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Materials of the earth'scrust

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    Materials of the earth'scrust Materials of the earth'scrust Presentation Transcript

    • Materials of the Earth’s crust The Geography Department 2011-12 1
    • Rocks are our world.The planet Earthis, essentially, just one biginteresting rock, sometimescalled "the third rock from thesun."The multi-faceted rock we liveon supports life in many ways.The deep oceans, the vastdeserts, and the highmountains, are just a few ofthe ways rock emerges and The Geography Department 2011-12 2supports life.
    • The Geography Department 2011-12 3
    • What are rocks made up of ? The Geography Department 2011-12 4
    • Rocks and minerals A mineral is defined as a naturally occurring inorganic substance, which has definite physical properties and chemical composition. Eg. Quartz (SiO2), Feldspar (K2O.Al2O3.6SiO2), Mica (K4AlSi3O10(OH)2) etc are minerals. A rock is defined as an aggregate or mixture of minerals. Eg. Granite contains quartz, K-feldspar and K- mica. Marble contains Calcite (CaCO3) and Quartz. The Geography Department 2011-12 5
    • Common Rock-forming minerals1. Quartz –2. Feldspar –3. Mica –4. Calcite –5. Clay – The Geography Department 2011-12 6
    • Quartz – Most common mineral; found in almost all rocks; shades of white, gray, and pink, mostly colourless with a glassy lustre. The Geography Department 2011-12 7
    • FeldsparFound in rocks like granite and basalt; colour may vary as K is replaced by Ca or Na. K-feldspar is pinkish or whitish while Ca and Na feldspar is green or black The Geography Department 2011-12 8
    • Micawhite or colourless flakes in granite and as black needles in basalt. K may be replaced by Ca or Na. The Geography Department 2011-12 9
    • Calcite – Occurs in rocks likelimestone and marble. Colourlessor white; crystalline or amorphous. The Geography Department 2011-12 10
    • Clay Similar to mica as it occurs as thin layers differ as it has high water absorption capacity;found in rocks like shale, conglomerate etc. The Geography Department 2011-12 11
    • AbsoluteHardness Mineral Hardness 1 Talc (Hydrated magnesium silicate) 1 2 Gypsum (Hydrated calcium sulfate) 2 3 Calcite (Calcium carbonate) 9 4 Fluorite (Used in toothpaste) 21 5 Apatite (Used in fertilizers) 48 6 Orthoclase 72 7 Quartz 100 8 Topaz 200 9 Corundum 400 The Geography Department 2011-12 12 10 Diamond 1500
    • Types of rocksRocks are divided according to their origininto igneous, sedimentary and metamorphicrocks. The Geography Department 2011-12 13
    • Igneous Rocks Igneous Rock- rock that has been formed by the cooling and subsequent solidification of a molten mass of rock material, known as magma. Depending upon the conditions under which the magma cooled, the resulting rocks may be coarse-grained or fine- grained. The Geography Department 2011-12 14
    • Types of Igneous rocks Any molten rock material is known as magma as long as it remains within the crust. If the magma erupts out of a volcano and spreads out on the surface of the earth, it is known as lava. Besides, magma contains dissolved gases which are liberated once it comes out on the earth’s surface. Based on the location where magma cools and solidifies, the resultant igneous rocks can be classified as follows. The Geography Department 2011-12 15
    • Intrusive Igneous rocks They are also called plutonic rocks. They are formed due to the cooling and solidification of magma buried deep within the earth (in the magma chamber). A magma chamber that has cooled down and solidified is called a pluton. Due to the lesser temperature difference between the magma and surrounding rocks, the magma cools down very slowly. There is a lot of time for the mineral crystals to grow in size. As a result, the mineral crystals are large and visible and the resultant rock is crystalline or coarse- grained. Examples-Gabbro & Granite The Geography Department 2011-12 16
    • Extrusive igneous rocks They are also called volcanic rocks. They are formed due to the cooling and solidification of lava on the earth’s surface under atmospheric conditions. Due to the greater temperature difference between the lava and atmosphere, the lava cools down very quickly. There is very little time for the mineral crystals to grow in size. As a result, the mineral crystals are very small and the resultant rock is glassy or fine-grained. Examples- Basalt & Rhyolite The Geography Department 2011-12 17
    • Hypabyssal igneous rocks They are formed due to the cooling and solidification of magma within the cracks and fissures of the surrounding rock. The magma cools down at an intermediate rate, therefore the mineral crystals are intermediate-sized and the resultant rock is medium-grained. Structures formed due to the cooling and solidification of magma within the cracks and fissures of the surrounding rock are known as igneous intrusions. They may be of the following types. a) Dyke – A wall shaped igneous intrusion, which cuts across the layers of surrounding sedimentary rocks. b) Sill – A flat igneous intrusion that lies between two layers of sedimentary rock. c) Batholith – An irregularly shaped igneous intrusion. The Geography Department 2011-12 18
    • The Geography Department 2011-12 19
    • Sill Dike The Geography Department 2011-12 20
    • TYPES OF IGNEOUS ROCKS Basaltic magma Granitic magma Extrusive or Basalt Rhyolite Volcanic Hypabyssal Dolerite PegmatiteIntrusive or Plutonic Gabbro Granite The Geography Department 2011-12 21
    • INTRUSIVE V/S EXTRUSIVE IGNEOUS ROCKS GRANITE • BASALT GABBRO • • PEGMATITE • RHYOLITE The Geography Department 2011-12 22
    • Uses of igneous rocksGranite and basalt are used extensively as building stones since they are very strong and durable.Mica, which is used as an insulator and in lubricants, is found in pegmatite.Basalt is also used as a road metal. The Geography Department 2011-12 23
    • Sedimentary Rocks Sedimentary rocks are so called because they are formed out of sediment, which is the term given to broken rock fragments. These rocks are formed due to deposition, compaction and cementation of the broken rock fragments weathered by the agents of gradation. The Geography Department 2011-12 24
    • The Geography Department 2011-12 25
    • Process of Sedimentation of rocks a) Deposition – Accumulation of sediment in a low-lying area of the earth’s surface, usually the continental shelf, river basin or a lake. The sediments are deposited in layers, also called stratified (stratum meaning layer) rocks. b) Compaction – On account of continuous accumulation of sediments, the underlying sediments are subject to pressure due to which they tend to occupy the least possible volume. This process is called compaction. c) Cementation – In this process, the rock fragments are bound together bycalcium carbonate, silica of iron oxide. Rainwater dissolves atmospheric gaseslike carbon dioxide and results into a weak carbonic acid. This carbonic acidtakes the chemically weak minerals like mica, calcite and feldspar intosolution. This solution percolates through the sediment and occupies thespaces between the rock fragments thereby cementing them. The processes of26 The Geography Department 2011-12compaction and cementation are often named collectively as lithification.
    • The Geography Department 2011-12 27
    • Types of Sedimentary Rocks Mechanically formed Sedimentary rocks They are also called fragmental or clastic rocks. Dynamic agents like rivers, glaciers, sea waves and wind erode rocks. Sediments are transported and deposited in low-lying areas of the earth where they undergo the process of lithification. Examples of mechanically formed sedimentary rocks include Sandstone – A rock made up of well- rounded grains of quartz cemented together. Shale – A rock made up of very small flat grains of clay and mica cemented together. Conglomerate. – A rockGeography Department 2011-12 The made up of large 28 pieces of other rocks cemented together
    • Types of Sedimentary Rocks Chemically formed sedimentary rocks They are also called non-clastic rocks. Some minerals or shells of microscopic marine organisms are dissolved by water. Minerals precipitate directly from a saturated solution followed by evaporation of the water. Examples of chemically formed sedimentary rocks include Limestone – A rock formed by the compaction and cementation of shells in shallow sea Gypsum - A rock formed by the precipitation of calcium sulphate from sea water Rock salt – A rock formed by the compaction of sodium chloride under pressure The Geography Department 2011-12 29
    • Types of Sedimentary Rocks Organically formed sedimentary rocks They are formed due to the decay of organisms and their subsequent burial under sediments Examples of organically formed sedimentary rocks include Coal – Formed due to the decay of dead plants under fresh water conditions like those in a riverbed. Petroleum - Formed due to the decay of dead animals under marine water conditions like those in a continental shelf. The Geography Department 2011-12 30
    • Uses of sedimentary rocks1. Rocks such as sandstone and limestone are widely used as building stones.2. Sedimentary rocks contain deposits of important minerals like iron ore, manganese, bauxite, gypsum, coal and petroleum.3. Fossils present in sedimentary rocks help to determine the absolute and / or relative age of rocks. The Geography Department 2011-12 31
    • Metamorphic RocksWhen other rocks are subjected to conditions of heat and pressure, they convert to metamorphic rocks.As a result of metamorphism, rocks lose their original physical structures (such as layering in the case of sedimentary rocks) and their chemical composition is also altered (new minerals are formed).Rocks shown here- Micaschist, The Geography Department 2011-12 32 Quartzite & Marble
    • Agents of Metamorphism The Geography Department 2011-12 33
    • The Geography Department 2011-12 34
    • The sources of heat and pressureinvolved in the formation ofmetamorphic rocks are listed asfollows.Heat – Magma, friction caused by the rubbing of lithospheric plates against each otherPressure – Overlying sediments, rising magma, collision of lithospheric plates The Geography Department 2011-12 35
    • Areas where metamorphic rocks arefound1. Near igneous intrusions2. Mountain belts3. Deep in the earth’s crust The Geography Department 2011-12 36
    • Types of metamorphism Contact metamorphism Occurs due to alteration of surrounding rocks by magma, hence common near igneous intrusions. Area of rocks affected is very less, not beyond a few hundred metres from the magma. Heat is the dominant agent The Geography Department 2011-12 37 of metamorphism
    • Types of metamorphismRegional metamorphismOccurs due to movement of lithospheric plates, hence common in mountain belts.Area of rocks affected is very large, often thousands of square kilometres.Both heat and pressure play a predominant role. The Geography Department 2011-12 38
    • Examples of metamorphic rocks Schist The Geography Department 2011-12 39
    • Examples of metamorphic rocks Gneiss The Geography Department 2011-12 40
    • Examples of metamorphic rocks Marble The Geography Department 2011-12 41
    • Examples of metamorphic rocks Basalt ------->Schist Granite ------->Gneiss (pronounced as ‘nice’) Shale ------->Slate Slate ------->Schist Sandstone ------->Quartzite Limestone ------->Marble Coal ------->Graphite Take a Quiz http://www.fi.edu/fellows/fellow1/oct98/expert/index.html The Geography Department 2011-12 42 http://www.kidsgeo.com/geology-games/rocks-game.php
    • The Rock Cycle The Geography Department 2011-12 43Interactive rock cycle: http://www.learner.org/interactives/rockcycle/diagram.html
    • THE ROCK CYCLE The Geography Department 2011-12 44
    • Rock Cycle  The classic rock cycle illustrates the relationship between the three main types of rock found on the Earth. In its simplest form, it demonstrates that igneous rock, which is formed by the cooling of magma, is in turn exposed to natural processes such as weathering, erosion, and compaction, creating sedimentary rock or exposed to heat and pressure, creating metamorphic rocks. The application of heat then turns sedimentary rock into metamorphic rock or exposure to agents of gradation converts them back into sediments, and further heating causes the metamorphic rocks to melt and in process to turn full circle, creating magma once more whereas further pressure can convert them into another metamorphic rock. However, the cycle does not necessarily have to pass through all these stages. The Geography Department 2011-12 45
    • ORES AND GEMSTONES The Geography Department 2011-12 46
    • ORESA mineral is said to be an ore if it contains one or more elements, usually metals that can be extracted from it in a profitable manner The Geography Department 2011-12 47
    • ORES Examples of minerals that are oresHaematite (Fe2O3) – Ore of IronChalcopyrite (CuFeS2) – Ore of CopperMagnetite (Fe3O4) – Ore of IronGalena (PbS) – Ore of LeadBauxite (Al2O3) – Ore of AluminiumSphalerite (ZnS) – Ore of ZincPyrolusite (MnO2) – Ore of Manganese The Geography Department 2011-12 48
    • GEMSTONESGemstones are minerals that are treasured for their beauty and durability.Their value generally depends on four features: The beauty of the stone itself Its rarity Its hardness and toughness The skill with which it has been cut and polished. The Geography Department 2011-12 49
    • GEMSTONES The Geography Department 2011-12 50
    • GEMSTONESMonth of birth Birthstone Colour January Garnet Red February Aquamarine Blue-green March Amethyst Purple April Diamond Colourless May Emerald Green Metallic white with a June Pearl The Geography Department 2011-12 play of colours 51
    • GEMSTONESMonth of birth Birthstone Colour July Ruby Red Honey yellow or August Peridot green September Sapphire Blue Metallic white with a October Opal play of colours November Topaz Yellow Blue-green to December Turquoise The Geography Department 2011-12 greenish-grey 52
    • A quick Recap Answer the following questions by clicking on the right choice. If your answer is right you will move on to the next question by clicking on the arrow If your answer is not correct, you must go back to the question by clicking on the arrowPlease do not skip any slideHave a nice time and fun learning. The Geography Department 2011-12 53
    • Can wood be called a mineral?Yes, it is naturally occurringNo, it does not have a chemical formulaYes, it has a fixed chemical formulaNo, its organic The Geography Department 2011-12 54
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 55
    • CORRECT!Move on to the next question. The Geography Department 2011-12 56
    • Mineral is to compound as Rock is toElementCompoundMixtureSolution The Geography Department 2011-12 57
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 58
    • CORRECT!Move on to the next question. The Geography Department 2011-12 59
    • Which of the following is NOT a correctpoint of difference between lava andmagma?  Lava is found outside the earth while magma is found inside the earth.  Lava does not contain gases while magma contains gases.  Cooling of lava results in extrusive rocks while cooling of magma results in intrusive rocks.  Lava is less viscous (flows faster) ; magma is more viscous(moves slowly) The Geography Department 2011-12 60
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 61
    • CORRECT!Move on to the next question. The Geography Department 2011-12 62
    • Which of the following is NOT acharacteristic of intrusive rocks?They are dark in colour.They form inside the earth.They form due to slow cooling of magma.They have large crystals. The Geography Department 2011-12 63
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 64
    • CORRECT!Move on to the next question. The Geography Department 2011-12 65
    • Which of the following is a wall shapedigneous intrusion cutting across layers ofsedimentary rocks? Sill Dyke Batholith Laccolith The Geography Department 2011-12 66
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 67
    • CORRECT!Move on to the next question. The Geography Department 2011-12 68
    • Match the following A Pegmatite 1 Basaltic equivalent of granite B Gabbro 2 Hypabassal basaltic rock C Rhyolite 3 Hyabassal granitic rock D Dolerite 4 Extrusive rock of granitic composition•A-2; B-1; C-4; D-3•A-3; B-4; C-1; D-2•A-3; B-1; C-4; D-2•A-4; B-1; C-3; D-2 The Geography Department 2011-12 69
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 70
    • CORRECT!Move on to the next question. The Geography Department 2011-12 71
    • Which of the following is the blackcoloured rock used as a kitchen platform?BasaltLimestoneGraniteMarble The Geography Department 2011-12 72
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 73
    • CORRECT!Move on to the next question. The Geography Department 2011-12 74
    • Which of the following rocks is made upof well-rounded grains of quartzcemented together? Shale Conglomerate Limestone Sandstone The Geography Department 2011-12 75
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 76
    • CORRECT!Move on to the next question. The Geography Department 2011-12 77
    • Which of the following rocks will form dueto the evaporation and compaction of asuper-saturated solution of calciumsulphate? Rock Salt Gypsum Limestone Dolomite The Geography Department 2011-12 78
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 79
    • CORRECT!Move on to the next question. The Geography Department 2011-12 80
    • Which process leads to the formation oflimestone?Compaction and cementation of shells in shallow parts of the continental shelf.Dissolution of shells in the deep sea followed by super saturation and evaporation.Dissolution of existing limestone by rainwater followed by deposition in underground caves and channelsAll of the above. The Geography Department 2011-12 81
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 82
    • CORRECT!Move on to the next question. The Geography Department 2011-12 83
    • Which of the following is NOT TRUEabout the formation of coal?It forms in fresh water conditions.It forms due to decay of dead plants.It can also form due to decay of dead animals.It requires a protective environment for its formation. The Geography Department 2011-12 84
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 85
    • CORRECT!Move on to the next question. The Geography Department 2011-12 86
    • Which of the following is NOT TRUEabout the formation of petroleum? It forms only in marine conditions. Marine micro-organisms like foraminifera are a must for its formation. After its formation, it remains at the same place. It forms due to decay of dead bodies of animals. The Geography Department 2011-12 87
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 88
    • CORRECT!Move on to the next question. The Geography Department 2011-12 89
    • Which of the following mineral is notfound in sedimentary rocks?Iron OreMicaBauxiteGypsum The Geography Department 2011-12 90
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 91
    • CORRECT!Move on to the next question. The Geography Department 2011-12 92
    • Which of the following is NOT TRUEabout metamorphism?It involves a physical change in the physical properties of a rock.Minerals do not change.Even metamorphic rocks can be metamorphosed.It may occur on account of heat or pressure or both. The Geography Department 2011-12 93
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 94
    • CORRECT!Move on to the next question. The Geography Department 2011-12 95
    • Where can you find metamorphic rocks?Near Igneous intrusions.Deep in the earth’s crust.Fold mountain belts.All of the above. The Geography Department 2011-12 96
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 97
    • CORRECT!Move on to the next question. The Geography Department 2011-12 98
    • Which of the following is not ametamorphic rock?BasaltMarbleSchistGneiss The Geography Department 2011-12 99
    • OOPS!That’s the wrong answer. Try Again The Geography Department 2011-12 100
    • CORRECT!Move on to the next question. The Geography Department 2011-12 101