Alabama Landscapes

Geology, Geologic Processes and Geologic History

Igneous Rocks

Igneous rocks form by cooling and solidification of magma (molten rock material formed by partial melting of rocks in the Earth's interior)

Extrusive Igneous rocks form on or above the Earth's surface.
The most common extrusive igneous rock is basalt, a dark-colored very fine grained (individual crystals are so small that they cannot be seen) rock.

Intrusive Igneous rocks form beneath the Earth's surface.
The most common intrusive igneous rock is granite, a light-colored coarse-grained (individual crystals can be seen) rock.