The type of rocks formed from cooling magma are called igneous rocks. These rocks can form either below the Earth's surface as intrusive (or plutonic) rocks or above the surface as extrusive (or volcanic) rocks. When magma cools and solidifies slowly beneath the surface, larger crystal formations can occur, typical of intrusive igneous rocks like granite. Conversely, when magma erupts onto the surface and cools rapidly, it forms extrusive igneous rocks, such as basalt, which have much smaller crystals. Igneous rocks play a critical role in Earth's geology, being a source of minerals and forming the foundation of many landscapes.