DOCSLIB.ORG

Constitution of the Earth's Interior

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Constitution of the Earth's Interior Component-I (A) - Personal Details Role Name Affiliation Principal Investigator Prof. Masood Ahsan Siddiqui Department of Geography ,Jamia Millia Islamia, New Delhi Paper Coordinator, if any Dr. Sayed Zaheen Alam, Dayal Singh Singh College, Delhi University Content Writer/Author (CW) Dr.Ramashray Prasad DrBhim Rao Ambedkar Associate Professor College (University of Delhi) Yamuna Vihar, Delhi Content Reviewer (CR) Dr. Sayed Zaheen Alam, Dayal Singh Singh College, Delhi University Language Editor (LE) Component-I (B) - Description of Module Items Description of Module Subject Name Geography Paper Name Geomorphology Module Name/Title CONSTITUTION OF THE EARTH’S INTERIOR Module Id GEO/13 Pre-requisites Objectives Keywords SIAl, SIMA, NIFE, Volcanicity, Seismology Introduction Learning Objectives Meaning of Composition and Structure Studying the Earth’s Interior a. Artificial Sources and b. Natural Sources a. Artificial Sources: Density Pressure and Temperature Density Pressure Temperature Relationships of Density, Pressure and Temperature with Depths in the Interior b. Natural Sources Volcanism and Seismology. Volcanicity Seismology Primary, Secondary and Surface waves Characteristics of Primary (P) waves: Characteristics of Secondary (S) waves: Characteristics of Surface (L) waves: Interpretation of Propagating Different Waves Seismology and Constitution of the Earth’s Interior Chemical Composition of the Earth SIAL: SIMA: NIFE Earth’s Internal Structure Crust Mantle Core Conclusions Multiple Choice Questions Answers of MCQs References Web Links ================== CONSTITUTION OF THE EARTH’S INTERIOR Introduction The interior of the earth is that portion which is, possibly, not reachable for us. The parts, from where the sample is not supposed to be taken in our hands, are difficult to understand very well directly. You must have seen the vendor selling watermelon on roadside who used to get a slice out of it. We can see the quality of watermelon by your own eyes, or even you can test the same before buying. Our earth is not like the watermelon from where we can get the sample slice to study in detail.Constitution of the earth’s interior is the study to understand the internal parts of the earth, in terms of the real conditions existing there. These conditions could be about the state of rocks, or temperature, or pressure, or the chemical composition of the rocksat various depths. The study is facilitated by different branches/ disciplines of modern knowledges like science in general and physics, chemistry, seismology in particular. Let us study them systematically in detail. Learning Objectives After studying this module, you will be able to: understand the changing conditions of temperature and pressure in the earth’s interior, explain the density variations with increasing depth from the earth’s surface, describe the propagation of earthquake waves, infer the state of rock based on the waves propagated, explain the reasons of varying conditions in the interior and comprehend different layers of the earth’s internal parts. Meaning of Composition and Structure In a very simple term, meaning of composition is what something is consist of. In another words, it is unit of different parts for making a total. When we are referring the composition of the earth, we are supposed to study the earth with respect to the material of which it is composed of. The materials of earth’s surface are different than the interior. By material, we generally denote about different kinds of rocks occupying different volume and mass it has. It includes the physical state of rock, density, temperature or even the pressure they are bearing at different depths. Structure is something to do with the overall assemblage of an object. In another words, it is the unified total made up of different parts. When we are referring to the structure of the earth, we are supposed to study the earth with respect to the parts making the total. The arrangement of different parts of the earth give a clear picture of the whole of the earth. Therefore, the structure of the earth is the way different parts are put together to get the plan or design of the earth. Studying the Earth’s Interior The real sample is not possible to get from the earth’s deeper internal parts. Even if the internal material is ejected or received provides a different condition at the earth’s surface. The material’s temperature or the pressure recorded in the interior is different in comparison when it come at the surface. Therefore, to study the earth’s interior, we have to take the help of two sources: c. Artificial Sources and d. Natural Sources Artificial Sources: Artificial sources are those sources which are basically derived from the mathematical assumptions and calculations. Important among them are: Density, Pressure and Temperature Density The earth is made up of various types of rocks. Rocks are composed of minerals. Rock may be composed of one mineral or many minerals. The characteristics and properties of the minerals determine the rocks. The rocks available under our feet while walking can be simply examined very well in our laboratory. The rocks of various places are not alike but are different. The rocks lying in our agricultural field is different from the mined rocks. It could be different types like igneous or sedimentary or metamorphic. The rocks of the earth’s surface is different from the interior. Tostudy the density is one way to know it. The density is the property of the rock’s compactness. When the molecules of the rocks are very close, it is denser. In another words, it is defined as the relationship between the mass of the rock and how much volume it occupies. Thus, a rock with greater mass and lesser volume will become denser but when the mass is less and volume is more, the density is lower. Therefore, density is equal to the mass of the rock divided by its volume. D=m/v Where D=Density, m=mass of the rock and v=volume of the same rock By this formula, the result received is expressed as that much of gram/cm3. Probably, for the first time British scientist Henry Cavendish (1798) attempted to calculate the density of the earth on the basis of Newton’s law of Gravitation. He found it to be 5.48 gm/cm3. Poynting (1878) calculated the earth’s density and found it to be 5.49 gm/cm3. The density of the rocks found at the surface rocks: 2.7 - 2.9 gm/cm3 The density of rocks found at the sea floor is around: 3.0 gm/cm3 It is quite obvious that the central part of the earth is more than: 5.5 gm/cm3 The average density of the earth: 5.52 gm/cm3 The density calculated at different depths in the interior of the earth is given in the following Table 1. Table 1: Density of Rocks at Different Depths in the Interior Depth in km Density in gram/cm3 (Surface/ Sea Level) 0 2.70 to 2.90 100 3.38 Ite 500 3.85 1000 4.58 2000 5.12 2890 5.56 2900 9.90 4000 11.32 5000 12.12 5500 12.92 6371 13.09 It is also very clear throughthe Table 1 that the density of the inner most part of the earth is around 13 gm/cm3. The increase in the density in the interior of the earth is not a continuous affair but changes very abruptly at different depths. The changing density at different depths in the interior may very clearly be seen at a glance through Figure 1. Figure 1: Density in the Interior Source: http://hs.umt.edu/geosciences/faculty/sheriff/courses/438-gravity- electromagnetics/images/Density%20Depth.gif Pressure It is quite obvious that the density of the rocks lying in the interior is greater. It is scientifically proven that the density of the matter is increased when it is compressed. Earlier it was assumed that the density of the interior rock is grater due to increasing pressure of the rocks lying above. To some extent, this assumption is true but it is also universally proven fact that the density of the rocks cannot be increased beyond a certain limit, simply by compression or more pressure. Hence, the inference that the increasing pressure is the reason for greater density is not true. The higher dense material of the interior can be explained through the constituent of the rocks. It is now confirmed that the core is composed of essentially heavy metallic materials which have higher density. The pressure in the interior keeps on increasing with depth (Figure 2). Figure 2: Pressure in the Interior Temperature With the advancement in technology and knowhow to use the minerals, the mining activities started. We have been digging the earth since many centuries. But the deeper mining and oil exploration has led drilling the crust to the much deeper level in recent times. Our own observations record a rate of increase in temperature and it is about 30C per100 meter depth or about 300C per km. If we calculate the temperature at this rate, the earth’s core would witness a temperature of more than 1,90,0000 C. it is unimaginable. Probably, this much of high temperature would melt the entire earth. The above calculationhas not taken the increasing pressure into account. A recent experiment conducted and calculated by the scientists suggests that the inner part of the earth, core, has about 50000 C temperature with a variation of 5000 C plus or minus. Hence, these two temperatures are contradictory to each other. The increase in temperature observed in the top layer of the earth is not constant. The rate may be higher near the surface for a few km but it is not true for the much deeper part of the earth.
Load more

Recommended publications
  • Reading Notes on KKV Ch 2: the Interior of the Earth 2.1 EQ
    Reading notes on KKV Ch 2: The interior of the earth 2.1 EQ SEISMOLOGY seismic waves, their speed double couple model and focal mechanisms. elastic rebound theory --EXPLAIN how the fault plane and auxiliary plane are different than a fault plane and its conjugate seismic tomography - like medical xrays - an energy source, illuminates the volume, and detected on the other side. in medical you know the energy and the distance travelled - all delays and attenuation of energy arrival at the detector can be attributed to complex paths and rigidity of materials. in earth, beat down the uncertainties by using more and more earthquakes and more and more stations. tomography techniques typically use one type of wave at a time. For body waves (p and s) use travel time, better for deeper imaging of velocity structure. surface waves can be better for picking up anisotropy and shorter wavelength changes. Iterative - between velocity structure and raypath. this process improves earthquake location and magnitude estimation. 2.2 VELOCITY STRUCTURE OF THE EARTH Moho was discovered in 1909. Key observation was that at 200 km from epicenter, p-wave arrivals were before predicted because the crustal paths were at 5.6 km/s and the mantle speed was 7.9 km/s. calculated depth was 54 km. same pattern is found globally - strong velocity contrast from 5.5-6 to 8 km/s at depths of 20 (new cont or rift) -80 (Himalaya) km. mean 40 km. Made my own diagram - purple is direct wave. red is a path to a station near the epicenter pink is a path to a station farther from epicenter.
    [Show full text]
  • Plate Tectonics
    Plate tectonics tive motion determines the type of boundary; convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative move- ment of the plates typically varies from zero to 100 mm annually.[2] Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the globe remains the same. This predic- The tectonic plates of the world were mapped in the second half of the 20th century. tion of plate tectonics is also referred to as the conveyor belt principle. Earlier theories (that still have some sup- porters) propose gradual shrinking (contraction) or grad- ual expansion of the globe.[3] Tectonic plates are able to move because the Earth’s lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topog- raphy and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. The relative im- portance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.
    [Show full text]
  • STRUCTURE of the EARTH Module-2/3
    STRUCTURE OF THE EARTH Module-2/3 On the basis of data assembled from studies of the travel habits of earthquake waves the earth has been divided into three major zones. (i) Crust (ii) Mantle (iii) Core The Crust The outermost thin layer of the lithosphere is crust. Its thickness varies from 16 to 40 km.The crust contain the continental landmass and the ocean basins. In the continental areas, crust is about 40 km thick and in the ocean basin, the thickness of the crust is 5 to 10km.From seismic waves it seems that the surface layer of the continent is composed mainly of granite rocks with specific gravity 2.65 where the seismic velocity is 6km/sec.Because these rocks contain a large proportion of silica and aluminum they are collectively called SIAL. The basement layer is continuous which is exposed on the ocean floor or the ocean basin. The specific gravity is 3.0 and the earthquake waves travel at a speed of 6.7km/sec. The rocks contain silica and minerals rich in magnesium and iron. This layer of basic rocks is termed as SIMA. The Mantle Below the earth’s crust is the second zone, themantle, having mean density of 4.6 gcm-3extends to a depth of approximately 2900km, into the interior of the earth. The line of function between the earth crust and the mantle is called Moho discontinuity after the scientist Mohorovicic who discovered it in 1909.Moho discontinuity lying at a depth of up to 40kms beneath the continents and 6-10 km beneath the ocean floor.
    [Show full text]
  • Geology of Saipan Mariana Islands Part 2
    Geology of Saipan Mariana Islands Part 2. Petrology and Soils GEOLOGICAL SURVEY PROFESSIONAL PAPER 280-B-D Geology of Saipan Mariana Islands Part 2. Petrology and Soils GEOLOGICAL SURVEY PROFESSIONAL PAPER 280-B-D Chapter B. Petrology of the Volcanic Rocks By ROBERT GEORGE SCHMIDT Chapter C. Petrography of the Limestones By J. HARLAN JOHNSON Chapter D. Soils By RALPH J. McCRACKEN UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1957 UNITED STATES DEPARTMENT OF THE INTERIOR Fred A. Seaton, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. CONTENTS OF PART 2 Page Chapter B. Petrology of the Volcanic Rocks .... 127 Chapter C. Petrography of the Limestones ...... 177 Chapter D. Soils ................................ 189 m GEOLOGICAL SURVEY PROFESSIONAL PAPER 280 Geology of Saipan, Mariana Islands Part 1. General Geology Chapter A. General Geology By PRESTON E. CLOUD, JR., ROBERT GEORGE SCHMIDT, and HAROLD W. BURKE Part 2. Petrology and Soils Chapter B. Petrology of the Volcanic Rocks By ROBERT GEORGE SCHMIDT Chapter C. Petrography of the Limestones By J. HARLAN JOHNSON Chapter D. Soils By RALPH J. McCRACKEN Part 3. Paleontology Chapter E. Calcareous Algae By J. HARLAN JOHNSON Chapter F. Discoaster and Some Related Microfossils By M. N. BRAMLETTE Chapter G. Eocene Radiolaria By WILLIAM RIEDEL Chapter H. Smaller Foraminifera By RUTH TODD dhapter I. Larger Foraminifera By W. STORRS COLE ^Chapter J. Echinoids By C. WYTHE COOKE ~Part 4. Submarine Topography and Shoal-Water Ecology ^Chapter K. Submarine Topography and Shoal-Water Ecology By PRESTON E. CLOUD, JR.
    [Show full text]
  • Journey to Center of Earth Rocks at the Earth Surface Igneous Rocks
    Oceanography 101, Richard Strickland Lecture 3 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 3 © 2006 University of Washington Journey to Center of Earth Rocks at the Earth Surface • Types of rocks Garrison Fig. 3.5 p. 59 • Igneous: that make up the – Cooled directly from liquid rock (magma) Earth • Sedimentary • Internal layers of – Formed from small particles (sediments) the Earth that sink to the sea floor • Ocean • Compressed to form rock (lithified) sediments • Metamorphic – Igneous or sedimentary rocks altered in shape and chemistry by pressure, heat, and bending 1 2 Oceanography 101, Richard Strickland Lecture 3 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 3 © 2006 University of Washington Igneous Rocks What Does Color Tell Us? • Liquid rock is called: • Density – Magma below the Earth’s surface – g/cm3 (water = 1) – Lava on the Earth’s surface – Denser rocks are darker in color • Classified by two properties • Chemical composition – Color – Inclusion of heavier elements makes rock • Indicates density denser – Size of crystal grains – Heavier elements are darker in color • Indicates where it formed • Online study guide to igneous rocks: – http://volcano.und.edu/vwdocs/vwlessons/lessons/Igrocks/Igrocks1.html 3 4 Oceanography 101, Richard Strickland Lecture 3 © 2006 University of Washington Oceanography 101, Richard Strickland Lecture 3 © 2006 University of Washington Color, Density, & Chemistry Color, Density, & Chemistry • Dense and dark color • A denser, darker – More
    [Show full text]
  • Chapter – 2 (Geography) Class-- 7 Inside Our Earth
    Chapter – 2 (Geography) Class-- 7 Inside Our Earth Match the following: Column I Column II Core Earth's surface Minerals Used for roads and buildings Rocks Made of silicon and alumina Clay Has definite chemical composition Sial Innermost layer Changes into slate Process of transformation of rocks Colum Column I n II (a) Continental Masses (i) Nife (b) Oceanic crust (ii) Sial (iii) (c) Core Sima (d) Basalt (iV) Sand grains (e) Granite (V) Deccan Plateau (f) Sandstone (VI) Large grains Multiple Choice Questions (1) The rock which is made up of molten magma is a. Igneous b. Sedimentary c. Metamorphic (2) The innermost layer of the earth is a. Crust b. Core c. Mantle (3) Gold, petroleum and coal are examples of a. Rocks b. Minerals c. Fossils (4) Rocks which contain fossils are a. Sedimentary rocks b. Metamorphic rocks c. Igneous rocks (5) The thinnest layer of the earth is a. Crust b. Mantle c. Core Answer the following questions (1)What are the three layers of the earth? (2) What is a rock? (3) Name three types of rocks. (4) How are extrusive and intrusive rocks formed? (5) What do you mean by a rock cycle? (6) What are the uses of rocks? (7) What are metamorphic rocks? Fill in the blanks (1) …….. are used to make buildings. (2) …….. is an intrusive igneous rock. (3) The middle layer of the earth is the…… (4) Rocks change their form in a…….. manner. (5) Earth is a ……………. place. (6) The earth is made up of several …….. layers. (7) The innermost layer of the earth is called the………… (8) When the magma solidifies deep inside the earth, …………….
    [Show full text]
  • Dynamic Surface of the Earth
    MODULE - 2 Changing face of the Earth 3 Notes DYNAMIC SURFACE OF THE EARTH In the previous lesson, we have learnt that the interior of the earth is very hot. Earthquakes and volcanoes are concentrated along a few narrow belts. The type and density of rocks of the crust are variable. The surface features are dynamic in character. This dynamism is due to two forces — endogenetic and exogenetic. Endogenetic forces are those which are caused from below the surface. Due to this, an area may get elevated or gets submerged. These forces try to make the surface irregular while exogenetic froces are those which operate from above the surface. They try to eliminate the irregulari- ties of the surface through the process of denudation about which we will be reading in lesson. In this lesson we will be studying about the endogenetic forces. OBJECTIVES After studying this lesson, you will be able to : define isostasy; describe the variation in relief features on the earth’s surface; explain the isostatic adjustment by various experiments; explain the views of Airy and Pratt and distinguish between the ideas of both; explain the concept of continental drift; enumerate the evidences of continental drift; explain the concept of plate tectonics; identify and locate different plates on the world map; GEOGRAPHY 45 MODULE - 2 Dynamic Surface of the Earth Changing face of the Earth explain the mechanism of plate movement; identify various plate boundaries and associated features; explain the distribution of land and water on the globe and associate earthquakes and volcanoes with plate boundaries. Notes 3.1 CONCEPT OF ISOSTASY The term “Isostasy” is derived from “Isostasios”, a word of Greek language meaning the state of being in balance.
    [Show full text]
  • Plate Tectonics | Sample Answer
    Plate Tectonics | Sample Answer Destructive Plate Boundaries (2018 Q3C) A plate boundary is how the earth’s crust is broken into plates, where 2 plates meet is known as a plate boundary. Different plate boundaries exist as plate boundaries move by convection currents. Land is usually destroyed at destructive plate boundaries. At continental-continental destructive plate boundaries, fold mountains are formed e.g. the Himalayas formed where the Indian and Eurasian plates slowly collided. Continental crust is 40- 60km thick, made of SIAL-rich rock, and is older than oceanic crust. The Eurasian plate crumpled and rose forming the Tibetan Plateau and the Himalayas. When 2 continental plates collide, neither sinks, sometimes they move upwards or sideways causing shallow earthquakes, for example in Pakistan in 2005, a shallow earthquake occurred and 89,000 people died. Fold mountains are usually made from sedimentary rock as they form underwater, and marine fossils are found in the Himalayas. At Oceanic-continental destructive boundaries, the oceanic plate subducts under the lighter continental plate into the mantle. It melts, turns to magma, moves up through the continental crust, causing an explosive volcano to form, e.g. Mount Saint Helens, USA. The oceanic plate subducts beneath the continental crust as it is heavier and made of more dense SIMA rock. Deep earthquakes are also common at these boundaries. A trench is created at the junction of two colliding plates. This marks the subduction zone e.g. Peru-Chile Trench. The Pacific Ring of Fire is an area which contains 452 active volcanoes at the subduction zone at the edge of the Pacific Plate.
    [Show full text]
  • Geography) Inside Our Earth (Module – 1/1) Worksheet Class Vii 1
    CHAPTER – 2 (GEOGRAPHY) INSIDE OUR EARTH (MODULE – 1/1) WORKSHEET CLASS VII 1. Answer the following questions. (1) What are the three layers of the earth? ANSWER The three layers of the earth are as follows: Crust : The uppermost layer over the earth’s surface is called the crust. Mantle : Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust. Core : The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife (2) What is a rock? ANSWER i.The earth’s crust is made up of various types of rocks. ii. Any natural mass of mineral matter that makes up the earth’s crust is called a rock. iii. Rocks can be of different colour, size and texture. (3) Explain the mineral constituents of the continental mass and oceanic crust? ANSWER The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina). The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium) (4) Define minerals. ANSWER Minerals are naturally occurring substances which have certain physical properties and definite chemical composition. (5) What are Igneous Rocks? Name the two types of igneous rocks. ANSWER When the molten magma cools, it becomes solid. Rocks thus formed are called igneous rocks. They are also called primary rocks. There are two types of igneous rocks: intrusive rocks and extrusive rocks.
    [Show full text]
  • Melting of Mafic and Felsic Sources to Produce the Hree-Depleted Dacites of the Michipicoten Greenstone Belt, Ontario: P.J
    MELTING OF MAFIC AND FELSIC SOURCES TO PRODUCE THE HREE-DEPLETED DACITES OF THE MICHIPICOTEN GREENSTONE BELT, ONTARIO: P.J. Sylvester, Code SN4, NASA/Jobnson Space Center, Houston, TX 77058, K. Attoh, Dept. of Geology, Hope College, Holland, MI 49423, and K. J. Schulz, U.S. Geological Survey, Reston, VA 22092 HREE-depleted dacites and tonalites comprise a significant component of the Earth's Archean sialic crust. They are widely believed to have formed by 10-30% melting of mafic source rocks in the lower crust [I, 21, and thus reflect a simple transformation of simatic to sialic material during the Archean. We have shown previously on the basis of trace element data [31 that the HREE-depleted dacites of the Michipicoten greenstone belt, Ontario may be derived anatectically from granulite facies mafic gneiss of the Kapuskasing structural zone. (The Michipicoten belt and Kapuskasing zone are interpreted to be upper and lower levels, respectively, of an uplifted oblique section of Archean crust [4].) This model requires, however, that significant amounts of biotite and orthopyroxene remain in the residue after about 9% melting, and that tonalitic veinlets in the gneiss form as restite following melting of an andesitic component in the largely mafic parental material. Field and petrographic examination of the Kapuskasing gneisses [5, 61 suggests that only trace amounts of biotite and orthopyroxene are typically present in the mafic residue, the tonalitic veinlets probably comprise a felsic melt fraction derived via anatexis of a mafic parent, and both mafic gneiss and felsic paragneiss underwent melting. We have thus re-evaluated the origin of the Michipicoten HREE-depleted dacites by taking these observations into account.
    [Show full text]
  • ( Physical Geography : Paper - 1) Topic : Internal Structure of the Earth
    B.A. PART - 1 ( PHYSICAL GEOGRAPHY : PAPER - 1) TOPIC : INTERNAL STRUCTURE OF THE EARTH - Prof. KUMARI NISHA RANI Structure of the earth’s interior is fundamentally divided into three layers – crust, mantle and core. CRUST • It is the outermost solid part of the earth, normally about 8-40 kms thick. • It is brittle in nature. • Nearly 1% of the earth’s volume and 0.5% of earth’s mass are made of the crust. • The thickness of the crust under the oceanic and continental areas are different. Oceanic crust is thinner (about 5kms) as compared to the continental crust (about 30kms). • Major constituent elements of crust are Silica (Si) and Aluminium (Al) and thus, it is often termed as SIAL (Sometimes SIAL is used to refer Lithosphere, which is the region comprising the crust and uppermost solid mantle, also). • The mean density of the materials in the crust is 3g/cm3. • The discontinuity between the hydrosphere and crust is termed as the Conrad Discontinuity. 1 MANTLE • The portion of the interior beyond the crust is called as the mantle. • The discontinuity between the crust and mantle is called as the Mohorovich Discontinuity or Moho discontinuity. • The mantle is about 2900kms in thickness. • Nearly 84% of the earth’s volume and 67% of the earth’s mass is occupied by the mantle. • The major constituent elements of the mantle are Silicon and Magnesium and hence it is also termed as SIMA. • The density of the layer is higher than the crust and varies from 3.3 – 5.4g/cm3. • The uppermost solid part of the mantle and the entire crust constitute the Lithosphere.
    [Show full text]
  • The Earth's Layers Lesson #1
    The Earth's Layers Lesson #1 The Four Layers The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier, denser materials sank to the centre and the lighter materials rose to the top. Because of this, the crust is made of the lightest materials (rock- basalts and granites) and the core consists of heavy metals (nickel and iron). The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The Outer and Inner Cores are hotter still with pressures so great that you would be squeezed into a ball smaller than a marble if you were able to go to the centre of the Earth!!!!!! The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans (oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celsius) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350 degrees Fahrenheit, at 1600 degrees F. rocks begin to melt. The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, plastic mantle which is located below the crust. These plates usually move along smoothly but sometimes they stick and build up pressure.
    [Show full text]