6.2 Igneous Rocks

Igneous Rock

Rock that forms in or around volcanoes from the cooling and solidification of magma or lava.

Extrusive Igneous Rock

Forms when lava cools quickly on Earth's surface.

Intrusive Igneous Rock

Forms from magma that cools slowly underground.

Texture of Igneous Rocks

Depends on whether they form underground (coarse-grained) or on the surface (fine-grained).

Magma

Liquid rock beneath the Earth's surface.

Felsic Rock

Igneous rock that is high in silica and lighter in color.

Mafic Rock

Igneous rock that is rich in magnesium and iron and typically darker in color.

Cooling Rate

Determines the crystal size in igneous rocks; slow cooling forms larger crystals, fast cooling makes tiny or no crystals.

Rock Cycle

The continuous process by which rocks are created, changed, and transformed.

Fine-Grained Rock

Igneous rock with small crystals formed by rapid cooling.

Coarse-Grained Rock

Igneous rock with large crystals formed by slow cooling.

Lava

Liquid rock that erupts from a volcano onto Earth’s surface.