igneous rock

A lava fountain on Kilauea Iki, Hawaii, USA. As magma reaches the earth's surface escaping gas sprays lava into the air.

Basalt rock through a polarized microscope. Basalt is formed from solidified lava.

Olivine gabbro through a polarized microscope. Gabbro is a coarse-grained igneous rock.

Basalt formations by the beach at Vik, in southern Iceland. Basalt is a hard, igneous rock, formed by the rapid cooling of magma as it comes in contact with air. These hexagonal columns are typical of basalt.

Granite is an igneous rock, normally found deep in the earth's crust and made of crystals formed from the cooling of molten magma. It is sometimes exposed at the surface where the sedimentary rock, such as sandstone, has been eroded. Surface concentrations of Cornish granite can be found on the highlands of Land's End and Bodmin Moor.

Rock formed from the cooling and solidification of molten rock called magma. The acidic nature of this rock type means that areas with underlying igneous rock are particularly susceptible to the effects of acid rain. Igneous rocks that crystallize slowly from magma below the Earth's surface have large crystals. Examples include dolerite and granite.

Igneous rocks that crystallize below the Earth's surface from magma are called plutonic or intrusive, depending on the depth of formation. They have large crystals produced by slow cooling; examples include diorite and granite. Those extruded at the surface from lava are called extrusive or volcanic. Rapid cooling results in small crystals; basalt is an example.