Igneous rocks begin as magma. Intrusive igneous rocks, like granite, form when magma cools inside the Earth. Extrusive igneous rocks, like the basalt lava flow in this photo, form at the Earth's surface.
Volcanic rocks are extrusive igneous rocks.
Photograph by Steve Mattox, July 1990. Lesson at a glance, Key Concepts, and Lesson Outcomes are available by clicking here . How Chemistry Controls Volcanoes Click here for a list of activities and teaching suggestions about Minerals, Magma, and Volcanic Rocks. Click here for a list of references about Minerals, Magma, and Volcanic Rocks.