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Types of rocks - Coggle Diagram
Types of rocks
Igneous rocks
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less affected by chemical weathering(by water), weathered by mechanical weathering
fine grained, smooth and compact OR large crystals with coarse texture
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Formed due to the cooling, solidification and crystallisation of magma, the hot molten material found at great depths in the inferior of the earth
Called primary rocks or parent rocks because they were the first rocks to be formed and the form the basis of formation of other rocks.
Igneous rocks are compact and are used by builders and sculptors. They may also be ores of metals(used to extract metals)
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based on origin
Intrusive
Batholiths
deep seated, no definite floor, dome shaped, exposed to the surface due to erosion, mostly composed of granite, Eg: Ranchi Batholiths
Laccoliths
just below crust, flat bottom, dome shaped
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Volcanic Necks
passage of an extinct volcano, known as neck or plug
within earth's crust, cools slowly, coarse, hard, with large crystals, eg: granite
plutonic/abyssal
depth within crust, coarse grained, forms batholiths
subvolcanic/hypabyssal
near the surface, medium grained, forms dykes, sills, laccoliths
Lopolith
parallel to the bedding of the rock that encloses it; roughly horizontal top and a shallow convex base.
phacolith
parallel to the bedding of the rock that encloses it; lens shaped; occupying the crest of an anticline or the bottom of a syncline
Extrusive
on earth's surface, cools fast, smooth, crystalline, fine grained, aka volcanic rocks, eg: basalt
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Metamorphic rocks
Thermal Metamorphism
Chemically active hot gases while passing through the rocks change their chemical composition. The minerals get arranged in a series of bands known as foliation.
Eg: marble from dolomite, chalk or limestone
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Dynamic Metamorphism
when a small area is affected this is known as local or contact metamorphism. This happens when hot magma affects the cracks or layers of rocks and these areas are transformed into metamorphic rocks
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Formed by the pressure of overlying rocks and intense heat caused by large scale earth movements when due to mountain building process, igneous and sedimentary rocks are buried deep inside the crust.
Regional Metamorphism
Transformation takes place due to influence of high temperature from hot magma or from friction of moving rock layers
Eg: slate from clay, graphite from coal
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Metamorphism refers to the alteration of the composition or structure of a rock by heat, pressure or other natural agents
the rocks were once igneous or sedimentary which underwent change through physical or chemical processes.
the minerals the rocks are composed of, may change their composition and texture under great pressure and temperature
Sedimentary rocks
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Glacial rocks
formed by the glacial deposits in the form of debris or tills; glaciers erode the surface and sides of a valley and transport the eroded material further. When the glacier melts due to heat, the debris are left behind in the form of moraines which formed glacial rocks
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Aeolian rocks
formed with sand particles brought by winds. The deposition of these particles one over the other makes them hard and form rocks. Found in deserts.
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Marine rocks
Calcarious
formed by the deposition of shells and skeletons of sea organisms. They live on ocean floors and extract calcium carbonate from ocean water. Eg: chalk and limestone
Carbonaceous
formed by the sea plants which remain buried for a long period. Known as fossils. Converted into rocks due to pressure of overlaying rocks. Eg- coal and liganite
Chemically formed
these are by the direct precipitation of mineral matter from solution. The accumulation takes place in lakes and lagoons. They are compacted trough eveporation. Eg: gypsum and potash
Mechanically formed
Contain fragments from breaking up of other rocks, called clastic sediments. Breaking up of older rocks takes place through denudation. Sediments are squeezed by the weight of overlying sediments and the lower layers harden. Since they are formed in layers, they ate known as stratified rocks. Eg: sand becomes sandstone.
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igneous rocks are exposed to the surface of the earth, are broken down by weathering and carried away by forces. Then they are deposited as sediments. These sediments are solidified into rocks. Since they are formed in layers or strata, they ate known as stratified rocks
not crystalline, they are soft and layered
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minerals
earth full
iron, silicon, magnesium, nickel, calcium, sulphur
earth crust
iron, silicon, magnesium, alluminium, calcium, pottasium, sodium
solid, inorganic substances occurring naturally
four mineral groups: silicates, carbonates, sulphides and metallic