Formation of Rocks (Cambridge (CIE) IGCSE Environmental Management): Flashcards
Exam code: 0680
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Define igneous rock.
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Define igneous rock.
Igneous rock is rock that forms when molten rock (magma or lava) cools and solidifies.
How does magma differ from lava?
Magma is molten rock beneath the Earth's surface, while lava is molten rock that reaches the surface.
Define intrusive igneous rock.
Intrusive igneous rock forms below the surface when magma cools slowly, so it has large crystals, for example granite.
True or False?
Igneous rocks are soft and erode easily.
False.
Igneous rocks are hard and more resistant to erosion.
Define extrusive igneous rock.
Extrusive igneous rock forms on the surface when lava cools quickly, so it has small crystals, for example basalt.
Basalt is a dark, fine-grained rock found mainly in crust.
Basalt is a dark, fine-grained rock found mainly in oceanic crust.
Define sedimentary rock.
Sedimentary rock forms from sediments that are eroded, transported and deposited, then compacted and cemented over time.
What is limestone mainly made of?
Limestone is mainly made of calcium carbonate from the shells and skeletons of marine organisms.
Sandstone forms from sand-sized grains, mainly , that are buried, compacted and cemented.
Sandstone forms from sand-sized grains, mainly quartz, that are buried, compacted and cemented.
Which particles form shale?
Shale forms from clay and silt particles that settle in calm water, such as lakes or deep seas.
Define metamorphic rock.
Metamorphic rock is existing igneous or sedimentary rock changed by heat and/or pressure inside the Earth.
Which metamorphic rock forms when limestone recrystallises under heat and pressure?
Marble forms when the calcium carbonate crystals in limestone recrystallise.
True or False?
Metamorphic rocks form when existing rock melts and then cools.
False.
Metamorphism changes rock through heat, pressure or chemical processes without melting it.
Which metamorphic rock forms when the minerals in shale align into thin layers?
Slate forms when moderate heat and pressure align the minerals in shale.
Define rock cycle.
The rock cycle is a continuous process that shows how rocks change from one type to another over time.
Define weathering.
Weathering is the breakdown of rocks in situ, at or near the Earth's surface, into smaller pieces.
How does acid rain cause chemical weathering?
Acid rain causes chemical weathering through chemical reactions that dissolve minerals in rocks.
Freeze-thaw action is a type of weathering.
Freeze-thaw action is a type of physical weathering.
Define erosion.
Erosion is the removal of weathered rock particles from their original location.
True or False?
Plant roots growing into cracks cause chemical weathering.
False.
Plant roots and animals breaking down rock cause biological weathering.
Define transportation.
Transportation is the movement of eroded material (sediment) from one place to another by wind, rivers, glaciers or waves.
Which sediment particles travel furthest during transportation?
Smaller, lighter particles travel furthest, while larger, heavier particles move only short distances.
Define deposition.
Deposition is the dropping of sediment after transport, when the moving water, wind or ice loses energy and can no longer carry it.
Which landforms does deposition create?
Deposition creates landforms such as river deltas, sand dunes and beaches.
Define sedimentation.
Sedimentation is the process by which transported material settles and builds up in layers at the bottom of rivers, lakes and oceans.
True or False?
Sedimentation happens before deposition.
False.
Sedimentation starts after deposition, once dropped sediment begins to collect in layers.
Define compaction.
Compaction is when pressure from the sediment layers above squeezes the lower layers together.
During compaction, are pushed out from between the grains, so the sediment becomes denser.
During compaction, water and air are pushed out from between the grains, so the sediment becomes denser.
Define cementation.
Cementation is when minerals crystallise and glue compacted particles together to form sedimentary rock.
Which minerals bind sediment grains together during cementation?
Minerals such as silica or calcium carbonate fill the spaces between grains and bind them together.
Define crystallisation.
Crystallisation is the process by which molten rock cools and forms crystals, making igneous rock.
True or False?
Rapid cooling of lava on the surface produces large crystals.
False.
Rapid cooling produces small crystals, as in basalt; slow cooling underground produces large crystals, as in granite.
Define permeability.
Permeability is the ability of water to pass through the pore spaces of rock and soil.
Define pore spaces.
Pore spaces are the tiny gaps between rock or soil particles that let water and air move through.
True or False?
A porous rock is always permeable.
False.
Porous means the rock has spaces; if those pores are not connected, water cannot flow through, so the rock is impermeable.
Why are most sedimentary rocks permeable?
Most sedimentary rocks are permeable because they form from layers of particles that leave spaces between the grains.
Two examples of permeable rocks are limestone and .
Two examples of permeable rocks are limestone and sandstone.
Why does limestone let water flow through it?
Limestone lets water flow through because it has small cracks and spaces.
Define aquifer.
An aquifer is an underground layer of permeable rock that stores groundwater.
Why are igneous and metamorphic rocks usually impermeable?
Igneous and metamorphic rocks are usually impermeable because they have a dense, compact structure with few spaces for water.
True or False?
Shale is a permeable sedimentary rock.
False.
Shale is impermeable because its fine clay particles pack tightly together.
What happens to water that reaches an impermeable rock?
The water cannot soak in, so it flows over the surface or collects above the rock, forming springs or surface water.
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