Igneous Rocks

Igneous rocks are formed from the solidification of molten rock material (magma or lava).

The two main types of igneous rocks are intrusive (plutonic) and extrusive (volcanic).

Intrusive igneous rocks form from magma that cools slowly below the Earth's surface, while extrusive igneous rocks form from lava that cools quickly at the surface.

Granite is an intrusive igneous rock composed mainly of quartz, feldspar, and mica.

Basalt is an extrusive igneous rock that is dark in color and primarily composed of pyroxene and plagioclase.

Obsidian is a naturally occurring volcanic glass formed from rapidly cooled lava.

Pumice is a light, porous volcanic rock that forms when lava cools quickly and traps gas bubbles.

Slower cooling allows larger crystals to form, while faster cooling results in smaller crystals.

Magma is molten rock beneath the Earth's surface, while lava is magma that has reached the surface.

Crystal size can indicate the cooling history of the rock; larger crystals suggest slower cooling.