Rocks

Rocks can be divided into three groups based on their method of information.

Igneous rocks are formed by the cooling of igneous rock material. There are two types. There are the extrusive igneous rocks which form when lava cools above the Earth's surface, and the intrusive igneous rocks which form when magma cools below the Earth's surface.

Sedimentary rocks are formed by the solidifying of accumulated sediment. They can be clastic sedimentary rocks which are formed from sediment that has been produced by the sedimentary cycle, or non-clastic sedimentary rocks which are formed from chemical or organic deposits.

Metamorphic rocks are formed by the action of heat and pressure on pre-existing rocks. There are two types of metamorphic rocks. There are the contact metamorphic rocks formed when molten rocks comes into contact with pre­ existing rocks and alters it. There are also the regional metamorphic rocks which are formed over vast areas by sustained pressure and/or heat on pre-existing rocks.

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