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Cards In This Set
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What are igneous rocks formed by?
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Magma
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What are sedimentary rocks formed by?
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Particles
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What are metamorphic rocks formed by?
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Heat or pressure
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What is magma?
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Magma is hot, molten rock, found inside the earth, in the mantle.
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What is the earth's crust divided up into?
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Tectonic Plates
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What are tectonic plates?
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Parts of the earth's crust which float on the mantle.
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What causes tectonic plates to move a few mm a year?
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Convection currents
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Where to tectonic plates meet?
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Plate boundaries or plate margins
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What happens at convergent plate margins?
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Two plates move towards each other and crust is destroyed. fold mountains, earthquakes and volcanoes are common
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What happens at transform plate margins?
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Plates move sideways against each other and material is neither gained nor lost. Volcanoes are rare at these margins, but earthquakes are common
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What happens at divergent plate margins?
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Two plates move away from each other. magma rises from the mantle and new crust is created. this mostly happens under the sea. here volcanoe are common.
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What is weathering?
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The breakdown of rocks by physical, chemical or biological processes
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What happens in freeze-thaw action in temperate climates?
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Water gets trapped in cracks in the rock, which expands when it freezes pressurising the rock sides. As the water melts, it contracts, releasing pressure on the rock cracks. this causes the rock to weaken, resulting in pieces of rock breaking off.
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What happens in onion skin weathering in hot desert climates?
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Each day surface layers of rock heat up and expand. at night the cold makes them contract, this causes thin layers to peel off.
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What does biological weathering need to happen, and what is the process?
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It needs plant roots or decay. plant roots can grow down through cracks in rock surfaces and push them apart, loosening fragments. decaying plants and animal remains make acids which eat away at the rocks below.
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