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Rock Cycle (Earth energy (Transfer of heat within earth (Convection…
Rock Cycle
Earth energy
External energy
Energy that powers erosion, weathering, transportation and deposition
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Metamorphic Rocks
formed when heat or pressure, generated by tectonic forces, change pre-existing rocks into new ones. when pressure and heat increase existing rocks are not stable under the new conditions, which causes the chemical elements in the rock to react and re-form into new minerals. as new metamorphic minerals develop they become aligned into a parallel pattern due to forming under pressure. this gives them foliation.
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Slate
low grade, foliated metamorphic rock, destructive margin
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Schist
Medium grade, foliated, destructive margin
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Gneiss
high grade, foliated, destructive margin
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Texture
Grain size reflects how hot the metamorphic environment was, e.g. Destructive margin
Igneous Rocks
formed by the crystallisation of molten magma. when magma cools minerals crystallise from the melt and fuse together to form solid igneous rocks. 2 main types
Pluton or Intrusive
formed by the slow crystallisation of magma deep under-ground and are composed of large crystals of silicate minerals
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Volcanic or Extrusive
formed by the rapid crystallisation of surface lava and are composed of small crystals of silicate minerals
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Texture
Size of crystals is controlled by rate of magma cooling, which is affected by the degree to which the magma is insulated
Sedimentary Rocks
formed by the accumulation of weathered and eroded rock debris, or by the accumulation of dead animal and plant remains, such as coal and limestone, or by the evaporation of salt from sea water. most sedimentary rocks are composed of rock debris and fossil fragments, they have a clastic or grainy appearance, while evaporites have a crystalline appearance.
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Texture
grain size reflects power of transporting medium and movement energy (wind/ water) at the time the sediment settled
Medium
0.02 - 0.2mm
can be transported by wind and rivers under normal flow conditions or by sea waves and currents, deposited in rivers, deserts, beaches and other marine areas
Fine
0.02mm -
deposited only when water is still, deposited in lakes and deep sea
Coarse
0.2mm +
can be transported by fast flowing rivers during flood, deposited during river floods and on beaches during storms