Eruption of granite, from Louis Figuier's The World Before the Deluge, 1867 American edition. The theory at the time was that as the molten earth cooled, a thin crust formed on the surface. Waves on the ocean of molten material underneath would crack the crust, ejecting liquid granite which would cool in layers on the surface, forming the first mountains. Where the crust was too thick the granite did not penetrate the surface, as seen here. This image has been color enhanced.