SRAC Presents: Mineralogy for Kids

Igneous Rocks: In this session - Ted Keir will explain rocks formed from magma (volcanic lava.)

Igneous rocks are formed when magma cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.

Volcanic rock forms when hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back to the earth. Intrusive rock formations are created when the magma does not reach the surface.

The main effect of extrusion is that the magma can cool much more quickly in the open air or under seawater, and there is little time for the growth of crystals.