deeps and volcanic islands  Regions of crustal compression e.g. N. Africa

The Effects of Earthquakes Bunnett (1990) identifies four main effects of earthquakes as given below:  Displacement of parts of the earth’s crust either vertically or horizontally  Raising or lowering parts of the sea floor to form raised beaches. For instance, the Agdir earthquake in Morocco in 1960 raised the sea floor off the coast. In some areas, the depth of the sea decreased from 400 metres to 15 metres after the earthquake.  Raising or lowering coastal rocks. In the Alaskan earthquake of 1899, some coastal rocks were raised by 16 metres.  Land sliding and opening up deep cracks in the surface rocks. The El Asnam earthquake in Algeria, in 1954 destroyed an area of 40 km in radius and opened surface cracks up to 3 metres deep. Apart from the effects mentioned above, earthquakes are hazardous to human beings and their property. The shocks destroy buildings in villages, towns and cities and sometimes lead to loss of life as the one that occurred in Morocco early 2004. In December 2004, Asian countries such as Indonesia and Thailand were devastated by Tsunami which was caused by Earthquakes which occurred in the Indian Ocean.

Measurement of Earthquakes An instrument called Seismograph measures the intensity of an earthquake. The instrument records the vibrations produced by an earthquake. The Richter scale measures the magnitude of an earthquake. The scale ranges from 0 to 8.9. An earthquake with magnitude of 2.0 is ten times greater than 1.0 and one of 5.0 is 10,000 times greater than an earth of magnitude 1.0. The magnitude of an earthquake is the total amount of energy released. The intensity of an earthquake refers to the effect produced by the earthquake. This varies from place to place, but the magnitude doesn’t change.

5.4 Volcanic Activity Vulcanicity refers to all the various ways by which molten rock and gases are forced into the earth’s crust and on the earth’s crust and on the earth’s surface. Vulcanicity, therefore, includes volcanic eruptions, the formation of intrusive features such as batholiths, sills and dykes into the crust. The rocks in the asthnosphere have very high temperatures but great pressure is exerted on them by the crust, keeps the rocks in a semisolid state. High temperature coupled with a reduction in pressure caused by faulting and folding forces these rocks to become molten and semi fluid. Molten rock is called magma. It is a combination of lava and volcanic gas. As the magma rises, it forces its way into the cracks of the crust. However, if it does not manage to come out at the earth’s surface, it solidifies in cavities and fissures. If it pours out on the earth’s surface, it becomes lava. The type of magma and its chemical composition determines the intensity of a volcanic activity. When the proportion of silica in the lava is below 55%, gases easily escape; the basaltic lava is fluid and very hot. Eruptions are usually non-violent and flow for long distances before cooling. Magma that rises from the subduction zones at destructive plate margins contain silica between 55-70% and thus, the lava is very viscous and explosive. When magma cannot escape easily, it explodes. This breaks the lava into pieces that are thrown out as volcanic bombs, ash or dust.

Take Note Viscosity is the stickiness of the lava or its resistance to flow. It increases as lava spreads from the vent cooling. Rhyolite with over 70% silica is the most viscous larva of all. As the eruption ends, the remaining viscous lava often oozes out of the vent and accumulates up as a dome above it. Thus, volcanic cones, which form along destructive margins, have tall cones with steep sides. The cones are composed of a mixture of lava flows and beds of ash and hence are called composite cones.

5.4.1 Intrusive Volcanic Features

Most of the magma upwelling from the mantle cools and solidifies within the crust; it is forced into or between rocks. Thus, it has intruded into the pre-existing rocks. The resulting features from this activity include batholiths, laccoliths, dykes and sills.

Batholith This is a very large dome-shaped mass of rock usually of granite, formed by a large–scale, deep-intrusion of magma. Batholiths may form surface features only after being exposed to the surface of the earth by denudation.

Source: http://www.cr.nps.gov/history/online_books/geology/publications/bul/1347/sec2.htm Figure 5.3: Major Intrusive and Extrusive Volcanic Features Sometimes batholiths resist erosion and stand up as uplands as for instance, the Chaillu Massif in Gabon, which rises to about 1500m in Mant Iboundji.

Sill Is an intrusion of igneous rock of a tabular form resulting from very fluid magma when it is forced between the bedding planes of sedimentary or volcanic formations. Sills may form ridges similar to escarpments when they are exposed by erosion. The Three Sisters in Cape Province of South Africa have sill cappings. Some sills lie across riverbeds where they form water falls. The Kinken Falls near Pita in the Futa Djalon of Guinea are formed in this way.

Source: http://www.physicalgeography.net/fundamentals/10j.html Figure 5.4: Dyke

Source: http://revisionworld.co.uk/gcse-revision/geography/rocks/igneous-rocks Figure 5.5: A Sill

Dyke This is a feature which is produced when magma cools in vertical or inclined fissures. Some are easily eroded while others are resistant to erosion. If it happens that a dyke is easily eroded, it forms a shallow trench. If it resists erosion, it stands up as a wall-like ridge and may cause waterfalls or rapids. The Howick Falls on the River Mgeni in South Africa are a result of a dyke that stands across it.

Laccolith This is a dome-like shaped mass of igneous rock produced by more viscous lava when it pushes up the overlying strata and solidifies between layers. When these intrusive features are exposed on the surface of the earth, they reveal landforms of interest to geomorphologists. The features also have an impact on human activities e.g. in construction.

5.4.2 Extrusive Features of Volcanism Usually only a small proportion of the magma that tries to force its way upwards through the crust manages to extrude out the surface of the earth as lava. It either erupts from volcanic craters or pours out

along fissures. Extrusive volcanic features include volcanic mountains, lava plateaus, geysers, mud pools and hot springs. If magma emerges onto the earth’s surface through a vent (hole), it usually builds up a volcano which is cone-shaped. If it emerges from a fissure (crack), it may build up lava plain or a lava plateau.

Vent Eruptions Volcanic eruptions are strongly influenced by the type of magma that escapes. Some eruptions are explosive such as Mt. Etna in Sicily in the year 2001 while others are gentle such as Mt Kilauea in Hawaii islands. A volcanic cone may consist of lava, or a mixture of lava and rocks derived from the crust by molten magma. It may also consist of ash and small fragments of lava (cinders). The shape and size of the cone is largely dependent on the nature of the material it consists, and the type of eruption. The channel through which the lava escapes is called the pipe and the crater is its exit.

Lava Cone Fluid lavas usually give rise to gently sloping cones such as Nyamlagire, near Lake Kivu in the Democratic republic of Congo and Mauna Loa in Hawaii. Viscous lavas produce steeply sloping cones. Due to thickness, sometimes the magma plugs the vent to build a plug dome e.g. those of Atakor volcanic area of the Hogger Mts. of Algeria.

Source: http://www.earthlyissues.com/volcano.htm

Figure 5.6: The Structure of different types of Volcanic Cones 5.5 Lifecycle of a Volcano Volcanoes pass through three stages; active, dormant and extinct. In the early stage, eruptions are frequent and the volcano is said to be active. During the period when the eruptions become infrequent, the volcano is said to be dormant (sleeping) such as the Oldonyo Lengai in Arusha region Tanzania, and the Cascade volcano of North America. Extinct volcanoes are those that are unlikely to erupt again (Aber, et al; 2000:25). Mount Kilimanjaro is such an example. 5.6 Importance of Volcanic Activity to Man The lava which is poured onto the earth’s surface contains a variety of minerals some of which are important to the growth of plants. Volcanic soils are known for their good fertility and hence suitable for agriculture. A good example is the slopes of Mt. Kilimanjaro and Mt. Meru in Tanzania which for this reason, support dense populations.

Hot springs in volcanic regions may be used for central heating and production of electricity as in New Zealand. Hot springs occur at Majimoto in Serengeti district, Tanzania. Moreover, some hard volcanic rocks are used for building structures. In Tanzania such rocks are found in Kilimanjaro region. 5.7 Volcanic Activity as a Hazard Volcanic eruptions are a natural hazard (a threat) to man and property. When an explosive eruption takes place in a habited area, it can destroy buildings, cover roads, kill people and animals, destroy farms, etc. A good example is an eruption of a Mountain at Goma in Eastern Congo (in 2002), which forced residents to vacate the town with some casualties.

Activity 5.1 ? Highlight the various intrusive volcanic features.

Summary Internal forces in the Earth crust are responsible for the formation of landforms such as mountains, plateaus, plains and valleys. Tension forces which act away from each other, cause rocks to fault. If faulting is accompanied by upward and downward movements, block mountains, rift valleys and escarpments can occur. Compression forces can also produce these features if the area acted upon consists of resistant brittle rocks. If rocks are soft, folds are formed. Earthquakes and volcanoes result from a movement of tectonic plates as a result of built up of temperature and pressure into the crust. High temperatures and pressure cause the earth’s crust to be always under great tension. When the rocks cannot withstand the stress, they give way through a fracture and their dislocation produce shocks. Surface vibrations produce an impact on both physical and human structures. Earthquakes tend to be concentrated in plate margins belts. Earthquakes are a natural hazard, particularly in densely populated areas. The movement of magma into the crust or onto the surface of the earth is called vulcanicity. Internal features include batholiths, sills, dykes and laccoliths. External ones comprise of volcanoes, lava plateaus, hot springs and geysers. Vent eruptions produce ash and cinder, lava and composite volcanic cones. A volcano can either be active, extinct, or dormant. Volcanoes unlike earthquakes have both negative and positive impacts. Apart from their destructive nature, volcanic soils are in many cases fertile and excellent for agriculture.

Exercise 1. What is the cause of vertical and lateral movements into the earth’s crust? 2. With examples describe the formation of fold, block, volcanic mountains and rift valleys. What are the main characteristics of each? 3. Describe the main intrusive features of volcanism. 4. Explain ways in which the distribution of earthquakes (a) is similar to that of volcanoes (b) different from that of volcanoes. 33

5. Explain why earthquakes are formed along all plate margins. What are their impacts to human beings? 6. Examine the positive and negative impacts of volcanoes to man.

References 1. Arber, Nicola, Sue Lomas, Garrett Nagle, Linda Thomson and Paul Thomson (2000); A2 Geography: Heinemann Educational Publishers, Oxford. 2. Bowen, Ann and John Pallister (2001); A2 Geography: Heinemann Educational Publishers, Oxford. 3. Bunnett, R. B (1990); Physical Geography in Diagrams for Africa (8th edition). Longman Group Ltd. Hong Kong. 4. Clark, Audrey (1990); Geography Dictionary. Geographical Publishers Ltd London.

PART 3 External Geomophic Processes

Lecture 6 External Geomorphic Processes Weathering and Mass Movement

6.1 Introduction

In the foregoing lecture, we learned about internal processes that give rise to the formation of various landforms into and onto the surface of the Earth. In this lecture, you will be exposed to processes which take place on the surface. These processes embrace weathering, mass movement and erosion, which change the shape of the landforms. Weathering is the action of the weather on objects exposed to it. The action can lead to physical, chemical and or disintegration of rock in situ by exposure to water and the atmosphere. Weathering does not involve transportation of material. The main physical agents are shattering, frost actions and temperature change. Plant roots and burrowing animals are organic agents while chemical processes consist of carbonation, hydration, hydrolysis, oxidation, solution and corrosion (Clark 1990:354). You shall learn how they take place and the resulting features later in this lecture. Denudation which is the wearing away of rocks exposed on the Earth’s surface, includes the results of both weathering and erosion. Denudation involves weathering, erosion and transportation.

Take Note In situ refers to the fact that the breakdown of rocks takes place where the rock is situated without involving any transportation.

Learning Objectives At the end of this lecture, you will be able to:

 Describe the process of weathering, and resultant features;

 Describe the process of various types of mass movements and resultant features;

 Discuss factors that influence weathering and the main types of weathering;

 Critically analyse the significance of weathering to human beings and their environment.

6.2 Weathering

Weathering refers to the process of weakening, breaking up and finally disintegration of the rocks which form the surface of the Earth and rocks that lie exposed to weather. The process is called weathering

because the actions are driven by forces of the weather namely; changes in temperature, frost action and rain action. Weathering is divided into three main types; mechanical, chemical and biological. When weathering takes place, rock changes occur without involving any movement, whereas erosion (wearing away) takes place only with movement. Weathering and erosion work together thereby lowering the height of land surfaces. Weathering speeds up rates of erosion where particles and pieces of disintegrated or decomposed rock are subjected to the operation of mass movement down-slope due to gravitational force. Such particles can be transported to distant places by agents of erosion.

Mechanical Weathering This process is also called physical weathering. It breaks up the rock without any change to its exiting mineral structure. Such processes include freeze-thaw or alternate heating and cooling. It follows that the disintegration of rocks is a result of pressure release.

Temperature Changes This is significant in hot and arid environments. The daily changes in temperature cause rocks to expand during the day and to contract at night. This causes the outer parts of the rocks to experience internal stresses as the heating and cooling does not penetrate far below the surface. The stresses in the outer layer of rocks pull away from the layer beneath. This process is termed ‘exfoliation’. The plates of the rock that peel of and fall to the ground are further broken into smaller pieces by the force of alternate expansion and contraction. The remaining rounded structures resulting from this process are called exfoliation domes. However, with the development of cracks, the stresses can operate to greater depths.

Source: http://www.gly.fsu.edu/~salters/GLY1000/10Weathering_Erosion/Slide21.jpg Figure 6.1: Exfoliation Domes Formed by Mechanical Weathering Exfoliation domes occur mainly in hot deserts such as the Kalahari and Sahara. Where it happens that the rock is coarse-grained igneous rock, granular disintegration can also produce dome-shaped structures. When a rock absorbs water, various minerals expand and contract at different rates and thus granular fragments drop from the rock. The creation of joints near the surface increases the vulnerability of the rock to further mechanical weathering.

Frost Action Most rocks contain cracks and some contain joints. When water enters these and freezes its volume increases. Ice occupies 9% more volume than an equivalent mass of water. This exerts great pressure on the sides of the rock and continued cooling and expanding finally causes the rock to split along the lines of weakness. With time angular blocks later break into smaller particles. These drop from the rock and accumulate at the base of the slopes and are called screens. The whole process is called block disintegration. Frost action takes place both in the arctic and cool temperate regions where temperatures are very low during winter (Bowen, 2001: 100; Bunnett 1990: 52).

Source: slcss.edu.hk Figure 6.2: Block Disintegration

Biological or Organic Weathering This consists of both physical and chemical weathering. Micro-organisms such as bacteria cause both mechanical and chemical break-up of rocks by oxidising minerals. Plants and animals also increase the carbon dioxide content of the soil and this increases the weathering potential of the biosphere. On the other hand, roots of plants and trees, and the work of burrowing animals such as rabbits, cause rocks to disintegrate physically.

Chemical Weathering This is responsible for the rotting and decomposition of many types of rocks on a massive scale. Minerals in the rocks are decomposed by agents such as water, carbon dioxide and organic acids. Minerals in the rocks vary in their resistance to chemical agents. Because of this, weathering attacks rocks selectively. The rate of chemical weathering increases with temperature. For this reason, the largest rates of chemical weathering take place in the hot, wet tropics. Similarly, the highest and most rapid rates of vegetation decay and nutrient recycling is high in hot, wet tropics. As a consequence of this process, many organic acids are released by the vegetation on the forest floor thus spreading up the process of chemical weathering. Outside the tropics, the end result of chemical weathering are sand and clay, which are left, unchanged and thus remain stable (Bowen, 2001). In humid tropics, both sand and clay remain unstable and can be removed. Aluminium and iron are the most stable minerals. That is why tropical soils have a higher concentration of oxides of aluminium and

iron which attributes to their characteristic yellow–red colour. Chemical weathering consists of five processes: Solution, hydration, hydrolysis, oxidation and carbonation. These are discussed below in detail. Solution: Rocks can be weathered when the salts they contain dissolve in water to form a solution. Only a few minerals directly dissolve in water. However, some, particularly calcium carbonate dissolve freely in water containing Carbon dioxide. Rainwater dissolves both carbon dioxide and oxygen in the air such that it reaches the ground as a weak carbonic acid. This is able to turn many insoluble minerals into soluble minerals that can be carried away in solution. This kind of weathering is well-observed in limestone areas where solution renders joints to become widened and deepened. Thus, grooves called grikes which are separated by flat-topped ridges, called Clints develop. In humid tropics, so often the majority of minerals dissolve in water with the exception of iron and aluminium. These accumulate in the top layers of the soil through leaching thus developing lateric soils.

Source: http://gallery.nen.gov.uk/asset82421_1789-.html Figure 6.3: Grikes and Clints Hydration: This happens when certain rock minerals take up water and form new compounds. For instance, haemotite is an iron oxide and when it combines with water, it gives limonite which is another iron compound. Calcium sulphate absorbs water to form gypsum whereas felspar results into clay. Oxidation: This is a process of rock taking up oxygen from the air and then combines with a mineral. This process is more active in rocks that contain iron. When oxygen combines with the iron it forms iron oxide. The new minerals formed by oxidation are prone to being attacked by other weathering processes. Hydrolysis often precedes and accompanies oxidation. The oxidation of iron breaks the structure of a rock in which iron and a silicate are joined. Subsequently, the rock easily breaks. Carbonation: This is a chemical process in which rainwater charged with carbon dioxide forms carbonic acid that reacts and dissolves limestone and other basic oxides. Hydrogen carbonate ions react with a mineral to give a soluble compound, which can be carried away in solution. More often, hydrolysis accompanies carbonation. The two processes break down a felspar into clay, calcium carbonate into more soluble calcium bicarbonate. The last processes of chemical weathering which involves wearing away of rock or sand by chemical and solvent action are collectively referred to as corrosion.

6.3 Factors Affecting the Type and Rate of Weathering The main factors that influence weathering are the hardness, jointing and texture of rocks, relief and climate. The abundance of water, oxygen and carbon dioxide accounts for the fact that the major chemical weathering reactions are hydration, oxidation and carbonation. Rock Resistance: Rocks vary in their resistance to weathering. The rate of resistance is dependent on the constituent minerals of the rock and how they are cemented together in the rocks and the extent to which the minerals have been compressed. The hardness of the minerals in the rock is measured by Moh’s scale of hardness. The scale ranges from 10 (extremely hard) to 1 (very soft), quartz for instance is classified at 7 and gypsum at 2. Most igneous rocks are hard due to their mineral constituents such as quartz and feldspar. When the minerals cooled and crystallised, they were tightly bounded together. In contrast, sedimentary rocks tend to be soft because they are more often cemented together by soft cement. However, if the cement is hard, the rock is very resistant to weathering as in the case of rocks cemented with silica (Lines, et al 1996:60). The Texture of Rocks (The crystalline state): In many cases, coarse-grained rocks are likely to weather more rapidly than fine-grained rocks, which are composed of the same minerals. Usually one mineral in a rock is weathered more rapidly than others. The weathering of such a mineral loosens the whole fabric of the portion of the rock exposed to weathering. Rock Jointing: This influences the nature and rate of weathering in both mechanical and chemical weathering because the joints increase the surface area exposed to the agents of weathering. In limestone areas, chemical weathering concentrates along joints and bedding planes. The joints allow acidic solution, oxygen and carbon dioxide to enter the rocks thereby encouraging chemical decomposition. The pattern of jointing determines the character of the land features produced. For example, plutonic rocks such as granite have a jointing system that divides the rock into rectangular blocks. When these are chemically weathered, they form piles of semi-rounded boulders. In contrast, basalt has a well-defined jointing pattern, which forms vertical polygonal columns. Relief: This influences mechanical weathering. In order for mechanical weathering to continue, new rocks need to be exposed. Thus in highland areas, landslides, slump and solifluction result from the exposure of bare rock. A thick layer of soil or weathered material overlies non-weathered rock, protecting it from being weathered mechanically. Climate: Climatic conditions determine to a large extent, the process of weathering. For example, in tropical areas with low rainfall, chemical weathering is more moderate than in areas with heavy rains where it is stronger. Exfoliation and granular disintegration are most effective in regions with a large daily range of temperatures such as in the semi-arid and continental deserts. Cool climate provide freeze-thaw conditions which allow strong mechanical weathering. Human Activity: Now and again human beings intensify processes of weathering through cultivation, building and construction as well as mining. Also, the introduction of gases, car emissions and other pollutants into the atmosphere accelerates chemical weathering.

6.4 Mass Movement Mass movement refers to the transfer, sliding, falling, creeping or flowing of rock materials produced by the agents of denudation (weathering and erosion down slope) under the influence of gravity. It is a link between weathering and transport by agents of erosion. The force of gravity acts constantly on all rocks and debris. While gravity forces loose materials down slope, there is resistance to movement from friction and cohesion that have to be overcome before any movement can take place. Water is well-known for achieving this since a mass of rock material, which is well watered, moves easily than a dry mass of rock material (Bowen, 2001:106)

Usually mass movement takes place slowly, but sometimes it takes place suddenly! The rate of movement depends on the steepness of the slope. The rate of movement of loose material moves down faster over steeper slopes. Other factors influencing movement include the nature and weight of materials, and the amount of water in the material. More dense materials tend to move quickly on a steep slope whereas light materials move slowly. Sudden movements give rise to landslides.

Land Slide A landslide is the sliding down under force of gravity of a mass of land on a mountain or hillside. This takes place when large quantities of loosened surface rocks and soil suddenly slide down a cliff face or valley side. A landslide may either take the form of sliding or slumping. The latter is common on slopes made of clay (Clark, 1990:55). A number of actions may trigger the occurrence of a landslide. The undercutting of the base of a steep slope by a river or by the sea and the steeping of a slope by human activities such as quarrying or clearing up vegetation from a steep slope. An earthquake or prolonged heavy rains in mountainous areas such as in the Usambara cause landslides. Buildings and roads can be buried. When landslides occur in a populated area, loss of life and property may take place.

Source: http://atlas.nrcan.gc.ca/site/english/maps/environment/naturalhazards/landslides/fig_6_land_slide_movement.jpg/image_view Figure 6.4: Land Slide

Soil Creep This is the slow downward movement of soil under force of gravity common on all sloping land. Rainwater enables soil particles slide over each other. Boulders and stones in the soil, or resting on it, are carried down the slope by the soil. Other factors, which influence soil creep, include heating and cooling of soil, alternate wetting and drying of the soil, tramping of grazing animals and burrowing of animals in the soil. Soil creep can be recognised by fences and trees that lean down the slope.

Mudflow This is a moving mass of soil made fluid by continued heavy rains or melting snow on a slope. Mudflows can take place on desert slopes that are unprotected by vegetation cover. Other places where mudflows take place are on the slopes of an erupting volcano when heavy rains fall on the volcanic ash, in tundra regions during early summer, when frozen soil thaws and turns into a semi-liquid state, thus able to slide over the still frozen subsoil (Bunnett, 1990:54).

Rock Fall This is a free fall of individual boulders or blocks of bedrock down any steep slope due to the force of gravity.

Rock Avalanche This type of fall usually forms when a massive rock fall explodes apart on contact with a slope. As this occurs, thousands of rocks continue their flying trajectories down slope, colliding with each other and the slope itself, overwhelming anything in their paths. A rock avalanche is a transitional sort of mass wasting event, changing from a pure rock fall to something more like a rapid flow of material as the material moves further from the base of a slope.

Rock Slide This type of slide occurs where there is a tilted, pre-existing plane of weakness within a slope which serves as a slide surface for overlying sediment/rock to move downward. Such planes of weakness are either flat sedimentary surfaces (usually where one layer of sediment or sedimentary rock is in contact with another layer), planes of cleavage (determined by mineral foliation) within metamorphic rocks, or a fracture (fault or joint) within a body of rock. Rock slides can be massive, occasionally involving an entire mountainside, making them a real hazard in areas where a surface of weakness tilts in

Activity 2 ? List the factors influencing mass movement.

Summary In the past, weathering was seen as a distinctive process of landscape formation, today it is placed in the broader context of landform development and the various types of weathering are tolerated as simultaneous and interrelated processes. In the analysis of landscape formation, weathering is seen to contribute to the formation of rock waste, which is an initial input into the system. Weathering and surface transport are also regarded as the two main processes responsible for slope formation. Moreover, the study of soil formation also starts with rock weathering. When weathering takes place, rock changes occur without involving any movement. The two most important factors influencing weathering are rock structure and climate. Chemical and physical weaknesses make a rock susceptible to at least one type of weathering. Granite is a strong, resistant rock, but its mineral- felsipar is affected by hydrolysis and breaks down chemically. Limestone is affected by carbonation. Temperature changes in hot arid environments cause exfoliation. Chemical weathering is enhanced by increases in temperature coupled with rainfall. It takes place by solution, hydration, hydrolysis, oxidation and carbonation. Generally, the rate of weathering is influenced by the mineral composition, the texture of rocks, rock jointing, relief and climate. Human beings also intensify the process of weathering through cultivation, grazing, building, mining and construction. Mass movement involves the transfer of large quantities of weathered material down slope. The movement may be a slow one as in the case of soil creep or rapid as it happens in landslides. The four 42

main types of mass movement are soil creep; mudflow, landslide and rock fall. The latter two are hazardous to human beings.

Exercise 1. Discuss with examples, the main types of rock weathering. 2. Compare and contrast weathering processes in a hot arid environment with that in a hot humid environment. 3. Briefly explain the factors which influence the rate of weathering. 4. Examine the advantages and disadvantages resulting from rock weathering. 5. Describe the various types of mass movement and name the resultant features.

References 1. Bowen, Ann and John Pallister (2001), A2 Geography. Heinemann Educational Publishers; Oxford. 2. Arber, Nicola, Sue Lomas, Gerrett Nagle, Linda Thompson and Paul Thompson, (2000), A2 Geography, Heinemann Educational Publishers; Oxford. 3. Bunnett, R. B (1990), Physical Geography in Diagrams for Africa, Longman Group; Ltd. Hongkong 4. Clark, Audrey N. (1990), Dictionary of Geography; Geographical Publications Ltd, London. 5. Lennon, J. Barnaby and Paul G: Cleves, (1983), Techniques and Field Work in Geography. UN Winhyman Ltd. London. 6. Lines, C; Laurie Bowlwell and Anne Fielding Smith (1996), A Level Geography. Letts Educational, London.

Lecture 7 River Action and Landforms Produced

7.1 Introduction Erosion is the process of the weathering away of the land surface by natural agents such as running water, ice, wave action, wind and the transportation of the resultant rock debris (Clark, 1990:107). The process does not involve weathering of rocks in situ or mass movement. Processes of erosion include abrasion, corrassion, attrition and plucking. Once weathering breaks down rock surfaces, the various agents of erosion are able to carry out their work easily. Water is the main agent of erosion at work in the world (Arber, et al, 2000:32). This lecture highlights the various erosion processes carried out by the agents of erosion such as running water, waves, winds and human beings and a discussion of various features they form. Glacial action is not considered here for convenience. However, you are advised to read on how it operates.

Learning Objectives At the end of this lecture, you will be able to:

 Discuss the main agents of erosion;

 Describe the process of river action, wind action and wave action;

 Describe the processes of deposition by various agents and the resultant landforms;  Explain the significance of erosion to human beings.

7.2 Erosion and Deposition by Running Water When it rains, only a small proportion of rainfall reaches the river channel directly. A large part is held and stored in leaves and branches of plants. This is called the interception zone. The amount intercepted depends on the type and density of vegetation as well as rainfall intensity. Rain from heavy rainstorms saturates soil more easily than gentle drizzle. Before rainfall reaches the surface of the earth, some is evaporated into the atmosphere. The water that reaches the surface moves into the soil and this process is called infiltration. The soil ability to absorb rainwater is called infiltration capacity before saturation. The soil has a limit to absorb rainwater. The water which infiltrates flows by gravity into the soil to the water table. It may also flow as underground water and finally reach a river channel. Once it becomes part of a river, flowing water transports and deposits material far away from their original place. The water that exceeds the soil’s infiltration capacity flows on the surface of the earth as runoff, depending on its volume, slope and nature of the soil. Runoff erodes soil and at the same time forms small streams that join together to give larger streams, which subsequently join to form a river. Where streams join to form a river is called a confluence and the streams are called tributaries.

Erosion by River Action The amount of material carried by a river depends on steepness and resistance of the rocks, the amount of water flowing down into it and the material delivered down the valley slopes. The flow of a river depends on the energy provided by gravity which is also determined or related to the gradient of its bed and volume increases. There is a relationship between velocity of water in the river channel and the particle sizes, which can be eroded, transported and deposited. Lower speeds allow small particles to be moved on the channel bed while high speed can carry larger particles. Consequently, the larger the particles, the greater the velocity required to transport them (Lines et al, 1996:70). A river can erode material through attrition, corrasion, solution and hydraulic action. Attrition: It is an action or process by which the load of the river gets broken down when particles rub against each other. Accordingly, as the load is transported, the fragments get smaller. Corrasion: It is a process of mechanical erosion of a rock surface by the friction of rock material with the surface. The rock material can be moved under gravity or by running water (waves, glaciers) or by wind. Corrasion wears away the bed of a river’s channel, which causes the load to increase. Solution: It involves transportation of material which has dissolved in water. It has already been discussed under lecture four. Hydraulic Erosion: Refers to the force of moving water that is able to remove loose material such as gravel, sand and silt. The action is able to weaken solid rock when it enters into cracks of a rock. Nonetheless, hydraulic action leads to little erosion if the river has little or no load. The four processes described above are responsible for the undercutting of a river’s channel. The erosion is achieved by head ward and vertical erosion, which deepens its channel. A river's channel is also widened when its sides are won out by lateral erosion.

Transportation by a River The load of a river is transported by traction, saltation, and suspension and by solution. Traction refers to the dragging of large material such as pebbles along its bed. Saltation is the bouncing of smaller pieces down its bed. Under suspension, light materials, such as silt and mud are carried in water as the river flows. Finally those minerals that dissolve in water are transported by solution. A river transports its load until when it has insufficient energy to transport it any further. When this condition happens, the river deposits its load.

7.3 Factors Which Reduce Energy of a River Water in a river flows in two ways – lamina (in layers parallel to the bed) and turbulent flow (in circular form). When a river’s flow is turbulent, its energy decreases when it overcomes the friction either on its bed or on the sides. Bends tend to increase friction and give out energy as heat into the atmosphere. The shape of a river channel also affects the amount of energy a river possesses for erosion and transportation. A river uses more energy to flow through a flat, wide channel than through a narrow deep channel. In addition, energy is lost when the materials transported are in suspension than moving material along the riverbed. When the energy of the river is unable to transport its load, it starts to deposit it starting with coarse material and ending up with fine material.

7.4 Features Produced in the Upper Course of River Valley

It is characterised by V-shaped valleys, potholes, interlocking spurs, waterfalls and rapids. V-shaped valley: The V-shaped valley is deepened by vertical corrasion and widened by weathering and mass wasting. If there is a resistant rock in the course of a river, vertical corrasion takes place, causes the valley to deepen with very narrow vertical banks. Such a valley is called a gorge. When it is large in size, it is called a canyon. Pot-holes: Potholes are cylindrical holes drilled into the bed of a river that vary in depth & diameter from a few centimetres to several metres. They’re found in the upper course of a river where it has enough potential energy to erode vertically and its flow is turbulent. In the upper course of a river, its load is large and mainly transported by traction along the river bed. When flowing water encounters bedload, it is forced over it and downcuts behind the bedload in swirling eddie currents. These currents erode the river’s bed and create small depressions in it. Water falls and Rapids: A waterfall is either a sudden deep or perpendicular drop of water in the bed of a river, occurring where the flow of the river is broken by an almost horizontal bed of hard rock overlying soft rock easily eroded (Clark, 1990.352). If the face of the rock is steep, horizontal and dips gently down-river then a rapid develops. One of the largest waterfalls in the world is the Victoria Falls on the Zambezi.ater

A Waterfall

Source: http://www.bbc.co.uk/schools/gcsebitesize/geography/water_rivers/river_landforms_rev1.shtml Figure 7.1: Features in the Upper course of a River Interlocking Spurs: A river tends to flow around resistant rocks such that a river takes a winding course. Prolonged process causes the bends in the river to become more pronounced since the water on the outside of a bend flows more quickly and erodes more this side. This finally causes projections of highland called spurs which appear to be interlocking.

Source: Bunnett, F. B. (1990: 74) Figure 7.2: Cut Spur and Widened Valley

7.5 Features Produced in the Middle Course of a River Valley In the middle course of a river, lateral corrasion is more active than vertical corrasion. As a result, the river passage develops an open appearance. When more tributaries join it, the volume and the load increases. Here, the interlocking spurs are cut back by lateral corassion to form bluffs and this widens the valley floor. Deposition begins especially inside of meanders and river cliffs and slip-off slopes develop on the inside of the banks.

Meanders Water flows fastest on the outer bend of the river where the channel is deeper and there is less friction. This is due to water being flung towards the outer bend as it flows around the meander, this causes greater erosion which deepens the channel, in turn the reduction in friction and increase in energy results in greater erosion. This lateral erosion results in undercutting of the river bank and the formation of a steep sided river cliff. In contrast, on the inner bend water is slow flowing, due to it being a low energy zone, deposition occurs resulting in a shallower channel. This increased friction further reduces the velocity (thus further reducing energy), encouraging further deposition. Over time a small beach of material builds up on the inner bend; this is called a slip-off slope or point bar.

Source: http://www.acegeography.com/landforms Figure: 7.3 River meanders

Ox bow lake As the outer banks of a meander continue to be eroded through processes such as hydraulic action the neck of the meander becomes narrow and narrower.

Eventually due to the narrowing of the neck, the two outer bends meet and the river cuts through the neck of the meander usually during a flood event when the energy in the river is at its highest. The water now takes its shortest route rather than flowing around the bend. Deposition gradually seals off the old meander bend forming a new straighter river channel. Due to deposition the old meander bend is left isolated from the main channel as an ox-bow lake. Over time this feature may fill up with sediment and may gradually dry up (except for periods of heavy rain). When the water dries up, the feature left behind is known as a meander scar.

Source:https://www.google.com/search?q=diagram+of+oxbow+lake

7.6 Features of a Lower Course of a River Valley Deposition is the main activity in the lower course. Nonetheless, lateral corrasion continues to cut back the banks while vertical corrasion is almost over. At this stage, a river contains the maximum of its volume. Since the gradient decreases, deposition takes place across the width of the valley floor. The deposition of material on the valley floor sometimes causes the river to split into several channels such that it becomes a braided river. The deposited material may also produce a gently sloping surface called flood plain. Flood Plain: It is a gently sloping plain of alluvium which covers the valley floor on which the river flows in a meandering channel. The plain can have marshes and ox-bow lakes left after the meanders have been cut off. During floods, the river overflows on the banks, depositing fine sediments on the flood plain. The deposition on the banks build up a ridge-like feature called a levee. The meanders still prevail at this stage but no longer reach the sides of the valley. The Nile flood plain is the best example.

Source: http://www.sln.org.uk/geography/schools/blythebridge/gcseriversrevisionlc.htm

Figure 7.5: Bluffs, Flood Plain, Levee and Ox-bowl Lake Rivers that flow above their flood plain are troublesome to settlements such as the Hwang Ho, Yangtse Kiang and the Mississippi.

Levees Levees are natural embankments produced, ironically, when a river floods. When a river floods, it deposits its load over the flood plain due to a dramatic drop in the river’s velocity as friction increases greatly. The largest & heaviest load is deposited first and closest to the river bank, often on the very edge, forming raised mounds. The finer material is deposited further away from the banks causing the mounds to appear to taper off. Repeated floods cause the mounds to build up and form levees. Levees aren’t permanent structures. Once the river’s discharge exceeds its bankfull discharge1, the levees can be burst by the high pressure of the water. Levees increase the height of the river’s channel though, so the bankfull discharge is increased and it becomes more difficult for the river to flood.

Deltas Deltas are depositional landforms found at the mouth of a river where the river meets a body of water with a lower velocity than the river (e.g. a lake or the sea). For a delta to develop, the body of water needs to be relatively quiet with a low tidal range so that deposited sediment isn’t washed away and has time to accumulate.

When a river meets a stationary body of water, its velocity falls causing any material being transported by the river to be deposited. Deltas are made up of three sediment beds that have been sorted by the size of the sediment. The bottom most bed, the bottomset bed, is composed primarily of clay and some other fine grained sediments. Clay is the main constituent because when clay meets salt water a process called flocculation takes place where clay & salt particles clump together (flocculate) due to an electrostatic charge developing between the particles. This makes the clay particles sink due to their increased weight producing the bottomset bed. The bottomset bed stretches a fair distance from the mouth of the river as the fine sediments can be transported a reasonable distance from the river’s mouth.

The foreset bed lies on top of the bottomset bed. The foreset bed is composed of coarser sediments that are deposited due to a fall in the river’s velocity and aren’t transported very far into the stationary body of water that the river flows into. The foreset bed makes up the majority of the delta and is dipped towards deep water in the direction that the river is flowing in.

The topset bed is, as the name suggests, the topmost bed of the delta. It too is composed of coarse sediment but, unlike the foreset bed, the topset bed doesn’t dip, it’s horizontally bedded.

The necessary conditions for the formation of a river delta are: (a) A river must have a large load (b) The velocity of a river must be sufficiently low to allow most of its load to be deposited in the rivers’ mouth. (c) The rivers load must be deposited faster than it can be removed by the action of tides and currents.

Take Note River Congo has a large load but no delta because the high velocity near its mouth enables most of the load to be carried away.

7.7 Types of delta

Arcuate Delta: This is a fan shaped delta with rounded outer margin, the arc of the fan spreading into the sea. The delta consists of both coarse and fine sediments. It is also crossed by a number of distributaries such as the delta of the Nile and the Ganges. Form when a river meets a sea with alternating current directions that shape the delta so that it looks like a triangle.

Source: http://www.e-c-h-o.org/khd/location.html Figure 7.6: Arcuate Delta

Bird’s Foot Delta: Is a delta where relatively narrow borders of sediments, projecting seawards in pattern of a bird’s foot flank distributaries. It consists of fine material and has a few long distributaries that are bordered by levees, which stick out from the shore. The delta develops when the power of the waves and currents are low for instance, the delta of the Mississipi. They extend reasonably far into a body of water and form when the river’s current is stronger than the sea’s waves. Bird’s foot deltas are uncommon because there are very few areas where a sea’s waves are weaker than a river’s current.

Source: https://www.fas.org/irp/imint/docs/rst/Sect14/Sect14_10a.html

Figure 7.7: Bird’s Foot Delta

Cuspate Delta Cuspate Delta (tooth-shaped) e.g. Tiber River, usually has one major tributary. re vaguely shaped like a V with curved sides. Cuspate deltas form when a river flows into a sea with waves that hit it head on, spreading the deposited sediment out.

Source: http://www.americaswetlandresources.com/background_facts/detailedstory/RiverDelta.html

Figure 7.8: Cuspate Delta Estuarine Delta: The delta develops in an estuary (tidal mouth of a river) from materials deposited in the submerged mouth of a river and thus takes the shape of the estuary. For instance the delta of River Ob in Russia. Estuarine delta e.g. Seine River of France. The river empties in a narrow estuary.

Source: http://www.americaswetlandresources.com/background_facts/detailedstory/RiverDelta.html

Figure 7.9: Estuarine Delta

Summary Erosional and depositional processes are largely responsible for the continuous shaping of the earth’s surface. Running water is an agent of erosion in the tropics. The erosive power of a river depends on its volume and the gradient of its bed. Generally the volume of water increase from a rivers’ source to its mouth but the gradient decreases from the source to the mouth. When the energy of the flowing river. Slackens, some of its load is deposited. Water falls; rapids, the flood plain, meanders and deltas are some of the outstanding features produced by a river.

Exercise 1. Define the term River and explain its erosional processes 2. Discuss river erosional and depositional landforms 3. What is delta? Give necessary conditions for delta formation 4. With diagrams and examples discuss types of delta

5. Clark, Audrey (1990), Geography Dictionary, Geographical Publishers Ltd.

Lecture 8 Erosion and Deposition by Action of Waves

8.1 Introduction The coastline is the margin of the land, and shoreline is where the shore and water meet. Where sand is deposited on the shore is called a beach. Coastal lines are constantly being modified by wave erosion. Wave erosion causes some shore lines to retreat while wave deposition causes others to advance. Coasts are varied in character. Some costs are high while others are low. Some are steep, gentle, and rocky while others are sandy. The nature of a coast results from wave action, tidal currents, and the nature of climate. Other coastal changes may be caused by human activities (Bunnett, 1990.105).

Source: http://www.rgbstock.com/bigphoto/mhbGuHk/Red+cliffs Figure 8.1 Sea, Shore, Coast and Cliff Waves are formed by blowing wind whose lower layer encounters friction with the surface of the sea causing the various layers of wind to travel at different speeds. As the air develops a circular motion causes the surface water to take the form of a wave. It is not the water that moves but rather the waveform. When a wave travels in shallow water its water and its top fall forward, throwing the water up the beach. This is called a swash. When the swash drains back down the beach it is termed the backwash. The apex of the wave is the crest whereas the lower part is the trough. The height and power of a wave depend on the strength of the wind and the distance of open water on which it travels. Wave action consists of three main actions, corrasion or abrasion, hydraulic action and attrition. Boulders, pebbles and sand that bounce against the base of a cliff by breaking waves thereby undercutting and breaking rock cause abrasion. The second action is hydraulic action, which is caused by water which is thrown against a cliff by breaking waves. The water, which enters cracks, causes them to expand and eventually crushing the rocks. Finally, we have attrition. This is the breaking up of boulders and rocks as they are pushed against the shore and against each other by breaking waves (Bunnet, 1990:107).

8.2 Features Produced by Wave Erosion

Cliff: A cliff is a high steep or perpendicular face of rock produced by wave erosion. The cliff continues to sharpen as its base is attacked by wave action. Finally, the upper part of a cliff may collapse providing the waves with material for further erosion. Resistant rocks form headlands while non-resistant ones form bays.

Source: https://www.google.com/search?q=sea+cliff+diagram Figure 8.1.: Sea Cliff Cave A cave is a tunnel like opening at the base of a cliff face developed along a line of weakness through continued wave erosion. If a passage from the cave opens upwards to reach the top of the cliff it produces a blow-hole. Eventually, the roof of a cave collapses and a long narrow inlet called geo, form. When a cave in a headland is eroded it forms an arch and when this collapses, the end of the headland stands up as a stack. Arches Formed when cave formed on a headland, it might eventually break through the other side and form an arch. Stacks As the arch becomes bigger, it will eventually not be able to support the top of the cave or arch. The top of the arch collapses and leaves the headland, and a bit further away something what is called a stack (column of rock). Stumps The stack will be attacked by the waves at its base. This eventually weakens the stack and it collapses forming a stump.

Source:: https://101coastsgroup1.wikispaces.com Figure 8.2: Headland, Bay, Arch and Stack

8.3 Features Produced by Wave Deposition Where there is an abundant supply of unconsolidated material along the coast, the predominant geologic process is deposition. As waves approach the shore head-on, they sweep up loose sediments and carry them landward. The return flow of water washes much of the sediment back toward the sea. In addition, waves that meet the shore at an angle may create longshore currents, which transport material parallel to the shoreline. This complex reworking of coastal sediments is responsible for the development of several different types of depositional features. Depositional features created by sea waves include beaches, spit, tombolo and mud fall:

Beach A beach is the accumulation of loose unconsolidated material on the shore of the sea at or near the limits of wave action, normally between the low water tide line and the highest point reached by storm waves at high tide (Clark, 1990:33). Waves can deposit material in a bay to form bay-head beaches. These beaches do not extend to the headlands where erosion is dominant.

Barrier Beach A barrier beach is a ridge of sand that is parallel to the coast. The beach develops from an under water offshore bar. It is a large narrow beach which has been formed by materials deposited on it. The material is gradually carried along the shore by the swash and backwash movement which together result in long shore drift. Therefore beaches are constantly undergoing changes.

Barrier Island Barrier Island: beach ridge separated from coast by low-energy lagoon. Example,barrier island off the east coast of the USA,

Spit

Spit is an elongate ridges of sand and gravel that project from the land to the sea are called spits. Most spits are simply extensions of bars, and they are built as longshore currents deposit sediment in areas where the water suddenly deepens, such as at the mouth of a bay. A spit is a narrow ridge of sand and pebbles resulting from long shore drift, attached to the seashore at one end, extending some distance seaward, terminating in the open water at the other (Clark, 1990:302). A spit is formed by deposition of material by long shore drift. If the waves meet the coast obliquely, the end of the spit is curved or hooked such as that in Walvis Bay, Namibia.

Bar A bar is described by Bunnett (1990) as a ridge of sand material that lies parallel or almost parallel to the coast unattached to the coastland. Bar is a generic term applied to any of a number of forms of elongate embankments of sand and gravel built on the sea floor by the action of waves and/or currents. These depositional features are further described by their positions in relationship to other coastal features. For example, a baymouth bar is a bar that extends partially or entirely across the mouth of a bay. A crescent bar is a crescentic sand or gravel ridge that forms between two promontories, or headlands. These types of bars are formed by the flow of seawater into an inlet or bay; consequently, the curved outline of a crescent bar is concave toward the ocean. A cuspate bar is a pointed bar with a tip that projects seaward. These bars are formed where there are conflicting shore currents. A special type of bar, known as an offshore bar or barrier island, is a sand and gravel ridge that lies offshore and is isolated from the mainland. Barrier islands commonly contain dunes, vegetated zones, and swampy terraces of the lagoon side of Island

Tombolo Tombolos are ridges of sand or gravel that have been deposited in such a way that they connect one island to another or an island to the mainland. Tombolo formed when bar join an island to the mainland. A long tombolo occurs near Las Hafun in N. East Somalia.

Cuspate foreland The first stage was the formation of a spit from Fairlight Head, which was seaward of its current position. Cuspate forelands can be described as triangular beaches. They form due to logshore drift meoveing sediment in opposing directions. The two sets of storm waves build up a series of ridges, each protecting the material behind it, creating the triangular feature. Cuspate forelands form due to the positioning of the coast and theirorientation to incoming tides and prevailing winds

Mudflat Mudflat formed when large expanse of fine clay or silt deposited along gully sloping coasts and particularly in bays. At high tide such areas may be covered by water and or colonised by vegetation such as mangroves.

Source: http:// https://www.ck12.org/earth-science/landforms-from-wave-erosion-and-deposition Figure 8.3 : Bar Spit and Tombolo

Summary Erosional and depositional processes are largely responsible for the continuous shaping of the earth’s surface. Wave action is among the water, the main agents of erosion and depositon in the tropics. The erosive power of wave depends on the extent and power of wind blowing along the ocean and nature of rock materials found offshore and along the coast. Sea waves have great erosive power and are responsible for the shaping of coastlines. Wave erosion produces cliffs, arches and stacks depending on the resistance of rocks being acted upon. Wave Action is main determinant of coastaland features which are normally used for different social economic purpose.

Exercise 1. Define the term Wave and explain marine erosional processes 2. With aids of diagrams discuss Marine erosional landforms 3. Illustrate Coastal depositional features 4. Visit a sea shore and observe its erosive activity. Record features you see.

Lecture 9 Erosion and Deposition by Wind Action

9.1 Introduction

Wind action is important in arid and semi arid regions due to absence or little vegetation cover. Most of the arid regions lie in the trade wind belt where the dry winds blow offshore between 15-30°N and 15- 30°S. Major deserts include the Sahara, Arabian, Iranian, Thar, the Kalahari, the Namib, Great Australian desert and the Atacama deserts.

9.2 Processes of Wind Erosion Transport and deposition are the most significant processes of wind erosion. Wind blows away fine particles over long distances while the coarser particles bounce over the surface. The bouncing movement is called saltation. Similar to other agents, wind erosion takes place in various ways as given below:

Deflation: Deflation is the removal of the sediments by wind – Leaves heavy pieces behind wind can blow tiny particles away from larger rock pieces during deflation. Deflation happens when wind removes the top layers of fine sediment or soil and leaves behind larger rock pieces. Deflation can form certain land features. It can produce desert pavement , which is a surface made of pebbles and small, broken rocks. In some caces, the wind can scoop out small, bowl-shaped areas in sediment on the ground. These areas are called deflation hollows

Surface creep/ Abrassion This is the process of wearing down or wearing away by friction. The process involves gradual reduction in the size of pebbles as one rubs against another or bounces against rock surfaces.Surface creep - in a wind erosion event, large particles ranging from 0.5 mm to 2 mm in diameter, are rolled across the soil surface. This causes them to collide with, and dislodge, other particles. Surface creep wind erosion results in these larger particles moving only a few metres.

Saltation occurs among middle-sized soil particles that range from 0.05 mm to 0.5 mm in diameter. Such particles are light enough to be lifted off the surface, but are too large to become suspended. These particles move through a series of low bounces over the surface, causing abrasion on the soil surface and attrition (the breaking of particles into smaller particles).

Suspension tiny particles less than 0.1 mm in diameter can be moved into the air by saltation, forming dust storms when taken further upwards by turbulence. These particles include very fine grains of sand, clay particles and organic matter. However, not all dust ejected from the surface is carried in the air indefinitely. Larger dust particles (0.05 to 0.1 mm) may be dropped within a couple of kilometres of the erosion site. Particles of the

order of 0.01 mm may travel hundreds of kilometres and 0.001 mm sized particles may travel thousands of kilometres. Through this process, Australian soil has been carried to New Zealand and beyond. Fine dust may remain in suspension in the air until it is washed out by rainfall.

Attrition This is the wearing away of rock particles as they rub against each other when they are transported by wind.

9. 3 Wind Erosional Landforms

Rock Pedestals These are tower like structures formed by the wearing away of softer layers by wind abrasion. They are commonly seen in the Tibest Mountains in the Sahara desert.

A rock pedestal

Figure 9.1: Rock Pedestals

Zeugens These are ridge like structures which develop by wind abrasion in dessert landscape comprising layers of hard rock underlain by a large layer of soft rocks. The resistant rock form zeugens while the weak rocks form furrows. Wind abrasion lowers the zeugens and widens the furrows.

Figure 9.2 Zeugen

Inselbergs: These are isolated pieces of round topped masses of rock left standing after the removal of the original surface by wind erosion. Some of them are remains of Plateau edges, which have been cut back by the removal of the weathered debris by sheet wash. Others may be a result of a combination of wind and water erosion. Are steep sided hills that rise above a surrounding relatively flat plain. They appear to form because the rock making up the inselberg is more resistant to erosion than the rocks that once made up the surrounding plain. Inselbergs are common in desert regions, although they can also occur in other areas where differential erosion takes place.

Figure 9.3: Inselberg

Deflation Hollows These are hollows formed by continued deflation in desert landscapes. Sometimes these hollows reach down to the water bearing rocks. Where a swamp or an oasis develops. For example, the Quatara depression South West of Alexandria in Egypt was formed that way. A depression can be initially formed by faulting and then deepened by deflation.

Source: https://www.google.com/search?q=deflation+hollow+diagram

Yardang These are large area of soft, poorly consolidated rock and bedrock surfaces that have been extensively grooved, fluted, and pitted by wind erosion. The rock is eroded into alternating ridges and furrows essentially parallel to the dominant wind direction. The relief may range from one to several metres, and

there may be unconnected hollows and other irregular shapes. Yardangs occur in various deserts of the world including the Turkistan and the Mojave deserts.

Figure 9.4: Yardang

Ventifacts

These are pebbles faceted by sand-blasting. They are shaped and thoroughly polished by wind abrasion to shapes resembling Brazil nuts. Rock fragments, mechanically weathered from mountains and upstanding rocks, are moved by wind and smoothed on the windward side. If wind direction changes another facet is developed. Such rocks have characteristic flat facet with sharp edges. Amongst the ventifacts those with three wind-faceted surfaces are called dreikanter. These wind-faceted pebbles form the desert pavement a smooth, mosaic-like region, closely covered by the numerous rock fragments and pebbles

9.4 Features Produced by Wind Deposition Depositional features are mainly formed by sand or desert dust. As winds blow, they transport sand and dust from one place to another. The main features of wind deposition are sand dunes. These vary in size and shape.

Berchans Dunes Berchans Dunes are crescent shaped and lie at right angles to the prevailing winds with the horns pointing in the direction to, which the wind blows. Usually such features form when there is an obstruction such as a big rock or vegetation in the path of the wind. The sand accumulates behind the obstacle to form a mound. As the mound grows larger, its two edges are elongated downwind thereby forming the crescent shape.

Source: http://3.bp.blogspot.com/

Figure 9.5 : Barchans and Seif Dunes The windward side of the dune is gently sloping while the leeward side is steep and slightly concave. Barchans occur in groups and they can be seen near the Futa Djalon plateau in Northern Nigeria and in the Namib Desert.

Transverse Dunes Large fields of dunes that resemble sand ripples on a large scale. They consist of ridges of sand with a steep face in the downwind side, and form in areas where there is abundant supply of sand and a constant wind direction

Source: faculty.uml.edu/.../Instructor%20pdfs/Wind

Figure 9.6: Transverse Dunes

Seifs Seif (Longitudinal Dunes) - is Arabic word meaning sword, adopted to describe a knife-shaped ridge of sand or longitudinal dune. Its axis lies parallel to the direction of wind and may extend for many kilometers. These are ridge shaped sand dunes with steep sides lying parallel to each other. Seifs have very sharp crests and are separated by flat areas. A seif usually develops from a small sand ridge, and as it forms, it slowly moves forward in the direction of the prevailing wind. Examples of seifs are observable in the Namib Desert between Walvis Bay and Luderitc.

Loess Loess is a windblown deposit of fine silt and dust. It is unstratified, permeable, homogenous, calcareous deposit, generally of yellow colour. Very fine particles are blown beyond the desert margins and are deposited to form loess The loess deposits are found away from the source regions and away from the deserts. Extensive deposits of loess are found in central Asia, Northern China, North European plains, North Africa, Argentina and Central U.S.A.

9.5 Types of Desert A combination of wind and water action in desert landscape produces sandy, stony, and rocky desert landscape types. Stony desert or Erg: consists of undulating plain of sand whose surface is blown into ripples and sand dunes. An example is the sand Sea of Egypt. Rocky desert or Reg: is characterised by boulders, angular pebbles and gravels produced mainly by weathering. Rock desert or Hamada: It is a desert landscape consisting of bare rocks from which all fine materials have been removed by deflation. Abrasion polishes and smoothens the rock surfaces.

Source: http://kids.britannica.com/comptons/art-72219/Most-of-the-worlds-hot-deserts-lie-between-20 Figure 9.7: Major Hot and Temperate Deserts of the World

Activity 1 ? What are the features produced by wind deposition? What forms the depositional features?

Summary Erosional and depositional processes are largely responsible for the continuous shaping of the earth’s surface. Wind action is among the main agents of erosion in the tropics. The erosive power of wind depends on several factors including pressure and gradient force that sets air in motion. The erosional process of wind determined by power of wind nature of materials found on eath surface. Wind transport and deposition are the main agents of denudation in deserts and together they produce features such as barchans and seifs. Wind transports materials mainly by saltation. Wind erosion is responsible for the formation of rock pedestals, zungens, inselbergs and deflation hollows. Its erosive activity is mainly that of abrasion. Wind erosion and deposition are active in arid and semi arid landscapes. .

Exercise 1. Visit a nearby wind prone areas and examine ways by which a wind erodes material. 2. The power of wind determines its erosive power. What factors account for the energy of wind? 3. Describe the formation of various features of wind erosion and deposition. 4. Draw map of Africa and show distribution of desert and semi desert

References 1. Arber, Nicola, Sue Lomas, Gerrett Nagle, Linda Thompson and Paul Thompson, (2000); Heinemann Educational Publishers; Oxford. 2. Bunnett, R. B (1990); Physical Geography in Diagrams for Africa (8th edition). Longman Group Ltd. Hong Kong. 3. Clark, Audrey (1990); Geography Dictionary. Geographical Publishers Ltd. 4. Lines, C; Laurie Bowlwell and Anne Fielding Smith (1996); A Level Geography. Letts Educational, London.

Lecture 10 Glacial Erosional and Depositional landforms

10.1 Glacial Types and Processes

Glacial Erosional process: Glacier- a thick mass of flowing/moving ice. glaciers originate on land from the compaction and recrystallization of snow, thus are generated in areas favored by a climate in which seasonal snow accumulation is greater than seasonal melting. Glacial erosion consists of two processes:  Plucking or the tearing away of blocks of rock which have become frozen into the base and sides of a glacier, and  Abrasion or the wearing away of rocks beneath a glacier by the scouring action of the rocks embedded in the glacier.

Types of Glacier

Ice sheets Cover extensive areas of continental landmasses Long periods of extremely low temperatures Antarctica and Greenland almost completely covered by ice sheets.

Alpine glaciers Long, linear glaciers that occupy high altitude mountain valleys, Flow down valley, and increase in size as they accumulate and absorb smaller tributary glaciers from the mountainous terrain. Found throughout the world: Rockies, Andes, and Himalayas. High latitude, polar or arctic mountains, such as those in Alaska.

10.2 Glacial Erosional Landforms

Tarn Lake Tarn lake is small mountain lake especially one that collects in a cirque basin behind risers of rock material or in an ice gouged depression.

Paternoster Lake Connected string of small, circular lakes that occur in relict glacial valleys. Post glacial erosional features filled with rainwater or glacial meltwater. Result of either differential erosion of the bedrock, or the creation of small dams formed by glacial till deposits or end moraines. Precipitation or springs provide a renewable source of freshwater.

Hanging Valley Formed when smaller tributaries are unable to cut as deeply as bigger ones and remain ‘hanging’ at higher levels than the main valley as discordant tributaries. A valley carved out by a small tributary glacier that joins with a valley carved out by a much larger glacier Hanging valley is an abrupt, cliff-like features , remnants of a confluence between tributary glaciers and valley glaciers. Scour by the valley glacier erodes the original gradient of the tributary confluence. Hanging valleys are revealed when the glacier melts

Arete Steep-sided, sharp-tipped summit with the glacial activity cutting into it from two. They are saw-tooth, serrated ridges in glacial mountaints.Separate adjacent cirques and/or adjacent valleys.

Horn Ridge that acquires a ‘horn’ shape when the glacial activity cuts it from more than two sides. They are a single pyramidal peak formed when the summit is eroded by cirque basins on all sides.

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Source: http://www.geo.hunter.cuny.edu/~fbuon/GEOL_231/Lectures/Glacial%20Landforms.pdf

Figure 10.1: Glacial Erosional Landforms

Fjord Fjord created when glacially valleys intersect the ocean and are partially flooded. They are steep-sided narrow entrance-like feature at the coast where the stream meets the coast. Fjords are common in Norway, Greenland and New Zealand

Source:http://www.geo.hunter.cuny.edu/~fbuon/GEOL_231/Lectures/Glacial%20Landforms.pdf Figure 10.2 Fjord

10.3 Glacial Depositional Landforms During periods of glacial retreat, when ablation outpaces snow accumulation, glacial drift is left behind, resulting in depositional landforms. Glacial deposition occurs when debris is released from a glacier during transport. The debris, called glacial drift, can range in size from sediment particles to large boulders and can be deposited during glacial advance or retreat and during periods of stagnation. Debris deposited directly by glacial ice is called glacial till, which ranges in size from particles of clay to large boulders. Moraines are a distinctive landform made up of sediment deposited by a glacier. Several types of moraines exist in glaciated and previously glaciated landscapes: terminal moraines, recessional moraines, lateral moraines, medial moraines, ground moraines, and supraglacial moraines. At a glacier’s maximum extent, or terminus, are terminal oraines, which vary in size depending on how long a glacier stays in one place.

Lateral Moraine Long linear ridges of glacial till deposited along the side of the glacier parallel to its direction of movement. Lateral moraines form perpendicular to the terminus as debris is scraped away from the surrounding path and deposited on the margins. Glaciers typically have two lateral moraines parallel to one another, which are similar in size.

Medial Moraine long linear ridges that form along the contact where tributary glaciers with lateral moraines merge to join larger valley glaciers. The till deposits become incorporated as dark ridges of sediment oriented down valley and aligned parallel through the middle of the glacier.When two lateral moraines are pushed together by glaciers, the debris combines to form one line between the two ice streams. This process creates a debris ridge between the two glaciers, called Medial moraine.

Terminal moraines Linear, concave, arc-shaped depositional ridges that form at the terminus of a glacier. The till deposits mark the outward expanse or limit of glacial movement.

End / Recessional moraines They areconcave arc-shaped ridges deposited by the melting glacier. Smaller than terminal moraines, and they mark the gradual retreat of the glacial ice after it has already deposited its terminal moraine. Recessional moraines formed glacier pauses during recession, these landforms are the product of a quickly retreating glacier that does not pause long enough to deposit organized ridges of material.

Source: http://www.geo.hunter.cuny.edu/~fbuon/GEOL_231/Lectures/Glacial%20Landforms.pdf

Figure 10.2: Types of Moraines

Kettles Small depressions in the landscape, often filled with water post glaciations. Large blocks of ice are left by a retreating glacier .Outwash sediments deposited around the blocks, possible burial. Ice block melts, only a void or kettle remains. Subsidence and melting can deepen the kettle.Kettles lakes are sourced by rainfall or snowmelt.

Kames, Eskers Kames and Eskers are melt water deposits. Kames tend to be stratified and associated with surface deposits. Eskers form along melt water channels that are emerging from tunnels beneath the glacier. They are depositional ridges of sands and gravel that mark the “course” of the melting glacier or course of the melt water tunnel

Erratics Large, isolated boulders deposited by retreating, melting glaciers. Erratics, are generally the largest rocks left behind by the retreating glaciers. Generally smooth from glacial abrasion and appear “misplaced” in the landscape.

Drumlins Drumlins are long, linear hills of glacial till deposited by ice sheets. Similar to medial and lateral moraines, smaller, irregular shaped . Drumlin fields are areas with numerous drumlins.

Outwash Plains Extensive stratified deposits of glacial till below a glacier. Choked with glacial till and are fed by meltwater flowing from the base of the glacier often creating a braided stream environment.Sorting does occur finer materials transported downstream.

Source:http://www.geo.hunter.cuny.edu/~fbuon/GEOL_231/Lectures/Glacial%20Landforms.pdf Figure 10.3: Glacial Deositional landforms

Summary Erosional and depositional processes are largely responsible for the continuous shaping of the earth’s surface. Glacial movement is among the main agents of erosion in the temperate regions. Glacial Formation and movement of glacial depends on change of climatic condition whereas extreme decrease in temperature lead to formation of ice sheet while increase in temperature cause its movement. Glacial movement lead to formation of erosinal landforms including: Tarn lake, Hanging Valley, Trough, Peternoster lake, Cirque, Arete, Horn. Glacial Landforms are: Moraines, Eskers, Outwarsh plain, Kame and Kettle. .

Exercise 1. What is the cause of glacial movement? 2. With examples describe glacial erosinal landforms. 3. Explain processes of glacial erosion. 4. With specific examples diffrentiate between Ice sheet and Alpine glacier. 5. Examine glacial depositional landforms.

Lecture 11 The Study of Soil

11.1 Introduction Soil can be defined as the loose surface of the earth. To the common farmer it is the medium in which crops grow, although, with advanced technology it is now possible to grow crops in liquid mediums other than soil. Soil may also be defined as a mixture of mineral and organic matter, water and air. Broadly, soil can be defined in its evolutionary nature as a natural body of the earths’ surface having properties due to the integrated effect of climate, and living matter, acting upon parent material as conditioned by relief over periods of time. Proportions of the components of soil vary from time to time and from one place to the other. Soils form over periods of time at different rates and eventually develop features of maturity. For this reason, we have young and old soils. The nature of the soil is strongly influenced over time by climate, human beings, organisms and vegetation. Soil is very important as a natural resource. It is a medium for plant growth, land for agricultural use or food production. Soil is also a boundary between the atmosphere and the lithosphere. The soil collects and purifies water, and disposes of wastes. However, soil itself can be a pollutant as dust in the air and as sediments in waters. In this lecture, you will learn about factors which influence soil formation. You will also study the characteristics of soil, and how it can be degraded. Finally, you will gain knowledge of various methods of soil conservation. Soil is a function of the parent material, climate, organic matter, relief and time. The nature of parent material has a marked effect on young soils. However, its influence becomes less as the soil becomes older. Climate is of major importance in soil formation as it determines the type and rate of rock weathering. Organic life, rainfall, temperature and their variations affect soil. Organisms such as bacteria and earthworms have a marked effect on soil formation of organic material. Vegetation despite of being influenced by climate it supplies organic material and influences microclimates too. Therefore, if vegetation is altered or interrupted, the microclimate changes simultaneously.

Learning Objectives At the end of this lecture, you will be able to:

 Define and describe the main constituents of soil;

 Describe the properties of soil colour, texture and structure;  Discuss the factors for soil formation;

 Identify and explain soil horizons with focus on level of consolidation;

 Explain factors which influence soil fertility;

 Describe the various methods of soil conservation.

11.2 Soil Profile The soils on the earth’s surface are always undergoing continual change. This phenomenon is clearly understood by observing a vertical section of a series of layers or horizons of the soil surface. Growth of plants results in the accumulation of some organic residues. These plus animal remains form the organic part of the soil.

Figure 11.1: A Soil Profile

When the surface layer of the soil attains a thickness and a darkened colour due to accumulation of organic matter an ‘A’ horizon is formed. Below it is the B-horizon where colloidal particles accumulate through percolation. Such colloids include clay, organic matter and oxides of iron and aluminium. Below the B-horizon is found the C-horizon composed of the parent un-weathered rock. The three horizons form what we call a soil profile. The horizons are characterized by differences in colour, composition and texture. While the upper part of the soil profile is rich in organic matter, the lower soil horizons, contains more stones due to proximity to the bedrock.

11.3 Constitutes of Soil

Mineral Soil About 98% of the earths crust is composed of 8 chemical elements. Among them oxygen and silicon comprise 75% of it while others occur in small quantities (Young 1989). We should bear in mind that these elements and their compounds are not evenly distributed. Weathering of rocks results in the destruction of existing minerals and synthesis of new minerals. In this way, clay minerals are formed and nutrients are made available for plants. Even life in the seas awaits nutrients released by weathering on the land and carried to sea by rivers. Consequently, all life on earth depends largely on the minerals and weathering processes. As soil ages it looses most of its original minerals. In the early stages of weathering soils are dominated by gypsum and are considered as young soils. These are common in semi arid regions where chemical weathering is restricted by limited water. Soils that are in the intermediate stage often contain quartz in the fine silt and clay fractions. These are common in temperate regions and develop under grass or trees. They include the major soils of the wheat and corn belts of the world.

Activity 11.1 ? Which are the major wheat belts of the Worlds?

Soils in advanced stage of weathering are dominated by kaolinite and limonite. They have lost most of all the original minerals of the parent material weathering. These soils are characterised by extreme infertility. Most of the nutrients circulate through the vegetation and they are mainly found in the humid tropics.

Soil Water Soil water is held as thin water films around soil particles and micro pores. It can be acidic, alkaline or neutral. Soil water content varies from day to day with weather changes. It also changes from place to place and from one soil type to another depending on their position in the soil profile and water availability.

Soil water as a source of life provides plants with moisture and acts as a medium of transport for nutrients. Soils deficient in soil water are agriculturally poor since crops cannot obtain sufficient moisture and consequently die out. This is paramount particularly, in dry sub humid and semi arid environments, where availability of soil water frequently limits plant growth (Young, 1989:232). Nonetheless, too much water in soils is unsuitable for plant growth due to water logging. Water logged soils are poor because they have only few pores that can be occupied by air. Many micro-organisms that are essential for nutrient cycling live on oxygen and therefore, cannot survive in waterlogged soils.

Soil Air Soil air is usually saturated with water vapour and rich in carbon dioxide. The amount of air in the soil depends on the availability of pores, which in turn are determined by the texture of the soil. Air enables micro-organisms to act.

Soil Organic Matter When plants die and left out to rot bacteria act on them to decay. The organic material present in the soil consists of two parts; plant remains and fully decomposed organic matter; the humus (Ibid: 108). The nutrients of the decomposed dead plants are returned onto the ground. Organic matter is essential for enriching the soil. However, high concentrations of organic matter do not always correspond with highly fertile soils.

Concentration of organic matter in the soil varies considerably. Leafy plants supply large amounts of organic matter whereas root crops supply very little. Environmental conditions determine the nature of population of microbes present at any given time in the soil. Generally, the fertile, fine textured soils high in organic matter contain many more microbes than the coarse-textured soils which are low in organic matter. The actual volume of organic matter depends largely on the balance between the rate of gain and the rate of loss of matter. Drained, aerated soils allow a more rapid breakdown of dead vegetation and a more speedy return of nutrients to the soil than poorly drained soils. Soil organic matter is important in maintaining soil fertility because it maintains soil physical conditions, such as water-holding capacity, and provides a balanced supply of nutrients. The soil is in addition, protected against leaching until released by mineralization.

11.4 Factors for Soil Formation Soil can be defined as the solid material on the Earth’s surface that results from the interaction of weat hering and biological activity on the parent material or underlying hard rock. Soils develop as a result of the interplay of five factors; Parent material, climate, organisms, relief and time.

Parent Materials This is the material from which the soil has developed and can vary from solid rock to deposits like alluvium and boulder clay. It has been defined as ‘the initial state of the soil system’ The parent material can influence the soil in a number of ways: colour, texture structure, mineral composition, permeability/drainage

Climate This is probably the most important factor for soil formation. Climate governs the rate and type of soil formation and is also the main determinant of vegetation distribution. Soil climate has two major components; moisture (precipitation) and temperature, influencing evaporation. When precipitation exceeds evaporation, leaching of the soil will occur. Temperature determines the rate of reactions; chemical and biological decay and so has an influence on weathering and humification.

Living Organisms Organisms influencing soil development range form microscopic bacter ia to large animals including man. Micro or ganisms such as bacteria and fungi assist in the decomposition of plant litter. This litter is mixed into the soil by macro organisms (soil animals) such as worms and beetles. Soil horizons are less distinct when there is much soil organism activity. Higher plants influence the soil in many ways. The nature of the soil humus is determined by the vegetation cover and resultant litter inputs. Roots contribute dead roots to the soil, bind soil particles together and can redistribute and compress soil.

Relief (Landforms and Topography) Relief influences soil formation in several ways:  It influences soil profile thickness i.e. as angle of slope increases so does the erosion hazard,  It has an effect on climate which is also a soil forming factor gradient affects run-off, percolation and mass movement  It influences aspect which creates microclimatic conditions

Time Soils develop very slowly. In Britain it takes about 400 years for 10mm of soil to develop. Young soils retain many of the characteristics of the parent material. Over time they acquire other features resulting from the addition of organic matter and the activity of organisms

11.5 Physical Characteristics of Soil

Soil Texture Soil texture refers to the size of the particles that make up the soil. The three broad categories of soil are sands, loams and clays. Sand soils are light, well aerated and well drained and composed of fairly coarse material or grains. In contrast, clay soils are sticky and poorly aerated. They mainly consist of fine particles and are usually water logged. Loamy soils are a combination of sandy and clay soils. This type of soil makes up excellent agricultural soils, because it is both well drained and fertile. Intermediate soils include sandy loams and clay loams (Lenon and Cleves, 1983:37). Soil texture may be determined in one of two ways. The percentages of sand, silt, and clay may be tested in the lab. Once tested, the textural class of the soil can be determined by referring to the textural triangle (a device used to differentiate the several classes of soil). Soils with different amounts of sand, silt, and clay are given different names. For instance, a soil containing 40 percent sand, 20 percent clay, and 40 percent silt is called loam soil. The relative amounts of sand, silt, and clay may also be determined in the field using the ribbon method. Five textural classes may be etermined using this method.

The texture of a soil is important because it determines soil characteristics that affect plant growth:

Water-holding capacity is the ability of a soil to retain water. Most plants require a steady supply of water, and it is obtained from the soil. While plants need water, they also need air in the root zone. The ease with which air and water may pass through the soil is called permeability.

Soil workability is the ease with which soil may be tilled and the timing of the work. Soils with a larger percentage of sand are easier to work than soils with a larger percentage of clay. Clay soil tends to be tighter, making it more difficult to break up or cultivate, whereas sandy soil is looser. It also takes longer for a clay soil to dry after a rain than a sandy soil. Soil Structure Soil structure is the arrangement of the soil particles into aggregates of various sizes and shapes. Aggregates that occur naturally in the soil are referred to as peds , while clumps of soil caused by tillage are called Clods Aggregates are created through a number of ways, including freezing and thawing, wetting and drying, fungal activity, tillage, and by plant roots that surround the soil and separate the clumps. Weak aggregates are cemented to make them distinct and strong. Clay, iron oxides, and organic matter often act as cements. When soil microorganisms break down plant residues, gums are produced that glue peds together.

Types of Soil Structure: There are eight primary types of soil structure, including blocky, columnar, crumb, granular, massive, platy, prismatic, and single grain.

 Blocky—The units are block-like. They consist of six or more flat or slightly rounded surfaces.

 Columnar—The units are similar to prisms and are bounded by flat or slightly rounded vertical faces. The tops of columns are very distinct and normally rounded.

 Crumb—The aggregates are small, porous, and weakly held together.

 Granular—The units are approximately spherical or polyhedral. The aggregates are small, non- porous, and held together strongly.

 Massive—There is no apparent structure. Soil particles cling together in large uniform masses.

 Platy—The units are flat and plate-like. They are generally oriented horizontally. Plates overlap, usually causing slow permeability.

 Prismatic—The individual units are bounded by flat to rounded vertical faces. Units are distinctly longer vertically. The tops of the prisms are somewhat indistinct and normally flat.

 Single grain—There is no apparent structure. Soil particles exist as individuals and do not form aggregates.

Source: http://www.carlisle.k12.ky.us/userfiles/1044/Classes/6685/040070.pdf Figure 11.2: Types of Soil Structure

Soil Temperature Soil temperature is important for the germination of seeds and plants. Below certain critical temperatures, germination and growth will not take place. Corn seeds for example begin to germinate once the soil temperature rises above 7-10°Celsius and reaches optimum growth around 35°C.

Soils are heated by insolation. Different soils heat up and conduct warmth more rapidly than others. Water content is the most important single characteristic which controls the rate at which a soil heats up. Because of this, removal of excess water from a soil will facilitate changes in soil temperature. The use of mulches and various shedding devices also controls soil temperature. Mulches limit the amount of solar radiation absorbed by the soil and loss of heat energy from the soil by radiation. In addition, infiltration of water and loss of water by evaporation can be altered. In regions where summers are cool reduced soil temperature, cause reduction in crop yields. As such, black plastic mulching is used to absorb solar radiation and reduce heat loss from the soil by radiation and at the same time reduce evaporation of water from the surface. The net effect of this practice is to increase soil temperature and hence increase crop yields, although it is costly.

Soil Colour Generally soil colour is determined by the amount of organic matter and the state of the iron. Soil colour is also related to soil drainage, with free draining, well AERATED soils (with pore space dominated by oxygen) having rich brown colours. In contrast, poorly draining soils , often referred to as gleys, develop under ANAEROBIC conditions (the pore space dominated by water) and have grey or blue-grey colours.

Soils with periodic waterloging are imperfectly drained and are often highly mottled with blotches of contrasting colour. MOTTLES are often rusty in colour and are due to iron concentration. Such colours are the result of oxidation-reduction; iron is the main substance affected by these processes. If the iron is released in an anaerobic environment, then it stays in the reduced state giving it the grey blue colour of waterlogged soils.

Soil pH The pH value of a soil is a measure of the concentration of hydrogen ions in the soil water. Usually soils of humid regions are acidic and soils of arid regions are alkaline. In acid soils, the soil solution contains more hydrogen ions (H+) than hydroxyl ions (OH-) and vice versa in alkaline soils. In most soils pH values lie between 5 and 9. A pH value of less than 7 is acidic whereas that greater than 7 is alkaline. A pH of 7 is neutral. The significance of pH value of the soil does not directly affect crop growth except in cases of extreme acidity or alkalinity. The major effects of soil pH are biological. Some organisms have small tolerance to variations in pH others have a wide range. The pH affects the availability of nutrients for plant growth. In alkaline soils some nutrients essential for crop health such as iron and magnesium become scarce at pH values of 7.5 and above. On the other side, in acid soils below pH 5.0, the over abundance of nutrients such as aluminium and iron, mobilised by the acid, may prove toxins to crops (Lenon et al., 1983).

11.6 Soil Fertility Soil fertility is the capacity of soil to provide an optimum growth of plants, on a sustained basis, under given conditions of climate and other relevant properties of land (Lines et al., 1996:110). Usually fertile soils maintain high yields and infertile soils lead to low yields. Low crop yields can be due to low soil fertility, caused by natural soil conditions, or decline in soil fertility by past unsustainable agricultural practices. Fertile soils are generally associated with:  deep and well-aerated rooting zone  availability of organic matter  suitable conditions for organic decomposition and the incorporation of organic matter in the soil  appropriate soil chemicals  Optimum levels of soil acidity and alkalinity (pH).

11.7 Soil Erosion, Conservation and Sustainability The main types of erosion are:

 Sheet erosion, which is more or less uniform erosion of the whole surface of a field. The roots of plants, tree roots and poles are increasingly exposed.

 Rill erosion is the development of small natural depressions caused by surface run-off. While normal cultivation often hides the damage, much fertile soil is still lost.

 The third type of soil erosion is gully erosion. It causes deep fissures in cultivable land. If left unchecked, gullies eat their way gradually back into the hill.

 Finally we have stream bank erosion that converts deep, fast flowing streams into wide and sluggish meandering watercourses with extensive mud banks. It can cause serious loss of cultivable land.

Soil erosion occurs when farming practices in use fail to take account of the ease with which soils can be washed or blown away. Examples of such practices are; overstocking and overgrazing, shifting cultivation over short fallow periods, deep ploughing for 2-3 times in a year, crop rotation and planting wrong crops in the wrong place. The consequences of erosion to mankind are severe and many. Foremost, land is left bare and unproductive, silting reduce fish catch in shallow rivers, and reservoir lifetime of hydroelectric plant. Gully erosion on the other hand, eats into cropland, while mud banks reduce navigability of a river, crops are grown on large unprotected fields, badly managed pasture suffers from wind erosion and frequently flooded villages become deserted. When land cannot support people, the poor people migrate to cities giving rise to slums.

Soil Conservation Soil conservation has more often been interpreted to stand for soil erosion control. However it has a wider meaning. Soil conservation, includes both control of erosion and maintenance of fertility. This requires maintenance of organic matter, soil physical properties, nutrients and avoidance of toxicities in the soil and its surroundings. A broader field is that of soil and water conservation, since reduction of water through run off is an integral part of soil conservation (Young, 1989:10). As one goes around in Tanzania some sections of the country show signs of soil mismanagement. Some farms have been depleted in organic matter content as revealed by a lighter colour and lower productivity compared to the surrounding soil. To improve depleted soils, use of improved methods of managing the soils such as application of manure and sustainable land use including crop rotation is important. This is very essential especially in African countries where food insecurity is predominant.

Prevention and Repair (Control of Soil Erosion) Human intervention is always necessary in order to enhance soil erosion control. Techniques to accomplish it are biological and physical. Biological ones involve a fundamental assessment of the suitability of land and the techniques used to farm it. Physical techniques include many forms of terracing, methods of gully control, dams for controlling flood and siltation, and over all water shed management.

Biological Methods  Assess growing conditions and choose the right crop  Use proper crop management such as strip cropping, crop rotation  Apply plantation crop combinations for example agricultural crops with multipurpose trees  Alley cropping and barrier hedges  Trees on erosional control structures  Windbreaks and shelters are a proven potential to prevent wind erosion  Sylvopastral practices i.e. inclusion of trees and shrubs as part of overall pasture improvement  Reclamation forestry leading to multiple use Physical Methods  Storm water or diversion drains  Ridges and bunds  Grass and bunds and Grass water ways  Bench terraces  Platform, orchard terraces.

The importance of soil conservation is summarized by FAO; (2000:2) in the following words: “A nation without soil is bankrupt but a nation with appropriate land use patterns and farming techniques, where erosion has been controlled and contained, is poised on the springboard of development.’’ All countries should strive to prevent its soils from being eroded.

? Activity 11.3 Highlight the physical characteristics of land soil.

Summary Soil is a function of the parent material, climate, organic matter, relief and time. Proportions of the components of soil vary from time to time and from place to place. The proportions are a result of integrated effects of climate and living matter acting upon the parent rock. The volumes of soil water and soil air are inversely related. As water enters into the soil, air is freed. Soil water is important for agriculture, as it is the medium through which nutrients are transported. Nonetheless too much or too little of it is not suitable for agriculture. Time affects the quality of a soil. As a soil grows old it looses most of its original minerals. In order to maintain its fertility, new minerals should be added to the soil according to crop requirements. These minerals are applied in form of chemical fertilizers, farmyard manure or sound methods of soil conservation. The degree of soil acidity and alkalinity is also important to plants since some nutrients become less available to plants at the extremes of pH values. In tropical areas leaching of silica is very heavy. Leached soils tend to be infertile due to inadequacy of humus. To sustain crop production, sustainable soil management is indispensable.

Exercise 1. Define and describe the main constituents of soil. 2. Go to the field and observe properties of soil colour, texture and structure. 3. Critically, discuss factors for soil formation. 4. Explain the importance of various constituents of soil. 5. Discuss factors which influence soil fertility. 6. Give an analysis of the various methods of soil conservation.

References 1. Lennon, J. Barnaby and Paul G: Cleves, (1983); Techniques and Field Work in Geography. UN Winhyman Ltd. London. 2. Lines, C; Laurie Bolwell and Anne Fielding Smith (1996); A Level Geography. Letts Educational, London. 3. Young, A (1989); Agro Forestry for Soil Conservation. CAB International, Wallingford.

PART 4 Human Geography

Lecture 12 Constituents of Human Geography

12.1 Introduction In Lecture two, we defined geography as the description of the earth. This definition obscures human activities particularly by considering the natural environment alone. Apart from physical geography, which mainly deals with the physical phenomena, geography also deals with human phenomena on the surface of the earth. Fellman et al., (1999:4) underscore geography as the relationships between human activities and the natural environment which they occupy and change. Geography also links physical phenomena and human activities in one location of the earth with other areas. Apart from natural processes such as volcanic activity and earthquakes, much of what is observed on the surface of the earth is a product of human activities. In their struggle for development humans use natural resources to improve their well-being. In this process, depending on their level of technology they may improve or degrade the resources. Therefore, humans are capable of shaping their life and the appearance of the earth. This section examines those aspects of geography which are created by human activities.

Learning Objectives At the end of this lecture, you will be able to:

 Describe the main constituents of human geography;

 Explain the relationship between the level of technology of a society and its level of development;  Discuss the role of innovation and diffusion in changing the way people live and behave;

 Explain the importance of harmonising human activities with environmental characteristics for sustained development.

 12.2 Main Concerns of Human Geography Human geography puts emphasis on people. It examines where people live, how they interact over space and the kinds of landscapes of human use they erect on the natural landscapes they occupy. It is also concerned with agriculture, politics, cartography, transportation and the economy. In this way, it integrates with other social sciences and draws on other social sciences as well.

Figure 12.1: The Branches of Human Geography and Related Fields

The main significance of human geography is that it:

 Helps us to understand the world we occupy and to appreciate the circumstances that affect people and countries other than our selves.  Clarifies the contrasts in societies, cultures and human landscapes in various regions of the earth.

 Provides models and explanations of how things are interrelated in space thereby providing us a clearer understanding of the economic, social and political systems within which we live and procure livelihood.  Enables us to be better informed citizens and better prepared to contribute solutions to societal problems.

 Makes us more aware of the realities and prospects of our society in a changing world.

 Opens the way to rewarding and diversified careers as professional geographers. The above benefits are possible if people interact. People in spatial interaction are the starting point of human geographic study. The way people interrelate depends on their culture. This can be defined as the specialised behavioural patterns, understanding, adaptations and social systems that summarise a group of peoples learned way of life (Fellman, 1999:34). Culture is responsible for the creation of its own cultural landscape and hence the root of regional differences. Farming patterns, language, political organisation and ways of earning a living are part of the spatial diversity of human geography. The persistence of differences from place to place makes human geography to address the question. Why are cultures varied? Fellman and others find the answer to this question in the way separate human groups developed techniques to solve regionally varied problems of securing food, clothing, and shelter. In the process distinct behaviours and attitudes were developed. Due to this, a set of culture regions showing related cultural complexities and landscapes may be grouped to form a culture realm or territory.

12.3 People and Environment People interact among themselves and with the environment. The environment in which they interact partly contributes to differences among people. In less developed societies, the acquisition of food, shelter and clothing depends on the use of natural resources available. In more developed societies environmental determinism has been overcome. The interrelationship of people to their environment, their perceptions and its utilization and their impact on it constitute a cultural ecology. A cultural ecology is the study of the relationship between a culture group and the natural environment it occupies.

Take Note Environmental factors alone cannot account for the cultural variations that occur around the world. The environment only places certain limitations on the human use of territory depending on technologies, national aspirations and existing linkages with the larger world.

Since environmental determinism does not fully explain the development of culture today a viewpoint of possibilism has attracted the attention of many scholars. This view holds that the dynamic forces of cultural development are the needs, traditions and the level of technology of a culture. These affect how that culture assesses the possibilities of an area and shape choices the culture makes regarding them (Fellmann et al., 1999:37). Close examination reveals that each society uses natural resources in accordance with its circumstances. Changes in a group’s technical abilities or objectives bring about changes in its perceptions of the usefulness of the land resources. The perception of environmental opportunities seems to increase directly with economic growth and cultural development. Notwithstanding the foregoing argument, the distribution of human population suggests some environmental limitations on the use of land in certain locations. For instance, the majority of world’s population is concentrated on less than half of the earth’s land surface, mainly in the northern hemisphere (ibid). Densely populated areas are those with relatively mild climates that offer fresh water, fertile soil and abundant mineral resources. This reflects partly, the different potentials of the land under earlier technologies to support population. Sparsely populated areas include Polar Regions, very high rugged mountains, deserts and some hot, humid lowlands. If people recognise or find resources for feeding, clothing and housing, they are normally attracted to occupy the territory. Recent exploration of Tanzanite in Mererani-Arusha, and opening up of goldfields in Kahama and Bulyanhulu in Tanzania has attracted many people into those areas today than ever before.

12.4 Major Environmental Problems in Tanzania

Land Degradation Human impacts on deforestation, soil erosion, overgrazing, and degradation of water resources and loss of biodiversity have all resulted into land degradation. Poor agricultural practices such as shifting cultivation, lack of crop rotation practices, lack of agricultural technology and land husbandry techniques exacerbate the problem. Liviga (1999), contends that the effects of overstocking, which are localized, give rise to serious degradation in places such as Shinyanga and Mbulu where livestock units have exceeded the carrying capacity. This situation is seen as a good indicator of each of capacity for the decentralized institutions at

the local level to enforce laws and instruments which are meant to ensure sound environmental management.

Pollution Management and Urbanization Pollution is a major problem in urban areas of Tanzania. Improper treatment and disposal of solid and liquid wastes are the major contributors to urban area pollution. The combined results of these problems are that both air and water have been contaminated with pollutants, which are detrimental to human health. In Dar es Salaam, for example, less than 5% of the population is connected to a sewage system. Where a sewage system exists, raw sewage is discharged directly into the Indian Ocean without prior treatment. Thus a workable water supply and sewage treatment is needed for the urban areas.

Agricultural and Range Land Resources Management

Agriculture and rangeland resources are the backbone of Tanzania's economy. It is estimated that about 55% of the land could be used for agriculture and over 51% for pastoral lands. However, only about six percent of the agricultural land is cultivated with the practice of shifting cultivation which causes deforestation and land degradation on the pastoral land. Lake Manyara basin, Geita Gold Mines, Usangu Wetlands and Ngorongoro. The main cause for these problems is due to lack of proper instruments of enforcement of the existing legislation, policy and by-laws by local authorities. Again where the mandates of central and local institutions on environmental management are weak, conflicting and confusing; enforcement of laws and implementation plans becomes difficult if not impossible.

Management of Forest Resources Forest resources provide both direct products and by -products. The forest reserves are also linked with agriculture, beekeeping, energy, water uses and biodiversity. It is estimated that fuel wood and agricultural residues account for 92% of the total energy consumption in the country. As a result, the mismanagement of fuel resources significantly contributes to deforestation and environmental degradation. Hence, highlighting the central and local governmental institutions inability o solve the problem.

Management of Wildlife Resources Tanzania is one of the few countries with vast number of wildlife resources. For example, Tanzania's "protected areas" cover about 25% of the total land (Nshala: 1999). The protected land is comprised of national parks, game reserves, game controlled areas and the Ngorongoro Conservation Area.Unfortunately, communities living around these protected areas do not benefit from the wildlife industry. They live in uncertain conditions visited by persistent attacks by the wild animals and destruction of their crops. This has resulted in an antagonistic relationship between the wildlife authorities and the local populace. Local communities resort to activities like poaching to gain access to and benefits from the wildlife and other natural resources. This is a direct result of the central government excluding local communities from wildlife management.

Management of Mineral Resources With respect to mineral resources, a Joint Appraisal Mission Report (1999) noted conflicting authorities on matters regarding mineral prospecting and mining. Additionally, local authorities have a minimal role in the mineral resource management process, despite the fact that mineral depletion is occurring in the local communities area. Any attempts made by local authorities to make by-laws imposing mineral levy such kind of by-laws have been met with an "outcry of double taxation" by mineral concessionaires against both the central government and the local authorities. The Tanzanian economy depends upon

mineral resources for a major source of its revenues. However, mineral exploitation is often done without regard to environmental and social impacts. Thus the Mining Act of 1998 addressed this problem and required mining companies to conduct environmental impact assessments. Mining activities a major cause of environmental degradation by deforestation, destruction of habitat, loss of biodiversity and general damage to the land.

Urbanization Dubey (1990:17) defines urbanization as a community consisting of a large concentration of population in a relatively limited geographical area. This is activated by the production of manufactured goods and distribution of various types of goods and services involving high degree of specialization and complicated technology Pollution Management and Urbanization Pollution is a major problem in urban areas of Tanzania. Improper treatment and disposal of solid and liquid wastes are the major contributors to urban area pollution. The combined results of these problems are that both air and water have been contaminated with pollutants, which are detrimental to human health. In Dar es Salaam, for example, less than 5% of the population is connected to a sewage system. Where a sewage system exists, raw sewage is discharged directly into the Indian Ocean without prior treatment. Thus a workable water supply and sewage treatment is needed for the urban areas. Population Increase Population refers to number of people residing in a certain geographical area over a specific period of time. In the recent years, human population increase has made it necessary to increase the rate of production of materials such as manufactured goods to sustain human life. This has increase the rate of resource utilization. Both renewable and non renewable resources are being exploited to the maximum. For example, forests and wildlife are being used without limit in order to meet human needs for food production, manufacturing and processing of finished goods and packaging. All these increased rates of use have raised the rates of waste generation and regrettably the present technologies can not cope with the increased rates of disposal. Population and Environment The Tanzanian population increased from about 7 million people in 1948 to 34 million in 2002 (Madulu, 2004). The present annual growth rate of the population is 2,8%, and the population is expected to further increase to about 44 million people in 2015 (World Bank,2003). Although linkages are complex, the population increase increases pressure on the natural resources in Tanzania. The population issues are not explicitly assessed in MKUKUTA.

The rural-urban migration in Tanzania is high. The urban population increased from 15 % of the total population in 1980 to 33% in 2001(World Bank, 2003) and it has been estimated that by 2025 more than half of the population in Tanzania will live in urban areas. Today the urban planning is inadequate. Consequently, the urban expansion lacks consideration of environmental issues (water quality and supply, sanitation and solid waste management) or urban-rural development effects. The poor are the most vulnerable since they are obliged to reside in the most marginal areas. The urban expansion put immense pressure on surrounding forests to support the need for charcoal. MKUKUTA recognizes the increasing problems related to urban poverty and include several operational targets related to integrated urban planning, water, sanitation, waste management15. Sustainable energy development is also mentioned, albeit in rather vaguely defined cluster strategies. The urban migration has its root cause in the inability of agriculture to sustain the livelihoods of a growing population. The MKUKUTA recognizes the growing rural-urban divide and the high levels of un- and underemployment as critical challenges. The strategy notes that “the opportunities for expanding and diversifying rural incomes, particularly for the vulnerable groups, from the sustainable use of natural resources is under-realized…” and that “…on and off-farm earnings need to be supported both by a strong agricultural

12.5 Human Impacts on the Environment The reactions of people to the physical environment have an impact on that environment. By using it, we modify it, for instance by starting farms, building roads and cities, thereby creating a cultural landscape, which is the modified earth’s surface by human actions. While human actions can be constructive, they can as well be destructive. For example, people have hunted elephants and reduced them to small numbers. Other animal and plant species have become extinct due to overexploitation. Bad methods of farming have rendered formerly productive regions sterile, for example parts of Ismani, Kondoa, and Shinyanga, in Tanzania. This brings us to the focus on resource management. Sustainable development is development which is continuous. It requires a long-term accommodation between human actions and environmental circumstances. When that accommodation is upset either through poor management of resources by an exploiting culture or through natural environmental alteration unrelated to human actions, such as the catastrophic drought the society fails to use it and development of the region become unsustainable. Former patterns are disrupted. Spontaneous changes in the environment may also bring down the works of organised society. The incidences pointed out above, show that human geography is not static. It is always undergoing changes. Some changes are minor while others are major and persistent. For instance, the increasing employment of women in waged activities has taken place slowly and could be regarded as a minor achievement when compared with the impact of industrial revolution with its accompanied urbanisation on societies. Most of the changes are a result of innovation and diffusion of innovation. Innovation implies changes to a culture that result from ideas created within the social group itself and adopted by the culture. It may be the improvement of technology or simply changes in the social structure. These changes spread through spatial diffusion. This is a process by which an idea or innovation is transmitted from one individual or group to another across space. The process of diffusion of an idea takes place when people move to another area and take the innovation with them such as seeds or religion. The information about an innovation also spread through mass media advertising such as the use of handy cell phone and television sets. Industrialisation is the best example of diffusion of innovation. It originated in Western Europe and was spread to the rest of the world. When an innovation remains and spreads from one place to others then diffusion has taken place. In many cases, ideas spread internationally from bigger cities to smaller towns and down to rural areas, or from prominent people to less prominent ones. This is termed hierarchical diffusion. There is also, relocation diffusion in which migrants physically carry the innovation or idea to new areas. For example the Maasai men plait hair of Tanzanian women in urban areas in Maasai style. What we notice here is continuous spread of innovations from their point of origin and their integration into the structure of the receiving society such that today societies have no pure culture. Indeed, close observation shows that a big proportion of what forms a society culture comes from outside. Reflecting on this, a cultural landscape is constantly undergoing changes and this affects the way people organise space and hence their impact on the environment. The following lectures examine characteristics of human population and how men and women exploit natural resources in order to meet basic needs such as food, clothing, shelter and leisure.

Activity 1 ? How do humans affect the environment?

Summary Human geography puts more emphasis on people, and how they organise space to procure livelihood. It is also concerned with how people organise themselves politically and the impacts of such activities. It provides explanations of how things are interrelated in space and enables them to be well informed and hence prepared to contribute solutions to societal problems. The basis of human success in many activities is interaction. The way people interact is determined by their culture, particularly their level of technology. Variation in technology among societies is responsible for the spatial differences we observe. In less developed societies, basic needs are largely procured from nature. The environment determines people’s life. In contrast, developed societies use their improved technology to control the environment in the process of procuring livelihood. Due to this, Landscapes and peoples’ characteristics change through time as human societies interact with their environment and adopt new innovations from outside.

Exercise 1. Analyse the main differences between physical and human geography. 2. To what extent does the level of technology of a culture determine a society’s path towards development? 3. Discuss the role played by innovation and diffusion in altering the cultural structure in which you are a participant from that experienced by your great grand parents. 4. Why is adjustment of human activities and environmental characteristics important for sustained development?

Reference 1. Fellman J. D Arthur Getis and Judith Getis, (1998); Human Geography: Landscapes of Human Activities, 6th edition. The McGraw-Hill Companies, Inc.

Lecture 13 Population and Development

13.1 Introduction Population, in this lecture, is defined as the total number or a specified number of people in an area at a particular time. Population at a particular time is the function of births, deaths and migration (fertility, mortality and migration). The three determinants of population are also referred to as population dynamics. Population is a resource that requires sound management just like any other resource if it has to positively contribute to socio-economic development. The size, characteristics, growth and trend of today’s population shapes the well being of the future population. The number of people, patterns and trends in their fertility and mortality and rate of growth all affect and are affected by the social, political and economic organisation of a society. Through these, we come to understand how the people in a given area live, how they interact among themselves and with the environment and the pressure they exert on the land resources. The study of population characteristics is therefore crucial to the understanding of societal organisation and its needs. This is the main interest of population Geography. In this lecture, you will learn about various definitions of population terms, the main characteristics of population, population controls, and determinants of population distribution.

Learning Objectives At the end of this lecture, you will be able to:  Define population terms and explain factors influencing population growth, distribution and density;

 Relate concepts of overpopulation and under population to resources endowment and level of technology;  Use population statistics to explain population structure in respect to age problems;

 Discuss the impact of fertility, mortality and migration on socio economic growth;

 Discuss the consequences of migration on both origin and destination.

13.2 Population Terms

Birth Rate The Crude Birth Rate (CBR) is the normal number of live births per 1,000 populations regardless of sex and age composition. For example a population of 35 million with 700,000 births a year will have a crude birth rate of 20 per 1000. The birth rate of a country is influenced by the age and sex structure of its population and the family size preferred by the population. Population policies, of countries also influence the birth rate. Where there are no restrictions, a high population of young females in a population will yield a high birth rate whereas a low population of females will result in low birth rate.

Birth rates of less than 20 per 1000 are regarded as low and are a characteristic feature of industrialized, urbanised countries (Fellman, et al., 1999:100).

Fertility Rate Fertility is the frequency of child bearing among the population. Fertility rate refers to the relative frequency with which births actually occur within a population. Crude birth rates are inaccurate in displaying regional variability because the differences can be caused by age and sex composition or shortcomings in births among the reproductive age rather than the total population. Total Fertility Rate (TFR) is a more accurate measure since it tells us the average number of children who would be born to each woman during her reproductive cycle at the current years’ rate. For that reason, it is a more reliable figure for regional comparative and predictive purposes than the crude birth rate. A TFR of 2.1 is necessary just to replace present population (Ibid p. 101). The fertility rates of many less developed countries has been declining because of the adoption of family planning methods and an increasing demand over the costs of bringing up children today.

Death Rate The Crude Death Rate (CDR) also called the Mortality Rate (MR) is the number of deaths per 1000 population. It is calculated in the same way as the crude birth rate. The CDR is not an accurate figure for comparison across nations unless the countries under consideration have the same age structure. To overcome this lack of comparability, death rates can be calculated for specific age groups. The Infant Mortality Rate (IMR) is the ratio of deaths of infants aged one year or under per 1000 live births i.e. deaths less than 1 year/1000 live births. Mortality during the first year of life is usually greater than in any other year. Therefore the drop in infant mortality accounts for a large part of the decline in the general death rate. That is why Tanzania has given more weight to infant immunisation. In many countries-Tanzania included, the various vaccinations given to infants aim at reducing death rates in the above age category and that of the whole population. Death rates are low in the rich countries, which is within the range of 7 or less deaths per 1000 population and high in poor countries where 20 or more deaths take place per 1000 population. In some parts of Sub-Saharan Africa, the chief causes of death are infectious diseases such as malaria, typhoid, cholera, diarrhoea and malnutrition. Sanitation plays a big role in the reduction of mortality. Hence, there is a direct relationship between mortality rate’s status of a country and its level of development.

Natural Increase This is the increase of population caused by births. The rate of natural increase of a population is obtained by subtracting the crude death rate from the crude birth rate. By natural, we mean that increases or decreases caused by migration are excluded. A country with a birth rate of 32 per 1000 and a death rate of 12/1000 will have a natural increase of 20 per 1000. Since the rate is expressed as a percentage, in this example it would be 2%.

Population Doubling Time This is the time it takes for a population to double. The rate of increase can be used to derive this. Population doubling time can be closely determined by dividing the growth rate into the number 69. Thus a 2% rate of increase can be expected to double in 35 years while that of 3% will double in 24 years!

Activity 13.1 ? How long will it take for a population with annual increase of 2.5% to double?

If the fertility is high accompanied with declining mortality, the doubling time is shortened. This can compromise development efforts as the government might not have enough time to tape resources and provide the basic services to its population. Thus, a slowly growing population is preferred.

Population Pyramid A population pyramid is a graphic form of a pyramid drawn to express the age and sex composition of a human population. The age groups are in the vertical scale, starting with the youngest at the base and the number or percentage of males and females within each of the age groups on the horizontal. A pyramid with a wide base and narrowing upwards is termed expansive. It indicates a young expanding population with many children and a declining death rate. If the shape resembles a tall dome, it is termed stationery, denoting a stable, slowly growing population where there is decline in mortality and low birth rate (refer to Figure 8.1).

Source: http://www.scalloway.org.uk/popu4.htm Figure 13.1: Population Pyramid

The population pyramid is important in the analysis of population data as it provides a quick visualised demographic picture of immediate practical and predictive value. For instance, a country with a high proportion of young population has a high demand for educational facilities and health delivery services. It also means that a large proportion is too young to be employed. Conversely, if a large proportion is of old people, it means that, many people have to be supported, by a smaller proportion of the productive population. If this population does not possess advanced technology, it may fail to support dependants and fail to bring about development. Therefore, there is a need to manage well fertility, in order to have a balanced population and hence avoid negative effects arising from a young or aged population structure.

The Dependency Ratio It is a simple measure of the number of dependants; old and young that each 100 people in the productive years (15-64) must support. Population pyramids provide a visual evidence of that ratio. They may also foretell future problems resulting from present population policies and practices. It is predicted

that by year 2010 China will have about one million excess males a year entering the marriage market because of earlier preference for sons in the implementation of the one child policy.

Activity 13.2 ? Will such bachelors without families pose any social problems to China?

Governments when planning for fertility control should do so with long-term precautions to avoid sex and age imbalances in future.

13.3 Population Distribution Human population is unevenly distributed over the earth. Some land areas are densely populated, others sparsely settled while others are completely uninhabited. More than half of the population live on about 5% of the land and two thirds on 10%. Further analysis reveals that almost nine tenths of human population inhabit less than 20% of land. In addition, 80% of the population is found to live on land below 500 metres in elevation. More than half of the world’s population is found in rural areas and more than 40% are largely urbanites with a big proportion of this residing in very large cities. About 35-40% of the entire worlds land surface is inhospitable (Fellman, 1990:122). A number of factors are responsible for this situation. Temperature, length of growing season, slope and erosion problems limit habitation in high altitudes. However, not all lowlands are suitable for settlement. Much of the population lives on alluvial lowlands and river valleys. Generally, latitude, aridity and elevation limit the attractiveness of many areas. Great clusters of population are East and South Asia, Europe, north-eastern United States and South- eastern Canada. East Asia, including Japan, China, Taiwan, and South Korea contains 25% of all people on earth. South Asia comprising Bangladesh, India, Pakistan and Sri-Lanka account for another 21% of the world’s inhabitants. This is close to half of the world’s population. Europe accommodates another 13% of all inhabitants (Ibid).

Activity 13.3

What are the factors that have influenced population concentration in those areas?

The African population is concentrated mainly in areas with reliable rainfall and natural fertility. Therefore, rainfall and soil fertility are determinants of population distribution in Africa and Tanzania in particular. Areas such as the Southern highlands and the slopes of Mount Kilimanjaro which get sufficient rainfall of over 800mm per annum, are more densely populated than the poorly watered areas such as Singida (Yanda and Shishira, 1999: 9): This is observable at district level as well. For instance, in Kibondo district in Western Tanzania, 60% of the people live in the western highlands which get more than 1000mm of rainfall per annum (URT and Caritus, 1999:x).

13.4 Population Density

The term density, expresses the relationship between the number of inhabitants and the area they occupy. Although density figures are used widely, they are misleading because not all land is habited. The calculation is an average and thus does not reveal the quality of land, adequacy of food or levels of income.

Some of the inhabitants are made to this crude density by relating population to that area that may be cultivated. When total population is divided by arable land area alone, the resulting figure is the physiological density. This density is able to reveal actual settlement pressures, which are not pointed up by the crude density. The over all density of Africa is 16 people per square kilometre. This gives the impression that there is no population pressure in Africa. However, the reality is that the land suitable or open for human settlement is limited. For instance, cropland accounts for 5-6% of total land area on the continent and in many countries arable land available per capita is less than a half-hectare (White at al., 2001:69; World Bank, 2001:288). In Tanzania, only about 9% of the cultivatable land is of medium or high fertility. The rest is of poor fertility and is either semiarid or infested by tsetse fly. Since about 15% of cultivable land is already under cultivation, it means that the best land is already cultivated (UN and UDSM; 1993). Subsequently a growing population has to resort to areas with less suitable conditions for agriculture.

13.5 Overpopulation This applies to a situation whereby the population in an area cannot be supported adequately by the available resources under the given technology. When the number of people exceeds the optimum population, the standard of living declines and both economic and social aspirations cannot be realised. Overpopulation is not the necessary and inevitable consequence of high density of population. This is because overcrowding is a reflection not of numbers per unit area but rather of carrying capacity of land. The carrying capacity of an area is the maximum human population that a particular area can carry or support without suffering unacceptable deterioration given the prevailing technology. When in an area, the population exactly equals the carrying capacity, the area is said to have reached saturation level. The fact that carrying capacity is related to the level of economic development, it follows that an area that employs heavy use of irrigation, fertilisers and biocides can support more people at a higher level of living than one engaged in shifting cultivation. Based on the foregoing explanation overpopulation can be linked to levels of living which reflect imbalance between numbers of people and the carrying capacity of the land (Fellman et al., 1999:126). An indication of such imbalance might be the inadequacy of food supplies to meet normal nutritional needs. Bearing this in mind, many countries of Sub Saharan Africa can be said to be over-populated since per capita food production has been decreasing for more than two decades. From Figure 8.2 it is revealed that, Kenya, Uganda, Rwanda, Burundi and Nigeria are overpopulated compared to Tanzania. Notwithstanding the above, in contemporary world, insufficiency of domestically produced food cannot be considered as a sufficient measure of overcrowding. Only few countries are agriculturally self- sufficient. Japan, one of the developed countries with advanced technology imports about half of its food requirements. The international trade helps to solve the problem of overcrowding. Therefore, countries should strive to improve their economy.

13.6 Population Controls

Population pressure does not emanate from the amount of space humans occupy. They stem from the food, energy and other resources necessary to support the population. The declines in these factors that support population impede the continuous increase of the human population. Famine and wars have been recognised as the main checks on population in history. Thomas Robert Multhus (1766-1834) in a treatise published in 1798 noted that population is inevitably limited by the means of subsistence, celibacy and chastity, war, poverty, pestilence and famine (Fellman, et al., p.130): Today family planning through

the use of modern contraception is the chief mechanism that regulates population increase around the world. 13.7 Population Migration

Migration refers to the act or process of moving from one place to another, usually across a political boundary with the intent of staying at the destination permanently or for a relatively long period of time. Humans move from home areas to work or settle in another. Generally migration varies in volume, distance and duration and it is divided into two main types, mainly internal and external. Internal migration is when the movement is confined within the country or particular region whereas international migration takes place when the migrants cross international boundaries. In internal migration four major types of migration can be discerned. These are rural-rural, rural-urban, urban-urban and urban-rural.

13.8 Factors for Migration

Migration may be forced or voluntary or sometimes unwanted relocations imposed on the migrants by circumstances. Population growth, environmental deterioration, increasing pressures on land, fuel and water in the countryside, international and civil conflict or war force people to migrate. In forced migrations the decision to move is made by other people other than the migrants as was the case of millions of Africans who migrated to the Americas and Caribbean Islands between the 16th and 19th century. Reluctant relocation has been widespread in Sub Saharan Africa in the 1990s. International refugees from political turmoil numbered over 28 million in this period. Figure 8.2 shows the main countries of origin and destination.

Source: http://www.heindehaas.com/africaMap.html Figure 13.2: Pattern of Migration in Africa

Beside the above, the great majority of migrations are voluntary. Basically, migrations take place because migrants believe that their opportunities and life circumstances will be better at their destination than they are at the present location. Thus, economic forces are primary in influencing people to migrate. It has been observed that poor people may move from village to town and from town to city being pushed by poverty and being attracted by opportunities. Since poverty in developing countries is widespread in rural areas, rural urban migration is overwhelming. Migrants are attracted to urban areas because there are perceived opportunities in terms of income generation activities, employment and social services. The expected positive attractions of migrants at the area of destination are called pull factors while negative conditions at the origin are called push factors. Thus migration is largely a product of both perceived push and pull factors.

13.9 Consequences of Migration in Area of Origin and Area of Destination

Area of Origin In the area of origin, where immigrants are unskilled, those who remain behind are in high demand and wages rise. Emigrants usually send remittances, thereby increasing the incomes of those who remain home. Remittances can bring foreign currency when they act as an export commodity, as in the case of Egypt, Turkey and Thailand. Migrant workers tend to make money servings to buy cars, tractors and other consumables, which they take back to their families. That way, they may raise the living standards of their families. If the remittances are invested in production, the country can raise its Gross National Product. Nonetheless, there are negative consequences resulting from migration. Foremost, there are social costs due to long periods of separation. Some families break up permanently. Moreover when skilled professionals migrate, the country loses skilled people, a situation that leads to underdevelopment if it is at a large scale. When most of the youth and especially males migrate and stay for a long time, rural production declines as females fail to satisfy family needs due to their dual role as producers and reproducers.

Area of Destination In the area of destination, supply of labour, increases and wages decline. The host country can select migrants according to skills and education and employ them thus gaining labour by giving low wages. On the other hand, this can lead to high levels of unemployment if there are no vacancies. Additional population also adds burden for provision of social services. Socially, migrants may create tension in areas where they are concentrated. The residents normally dislike migrants as the case in Western Tanzania where refugees from Burundi and Rwanda have caused insecurity, destruction of the natural environment and plundering of land resources.

Activity 13.4 ? Throw light on the consequences of migration in area of origin and area of destination.

Summary Human population is the vital resource on earth. All other resources are exploited depending on the skills acquired by a population. Owing to this, it is very important to manage population. Patterns and trends of human fertility affect and are affected by the social, economic and political organisation of society. High birth-rate for instance gives rise to a youthful population structure with many dependants than producers. In such a society, efficient methods of production are required in order to support a growing population. Total fertility rate is a useful measure of fertility than the crude birth rate, as it allows comparison across nations. The difference between births and deaths determines to a big extent growth rate of population, which in turn determines the doubling time of population. If the population doubling time is very short, problems of maintaining the population arise. Thus, population has to be managed so as to control its rate of increase. Human population is unevenly distributed over the earths’ surface due to various factors such as temperature, degree of slope, soil fertility, availability of water and mining activities. About 35%-40% of

the earth’s surface is inhospitable. Areas with great concentrations of people experience population pressure on land resources. Thus, the concept of carrying capacity is central to the study of population and development. Sometimes people fail to get their basic needs from an environment and decide to migrate to another area. Migration has both positive and negative effects to both area of origin and destination. Hence, it is important to manage population in order to avoid negative effects of migration.

Exercise 1. Write short notes on the following terms: (a) Fertility rate, (b) Birth rate, (c) Death rate, (d) Mortality rate, (e) Population doubling time. 2. Examine the factors which are responsible for population distribution pattern in your country. 3. “Overpopulation and under population are dynamic conditions”. Elaborate this statement with focus to (a) the concept of carrying capacity (b) technological advancement. 4. Why is a youthful population considered to be detrimental to development? 5. Discuss the pros and cons of population migration to both the origin and area of destination.

References 2. Clark, Audrey, (1990); Dictionary of Geography. Geographical Publications Ltd, London. 3. Fellman J.D Arthur Getis and Judith Getis, (1998); Human Geography: Landscapes of Human Activities, 6th edition. The McGraw Hill Companies, Inc. 4. United Nations and UDSM: Population, Environment and Development in Tanzania, Dar es Salaam. 5. White, H; T Kllick, S. Kayizzi-Mugerwa and M Savage (Eds). (2001); African Poverty at the Millenium: Causes, Complexities and Challenges. Washington D. C: The World Bank. 6. Yanda, P. Z. and E. K. Shishira (1999); An Overview of Agricultural Resources Base, Utilisation and Potential in Tanzania Mainland. Report Submitted to the Ministry of Agriculture and Co-operatives, United Republic of Tanzania, Dar es Salaam. 7. World Bank. (2001); World Development Report 2000/2001: Attacking Poverty. www.worldbank.org/poverty/ 8. URT, Ministry of Agriculture and Co-operatives: Lake Zone Agricultural Institute, Maruku Agricultural Research Institute and Caritas-Kigoma. (1999); Agriculture and Food Security Survey in Kibondo District. Working Paper No 28, 1999. Dar es Salaam, December.

PART 5 Environment and Exploitation of Natural Resources

Lecture 14 Exploitation of Natural Resources: Agriculture

14.1 Introduction Agriculture is a branch of science which deals with the cultivation of crops and the keeping of domesticated animals for food, fibre or power. Economically, it is the combined businesses of farmers, who produce commodities, input for industries, which supply them with equipment, chemicals and finance, and distributors of commodities to consumers. Agriculture has replaced hunting and gathering as the main activity of livelihood where environmental conditions permit. It is estimated that crop farming covers some 15 million square kilometres worldwide, which is equivalent to 10% of the earths total land area. In developing countries agriculture is the leading economic activity employing about 75% of labour force (Fellman, 1998:270). In highly developed economies only a small proportion of the labour force is engaged in agriculture. For instance, in Western Europe the labour force in agriculture is less than 10% and less than 3% in the United States of America. Agriculture can be classified into subsistence, traditional (intermediate) and advanced. In subsistence agriculture, production is solely for family sustenance, using poor implements. Advanced agriculture is highly capitalised, specialised, nearly industrialised, and meant for off farm delivery. In between is traditional agriculture, where production is for home consumption, and partly oriented toward marketing at local, national or international markets. This lecture will concentrate on subsistence and commercial agriculture.

Learning Objectives At the end of this lecture, you will be able to:

 Differentiate subsistence from commercial farming;

 Explain how agriculture is organised in China;

 Discuss factors that contribute to success in agriculture in North America;

 Discuss the problems facing agriculture in Tanzania;

 Discuss the ways by which problems facing agriculture in Tanzania are being solved.

14.2 Subsistence Agriculture This economic system involves production largely for self-sufficiency on part of families. Production for exchange is minimal and each family relies on itself for food and most essential needs. This system is predominant in most of Africa, South and East Asia and Latin America where people are basically concerned with feeding themselves from their own land and livestock. Subsistence agriculture can be further divided into extensive and intensive agriculture. The main difference among the two is their carrying capacity. Extensive subsistence agriculture involves large areas of land and minimal labour per hectare. Both population and yields are low. In contrast, intensive subsistence

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agriculture involves cultivation with much labour per acre. Yields per unit area and population densities are both high.

Extensive Subsistence Farming A form of extensive subsistence farming practiced in the warm, moist latitude areas especially in Africa is shifting cultivation or slash and burn. It is one of the oldest and most widely spread agricultural systems of the world. It is practiced in parts of west central Africa, Northern part of Latin America and East Indies. About 5% of people worldwide are practicing this agricultural system whereas such type of agriculture covers 20% of the world’s area (Fellmann, 1999:273). In Tanzania sparsely populated areas practice some form of shifting cultivation. Outstanding examples are Dodoma, Singida, Tabora, Kigoma, Rukwa and Mtwara. Under shifting cultivation, farmers clear the natural vegetation, cut it into pieces and then burn the cuttings. The cleared land is planted with crops such as maize, millet, rice or cassava. The first and second harvests are usually good but yields quickly decline with each successive planting on the same plot. This is because soils lose most of their nutrients as they dissolve in surface and underground water or by being used up by plants. When the soil becomes exhausted, the plot is abandoned for regeneration of vegetation and a new plot is once again cleared and planted. Thus productivity is maintained by rotating fields rather than crops. It can take 5-10 years before the land left fallow can be re-cultivated. For this reason, each family requires extensive land to support it. Hence, the system supports few people. Once population increases, the fallow period has to be reduced and land is cultivated before it can fully regain its fertility. At this stage it is necessary to employ intensive methods of cultivation to maintain high yields.

Intensive Subsistence Farming Unlike the extensive subsistence farming which employs only 5% of the world’s population, more than 50% of the world’s people are engaged in intensive subsistence farming mainly in India, China, Pakistan, Bangladesh, Indonesia and some people of Africa and Latin America (Fellman et al, 1998). Crops produced include rice, wheat, maize, millet and pulses. Intensive subsistence farmers are concentrated in major river valley and deltas of the Ganges and Yangtse and other lowlands with fertile alluvial soils. Here rice is the chief crop grown and is used exclusively as human food. Let us turn our attention to how the Chinese organize their agriculture.

14.3 Agriculture Organisation in China Planned agriculture in China was started after 1949 by the government. China has managed to improve agricultural production by carrying out a comprehensive national scheme for rice control of the great rivers such as the Hwang Ho, Sikiang and the Yangtse. The river control project was multipurpose and activities included control of floods, irrigation, and generation of hydroelectric power. Also land reclamation, creation of navigable waterways, research in agriculture and mobilisation of human resources for development were other aspects addressed. Under the river control scheme about five times the natural land was brought under agriculture. Agriculture plans were set on duration of five years beginning 1953. The aim was to formulate techniques and methods of increasing agricultural output per hectare. Farmers were guided by eight slogans: 1. Fertilisation 2. Deep ploughing 3. Seed improvement 4. Close planting 5. Soil improvement 6. Plant protection 7. Tools improvement 8. Irrigation

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The government through rivers control project mainly undertook irrigation and water conservation. Much of the work of expanding irrigation was done by cooperatives and communes. With the formation of cooperatives and production teams, much more labour could be mobilised to build large earth dams and construct large network channels. This way, large areas could be irrigated and more food produced.

On Soil Improvement New and more efficient ways of mechanising soil were devised. Much emphasis was put on composition and making use of seaweed and mud from ponds to improve soil fertility. Agricultural colleges and research stations were responsible for developing quick maturing high yielding seeds. There was also great emphasis on pests and diseases control. All major types of modern pesticides and fungicides were introduced in large quantities. China demonstrates that in intensive agriculture, higher yields are a result of high inputs. An increase in production of existing arable land rather than expanding cultivated area has accounted for most of the growth of agricultural production over the past recent decades leading to what is known as the Green Revolution (Fellman et al., 1998:277).

Green Revolution This refers to a complex of seed and management improvements adapted to the needs of intensive agriculture that have brought large harvests from a given area of farmland. Between 1965-1995 world cereal production rose more than 90% and over three quarters of that increase was due to increases in yields per unit rather than expansions of cropland. This has been remarkable in Asia and Latin America where between 1980 and 1992 yields increased by nearly 25% and 33% respectively (Ibid). Genetic improvements in rice and wheat have formed the basis of Green revolution. Dwarf varieties have been developed that respond well to heavy applications of fertiliser, resist plant diseases and can tolerate shorter growing seasons. Adopting the new varieties and applying the irrigation, mechanisation, fertilisation and the required pesticides have brought this success. However, most of the poor farmers on marginal and rain fed lands have not benefited from the new plant varieties that require irrigation and high chemical inputs. Despite the high food production from the green revolution, there have been negative effects too. Irrigation has destroyed large areas of cropland due to excessive salinisation of soils resulting from poor irrigation practices. Moreover, the huge amount of water required for Green revolution irrigation has led to serious groundwater depletion, constraining industrial water needs. It is feared that most of the traditional varieties have been lost with the nutritional diversity and balance that multiple crop intensive gardening assured. The poor farmers who are unable to adopt it have been forced by circumstances to migrate to urban areas. Thus the Green revolution has not benefited all people engaged in agriculture.

14.4 Commercial Agriculture Few people still practice subsistence agriculture per se as they have adjusted their traditional economies in response to world trade. Nowadays, farmers produce for their own subsistence and primarily for a market off the farm. Farmers have become part of integrated exchange economies in which agriculture is part of. Farming activities respond to market demand through price. Thus, production is related to the consumption requirements of the larger society rather than the immediate needs of farmers themselves. Agriculture in developed countries is characterised by specialisation by farm, area and by country. Production is geared toward off-farm sale rather than subsistence production. It is also characterised by interdependence of producers and buyers through markets. Similar to subsistence agriculture, commercial agriculture can be intensive or extensive.

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Intensive Commercial Agriculture It is s characterised by application of large amounts of capital, high yields and high market value per unit of land. Crops grown include horticultural crops such as fruits and vegetables and farms are normally located close to markets. Included in this type of farming is livestock – grain farming which involves the growing of grain to be fed to livestock. In Western Europe, for example, three quarters of cropland is used for production of animal feed. In Denmark, 90% of all the grains are fed to livestock and in turn farmers sell meat, butter, cheese and milk. Unlike horticultural farms, these farms are located away from the main market centres because the value of the product per unit land is less than that of dairy farms.

Extensive Commercial Agriculture Mainly involves wheat farms and it is widely practiced in the North America. The farms are very large. For example, nearly half the farms in Saskatchewan are more than 400 hectares. Famous areas growing wheat include Kansas, North Dakota, Eastern Montana and Southern parts of the Prairie Provinces of Canada. Wheat farms require sizable capital inputs for planting and harvesting machinery, abundant land facilitates, and large-scale farming which allow the practice of leaving land under fallow.

14.5 Agriculture in Tanzania Agriculture plays a central role in Tanzania’s economy. It accounts for 60% of export earnings and 84% of employment. Outstanding components of the agricultural sector are food crops, livestock and traditional exports whose contribution stood respectively at 55%, 30% and 8% of the total agricultural Gross product by late 1990s (URT, 1997:3). An estimated 8% of land is under cultivation (UN and UDSM, 1993: 13). Food crops grown include maize, millet, sorghum, bananas, cassava, potatoes and a variety of pulses. The principal export crops are coffee, cloves, cotton, tea, cashew nuts, tobacco and sisal. Arable land is undergoing accelerated rate of land degradation due to soil exhaustion and erosion and desertification. This is particularly true in semiarid ecosystems dominated by agro-pastoral communities. The problem of soil erosion is prevalent, however in both areas of high agricultural potential as well as in areas of low potential devoted to livestock keeping. The majority of the smallholder subsistence farmers in Tanzania practice extensive subsistence farming and small-scale livestock keeping. Subsistence farming is often linked to environmental degradation because many farmers largely depend on the local experiences rather than new improved methods of agriculture (Madulu, 2000:47). The performance of the agricultural sector for the last two decades has been of much concern particularly the period ending in the mid 1980s. Export production declined between the 1970s and 1980s. This trend was accompanied with the decline in the international prices of the traditional export crops. This led to the drop in the real value of Tanzania exports. Consequently, the growth rate of total exports declined at the average rate of 4.5% per annum while the real value of imports grew at 0.7% annually over the period. A similar trend applied to food crops and livestock where food crops declined by 0.2% per annum between 1986 and 1991 while livestock registered negative growth before the mid 1980s. There were no remarkable improvements made in the 1990s (Op.cit.). The withdrawal of government and its agencies from the provision of agricultural services to farmers has not kept pace with the growth of the private sector’s participation in terms of its ability to effectively take over these services. Economic reforms have also affected cooperative unions. Debts and bad financial conditions have constrained their ability to provide agricultural services to farmers. Farmers cannot afford to buy fertilisers and other essential agricultural inputs and tools. Lack of credit facilities to majority of farmers prevents them from accessing inputs. The result has been unattractive farmer’s incomes and accelerated poverty among them.

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Poor agricultural performance in Tanzania is aggravated by the fact that some suitable research findings often fail to reach the farmers. Lack of clear research priorities and fragmented research activities adversely affect use of both government and donor funds. Farming as an enterprise is currently dominated by adult old farmers, a situation which threatens the maintenance of families. So far the agriculture sector has failed to attract youths as a profitable venture forcing them to migrate to towns and cities in search of other means of sustaining livelihood. As a consequence of the above, there is food insecurity and declining production of export crops. Apart from the government allocating fewer funds than required, other setbacks to agriculture include insufficient innovation and continued reliance on the hand hoe, frequent droughts, land degradation, inadequate application of fertiliser, and absence of linkages with industrial sector. Other problems are over dependence on rain-fed agriculture, morbidity and poor nutrition. Lack of reliable and profitable markets, pests and disease, and prevalence of Tsetse flies also affect production. All this entails that poverty in its various manifestations affects the performance of agriculture in Tanzania. Improvement of agriculture has to do with strategies that are geared at reducing poverty in rural areas.

14.6 Efforts in Improvement of the Agricultural Sector in Tanzania

To improve farmers’ knowledge in agriculture, several agricultural colleges and Sokoine University have been established. Extension officers are trained who in turn interact with farmers. Establishment of irrigation schemes and construction of dams aim to solve the problem of unreliable rainfall and over dependence on rain fed agriculture, for example, Mbalali and Kapunga projects, the Kagera and Rufiji Basin Development Authority. To overcome the market problem, farmers are encouraged to form cooperative unions for organising production and marketing of crops.

Key principles for Development of Agriculture sector includes:  Increasing control of resources by beneficiaries by increasing the voice of farmers in local planning processes and increasing their control in the design and implementation of priority investments and in the types of services that they need.  Pluralism in service provision by providing a wider choice in service provision to increase cost- effectiveness and competitions.  Resource allocations to Local Government Authorities (LGAs) are should be done through transparent and equitable through adopting and extending the local government grant system.  Integration with government systems. Existing government financing and planning systems should be used to ensure sustainability  Agriculture financing should be through general budget Support (GBS), Agriculture Sector Development Programme Basket Fund and Beneficiaries contributions.

Activity 14.1 ? Explain the intensive and extensive subsistence and commercial agriculture in Tanzania.

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Summary Agriculture is an economic activity most extensively practised in both subsistence and advanced societies. The form it takes first responds to the immediate consumption needs of the producers and then to needs of others. Whether it takes form of extensive or intensive production, it reflects the environmental condition under which it is practiced. Extensive agriculture can be practised where farmland is abundant. With land shortage and increasing population both subsistence and commercial farming are bound to be intensive. Farmers as part of integrated exchange economies respond to market demands through price. There is interdependence between producers and buyers. Agriculture in Tanzania is partially subsistence and in part commercial. The agriculture performance has been poor for three consecutive decades beginning in 1970s. Lack of improving the agriculture sector through government funding has left many small farmers to continue with traditional systems of farming that support low populations. With increasing population, poor knowledge and lack of capital, farmers have failed to manage land resources sustainably. Land has been degraded with an associated result of declining yields. This has pushed most of the youth from the agriculture sector such that, the sector is dominated by the elderly.

Exercise 1. Compare and contrast subsistence and commercial systems of farming. 2. How does extensive subsistence farming differ from intensive subsistence farming? 3. What measures did China take to improve agricultural production since 1949? What can your country learn from this experience? 4. Examine the main features of commercial farming. 5. Provide an analysis of manmade and environmental problems facing agriculture in Tanzania. Suggest remedial measures. 6. What are the measures that have been taken by the government of Tanzania to modernise its Agriculture?

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5. URT (1998); The National Poverty Eradication Strategy, The Vice Presidents Office, Dar, Govt Printer. 6. White, H. T. Kllick, S. Kayizzi-Mugerwa and M. Savage (Eds) (2001); African Poverty at the Millenium: Causes, Complexities and Challenges. Washington DC: The World Bank. 7. URT; (1997); Agriculture and Livestock Policy. Ministry of Agriculture and Cooperatives, Dar es Salaam, January.

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Lecture 15 Exploitation of Natural Resources: Mining

15.1 Introduction Natural resources refer to natural wealth supplied by nature and available for human use. They include mineral deposits, soil fertility, timber, energy, waterpower, fish, wildlife and natural scenery. The list is not exhaustive because what constitutes a resource depends on technological awareness, which enables people to perceive it to be necessary and useful for their economic and material well-being. The assessment of what constitutes a resource is constantly changing with the development of technologies to exploit them. Natural resources result from physical processes over which human beings have no direct control. If a substance is not known to be useful, then it is not a resource. What makes people to perceive a substance as a resource is their culture. Cultural awareness of its value and technology to exploit it are therefore, fundamental in resource exploitation. This lecture explores the exploitation of flow, stock and continuous resources with particular focus on mining, forestry, fishery and tourism in Tanzania. The lecture also puts emphasis on problems associated with the exploitation of the three main categories of natural resources in Tanzania.

Learning Objectives At the end of this lecture, you will be able to:

 Distinguish between renewable and non-renewable resources;  Assess the contribution of at least three natural resources to the development of a selected country;

 Evaluate the place of mining sector in industrial development and economic transformation;

 Evaluate the importance of tourism to national economies;

 Discuss the main problems encountered in the exploitation of natural resources in your country;

 Propose sustainable strategies for exploiting resources.

15.2 Classification of Natural Resources

Natural resources are classified into three main categories as pointed out above. Flow resources are those which are renewable, that means they are always available and open to human modification. Humans or natural forces can replenish them relatively quickly. Resources falling under this category include, fish, soils, forests and water. Stock refers to non-renewable resources such as minerals. Natural processes so far cannot replace minerals whereas continuous resources are always available and independent of human action. Examples include solar and wind energy. The first two categories can change with time. For instance, renewable resources such as forests and non-renewable minerals such as gold can be exploited to extinction.

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The maximum yield of a resource is the maximum volume or rate of use that will not impair its ability to renew or to maintain the same future productivity. In case of a forest, that level is marked by a harvest equal to the net growth of the replacement stock (Fellman et al., 199:292). Overexploitation of a resource causes this maximum volume to be exceeded, such that the renewable resource turns out to be a non- renewable one. Therefore, the extent to which resources can be exploited for sustainable development depends on the wise exploitation of such resources.

15.3 Mining Industry

Mineral is a solid substance, formed through biogeochemical processes, that has a specific chemical composition and physical properties. There are over 2,500 different types of minerals as diverse as coal, gold, and rubies. A rock is a solid composed of different minerals and other substances.

Mining is a process whereby companies operate processes to extract or take away mineral from the surrounding rock. A rock that contains a commercially profitable quantity of one or more minerals (or metals in particular) is called an ore. The left-over, worthless rock material from the ore is called gangue. The content of the ore, the cost per unit weight of the extracted mineral, is measured on a scale called the grade . Minerals are generally measured in ton, though gemstones are measured in carats. (One carat is equal to approximately 200 milligrams.) Minerals can vary in quality. Coal, for example, ranges from brown coal , used for electric power plants, to anthracite coal, used for residential space heating. Minerals are also found in varying states of purity. Gold’s purity is commonly measured in karats (not to be confused with the weight measure of carats ). Most minerals must be refined for their end use. For example, after tantalum is taken out of the ground it often needs to be chemically refined, a process that separates the tantalum from other particles that might.

15.4 Mining in Tanzania Geological investigation carried out more than 60 years together with mineral statistics show that Tanzania has a rich and diverse mineral resources base with higher economic potential. These comprise gold, base metals and a wide variety of gemstones such as Tanzanite, ruby, rhodolite and emerald. Other minerals include coal, uranium, soda, kaolin, tin, gypsum and phosphate. Gold and diamonds have always been the main stay of the country’s mineral production. The mining sector contributes about 2.3% of the Gross Domestic Product (GDP) which was projected to account for 10% of GDP in 2005 as stated in the development vision 2025. It is one of the sources for generating foreign exchange earnings within the non-traditional exports. In Tanzania the sub-sector of mining industry is already a source of livelihood for over 0.5 million people (Tanzania Government website, 2004). It has a potential of holding back rural-urban migration, stimulating local processing and manufacturing industry, thereby alleviating poverty.

Coal This was the earliest mineral in importance in the world and is still the most plentiful of the mineral fuels. It was the first to be used as an industrial energy source. Although coal is a renewable resource, world supplies are great; about 10,000 billion tons. Concentrations of coal deposits are found in the U.S.A and China. Other major coal producers are Russia and Germany. Coal mining areas attracted early industries such as iron and steel industries. These became concentrated in coal rich regions such as the Midlands of England, the Ruhr district of Germany and the Donets Basin of Ukraine.

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In Tanzania, coal occurs in the Ruhuhu and Songwe–Kiwira basins in the Southwest of Tanzania. A Total of about 1.5 billion tonnes in reserves have been identified. The country’s only coal mine at Songwe– Kiwira, has annual output of 35,000 tonnes, all of which is consumed mostly locally for power generation.

Petroleum Petroleum was first extracted commercially in the 1860s in U.S.A and became a major power source. It is both a source of energy and a raw material in fertiliser and plastic industries. Petroleum is unevenly distributed around the world. About 80% of proved resources are concentrated in eight countries and 90% in 12 countries. Iran and the Arab states of the Middle East alone control about two-thirds of the World total.

The dependence of the United States and many other advanced industrial countries on imported oil gave the oil-exporting states much power. For instance, in 1973-74, and 1979-80 the selling price given by the Organisation of Petroleum Exporting Countries (OPEC) was very high. The result was world wide economic recessions for some importing countries and large net trade deficits as more funds were used to import petroleum beyond the budget. Those years are referred to as the “oil-shocks”. When the oil price declined in mid 1980s, economic activities were stimulated and hence increased use of oil. OPEC countries include Saudi Arabia, Nigeria, Iraq, Iran and Kuwait.

Although U.S.A does not have much deposits of petroleum, it is the second producer in the world because it appropriates crude oil from the Middle East and other African countries.

Diamonds The bulk comes from the Williamson diamonds mine at Mwadui, Shinyanga region where commercial production begun in 1925. Over 300 kimberlites are known in Tanzania of which about 20% are diamondiferous.

Gold Gold exploration has grown rapidly in the 1990s using modern technology and refined models. Investigation has mainly focused on the greenstone belts around L. Victoria. Currently big gold mines are found in Kahama, Nzega and Geita districts.

Tanzanite This is a gemstone unique to Tanzania. It is mined at Mererani in Arusha region from weathered rock, sometimes in association with bands which are also of commercial value.

Natural Gas Efforts made to explore petroleum along the coast are still underway. Currently, natural gas is being mined in the south Eastern part at Songosongo in Kilwa district. The gas is used to produce electricity and for domestic use.

Over the decade, the global mining industry has undergone dramatic changes, which may have far- reaching implications for Tanzania. The globalisation of finance and investment and the deepening of financial mechanisms have opened up new frontiers leading to the increase in the exploration and mining development. New technology has allowed the discovery of deep-seated and new deposits.

The profound economic reforms and structuring undertaken by Tanzania during the second half of 1980s and 1990s have marked a clear shift in favour of private sector development and market-oriented economic management. Consistent with the reforms, the role of the government has shifted from that of owning and operating mines to that of providing clear guidelines, stimulating private investment in mining and providing support for investors. Through privatisation, foreign investors have dominated the mining sector.

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15.5 Problems Associated with Mining in Tanzania Despite the rich mineral endowment, Tanzania is among the four poorest countries in the world. Efforts made by the government since independence to develop the mining sector have not succeeded in mobilising the necessary investable resources due to:  Late recognition of the sector’s role in restoring the economy given the changing economic environment.

 Lack of or absence of appropriate and consistent mineral sector policies to provide an enabling environment for mineral development by the private sector investment.  Lack or absence of appropriate and consistent mineral sector policies oriented towards private participation.

 Lack of adequate capital resources and their management  Limited use of appropriate and advanced technologies

 Inadequacy of modern management and technical skills. The artisanal and small-scale miners face technical, financial, marketing, social and environmental problems. In order to maximise its benefits to the country, there is need to improve the management of resources to ensure that it contributes to poverty alleviation.

Activity 1 ? What mechanisms does the USA use in order to acquire crude oil from the Middle East and other African oil producing countries?

Summary Mining is an economic activity most extensively practiced by larger companies and indigenous people. Mining activities in Tanzania includes: coal, gold, Diamond, Tanzaniate and gas. However,the form it takes does not responds to the growth of economy of the countries. Lack of commitment towards development of this sector, poor technology, capital , poor policy and corruption are some of factors for poor performance of mining sector in Tanzania.

Exercise 1. Compare and contrast subsistence and commercial mining systems in Tanznaia 2. Discuss problems associate with small scale mining activities. 3. Examine strategies for mining in Tanzani 4. Discuss strategies taken by government to develop mining Industry in Tanzania..

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References 1. Fellman J. D Arthur Getis and Judith Getis, (1998); Human Geography: Landscapes of Human Activities, 6th edition. The McGraw-Hill Companies, Inc. 2. Kaduma, S (1994); Issues for Agriculture: “Challenges for the 21st Century”. In Msambichaka, L.A. H.P.B. Moshi and F.P. Mtatifikoro (Eds): Development Challenges and strategies for Tanzania: An agenda for the 21st Century. DSM DUP 91-110. 3. Madulu, N. F (2000); “Population dynamics and Natural Resource Management in Tanzania”. In: Journal of the Geographical Association of Tanzania NR 28 July 2000 p. 35-55 4. United Nations and UDSM: Population, Environment and Development in Tanzania, Dar es Salaam. 5. URT (1998); The National Poverty Eradication Strategy, The Vice Presidents Office, Dar, Govt Printer. 6. White, H. T. Kllick, S. Kayizzi-Mugerwa and M. Savage (Eds) (2001); African Poverty at the Millenium: Causes, Complexities and Challenges. Washington DC: The World Bank. 7. URT; (1997); Agriculture and Livestock Policy. Ministry of Agriculture and Cooperatives, Dar es Salaam, January

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Lecture 16 Exploitation of Natural Resources: Fishing

16.1 Introduction

Fishing provides about 19% of animal protein intake of the developing world’s population or 7% of protein supply worldwide. People of Eastern and South East Asia depend much on fish; which provide about 50% of animal protein. In Africa and Latin America, fish provide between 15% and 20% of animal protein. Moreover, about 70% of the world annual fish catch is consumed by humans whereas only 30% is processed into fish meal to be fed to livestock or used as fertiliser (Fellman, et al, 1998: 292). Reflecting from this, fish is very important for a significant proportion of the world population. The same authors’ further point out that about 20% of the annual fish supply currently comes from inland waters such as lakes, rivers and farm ponds. The rest 80% comes from oceans mainly from coastal wetlands, estuaries and shallow waters above the continental shelf. Waters in these areas supply nutrients to plankton; an environment conducive for fish production

Take Note Plankton is a minute plant and animal life that forms the base of the marine food chain.

Tropical fish species are less found in the commercial market due to their high oil content. Nonetheless, they are of significant importance for local consumption. Commercial fishing is predominant in the Northern waters where warm water and cold water currents join and mix forming a congregation zone for fish. Common species found include herring, cod, haddock and flounder.

16.2 Fishing in Tanzania

Tanzania is endowed with fishery resources. She has both marine and inland fisheries potential. Tanzania has a coastline of about 800 km as its Exclusive Economic Zone but due to poor fishing gear, it has not yet been fully exploited. The marine water covers 64,000sq km, which includes the Indian Ocean, and the Exclusive Economic Zone, which covers 223,000sq km. Fresh water includes Lake Victoria, Tanganyika, Nyasa, and other minor ones. In totality they cover 58,000sq km.

The fisheries can be divided into the following subsectors: marine and inland capture fisheries, aquaculture, and fish processing. About 85% is from inland fisheries, 14% from marine fisheries and just 1% from aquaculture (URT, 2016). The scale of operations ranges from small-scale subsistence fishing to industrial fish processing. There is a vibrant export market, exploited by small-scale fish processors and traders serving the regional market, and by large fish processors selling into international markets. The annual fish catch amount to 350,000 metric tons. There are about 80,000 fishermen who account for about 90% of the total fish catch in the country. This means that only 10% is derived from Industrial fishing. Most of the fish caught is consumed locally while the Nile Perch, sardines and prawns are exported mainly to the European market. Fish contributes about 30% of the total animal protein intake of Tanzania’s population.

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Fishing is also a source of employment, livelihood to the people, recreation, and tourism in order to create foreign income. In 2014, there were some 183,800 persons engaged in fishing, accounting for about 0.7% of the work force, with a large, but unknown number, also engaged in fish trading and processing (URT, 2016). The contribution of the sector to Gross Domestic Product (GDP) since 2005 has been staggering between 1.6 and 3.1%. Even so, it contributes about 10% of total foreign exchange. The industry remained uncoordinated until 1997, when a National Fisheries Policy came into being. One of Tanzania’s Fisheries Policy is to increase production and incomes of artisanal fisher folks by improving traditional technology, modernization of infrastructure as well as by protecting the country’s territorial waters.

16.3 Problems of Fishing in Tanzania Over fishing on the oceans is a prominent problem affecting the fishing industry because it is believed that oceans are common property and hence no one is responsible for its maintenance or protection or even improvement. Since 1976, coastal states have been claiming 370 km Exclusive Economic Zone (EEZ) within which they are at liberty to regulate or prohibit foreign fishing fleets. This is part of the United Nations Convention on Law of the Sea Treaty. Still there is over fishing beyond the terrestrial waters – on the open seas. For example, on August 22, 2004 European trawlers were spotted illegally fishing in Tanzanian waters. These are part of the 70 ships estimated to be operating illegally, targeting tuna fish, kingfish, lobsters and prawns. It is shocking to note that to-date, the sustainability of the industry is threatened by over-fishing and use of destructive fishing methods such as, dynamite, and poison whose ultimate impact is reduced catch per unit effort. The country is losing a fortune to illegal fishing. Improper handling technology, lack of storage facilities and poor transportation facilities and infrastructure also constitute a big problem. About 20 percent of Tanzania’s annual fish catch does not reach the consumer due to post harvest losses caused by poor handling. To date Tanzania still faces a problem of promoting sustainable exploitation, utilisation and marketing of fish resources.

Summary Fishing is an economic activity that practiced in both subsistence and commercial purpose.There are various types of fisheries in Tanzania, namely, marine fisheries, inland (or freshwater fisheries), industrial fisheries, artisanal fisheries and aquaculture. The marine fishery is practiced along the EEZ in the islands of Zanzibar and Pemba. Freshwater fishery is mainly on Lake Nyasa, Lake Tanganyika and Lake Victoria. Although government take several initiatives to develop fishing sector water pollution and illegal fishing still remain main challenges of fishing industry in Tanzania.

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Exercise 1. Compare and contrast indigneous and commercial fishing in Tanzania. 2. How does enironmemtal pollution affect fishing industry? 3. What measures did government take to improve fishing Industry in Tanzania? 4. Examine the main features of commercial fishingg. 5. Provide an analysis of problems facing fishing industry in Tanzania.

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Lecture 17 Exploitation of Natural Resources: Forestry

17.1 Introduction A forest is all land bearing a vegetative association dominated by trees of any size, capable of producing wood or water regime or providing shelter to livestock and wildlife. Forest resources include all wood and non-wood-based resources in the forests. According to Tanzania government website (2004), Tanzania has about 33.5 million hectares of forests and woodlands. Out of this total area, almost 2/3 consists of woodlands on public lands, which lack proper management. About 13 million ha of this total forest area have been gazetted as forest reserves and over 80,000 hectares of the gazetted area is under plantation forestry while about 1.6 million hectares are under water catchments management. Public lands are under great pressure from expansion of agricultural activities, livestock grazing, fires and other human activities (URT, 1998:7). The forests are of much benefit as they offer habitat for wild life, beekeeping, unique ecosystems, and genetic resources. Moreover, bio energy is the main source of fuel for rural population accounting for about 92% of total energy consumption in the country. Other services derived from the sector include pasture for livestock, raw materials for industries, protection of watersheds, source of water for irrigation, generation of electricity, environmental protection, control of soil erosion and nutrients. Therefore, forests are an important economic base for the country’s development. The sector provides nearly 730,000 person years of employment that are engaged in various forest activities. However, labour involved in the collection of fuel wood and other products is not recorded. The sector’s contribution to GDP is between 2.3 to 10% of the country’s registered exports. The wood industry accounts for nearly 50% of the sector’s contribution to GDP. Non-wood products and services contribute the other half. In 1999 only 26.269.78 cum were harvested from natural forests and 127,202.11 cum from plantations. Export trade is mainly in fine hard wood timbers to earn foreign income (URT, 2004). Since 1986 Tanzania embarked on policy and institutional reforms whose overall objectives have been to restructure the national economy and facilitate economic growth. Nonetheless, very little has been achieved.

17.2 Problems Associated with Forestry in Tanzania (a) Tanzanian forests have great economic value if well cared. However, due to inadequate management, the actual contribution of the forest sector to the national economy is less significant. Wood fuels, gum Arabic, bee products, game, catchments and environmental values have not yet been adequately rewarded in Tanzania. (b) Deforestation is a big problem. There are no reliable data on deforestation. However, estimates, range from 130, 000 to 5000,000 ha per annum. The main reason for deforestation are clearing for cultivation, overgrazing, wildfires, charcoal burning and overexploitation of wood resources mainly in the unreserved areas.

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(c) Inadequate forestry extension services and inefficient wood-based industries. (d) Outdated machinery, poor transportation network, lack of working capital (< 1% of budget), non-reliable electricity and inadequate managerial skills (e) There are varieties of ecosystems some of which have medicinal plants. These ecosystems are threatened by human activities mentioned above. (f) Effective conservation of ecosystems has been impaired by lack of sufficient coordination between the sectors (agriculture, wildlife, land development, water, energy and minerals) concerned and inadequate knowledge among users. (g) Other problems include outdated legislation, fragmented administration at all levels between the centre and the local levels, lack of participation of various stakeholders in the management of the resources and poor data bases, outdated and non existence of management plans for efficient exploitation of resources. As a result of the above problems, there has been deterioration of ecosystems and soil fertility, reduced water flows and loss of biological biodiversity. The demand for wood products is higher than supply for both domestic and export markets. The utilisation of these resources could be developed through multipurpose forest management, local processing and improved marketing (URT, 1998:11).

17.3 Causes for Deforestation

1. Uses of forest products:  Local communities largely clear forest for subsistence farming while outsiders clear forest for for commercial purposes. For a long time the two groups have been undertaking legal and illegal economic activities in these forests.  The local communities are specifically engaged in charcoal burning, felling trees for timber extraction, making beehives, clearing forests for farm land and constructing houses around or in the forests. The outsiders are mainly involved in timber extraction, charcoal making business, trading in building poles and firewood.

2 Accessibility to the Forests and Forest Products - Easy access to the forests enables forest product traders and farmers to unlawfully cut down trees

3. Poor farming techniques constitute another reason for increased deforestation. Extension officers and some respondents mentioned shifting cultivation as one of the factors.

4. Increase in Population - the increase in the size of families is an important catalyst for forest depletion and, may be an indication of poverty. It is well documented that demand for forest products is determined by such factors as total population, household size, cooking methods, prices and availability of alternative fuels, and household.

Take Note Ecology is the scientific study of the interrelationships between living organisms and the environment in which they live. Why do you think there is a need to coordinate activities of all sectors related to ecosystems?

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Summary About 40% of the Tanzania’s 88 359 000 hectares total land area is covered by forests and woodlands that provide for wildlife habitat, unique natural ecosystems and biological diversity and water catchments amounting to 1.6 million hectares. These forests are however faced with deforestation at a rate of between 130,000 and 500, 000 ha per annum, which results from heavy pressure from agricultural expansion, livestock grazing, wild fires, over-exploitation and unsustainable utilization of wood resources and other human activities mainly in the general lands.

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Lecture 18 Exploitation of Ntural Resources: Tourism

18.1 Introduction Tourism is the practice of making journeys for pleasure or for reasons of business, inspection, education in several places or points of interest on the way ending out the place of origin for more than a day. It is synonymous for tourist industry that encompasses the whole business of providing hotel and other facilities and amenities for those travelling or visiting (Clark, 1990:331). Tourism is one of the world’s largest industries that are increasingly growing. Being the largest business sector in the world economy, tourism employs about 200 million people and generates about $ 3.6 trillion in economic activity. It is an important industry in the economy of many countries in terms of job creation and hence poverty alleviation (Pamba, 2004). According to the World Tourism Organisation, Africa received 29.1 million international tourists in 2002, which represented 4.1% of the world total. Statistics also indicate that the Southern Africa region could have a growth of over 300% in tourist arrivals by 2020. A similar impressive growth of 17% is expected in East Africa. So with sound management Tanzania stands a better chance of benefiting from tourism.

18.2 Tourism in Tanzania Tanzania’s tourism sector is among the sectors, which contribute greatly to the country’s economy. In 1997 tourism contributed 16% to the Gross Domestic Product and 54% of export earnings employing about 157,200 people countrywide (URT, 1999:3). Tanzania is a beautiful country endowed with numerous tourist attractions. It has 14 National Parks: These include the newly established park of Kitulo – in Makete, 31 Game reserves and 38 Game controlled areas. Additional natural attractions include the sand beaches in the north and south of Dar es Salaam and superb deep-sea fishing at Mafia. Thus Tanzania’s competitive strengths in tourism lie in abundant and diverse wildlife, varied landscapes and scenery. Some of the outstanding attractions include: 1. Mount Kilimanjaro: With a snow caped tip is Africa’s highest mountain standing 5895m high close to the equator (3°S). The mountain is an extinct volcano surrounded by dense forests full of amazing variety of flora and fauna. 2. Serengeti National Park: It covers an area of about 14763 sq kms and is the world’s wonder for its animal variety and bird species. 3. The Ngorongoro Crater: Once an active volcano, its cone collapsed about 8 million years ago. The crater is 610 metres deep and 20 kms in diameter. It covers an area of 311 sq km. The crater accommodates a crater lake and is the home of a variety of wild game and birds. 4. The Selous Game Reserve: The reserve extends for about 55000 sq km and is the largest wildlife reserve in Africa. It provides sanctuary to the biggest elephant herds on the continent.

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Tanzania is also well known for its rich heritage of archaeological, historical and paintings sites. Among these is the famous Olduvai Gorge, situated in the interior Rift valley. This is the cradle of mankind. The Tanzania National Parks (TANAPA)–established in 1959, manages the parks, which occupy about 4.5% of the country’s total area. Despite the small area they occupy, they play major role in biodiversity preservation and form the backbone of nature-based tourism in Tanzania. TANAPA manages national parks to ensure that there is a balance between preservation and use. It is guided by a clear policy, which seeks to promote the economy of the country and livelihood of the people, particularly poverty alleviation. There is emphasis on the development of sustainable and quality tourism that is culturally and socially acceptable, ecologically friendly and environmentally sustainable (URT, 1999:5). These objectives are to be fulfilled by the private sector, with the government providing conducive environment for investment. TANAPA values and recognises the role of communities surrounding the parks in achieving its conservation objectives. In this light it has an Outreach programme for Community Conservation Services or Ujirani mwema with a focus on local people and government at district level.

18.3 Community Participation in Tourism Most tourist attractions lie within local communities or at least in their vicinity. In some cases, tourist attractions co-exist with the communities and are sources of livelihood (e.g. the lakes and the seas) while others have great significance to the members within the communities. It is for these reasons that it is important for communities living within or around these areas to fully get involved in the development and management of these attractions within their areas. Policy strategies for community participation include:

 Educating and sensitising community to appreciate and value tourist attractions.

 Involving communities in the management of tourist attractions located within their areas and the making of development related plans and decisions with regard to tourist attractions especially where such plans are likely to have a direct effect on the live hood and well being of these communities.  Involving local institutions such as the office of the District Executive Director in the management of tourist areas, land and collection of revenue.

18.4 Tourism Limitations The country has yet to exploit the full potential of the abundant natural attractions and make Tanzania a favoured tourist destination. Areas that need improvement include:

 Expansion of international air access. Though currently the Royal Deutch Airline (KLM) flies daily in and out of Tanzania. The Tanzania Tourist Board has to find means, which will enable the country to benefit from tourism by providing efficient transport to and within different tourist destinations. Recently, introduced direct flight from Dar es Salaam to Johannesburg by Precision air for example is one among such efforts.

 Provision of higher quality accommodation.

 Most tourist attractions need to be better developed and utilized. The basic infrastructure such as roads, water, power supplies, and communication need to be improved or set in place.

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 Tourist products need to be better marketed and there is a need to advertise tourist products so that they are well known worldwide.  Inadequate regional and international tourist linkages. The existing ones are not fully capitalised for the development of the sector.

 There is poor coordination and inadequate land management for the development of tourism.  Shortage of appropriate and specialised core and skilled personnel in the tourist industry accompanied by poor planning for human resource development and investment.

 The inadequacy of awareness and appreciation especially on the part of local communities, of tourism and the importance of setting aside and preserving tourist attractions.  The deficiency in investment opportunities and limited indigenous and community participation in investment activities within the tourist sector.

 The meagre resources of finance, as well as financial institutions to cater for the development of the tourist sector (URT; 1999:3-4). To conclude, tourism has a great wealth creation potential in Tanzania. Given a conducive environment the wealth created through the proper management of the industry could play a significant role in the alleviation of poverty countrywide. The Ministry responsible for Tourism has the responsibility for the development of Tanzania’s tourist industry and coordinate policies that relate to tourism.

Activity 18.1 ? Emphasize on the fishing and forestry in Tanzania and the problems associated with it.

Summary Tanzanian Tourism Sector The Tanzanian Government is engaged with developing and promoting sustainable growth on the travel and tourism sector in Tanzania, in order to preserve its natural and cultural resources. The Government, therefore, is focused in attracting high-income tourists whom are less likely to spoil the culture and the natural environment. There are 16 National Parks in Tanzania, 28 Game Reserves, 44 Game controlled areas, 1 conservation area and 2 Marine Parks. Mount Kilimanjaro was declared Africa’s leading tourist attraction in 2016 during the World Travel Awards Africa and Indian Ocean Gala Ceremony in Zanzibar. Other additional natural attractions include the white sandy beaches of the Zanzibar archipelago, of north and south of Dar es Salaam, and excellent deep-sea fishing at Mafia and Pemba Islands.

However, the sector encountered with number of problems including poor transport nertwork, bureaucracy in license provision, land conflicts and invasion, Pouching as well incomplete of spectral privatization example The Kilimanjaro and Embassy hotels.

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Exercise 1. Provide an analysis of the main souce of tourist attraction in Tanzania. 2. Assess the impact of environmental pollution in tourism industry. 3. To what extent is the tourism sector is important in industrial development and the transformation of a county’s economy? 4. Examine the main problems facing tourism sector in Tanzania:

References 1. Clark, A. N (1990), The Penguin Dictionary of Geography. Geographical Publications. 2. Fellmann, J. D; Arthur Getis and Judith Getis (1999), Human Geography: Landscapes of Human Activities, Sixth edition. WCB/McGraw-Hill, Boston. 3. United Republic of Tanzania (URT); Ministry of Natural Resources and Tourism (1999), National Tourism Policy. Government Printer; Dar es Salaam. 4. United Republic of Tanzania (URT); Ministry of Natural Resources and Tourism (1998), National Forest Policy. Government Printer; Dar es Salaam. 5. www.world -tourism.org 6. www.tanzania.go.tz/-24k 4/6/2004 7. www.ippmedia.com/ipp/financial/2005/11/09

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PART 6 Practical Geography

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Lecture 19 Application of Statistical Data in Geography

19.1 Introduction Statistics is concerned with the scientific methods for collecting, organising, summarising, presenting and analysing data. It also involves drawing of valid conclusions and making reasonable decisions on the basis of such analysis (Spiegel, 1981:1). Statistics can be located on the map to show the spatial distribution or used to draw a graph to reveal differences. This gives a clear visual impression, which is actually the main purpose of graphic data representation. Data can be discrete or continuous. A variable, which can theoretically assume any value between two values, is called a continuous variable whereas that which assumes a fixed value is a discrete variable. For example, the number of children in a family cannot be 3.12 and thus it is a discrete variable. On the other hand, the age of a person can be 49.6 years; this is a continuous variable. Data that can be described by a discrete or continuous variable are called discrete and continuous data respectively. In this lecture, you will be introduced to various ways of summarising data statistically.

Learning Objectives At the end of this lecture, you will be able to:

 Describe the nature of geographical data;

 List and discuss the common sources of data;

 Discuss the common statistical measures used in presenting and treatment of data;

 Calculate the mean, the range and the standard deviation.

 19.2 Sources and Types of Geographical Data There are many sources of geographical data. These can be population, economic activities such as crop or industrial production, climate, and physical data. Other sources of data are official sources such as government publication, censuses and the international bureau of statistics. Data can also be obtained from personal sources. These, include private collections and bibliography.

Take Note Datum is singular and data is plural.

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There are four main types of data namely nominal, ordinal or ranked data, and interval data.

Nominal Data Refers to objects, which have names such as land uses. Thus, we can categorise settlements as hamlets, villages and towns and later express them in percentage of total land use.

Ordinal or Ranked Data Refer to objects, which have been placed in ascending or descending order. Dar es Salaam, Mwanza and Tanga can be ranked 1, 2, and 3 in terms of their population sizes without indicating their exact population figures.

Interval Data and Ratio Data Refer to real numbers. In interval data there is no true zero. This means that if the temperature in Dar es Salaam is 34°C and that of Kibondo is 17°C, we cannot state that Dar es Salaam is twice as warm as Kibondo. Ratio data, on the other hand, possesses a true zero. It is possible to have 0 mm rainfall or 0 kgs industrial production and so it is possible to say that Kibondo with 2000mm of rainfall is about twice as wet as Dar es Salaam, which receives 1000mm per annum.

19.3 Summarising Data In order to give meaning to collected data, it has to be summarised. Some statistics are simple while others are very complex. However, the most basic ones are simple descriptive statistics. These include measures of central tendency such as the mean, the median and the mode. The mean is the average. It is a value, which lies centrally within a set of data arranged according to magnitude. Several types of averages can be defined. The most common is the arithmetic mean or simply the mean. This is found by, totalling all values for all observations (n) and then dividing by the total number of observations (n). For example the number of health centres in eight districts is: 3, 10, 4, 6, 1, 4, 2 and 6. The average is 3+10+4+6+1+4++2+6= 36/8=4.5. The mean is distorted if there is only one extreme value. Nonetheless it is the most widely used summary because it can be used in further mathematical processing. Since there can be no half dispensary, we find that the mean is not always the best statistic. Therefore, sometimes we use the mode. This is the most frequently occurring number, group or class. In the example given above, 4 and 6 occur twice and these are modal groups. A pattern, which has two peaks, is known as bimodal. The mode is very quick to calculate but it cannot be used for further mathematical processing. Its other advantage is that it is not affected by extreme values. The average can also be found using the median. This is the middle value or value above and below which there is an equal number of items when all numbers are placed in ascending or descending order. The data given above could be arranged as 10, 6, 6, 4, 4, 3, 2, 1. When there are two middle values we take the average of the two. In this case, 4+4/2 = 4. The median is not affected by extreme values but it cannot be used for mathematical processing.

Summarising Groups of Data Sometimes the data we collect is best summarised in groups. This is very true of population data. For example, the population distribution of a hypothetical place may be recorded as shown below and in order to find the mean age, one has to multiply the midpoint or class mark of a class by the frequency. This is called the long method. Adding the lowest value and the highest value and then dividing by two

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gives the mid-point of a class. In the following table, the class mark or mid-point of the first class is found by 4+0/2 = 2. Table 11.1: Age Distribution of a Hypothetical Sample Class Mid-point × Frequency (f) Mid-point × frequency 0-4 2 20 40 5-9 7 37 259 10-14 12 42 504 15-19 17 39 663 20-24 22 64 1408 25-29 27 58 1566 Total N= 260 4440

The mean age fx/N is 4440/260 =17.07 years The mean, median and mode provide a summary value for a set of data. On their own however, we cannot get the idea regarding the spread of data around the average value. The idea of how far data given differs from the average is provided by measures of dispersion

Measures of Dispersion The range is the simplest way to show dispersion. It provides the difference between the maximum and the minimum values. This is the difference between the maximum (largest) and the minimum (smallest) values. It is limited on data where there is significant variation between the records as in the case of rainfall data. An alternative way is to find the deviation of the data from the median. This gives the inter-quartile range. This is similar to the range only that it gives the range of the middle half of the results. That means the extremes are omitted. It measures the spread of values around the median. The greater the spread, the greater the inter-quartile range.

Method

 Place the variables in rank order starting with the smallest and ending up with the largest.

 Find the upper quartile by taking the 25% highest values and finding the mid-point between the lowest of these and the next number.  Find the lowest quartile by taking the 25% lowest values and finding the mid-point between the highest of these and the next highest value.

 Find the difference between the upper and lower quartile. This is the inter-quartile range; a crude index of dispersion of values around the median. Example: 4, 5, 5,  7, 7, 9, 11, 12, 15, 15, 17, 17 6 10 15 The lower quartile is between 5 and 7. Their average is 6 (Q1). The median is between 9 and 11 and the average is 10 (Q2). The upper quartile is between 15 and 15 and the average remains 15 (Q3). The interquartile range is found by subtracting the lower quartile from the upper quartile (Q3-Q1). In this case, the inter-quartile range is (15-6) = 9 Sometimes the number of observations is not divisible by four. If for example there are 21 observations, the quartiles are at 5 ¼ and 15 ¾.

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In the following example: 75, 80, 84, 86, 125, 148, 184, 192, 195, 209, 210, 235, 274, 361, 390, 418, 452, 460, 538, and 807, the 1st Q 5 ¼ lies a quarter of the way between 125 and 148. On the other hand, the 3rd Q 15 ¾ lies three quarters between 361 and 390. The first quartile is found adding one quarter of the difference of 148 and 125 to 125 i.e. 125 +(148- 125)/4 = 130.75 The third quartile is found by adding ¾ of the difference of 390 and 361 from 361 i.e. 361 + 3(390- 361)/4 = 382.75. In this example, the interquartile range is from 382.75 –130.75 = 252 The spread about the mean or standard deviation is another way of expressing the spread of a data set. The greater the spread or range of data, the less useful is the mean as a summary of data.

Method

 Tabulate the values (x) and their squares (x²) Add the values of x and those of x² ( x and  x²)

 Find the mean of all the values of x(x) and square it.

 Calculate the formula  =  x² -x²/n or  (x-x)²/n

Where  is the standard deviation,  is the square root of,  is the sum of, n is the number of occurrences in the set of data ,x the mean of the values and (x- xˉ)² is the square of the difference between individual values. Let us find the standard deviation for the following data set; 7, 9, 12, 13, 40, 10 and 14. We first of all find the arithmetic mean as follows; 7+9+12+13+40+10+14 =105/7 which is 15. Subtract 15 from each value (x) and find its square. Table 11.2: Calculation of Standard Deviation for Ungrouped Data x x-mean (x- xˉ) (x- xˉ)² 7 7-15= -8 64 9 9-15 = -6 36 12 12-15 = -3 9 13 13 –15 = -2 4 40 40-15 = 25 625 10 10- 15= -5 25 14 14- 15 = -1 1 Total =784

The standard deviation S.D or  pronounced as sigma is 784/7 = 2.64 For grouped data, we use the class marks (class mid-points) and frequencies to calculate the standard deviation. The formula is:  = fx²/n –(fx/n)², where x is the class mark and f the frequency. We are not going into details about this method. You will learn about it in higher levels. The standard deviation is the best of the measures of dispersion because it takes into account all the values under consideration. The smaller the number, the smaller the deviation from the normal and vice versa.

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Activity 19.1 ? List the various sources and types of geographical data.

Summary Statistics can be located on the map to show the spatial distribution or used to draw a graph to reveal differences. This gives a clear visual impression, which is actually the main purpose of graphic data representation. A variable, which can theoretically assume any value between two values, is called a continuous variable whereas that which assumes a fixed value is a discrete variable. In order to give meaning to collected data, it has to be summarised. Some statistics are simple while others are very complex. However, the most basic ones are simple descriptive statistics. These include measures of central tendency such as the mean, the median and the mode. Sometimes the data we collect is best summarised in groups. This is very true of population data. For example the population distribution of a hypothetical place may be recorded as shown below and in order to find the mean age, one has to multiply the midpoint or class mark of a class by the frequency. This is called the long method. Adding the lowest value and the highest value and then dividing by two gives the mid-point of a class.

Exercise 1. Describe the following terms: Discrete, continuous, individual and grouped data. 2. List and explain the common sources of geographical data. 3 Use the frequency distribution of masses of 6 students at the Open University of Tanzania given in Table below to find the mean, median mode and the mass standard deviation. Comment on the spread of data around the mean. Table 11.3: The Masses of Students at the Open University of Tanzania Name Weight in kgs Mary Katuku 61 George Damas 64 Ntila Wilfred 67 Naomi Rugano 70 Ruthbertha Abel 73 Anna Leba 67

4. A student scored marks in seven subjects as follows: 74, 89, 64, 59, 85, 92 and 67. Determine the Arithmetic mean of the marks.

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5. Find the range, the inter-quartile range and the standard deviation for the following set of data: 70, 94, 126, 98, 78, 102, 106, 82, 110, 122, 74, 86, 114, 90, 118.

References 1. Lines, Cliff, Laurie Bowlwell and Anne Fielding Smith (1996), A Level Geography. Study Guide. Letts Educational, London. 2. Lenon, B. J and Paul. G Cleves (1983), Techniques and Field Work in Geography. NNWIN HYMAN Limited London. 3. Nagle G and Kris Spencer (1997), Geographical Enquiries: Skills and Techniques for Geography. Stanley Thornes (Publishers) Limited.

Lecture 20 Statistical Maps and Graphs

20.1 Introduction

Geographic data can be represented quantitatively or qualitatively. When data is represented qualitatively, it is merely described. For instance, in population census we can shade a census map according to ethnic distribution, education level or sex. When data is represented quantitatively, the actual numbers or proportions are used. Statistical maps and charts are commonly used in data presentation using cartographic methods.

Learning Objectives At the end of this lecture, you will be able to:

 Explain the various geographic methods;

 Describe the various statistical maps;

 Discuss about the advantages and limitations of bar graphs, pie charts and line graphs;

 Explain the concept of comparative and group line graphs.

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20.2 Statistcal Maps Three types of statistical maps used include, choropleth, dot maps, and isopleth and flow maps. In this lecture, focus is given to choropleth and isopleth maps.

Choropleth Maps These are maps in which areas are shaded according to a prearranged key, each shading or colour type representing a range of values. You need a base map and data for a given area. Find the area in your data and device a shading scale accordingly (see Figure 12.1). You should have no fewer than four shading types and no more than ten. Shading should be darker as the values increase. Shade the aerial units and draw a scale on the map. The scale of choropleth maps shows the number of items per unit area i.e. a relationship between quantity and the area. It is commonly used to show variation in population density.

Figure 20.1: Choropleth Map Tanzania: Regional Variation in Levels of Poverty

 Work out the density per unit area (per square km)

 Choose a suitable scale to divide the values range into the number of classes preferably with the same class interval for example, 10 units as in the case of scattergram classification.

 Choose the shade or colour for high density and light colour for light density or closeness of parallel increasing with the density.  Advantage: Choropleth maps give an immediate impression of variations in values. They can also be quantitatively interpreted in terms of the areas on which the data is based.

 Disadvantage of the Method: The boundary line between each density zone gives an impression of an abrupt change of density, which is a false impression. The shading relates to an average figure for each area so variations within the area are not shown.

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Isoline or Isopleth Maps Iso means equal and pleth means value. Thus, it is a line of equal value. Isolines are lines drawn on a map, which join points of equal value in respect to a certain phenomena such as contours on a relief map, isotherms of temperature and isobars of pressure. They allow data to be plotted for a region without internal boundaries interrupting the pattern. As such, they illustrate general trends with changes in values shown smoothly. Examples of isolines include: Isoneph: A line joining all places having the same amount of cloud cover per year. Isohel: A line that join places with the same amount of sunshine days or sunshine hours per year. Isohyt: A line joining all places with the same amount of rainfall. Isotherm: A line joining places with the same amount of temperature. Isobaths: A line that joins places of equal depth in the ocean. Isoseismals: Lines that join places with the same earthquake activity or intensity. Contour: A line that joins places with the same height above sea level. The result of these lines on a map is a pattern of lines showing distribution of values or magnetic variation.

LEGEND Scale: 1:50,000

Source: URT; Ministry of Lands, Housing and Urban Development; Surveys and Mapping Division, (1978).

Figure 20.2: A Contour Map of Rugunga Village in Western Tanzania

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How to Construct an Isoline Map Isolines can only be used when the variable to be plotted changes in a fairly gradual way across space and where plenty of data is available. When drawing, one must stick to the chosen interval. All isolines must have the same interval between them.

 Firstly obtain an outline base map and then mark on it the points and their values.

 Draw the isolines in pencil first.  When you are satisfied that the lines accurately depict the distribution of values, the lines can be linked and their respective values inserted.

 To enhance the visual impression, zones between successful isolines can be coloured or shaded progressively heavier with increased values i.e. the higher the value of isolines, the darker the shading in atlases. Greens for lowlands and white for very high mountains. You should establish a key.  If you do not shade, then mark their numerical value.

Advantages of Isoline Maps

 Isoline maps are versatile, that means they are able to accommodate more than one item of data such as crop data related to rainfall data.  Isolines are ideal for showing gradual changes over space and avoid unreal effect which boundary linens produce on choropleth maps (Lenan et al, 1983:78).

Disadvantages of Isoline Maps  Some data may be interpreted in different ways and this may produce different isoline maps from the same data.

 A large number of data points increase the difficult of producing the map.

 They are not suitable for partially distributions since a large amount of data is needed for an accurate isoline map and a good deal of personal judgement is always involved.  They disguise abrupt changes which may occur in features of human geography from one locality to another.

 There is a high degree of subjectivity both in deciding where to locate the values within areas and in the interpolation of the isolines.

Flow Line Maps Flow maps illustrate the movements or flows such as traffic flows along roads or flows of migrants between countries. Observation of the movement is done at a fixed checkpoint on the route or terminals, which may be a port, bus station or an airport. The volume of flow is shown by lines whose width varies proportional to the volume of goods or numbers of people move to a certain route. A line is drawn along a road or from the country of origin to that of destination, proportional in width to the volume of the flow.

Method  Draw a base map of the route using a pencil.  Mark in all the fixed check points and the flow value in each point and tabulate the data.

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 Choose the scale for the flow line width depending on: (a) the size of the map (b) the data value range (c) the route net work density. Avoid too large and too small scale. It is advisable to work out the width of the highest value first. If the values are too high, use their square roots.  Convert all values to the scale and tabulate them.  Draw the outline of the scale and tabulate them.  Draw the outline of the flow line in pencil and finally colour it. It should be along roads or from the country of origin to that destination, proportional in width to the volume. Note that a flow line map can show a movement of goods in two directions, which means every side of the route, will take full number of items (Ibid).

Source: http://rci.rutgers.edu/~oldnb/355/links.html Figure 20.3: A Flow Line Map

Advantages

 Flow data in statistical form is represented in much more easily interpreted visual impression.

 Problems of movement such as traffic congestion are shown clearly.

 If a good scale is chosen, the map is easy to draw.

Disadvantages  A big range between data creates a problem for scale assessment i.e. where to start and where to end.

 Lack of precise interpretation due to the lack of exact interpretation.

 They create a problem in drawing a parallel double track.

20.3 Statistical Graphs

These are sometimes called magnitude symbols. These include proportional symbols, pie graphs, Bar graphs and population pyramids.

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Proportional Symbols These are symbols drawn on maps proportional in size to the size of a variable being represented such as industrial out-put. More common of these symbols are proportional spheres and cubes drawn three- dimensionally. However, many geographers use proportional bars and circles (Lanon et al., 1983:80). The length of the bar or cube will be proportional to the volume it portrays. If they are too short, the difference between them is hard to see. The bars are drawn on the base map in the location where the phenomenon represented is found. Since they are not commonly used, this lecture concentrates on graphs and charts. You are, therefore, advised to find on your own how to draw them.

Pie Graph (Divided Proportional Circle) It is a graph or circle representing the total values. It is divided into sectors each sector being proportional to the value it represents. They involve some mathematical calculations and are used to portray quantities such as population which can be divided according to ethnic groups. The segments are proportional to the components (Lenon et al 1983:73)

Method of Construction of Pie Charts

 Choose a convenient radius of the circle not too large or too small. Divide the circle into segments proportions to values of individual components. This is found as:

 Percentage of total Component*100 Total value Where 100% = 360 degrees, then 1% = 3.6 degrees

 Component as the fraction of the total angle, calculated as a decimal of the fraction of 360 degrees.  The largest component should be placed to the right of the circle. The small segments should be placed around 270 degrees to avoid error accumulation due to pencil width.

 Printing on the chart should be printed in their segment.  Small segments should be coloured to make them visible.

Advantages of a Pie Chart

 It has a striking and effective impression especially if coloured well.

 It is easy to draw.

 Two or divided circles can be used for comparison purpose provided they are of the same size. The comparison should be on components not on totals.

Disadvantages

 Pie charts lack exactness when compared to bar graphs because they have no scale.

 It is difficult to quantify any data on the pie chart without the angle measurements.

 Accumulated pencil thickness may lead to the distortion of readings particularly of small segments.

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The following is the land use pattern in Kigoma region and how it can be represented using a pie chart.

Landuse in Kigoma Region

14%

Agriculture Forestry 49% 23% Water Others Total

9% 5%

Figure 20.4: A Pie Chart

Simple Line Graph These are used for portraying the relationship between two variables, an independent and a dependent variable. The independent variable is plotted on the horizontal axis while a dependent variable goes to the y-axis. The axes should always start at zero. Always mark on the axis what the variables are. Care should be taken when choosing the scale in order to give a superb visual impression. A line graph is simple to construct, to interpret and to compare. Line used to show variations or fluctuations of values over time. A line joins these different data points. The line can be straight, with emphasis on size and fall. This is prevalent in discrete data. The line can be carved to emphasise continuity of data is in the case of temperature graphs. In both cases interpolation of values is very difficult.

Method of Construction  The horizontal line is used to show the independent variable such as time, town or year.  The vertical axis represents the dependent variables which are values or quantities in percentages or absolute numbers.  The base of y-axis must be above the last value. It is advisable to draw two vertical lines on both sides of the horizontal line. Both lines should bear the same scale and units.  Large numbers with many zeros should not be written on the scale. Write tonnes in 00, 000 or kgm in 000 and then write number along the scale.  When plotting the graph do not use crosses but rather points.

Take Note Be careful when choosing the vertical and the horizontal scale. There should be no exaggeration. If two graphs are drawn for comparison purposes, they should be of the same scale.

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Source: http://valokuva.org/?p=60 Figure 20.5: Simple Line Graph

Comparative and Group Line Graph

Method of Construction  Plot points for one item and join them and then distinguish the lines by using different colours. If colours are not used then, join the points differently.

 Write the name of the items of represented on their respective lines on the graph.

 Avoid crossing of lines as much as possible to avoid confusion that can impede interpretation. A key is essential.

 The lines on one group should not be more than five. Trend of Coffee and Cotton Export Prices in Tanzania (US $/ton)

Source: http://www.tanzania.go.tz/economicsurvey/tables/chart11a.html

Figure 21.6: Comparative and Group Line Graph

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Bar Graphs This includes the following:

Simple Bar Graphs These are used to portray information where one variable has a quantitative value and the other does not. Bars are drawn proportional in height to the value they are representing. They can be drawn horizontally or vertically. Bars are similar to line graphs in the method of construction. Bars are very impressive. They give attention to individual amounts and their relative variations. They represent a more concrete and definite quantity than a line graph. Thus, they are more quantitative in aspect than line graphs.

Method of Construction

 The horizontal scale represents a dependent value. This can change when you have horizontal bars. Bars can be drawn in groups or singly. However, all bars must start at zero. If they are drawn for comparison purposes, they should be drawn to the same scale.

 Horizontal bars should be used when there is no element of time.

 When vertical bars are drawn, the sequence of time is from left to right.

 The scale of the graph should not be too small or too large. The width of bars is not to scale.

 There must not be more than five bars together.

Source: http://www.swiftchart.com/examplebar.htm

Figure 20.7: Simple Bar Graph Advantages  Horizontal bar graphs allow the addition of more information.  Bar graphs can be drawn in conjunction with line graphs.  A bar graph can acquire the idea of location when it is superimposed on the map where the data was collected.

Comparative or Group Bar Graphs In this type of a graph, bars are used for comparison purposes. Each bar stands for a particular item such as mineral or crop production. Whereas in line graphs, the rise and fall of lines is used for comparison, in bar graphs it is the length of bars that is used to compare items. The total length of individual bar put together or indicates the total production of minerals or crop production in that year.

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Population of Kigoma Region

1967 1978

1988 Population

Kigoma Urban Kigoma Rural Kasulu Kibondo District

Source: Tume ya Mipango na Ofisi ya Mkuu wa Mkoa wa Kigoma (1999): Hali ya Uchumi na Maendeleo ya Jamii Mkoa wa Kigoma uk. 9 Figure 20.8: A Comparative Bar Graph

Methods of Construction of Comparative Bar Graphs  Choose a suitable scale and draw them as simple bar graphs.

 To compare well, place the related bars close to each other. Usually the longest bar is drawn to the extreme left and then progressing to the right.  The bars for the values to be compared wit must be at the end of the right.

 Insert the key. For convenience it is better to compare not more than four bars in one bar graph. If bars represent two different phenomena, the scales must be two. For example: one for crop production and the other for rainfall.

Advantage of Comparative Bar Graphs  They offer a good visual impression of the total values and that of individual components.

 They are good in comparing individual items.

Disadvantages of Comparative Bar Graphs

 Group bar graphs do not give precise accurate information of the totals. This can be avoided by drawing the bars as percentage of the total.

 The attention is put more on quantities rather than the fall and rise. The graph depicts the deviation of quantities from a mean value or certain chosen value. The divergence bar graph is used to show the production trend with reference to an ideal quantity. The bars help to predict problems before they occur in production or consumption.

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Source: sciencedirect.com Figure 20.9: Divergent Bar Graph

Method of Constructing Divergence Bar Graphs  The average should be given a zero value and must be thickened on the x-axis.  The vertical axis should be scaled with positives above the zero line and negative below zero line.  Observe the highest and lowest values and then choose a scale.  Plot the values from the zero line.

Population Pyramid This is another form of bar graphs. The vertical axis shows age groups in five year intervals. The horizontal axis represents the actual number of people in each age group. The males are usually plotted on the left and females on the right of the vertical axis (Lenon, et al., 1983:74) The youngest age group form the base of the graph. The length of the column or bars varies with either absolute values or percentage of the total of that sex in the group. If the values are to be given in percentage, they are calculated as follows:  Divide the number of males in each age group by the total number of males times 100.  Divide the number of females in each group by the total number of females times 100.

Method of Constructing an Age-Sex Graph  Obtain statistics from regional or national census report taking the number of males and females separately.  On a graph or normal paper draw two vertical axes one centimetre apart. Indicate males on the left and females on the right to represent the age groups.  Construct the bars 5mm in width starting with one side then another. Care should be taken when choosing the scale to avoid too having too long bars.

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Source: Population Planning Unit and Bureau of Statistics (1995): Population Development in Tanzania, Dar es Salaam, p.8 Figure: 20.10: Population Pyramid Graph of Tanzania, 1990 Advantages  When used for comparison they reveal interesting sociological aspects as age groups with many or few people, age distribution of a developing or developed country.  Represents a clear picture of population summary. The total can be easily found.  When used for comparison, they can be superimposed.

Activity 1 ? What is the other name for statistical maps? List the various statistical maps used to depict the data in graphical form.

Summary Geographical data is best summarised and represented statistically by using statistical maps, and charts. Each type of representation is suitable for specific kind of data. It also has advantages and disadvantages. Continuous data is represented using line graphs while discrete data is represented by charts. It is, therefore, important to critically analyse the data before choosing a particular method of representation to use.

Exercise 1. Using the following climatic data of a hypothetical place, draw a vertical bar graph and comment on it.

Month J F M A M J J A S O N D Rainfall in mm 5.2 5.2 5.2 0 17.8 48.1 61.7 33.8 26.5 63.5 18.0 2.5

2. Use the following data to draw a horizontal bar graph and give your own comments. Cropland 6%, Pasture 40% Forest 48% Water and wasteland 6% 139

References 1. Lines, Cliff, Laurie Bowlwell and Anne Fielding Smith (1996); A Level Geography. Study Guide. Letts Educational, London 2. Lenon, B.J and Paul .G Cleves (1983); Techniques and Field Work in Geography. NNWIN HYMAN Limited London 3. Nagle G and Kris Spencer (1997); Geographical Enquiries: Skills and Techniques for Geography. Stanley Thornes (Publishers) Limited 4. Population Planning Unit, Presidents’ Office, Planning Commission, Bureau of Statistics, National Family Planning Programme, Ministry of Health (1995); Population and Development in Tanzania, Dar es Salaam 5. Tume ya Mipango na Ofisi ya Mkuu wa Mkoa wa Kigoma (1999); Hali ya Uchumi na Maendeleo ya Jamii, Mkoa wa Kigoma, Dar es Salaam 6. URT, The Vice President’s Office. (1998); The National Poverty Eradication Strategy. Dar es Salaam: Government Printer 7. URT, The Presidents’ Office-Planning and Privatisation (2003): The Economic Survey 2002, Government Printer, Dar es Salaam.

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Lecture 21 Topographical Map Interpretation

21.1 Introduction In the preceding lectures, you learnt about the extent to which your land can be developed to raise the standard of living of your society. Furthermore, you have been exposed to methods of measuring, recording and interpreting phenomena as geographers. In this last lecture, you will be further enlightened about topographical map interpretation. The word topography is derived from a Greek word topes, which means place. It is a term used to describe all physical features of a given area. Topographic maps are small-scale drawings of part of the earth’s surface to show location, landscape and cultural features. It is important to represent parts of the landscape in order to facilitate easy representation and interpretation of features.

Learning Objectives At the end of this lecture, you will be able to:  Explain the common types of maps in relation to their characteristics;

 Calculate areas from maps using a variety of methods;

 Calculate the bearing of a place through use of magnetic compass;

 Relate features on the map to those found on actual piece of land i.e. use of large-scale maps;

 Discuss the advantages and disadvantages of topographical maps compared to photographs;

 Draw a relief section and calculate gradient and vertical exaggeration. 21.2 Topographical Map A map is a portion or part of the features of the earth’s surface drawn to scale on a plane surface such as paper, card, plastic, cloth or some other material (Dura, 1990:1). The information given on a map sheet includes: the title of the map, the scale of the map, the indication of the North direction, the key, the boundary and, the latitudes and longitudes or grid lines. There are a number of maps. However, most of the maps are grouped into two main types – Topographic maps and statistical or distribution maps. The later were covered in lecture eleven. Here, our focus is on topographic maps.

Topographic Maps These are small-scale maps, which show both natural and man-made features. To make these maps aeroplanes are used to take pictures for an area for the first survey. Later, only certain points on land need to be measured and surveyed. When all the necessary data has been compiled it is then used to print and produce maps. The actual surface of the land is rarely smooth. Nevertheless, this is represented on a flat surface. The map must represent all surface relief on flat paper and the mapmaker cannot show all these details. More 141

often a mapmaker summarises information about the landscapes represented. Reflecting from this situation, maps are not true, detailed copies of portions of the earth’s surface (McMaster, 1978:5). Any topographical map is much smaller in size than the actual tract of country it represents. In order to be more realistic the mapmaker must reduce all the distances and areas on the ground in the same proportions. This constant relationship of lengths on the ground to the shorter areas on the map is the scale of the Statistical or Distribution maps The statistical or distribution maps are the type of maps which have been made with the help of exact statistics. These maps show such things as distribution of rainfall, temperature, pressure, vegetation, crops, minerals and many other things. The commonly used Statistical or Distribution maps are the Atlas maps. Atlas maps are maps drawn on small scales. They show whole countries, continents or even the world on a single sheet of paper or page.

21.3 Map Scale

A scale is the relationship or ratio between the distance on the map and the true distance on the earth’s surface. Scale = Distance on map/distance on earths surface We can identify three main types of scale: statement scale, representative fraction scale and linear scale.

Statement Scale This is the map scale stated in words. The scale may be stated verbally for example ‘one centimetre to one kilometre’.

Representative Fraction (R.F) This is a means of expressing the relative size of a map or drawing in terms of a fraction. R.F scale is frequently expressed as a fraction with the numerator as one. The ratio means that one unit on the map represents a given number of units on the ground for instance, R.F 1/100,000 or as a ratio 1:100,000. This means that one unit on the map represents 100,000 units on the ground. If the unit used is centimetres, it means that one centimetre on the map represents 100,000 centimetres on the ground (1 km. =1000m*100 cm) Conversion can be done as follows: (i) One centimetre to two kilometres 1 cm: 2 km 1 cm: 2*100,000 or 1/200,000 R.F =1:200,000

Linear Scale or Line Scale Is a line showing the distance on the map that represents a given distance on the ground. In many cases a linear scale is placed at the bottom of the map. It is divided into two sections.  The large section to the right is divided into equal units from 0 towards the end of the scale to the right. e.g. 0 1 2 3 4 km. This is also called the primary section.

 The small section or secondary section: This is a small section placed to the left of 0. It is subdivided into fractions indicating smaller units of measurements such as 0, 250, 500, 750 metres.

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m-1000-----500-----0------1------2------4------5-km Secondary section Primary section

Conversion of One Scale into Another According to McMaster (1978:6) a scale can be converted into another as follows:

 Given the R.F or ratio, to find the number of centimetres to the kilometre divide by 100,000 (the actual number of cm in a km) by the denominator of the fraction e.g. 1/250.000 write 250,000/100,000 which gives 40 cm to a kilometre.  Given the number of kilometres to a centimetre, to find the R.F: Multiply 100,000 by the number of kilometres to the centimetres and you will have the denominator of R.F e.g. two kilometres to the centimetre, write 2*100,000 which gives 1/200,000.  Given the number of centimetres to the kilometre, to find the R.F: divide 100,000 by the number of centimetres to the kilometre in the scale. What you get is the denominator of the R.F. For instance five centimetres to the kilometre: Write 5/100,000, which gives 1/20,000.

21.4 Types of Maps by Scale There are three common types of map scales; small, medium and large scale maps. On a small-scale map the degree of reduction is much less and the ratio will be a smaller number. In East Africa small scale maps are drawn to the scale of 1:1,000,000, 1:500,000, 1:250,000, 1:50,000. Medium scale maps are drawn at 1:25,000, 1:10,000 and 1:2500.

Take Note If a linear scale is doubled, areas will be quadrupled. It follows that a map on a scale of 1:100,000 can show four times as much country as one on the same sheet of paper at 1:50,000.

Activity 1 ? Why is the denominator of a small-scale map larger than that of a large-scale map?

The type of the scale therefore determines the size of the map or the distance on the map and the true distance on the earth’s surface.

Measurement of Distance along a Road or River You need to follow the following procedure:

 Divide the required route by light pencil marks into portions that are nearly straight.

 The next thing you should do is to measure carefully each of these sections with dividers or the edge of a piece of paper and note down the measurements.  Add the lengths of various sections together and measure the total length on the linear scale.

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Measurement of Areas Areas can be regular or irregular in shape. It is very simple to find their areas.

Regular Shapes These are in form of rectangles, squares or rectangles. For a four-sized figure, the area is found by multiplying the width times length. This implies that you first measure the lengths. The area of a triangular shape is found by first measuring the length of the base of the triangle, then measure the length of the perpendicular from the base to the apex. The area is half the first measurement multiplied by the second.

Irregular Shapes Unlike the regular shapes, irregular shapes cannot be accurately done using simple direct methods. What you need to do is:  Divide the required shape approximately into rectangles and triangles or even circles.  Calculate the area of these shapes and add up the result.  Another method is to divide the area into equal squares of known area.  Then count the number of full squares of known area and each part of a square as half square and then add them together to get the total area.  Instead of dividing the area into equal squares, you can also trace the area to be measured.  Trace off the outline of the area to be measured on square tracing paper and transfer the outline on square paper.  Tick off all completed squires in the outline and add up the total.  Mark with dots all the half squares. Add up the total and divide by two.  To get the total area add up the number of complete squares and that of the half squares.  Using the map scale provided, find the area of one square in order to calculate the approximate total area.

Striping Method  Trace the shape of the area on paper to be measured.  Draw stripes of uniform width to cover the whole area.  Calculate the areas of each strip, which is a rectangle. The area obtained is the sum of individual strips and should be given in the same units of the scale of the map. Find the area of the rectangle and the two triangles, and then add up their areas.

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Figure 21.1: Measurement of Area

Measurement of Direction Geography deals with places in relation to others. In order to determine the direction of a place, we need to choose one direction from which we can measure other directions. So, for this purpose we normally use the North and the needle of the compass used to measure direction points approximately towards the north. This direction is usually indicated at the top of a sheet of map or in the border. Where more than one north is given, stick to the true north or simply north. The geographic position of a place on a map may be shown using the following: (i) Place names (ii) Compass bearing, (iii) Latitude and longitude, (iv) Grid reference Names of places on maps are commonly used to locate position of an area or places. In Tanzania names of places such as Kigoma, Bukoba, Dar es Salaam are clearly indicated. However these have their disadvantages in that one name can appear in two places. Moreover the name occupies much space on the map than the area actually represented and thus difficulty to locate a place precisely. 1. The North Direction and Position of Places: Direction is best given using a compass. A compass is an instrument used to find direction. It consists of a free-swinging magnetised needle which points to the North and South magnetic poles. Using a geographic or true north, Magnetic North or a grid north may show the north direction on a map. The Geographic or true north is the direction towards the 90° North latitude. Magnetic North is the direction shown by magnetic compass, which always points to the magnetic north pole. This is situated to the left of true north and varies from year by year in relationship to the true north. The grid north is the direction towards the north in maps drawn to grid system. 2. Compass Directions: The compass directions are measured from the North along a 360° circle. The eight compass directions are: North, North East, East, South East, South, South West, West and North West. Each of these is 45° degrees from the next.

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Figure 21.2: Compass Directions Using the compass direction, the direction is given as an arc in 360° beginning from north, swinging right in a clockwise direction until you reach the point the point you want to measure. Therefore the direction of north is 0°, East is 90°, South is 180° and West is 270°. By using this method you are able to give an accurate measurement of direction to a degree or even a fraction of it. The direction of a place can be given with respect to another. Bearing of a Compass (or Direction): Compass bearing shows the direction of a place in relation to another point measured clockwise from 0° to 360°. The position of a point is given in degrees which can further be divided into minutes and seconds. To find the bearing of a place from another place you need to follow the following procedure:

 Join the two points. In our example below, join x and y with a straight line.

 At point x draw a line parallel to the north-south line given on the map.  Using a protractor, measure the angle of y from north towards line AB. The bearing of point y from x is 130° or y bears 130° from x or y is South East of x. Up to this point you are now aware that some of the problems encountered when using place names to determine location of places can best be solved by combining names with bearing and distance. For example Kibaha is twenty kilometres West of Dar es Salaam City. 3. Latitude and Longitude: The position of a place can also be given using latitudes and longitudes. Indeed, latitudes and longitudes provide the international reference system that locates any place on the earth’s surface. These are the most geographical way of giving position. For that matter, these measurements are always needed in making accurate maps. Longitudes and latitudes are indicated on map margins. Latitudes and longitudes are angular measurements from the centre of the earth. That is why they are given in degrees, minutes and seconds of arc. Latitude is measured northwards and southwards from the centre of the earth. It describes how far north or south of the equator a place is. A circle joining places of the same latitude at the earth’s surface is called a parallel of latitude. A longitude on the other hand is an angular measurement eastwards or westwards from the centre of the earth. A meridian of longitude is the shortest line that can be drawn on the surface of the earth. It joins the North Pole and the South Pole. Many countries have accepted the meridian of the Greenwich as the Prime meridian from where other meridians are measured. It is 0°.

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Take Note The Greenwich is just a convention. A country is at liberty to choose any other meridian as its prime meridian for its measurements.

Any point on the earth’s surface can be accurately pinpointed using these lines as there is only one point on earth that corresponds to any one set of figures. To be more precise, the N, S must be added to latitudes and E, W to longitudes. When stating the position you must first give the latitude and then the longitude. It is common to write minutes (´) and seconds (´´). For example the location of Dar es Salaam is 6°48´S 39°12´E. Large areas on the Atlas map can also be located by using lines of latitude and longitudes.

Activity 2 ? Using latitudes and longitudes, what is the location of your home district?

4. Grid Reference: Unlike latitudes and longitudes, Grids belong to the map and have no relationship to the ground. The network of gridlines forms perfect squares. In East Africa usually these squares have sides of 100 km, 10km and 1km. The grid lines are numbered from a particular point, usually the South-Western corner of the whole country. This is named the grid origin. From the origin all vertical lines (eastings) are numbered eastwards. In contrast, all horizontal lines are numbered northwards and they are called northings. The numbers at the top and bottom of a map refer to vertical lines i.e. the eastings. The numbers along the left and right hand borders refer to the edges of a grided square. The reading in a Grid system is referred to as a grid reference and is given in a six figure number. Always remember to give the eastward direction and then the northward direction.

Figure 21.3: Grid Reference The vertical lines are called easting because their numbers increase towards east. The horizontal lines are called northing because their numbers increase towards north. Grid reference is written in six digits. E.g.: 105605

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21.5 Relief Features on a Map The relief of an area is the surface form of the ground, which show size, shape, slope, etc., of the highlands and lowlands. The relief of an area may be represented in many ways on a map. These methods include indication of spot height, trigonometric points, hill shading, layer colouring and contouring. Our attention is drawn to contouring. Nonetheless you are free to look for details about other methods.

Use of Contours A contour is a line on a map connecting all places of equal height above sea level. When you interpret contour lines you are able to get the size and shape of highlands and lowlands. Contour lines never cross each other because no one point can be at two different heights above the Mean Seal Level (M.S.L). On very steep slopes they are close to each other but they cannot cross each other. Contours are drawn in regular steps measured vertically from M.S.L. These steps are called Vertical Interval (V. I) such as 100, 150 or 200 metres. The V.I is normally kept constant on a map and it is indicated in the margin of the map. It is common to thicken the contour lines at a given interval in order to make them easily identifiable. In many cases they are coloured in brown, orange and red. Contour lines are numbered along them to indicate their height above M.S.L. in such a way that higher ground lies above the figures. From the numbering of contours you can determine the direction of the slope and the height of the numbered contour lines correctly.

Some Facts about Contour Lines

 Contour lines close or join around hills, basins and depressions. In hills the higher contours are in the middle.

 Contour lines never cross each other.

 Contour lines form a V-shape pointing upstream to denote a valley and a V pointing down to denote a spur.  In contour maps all contour lines close or extend to the map edge.

Land Forms on Contour Maps

 Highland landforms: These include, plateaus hills, ridges, spurs, slopes, scarps, passes, saddles and watersheds.  Lowland landforms: These include gorges, levees, deltas, flood plains, and V-shaped valleys.

 Coastline landforms: They include, estuaries, cliffs and corals, fringed coastlines. Since you have already learnt how to represent these features using contour lines in your O-level secondary education we will only remind ourselves how to draw a cross section and calculate the vertical exaggeration and gradient.

Cross Section or Profile Maps show relief in plan. It is important to visualise the appearance of the features as they are seen from the ground. Constructing relief sections helps to do this. The following are steps to be followed when constructing a relief section (cross section).

 Identify the two end points of the required section on a map. Note their positions and heights and the vertical Interval. Mark them as A and B and join them with a pencil. 148

 Place the straight edge of a plain paper along the drawn line and mark the end points A and B.

 Mark along the edge of this paper, the positions and heights of contours, water features and important places that cut the line.

Source: http://user.gs.rmit.edu.au/caa/topo/contours.htm Figure 21.4: A Cross Section

 Remove the paper from the map and place it where you intend to draw the cross section. The width of the cross section will be the distance between A and B. Draw a line equal to the width.

 Find the appropriate vertical scale to show the heights of contours such as 1cm to 100m.

 Construct a frame for the relief-section by drawing perpendicular lines from A to B and divide the heights into equal parts according to the vertical scale you have chosen.  Place the marked paper along the base line so that AB on the paper lies on AB on the framework.

 Mark each contour line along the horizontal line and proceed with others according to their heights.  Connect all the points with a pencil. You should smoothen hills and valleys with a smooth curve.

 Mark and label the required information. Indicate the North, add a title to the cross section, as well as the vertical and horizontal scale.

Take Note The horizontal scale is the map scale. The vertical scale is usually exaggerated.

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The Vertical Exaggeration This is the amount or number of times by which the vertical scale or height is larger than the horizontal scale or distance. This relationship is important as it determines the shape and size of features shown such that they are not too small or too large. Horizontal Scale V.E = Vertical Scale If the map scale is 1:50,000 and the vertical scale is 1 cm to 100m, 5 0 , 0 0 0 V . E = 5 = 1 0 , 0 0 0

Horizontal Equivalent (H.E) Horizontal Equivalent is the horizontal distance between two contour lines. H.E is smaller when the slope is steep and larger when the slope is even or gentle. Where there is a cliff there is no horizontal equivalent.

Gradient Gradient is the slope of the land. It is expressed as a ratio between its Vertical Interval and Horizontal Equivalent. Thus, Difference in height in metres Gradient = Distance in metres For example, if the difference in height between two places is 100 metres and the horizontal distance is 1,000 metres, 100 G =1/10 or= simply 1 in 10 1,000 This means that for every 10 metres of distance travelled the land rises by 1 metre. Gradient can also be expressed as an angle.

Activity 21.1 ? How the measurement of direction is done using geographic position of a place on a map?

Summary The two main types of maps are topographic and statistical maps. Topographical maps are small-scale maps and mainly show natural and man-made features. These features are reduced in size on scale to fit them on a map. Three common types of scale include: statement scale, representative fraction, and linear scale. The three scales are convertible from one to another. On small scale maps actual distances are greatly reduced thus giving a big ratio as opposed to a large-scale map. Distance on a map can be measured using a pair of dividers, a piece of paper, or thread and then placed along a linear scale to get the actual distance. Measurement of area of both regular and irregular shapes is also possible using mathematical procedures. 150

Geography emphasises spatial location of phenomena. Thus, indication of location and direction of areas is very important. Indication of the True North direction is important for measuring direction of one place from another. The common ways of giving the location of places or features is the use of place names, compass direction, latitude and longitude and the use of grid reference. Apart from measurement of direction, distance and area on maps, we also show various features. Relief is well represented by contour lines. In order to get their actual appearance on the ground, we draw a relief section using two scales – the horizontal scale and the vertical scale. The horizontal scale is a map scale while the vertical scale is chosen when drawing the cross section. Owing to this, the actual size and shape of objects can be exaggerated. Therefore, after drawing a cross section, you are advised to calculate the vertical exaggeration in order to show the extent to which your features are larger than if they were drawn to the scale of the map. The land is not even. Sometimes we are interested in knowing the slope or gradient of the ground. This is easily found by dividing the difference in height by the difference in horizontal distance.

Exercise 1. Using a given map of part of Rugunga village in Kibondo district, Tanzania: (a) Explain the kind of landscape represented on the map. (b) Calculate the approximate area of land shown on the map. (c) Find the bearing of Kavogoro hills from Samvula hills. (d) Give the grid reference for Samvula hills.

Scale: 1:50,000 LEGEND

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Source: URT; Ministry of Lands, Housing and Urban Development; Surveys and Mapping Division, (1978).

Figure 22.5: Rugunga Map Extract 2. If the scale of a map is 1:50,000 what length on the map will represent a distance of 20 km on the ground. 3. Look at the map of Africa and give its location using latitudes and longitudes. 4. (a) Draw a cross section from A to B on the following hypothetical contour map. (b) Calculate the vertical Exaggeration of the resulting cross-section.

References 1. Dura, S.E (1990), Map Reading and Photograph Interpretation for Secondary Schools “O ” Level. ILM Publishers Ltd, Dar es Salaam. 2. McMaster, D.N. (1988), Map Reading for East Africa, (4th Ed), Longman Tanzania Ltd, Dar es Salaam.

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