by Achilles Windsor

Created on: March 22, 2007   Last Updated: May 02, 2007

The three main types of rock are igneous rock, sedimentary rock, and metamorphic rock. These rocks consistently go through a cycle in which they are changed into one another. This is known as the rock cycle.

Igneous rocks are solid rocks that have formed from liquid cooling magma. There are many types of igneous rocks. The differences in the cooling of the rocks, the content of the magma, and where the rock is formed.

The texture depends on the amount of grains on the surface. The amount of grains on the surface depends on how quickly the rock cooled. The size of the grains can vary greatly. Some rocks have large grains, making their texture very coarse. Other rocks cool very quickly and have microscopic grains, making their texture very glassy.

An example of an igneous rock is basalt. Basalt is an example of a rock, which is fine-grained, known as aphaeretic. An example of the opposite, phaneretic is granite.

The next type of rock I will go into depth about are sedimentary rocks. Sedimentary rocks are known as secondary rocks because of the way that they form. They, for the most part, form as the result of other rocks, when pieces of other rocks break off and are compressed. There are three types of sedimentary rock: Clastic, Chemical, and Organic.

Clastic rocks are the average type of sedimentary rock. They are formed when pieces of rock break off, accumulate, and compress.

Chemical rocks, for the most part, form when standing water evaporates and leaves behind minerals which accumulate.

Organic rocks form when bones from organic lifeforms, hence the name, accumulate and compress.

The last type of rock I will discuss is the metamorphic rock. Any rock can turn into a metamorphic rock. Metamorphic rocks are formed when rocks are moved out of equilibrium after going to a new environment, forcing them to change to keep their equilibrium. Some examples of metamorphic rock are slate, marble, and schist.

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