Igneous rocks form when molten material cools and hardens.
They may form either below or above Earth’s surface.
They make up most of the rocks on Earth.
Most igneous rock is buried below the surface and covered with sedimentary rock, and so we do not often see just how much igneous rock there is on Earth
In some places, however, large areas of igneous rocks can be seen at Earth’s surface. the Figure shows a landscape in California’s Sierra Nevada that consists entirely of granite, an igneous rock.