GENERAL GEOLOGY

Detailed explanation-1: -Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface. These are the rocks that form at erupting volcanoes and oozing fissures.

Detailed explanation-2: -Igneous rocks come from melted rock material, or magma, that lies beneath Earth’s surface. Igneous rocks form when magma from inside the Earth moves toward the surface, or is forced above the Earth’s surface as lava and ash by a volcano. Here it cools and crystallizes into rock.

Detailed explanation-3: -Igneous rocks form when magma (molten rock) cools and crystallizes, either at volcanoes on the surface of the Earth or while the melted rock is still inside the crust. All magma develops underground, in the lower crust or upper mantle, because of the intense heat there.

Detailed explanation-4: -Igneous rock is formed through the cooling and solidification of magma or lava.

Detailed explanation-5: -Igneous rocks contain randomly-arranged crystals. If the magma cools quickly, the crystals will be large (coarse grained). If the magma cools slowly, the crystals will be small (fine grained). Because igneous rocks are formed from molten rock, they do not contain fossils.