Explain what is the geologic cycle?

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The geologic cycle is referencing the rock cycle which is the process by which rocks change into different types of rocks.  3 types of rocks: sedimentary, igneous, and metamorphic.  The general conditions needed to form each type of rock are as follows:

Sedimentary rock: sediment needs to be created through weathering and erosion. Sediment is then deposited in layers and squeezed due to increasing amounts of pressure from additional sediment deposition. Water is likely present and squeezed out which causes a cementation like process.  Depending on the sediment size and pressure this process could create anything from sandstone to siltstone to slate to limestone. 

Metamorphic rock: extreme heat and pressure. The heat can be enough to melt it, but doesn't because of the high pressure. These conditions cause the minerals within the rock to change from one type to another.  Think coal to diamond. 

Igneous rock: create magma, let it cool/harden. Magma can be formed in a variety of way, but the simplest explanation is high heat and LOW pressure.  Liquids need space to expand in to, so that is why low pressure is needed.  

Any of those rocks types can change into the other type and it can even change into a different type of the original rock.  There is no set beginning and end to the geologic/rock cycle.  

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