Volcanoes form when magma rises from below the Earth's surface. When a volcano erupts, it can throw solid materials like ash and rocks into the air. The volcanic cone is formed over time from layers of ash and lava. Lava is magma that flows out of the volcano. The crater is the opening where materials exit, and the conduit is the shaft that carries magma upward. Below the volcano is the magma chamber, a pool of magma near the surface.