PROF P. SANKARA PITCHAIAH M.Sc. Ph.D., M.A., Ph.D. (Psy), PGDHRM

Professor of Geology & Psychologist Acharya Nagarjuna University Nagarjuna Nagar – 522510

1 Geology ▪ Mineralogy ▪ Petrology ▪ Stratigraphy ▪ Physical ▪ Structural ▪ Economic Geology Geology

• The word ‘Geology’ is derived from the Greek words ‘Geo’ meaning ‘the Earth’ and ‘Logos’ meaning ‘science’. Therefore, Geology is the science of the earth.

• It is a fascinating subject which feels the pulse of the earth. Branches of Geology

• Geology is an interdisciplinary subject and subdivided into many branches. But these subdivisions are arbitrary and overlap with each other. The major branches explained here. • Crystallography • Economic Geology • Engineering Geology • Environmental Geology • Fuel Geology • Gemology • Geochemistry • Geophysics • Geoinformatics • Geo-Tectonics • Geographic Information System (GIS) • Geographical Positioning System (GPS) • Historical Geology • Stratigraphy • Hydrogeology • Marine Geology (Geological Oceanography) • Meteorology • Mineralogy • Mining Geology • Paleontology. • Petrology • Photogeology • Physical Geology • Geomorphology • Remote Sensing • Rock Mechanics • Structural Geology MINERALOGY

• A mineral is a naturally occurring inorganic solid, with a definite chemical composition and an ordered atomic arrangement. The study of minerals is known as Mineralogy. • Some of the minerals are shown in Plates. Quartz Crystal Quartz

Orthoclase Feldspar Plagioclase Feldspar Some of the minerals (Contd…) Olivine Pyrite

Calcite Barite Some of the minerals (Contd…) Mica Asbestos

Garnet Gypsum Some of the minerals Formation of Minerals Minerals may be formed from; 1. Cooling and crystallization of magma or lava 2. Recrystallization due to metamorphic processes and metasomatism 3. Lithification, cementation and compaction during the diagenesis of sediments 4. Sublimation from volcanic gases 5. Precipitation/evaporation from aqueous solutions and hydrothermal brines 6. Formation by weathering, transportation and depositional processes

Methods of Study of Minerals

Minerals can be studied using two methods. They are; • Analytical Methods and • Observation of Physical Properties Analytical Methods

Most important laboratory methods of mineral analysis are given below. 1. The Chemical analysis 2. Emission spectral analysis 3. Flame photometry 4. Atomic-absorption analysis (AAS) 5. The X-ray spectral analysis 6. Radiometric methods 7. Radio activation analysis 8. X-ray diffraction methods 9. Electronic microscopy 10. The thermal method 11. Infrared spectroscopy 12. Optical spectrophotometry 13. Fluorometric analysis 14. Resonance Spectroscopy 15. Mass-spectrometry 16. Thermobarometric analysis Physical Properties of Minerals

Minerals can be described by various physical properties which relate to their chemical structure and composition. Common distinguishing characteristics include; Crystal habit Hardness Luster Diaphaneity Colour Streak Tenacity Cleavage Fracture Parting Specific Gravity Cohesion Elasticity Diapheneıty Twinning Acid Test Isotropism Anisotropism Polymorphısm Magnetism Taste Odour Feel PETROLOGY • It is the study of rocks including the origin, texture, mineralogical composition, distribution, structure, and history of rocks.

• Rock is a naturally occurring solid and an aggregate of one or more minerals or mineraloids (mineral without crystallinity) within a ground mass. • For example, granite is an aggregate of quartz, feldspar and biotite minerals. Geologists grouped rocks into three categories based on their origin: Igneous Sedimentary and Metamorphic Each category is then further subdivided.

Igneous rocks • An igneous rock is any crystalline or glassy rock that forms from cooling of magma. Igneous rock (derived from the Latin word igneous meaning of ‘fire’) forms through the cooling and solidification of magma or lava. This magma can be derived from partial melts of pre-existing rocks. • Igneous rocks are divided into two main categories: plutonic and volcanic. • Plutonic rocks result when ‘magma’ cools and crystallizes slowly at the deeper parts of the Earth's crust, ex., granite. Volcanic rocks originate from ‘lava’, ex., basalt. If magma exposed on to the earth it is called lava. • The rocks formed at the intermediate depths are called hypabyssal rocks, ex., Dolerite. About 64.7% of the Earth's crust by volume consists of igneous rocks. Granite and Basalt rocks are shown in Plates. Granite Basalt

Dolerite Sedimentary Rocks • The processes of weathering, erosion, transportation and deposition accumulates the sediment (loose grains). As sediment accumulates it becomes compacted and cemented with time (thousands of years) . Over a period of time the sediment will be lithified into the sedimentary rocks. Some common sedimentary rocks are shale, sandstone, limestone and conglomerate.

• Broadly, sedimentary rocks are grouped under three categories. They are : 1. Intrabasinal rocks 2. Extrabasinal rocks and 3. Pyroclastic rocks. 1. Intrabasinal rocks Three rock groups are placed under intrabasinal category (1) Carbonate rocks- Limestone (2) Authigenic rocks- Fe ore, Mn ore (3) Carbonaceous rocks- Coal 2. Extrabasinal rocks The important rock types included under this category are 1. Shales 2. Siltstones 3. Sandstones and 4. Conglomerates. 3. Pyroclastic rocks Ex: Pumice, Agglomerate . Sandstone Shale

Lime stone Laterite Some typical sedimentary rocks Metamorphic rocks • Metamorphic rock is any rock that has been altered by heat, pressure, and/or the chemical action of fluids and gases.

• This process is called metamorphism; meaning to "change in form". The result is a profound change in physical properties and chemistry of the rock. Classification • Metamorphic rocks are classified based on their structure.

1. Foliated rocks Slate, Phyllite, Gneiss, Khondalites

2. Non-foliated rocks Schist, Quartzite, Marble, Charnockite, Amphibolites, Hornfels

Some of the typical metamorphic rocks are shown in Plates. Slate Marble

Schist Gneiss Some typical metamorphic rocks STRATIGRAPHY Stratigraphy is the study of stratified rocks as a record of geological history. It is similar in content to Historical Geology. Principles • Lithology • Order of superposition • Present is key to the past • Correlation

PHYSICAL GEOLOGY • It deals with the internal and external agencies and various processes such as wind, water, glaciers and sea waves that bring about changes on the earth’s surface. Weathering disintegrates and decomposes rocks.

• Geomorphology is the study of the history and origin of earth’s landforms. The content is similar to Physical Geology. It also concerned with the features under the oceans, and chemical, physical, and biological factors that act on them. Geological Processes

• The term "geological process" describes the natural processes that shape the physical makeup of a planet. Weathering, erosion, transportation, deposition and plate tectonics are some of the such processes significantly mould the Earth’s surface and account for its major features. Weathering • Weathering is the breaking up of mineral and rock surfaces by the geomorphological agents, such as the air, ice and water. Because of weathering a hard rocks and minerals transformed into a soft loose sediment. There are two important types of weathering; o Mechanical weathering o Chemical weathering and o Biological weathering Mechanical Weathering • Mechanical weathering causes the breakdown of rock material into smaller and smaller pieces with no change in the chemical composition. The mechanical weathering occurs with the following processes. Chemical Weathering

• Chemical weathering is a process that decompose and breakdown rocks. This type of weathering changes the composition of rocks. Chemical weathering is a gradual and ongoing process as the mineralogy of the rock adjusts to the near surface environment. New or secondary minerals develop from the original minerals of the rock. Biological weathering

• A number of plants and animals may cause chemical weathering through release of acidic compounds. Mineral weathering can be initiated and/or accelerated by soil microorganisms. Lichens on rocks are thought to increase chemical weathering rates. Geomorphic processes Geomorphic processes are primarily classified into three categories depending on the origin. They are; 1. Exogenic process (Epigene) 2. Endogenic process (Hypogene) 3. Extraterrestrial process Geological work by Rivers

Fluvial Processes • River is the main agent in the fluvial environment. • The point at which a river starts is called its source. • As the river continues to flow downstream it may be joined by smaller rivers called tributaries. • The point at which these smaller rivers join the main river is known as confluence. • As the river continues its journey, eventually reaches the sea – the point where the river flows into the sea is known as the river mouth. • The path the river follows from its source to mouth is known as the river course. • When studying rivers we often divide it into 3 main sections, the upper course; middle course and lower course. Erosional Landforms • The important erosional landforms are; • Potholes • Rapids • Waterfalls • Pools and Riffles Depositional Landforms • Sand and gravel bars • Point bars • Dunes and ripples • Flood plains • Deltas • Alluvial Fans Erosional Landforms

Potholes Water falls

Point bars Flood Plains Alluvial Fans Ox-Bow Lake Geological work by Wind Aeolian processes • In aeolian processes, wind transports and deposits particles of sediment. • The particles deposited are of sand, silt and clay size. The particles are entrained in by one of four processes. • Rolling occurs when a particle rolls or slides across the surface. • Lift occurs when a particle rises off the surface due to the Bernoulli effect. • If the airflow is turbulent, larger particles are transported by a process known as saltation. Finally, impact transport occurs which one particle strikes another causing the second particle to move. Erosional Landforms • Deflation • Abrasion • Aeolian Landforms • Blowouts • Ventifacts • Yardang • Desert pavement • Desert varnish • Dreikanter Blowout Ventifacts

Yardang Depositional Landforms

• Dunes • Barchan dunes • Transverse dunes • Longitudinal dunes • Star dunes • Parabolic dunes • Transverse dunes • Longitudinal dunes • Star dunes Barchan dunes Transverse (Seif) Dunes Geological work by Glaciers

• Glaciers are large masses of ‘flowing’ ice formed by the accumulation and compaction of recrystallized melted snow about 10% of the earth's land surface. 96% of mass, currently in two glaciers, the Greenland and Antarctic ice sheets. Internal plastic deformation by slippage within ice crystals and recrystalization form the glaciers. Erosional Landforms • Glacial U-shaped Valleys • Fjords • Hanging Valleys • Cirques Depositional Landforms • Ice sheets and Alpine Glaciers • Ice caps • Piedmont Glaciers • Icebergs • Moraines • Paternoster Lakes • Kettles • Erratics • Drumlins • Outwash Plain • Eskers Cirques Hanging Valleys

Iceberg Drumlin Esker Geological work by Waves and Tides Coastal Processes • Coastal environments are under the influence of the marine, the terrestrial environment, the atmosphere, biosphere, fluvial systems and tectonic processes. • The shoreline refers to the exact area where the land meets the sea, and coast refers to the land adjacent to the shoreline. The ‘coastal area’, includes the coast, shoreline, and near-shore area. • The three important coastal processes that influence coasts are erosion, transportation and deposition. Coastal Landforms • Coastal landforms include shoreline and near- shoreline features, as well as some coastal plain landforms far removed from the modern ocean by long term sea-level changes. Erosional Land Forms • Sea Cliffs • Sea Arches • Wave-Cut Scarps and platforms Depositional Landforms • Beaches • Barrier Islands • Beach Ridges • Spits • Deltas Sea cliffs Sea Arches

Wave cut platform Spit Mass Movement/Wasting • Mass wasting is the down-slope movement of rock and sediments due to the attraction of gravity.

Types of mass movements • Soil creep- Slow downward progression of rock and soil down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress, the gradual downhill movement, under the force of gravity, of soil and loose rock material on a slope. • Mud flow- Flow of water that contains large amounts of suspended particles and silt. It has a higher density and viscosity than a stream flow and can deposit only the coarsest part of its load. Its high viscosity will not allow it to flow as far as a water flow.

Mudflow • Earth flow- An earth flow is a down slope viscous flow of fine-grained materials that have been saturated with water, and moves under the pull of gravity. It is an intermediate type of mass wasting that is between downhill creep and mudflow.

• Solifluction- The gradual movement of wet soil or other material down a slope, especially where frozen subsoil acts as a barrier to the percolation of water.

• Landslide- A collapse of a mass of earth or rock from a mountain or cliff. • Land slumps/slip- It is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or rock layers moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface.

• Rockfalls- An avalanche of loose rocks, refers to quantities of rock falling freely from a cliff face. Rockfall STRUCTURAL GEOLOGY

• It is ‘the study of structures found in rocks’, namely folds, faults, joints, unconformities etc.

• The Study of three-dimensional distribution of rock units with respect to their deformational histories is called Structural geology. Strike and Dip • Strike and dip are measurements of the orientation and slope of a rock. Geologists use these measurements to map geologic structures. • Strike: The strike of a rock is the orientation of a horizontal line drawn perpendicular to the dip. • Dip: The dip of a rock is the angle between horizontal and the slope of the rock. • Strike and dip are determined in the field with a compass and clinometer or a combination of the two, such as a Brunton compass. • Apparent dip: Any dip measured in a vertical plane that is not perpendicular to the strike line. Strike & Dip Folds • These are undulations, commonly form in rocks. Some folds are few miles away, others to be measured in feet or inches or even in fraction of an inch. • Parts of a fold: Looking at a fold surface in profile the fold can be divided into hinge and limb portions. The limbs are the flanks of the fold and the hinge is where the flanks join together. • The hinge point is the point of maximum radius of curvature for a fold. • The crest of the fold is the highest point of the fold surface, and the trough is the lowest point. The inflection point of a fold is the point on a limb at which the concavity reverses; on regular folds, this is the midpoint of the limb. Parts of a Fold • Fold tightness: Fold tightness is defined by the angle between the fold's limbs, called the interlimb angle. Gentle folds have an interlimb angle of between 180° and 120°, open folds range from 120° to 70°, closed folds from 70° to 30°, and tight folds from 30° to 0°.

• Fold symmetry: Not all folds are equal on both sides of the axis of the fold. Those with limbs of relatively equal length are termed symmetrical, and those with highly unequal limbs are asymmetrical. Types of folding Anticline: linear, strata normally dip away from axial center, oldest strata center. Syncline: linear, strata normally dip toward axial center, youngest strata center. Antiform: linear, strata dip away from axial center, age unknown, or inverted. Synform : linear, strata dip toward axial centre, age unknown, or inverted. Dome : nonlinear, strata dip away from center in all directions, oldest strata in the center. Basin : nonlinear, strata dip toward center in all directions, youngest strata in the center. Monocline : linear, strata dip in one direction between horizontal layers on each side. Chevron : angular fold with straight limbs and small hinges Recumbent : Recumbent fold has an essentially horizontal axial plane. When the two limbs of a fold are essentially parallel to each other and thus approximately parallel to the axial plane. Slump : typically monoclinal, result of differential compaction or dissolution during sedimentation and lithification. Ptygmatic : Ptygmatic folds generally represent conditions where the folded material is of a much greater viscosity than the surrounding medium. Parasitic : Short wavelength folds formed within a larger wavelength fold structure - normally associated with differences in bed thickness. Disharmonic: Folds in adjacent layers with different wavelengths and shapes. Some fold forms are shown in Plates. Anticline

Syncline Recumbent Fold Faults • Fault is a fracture / crack / joint along which there has been relative displacement of beds. • As a result, formerly continuous beds have been dislocated in a direction parallel to fault’s surface. The displacement may vary from a few inches or less, to hundreds of kilometres. • When subjected to great pressure, the earth’s crust may have to withstand shear force in addition to direct compression. • If the shear forces so induced become excessive, failure will result, movement will take place along the plane of failure until the unbalanced forces are equalized and a fault will be the result. A typical fault is shown in Plates. • Large faults within the Earth's crust result from the action of plate tectonic forces.

A typical fault

Terminology • The block above the fault is called Hanging Wall and the underlying block is Foot Wall. • The vertical component of the displacement between two originally adjacent points is called Throw of the faults. • The horizontal component of displacement is Heave and the angle of inclination to the vertical is called Hade of the fault. • A fault line is the surface trace of a fault, the line of intersection between the fault plane and the Earth's surface. Types of faults Plate Tectonics

Joints • Joints are planes or surface with a small displacement normal to their surfaces and virtually no displacement parallel to their surfaces.

• Joints normally have a regular spacing related to either the mechanical properties of the individual rock or the thickness of the layer involved.

• Joints generally occur as sets, with each set consisting of joints sub-parallel to each other. Many fractures in same area with similar orientation, is called a set. Typical Joints Typical Joints Unconformities • Unconformities are gaps in the geologic record that may indicate episodes of crustal deformation, erosion, and sea level variations. Unconformity is a surface of non-deposition or erosion which represents a break in the rock record. • It is a structure comprised of a sequence of geologic events in which there is often a significant portion of the geologic history lost. • The interval of geologic time not represented is called a hiatus. • Unconformities are useful to separate geologic time divisions. Angular unconformity ECONOMIC GEOLOGY

• It is a study of mineral deposits for using them as economic resource for economic and industrial developments. Economic minerals are valuable resources; as such the areas should not be selected for constructions.

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