Igneous rocks primarily form from the cooling and solidification of molten rock material known as magma (beneath the Earth’s surface) or lava (on the Earth’s surface). There are two main environments where igneous rocks are formed:
- Intrusive Igneous Rocks: These rocks form when magma cools slowly beneath the Earth’s surface. Because the cooling process is gradual, the minerals within the rock have time to grow large, resulting in a coarse-grained texture. Granite is a common example of an intrusive igneous rock.
- Extrusive Igneous Rocks: These rocks form when lava cools quickly on the Earth’s surface. Due to the rapid cooling, the minerals don’t have time to grow large, leading to a fine-grained texture. Basalt is a well-known example of an extrusive igneous rock.
In summary, igneous rocks can form deep underground or on the surface, depending on whether the cooling process occurs beneath the Earth or once lava erupts and solidifies on the surface.