9 A conical volcano

CHENG'S MISSION NOTES A CONICAL VOLCANO Volcanoes are made of rock that once lay deep underground and melted to become magma. When pressure in the Earth forces magma to the surface, it erupts as lava. The cone shape is formed by layers of dried lava that has hardened to form solid rock.

LIFE OF A VOLCANO There are thousands of volcanoes around the world. They are either active, dormant, or extinct. Active volcanoes can erupt at any time, and their magma chambers are full. Dormant volcanoes haven't erupted for a while, but they might become active again. Extinct volcanoes are long dead, and won't erupt again. They have empty magma chambers.