When hot molten magma escapes from the Earth’s core becoming cooler, and forming hard rocks, we refer to this process as volcanism. Volcanism takes place both above the surface of Earth, as well as beneath its surface. When molten lava escapes the Earth and reaches the surface geologists say that it is extrusive volcanism. When molten magma cools and hardens beneath the surface of the Earth, we say that it is intrusive volcanism. In some cases, molten magma cools and hardens deep beneath the surface of the Earth, far below the crust. When this happens, scientists call it plutonic volcanism.