Igneous Rocks formation

Igneous Rock Formation

Igneous rocks are formed from this molten magma. These rocks form when the magma cools and crystallizes. This can happen above ground as with lava. It can also form below the surface when the molten rock rises in the crust but does not reach the surface.

The Cooling off Period

When the magma reaches the surface it cools quickly, a matter of days or weeks. When the magma forms pockets underground it cools much more slowly. This could take thousands or even millions of years. The rate at which the magma cools determines the kind of igneous rocks that are formed. Faster cooling surface lava creates rock that is fine grained or aphanitic. The rapid cooling doesn’t allow large crystals to form. In addition most of the gasses are driven off into the atmosphere.The slower cooling that takes place underground allows larger crystal formation. The Granite pictured above is an example of this type of rock formation. 

Igneous Rocks Cycle

After igneous rocks have been formed they can be transformed into metamorphic or sedimentary rocks. They can even be re-melted to form new igneous rocks.