Compare and contrast the types of igneous rocks.

There are two types of igneous rocks, which are classified as intrusive igneous rocks or extrusive igneous rocks. Both types of igneous rocks are formed from the solidification and cooling process of molten rock material. The rate at which these rocks cool and where this cooling takes place are defining distinctions between the types of rocks.
Intrusive igneous rocks are created through a crystallization process that occurs below the surface of the earth. As the rock cools beneath the surface of the Earth, large crystals form, which is a defining characteristic of intrusive igneous rocks.
Extrusive igneous rocks are created on the surface of the Earth. These rocks cool more quickly than intrusive igneous rocks, and the result is a rock that is made of smaller crystals.