which type of rock does magma form when it hardens
When most people think of igneous rock they vision a volcano erupting pumice and lava. Igneous rocks form directly by crystallization from materials from a magma melt. Igneous rocks crystalize after the magma reaches the earth's surface. Igneous rock is divided into 2 groups, extrusive and intrusive. Extrusive rocks form when magma flows onto the surface of the earth or floor of the ocean through deep cracks or fissures and at volcanic vents, and then cools and hardens.