A volcano is a hole or vent in the Earth's crust through which molten rock and other materials are expelled onto the surface in a volcanic eruption. Often times when a volcanic eruption occurs it can explode with a huge destructive force. As the molten rock and other extruded materials cool and harden, in particular near the vent, a large volcanic cone is created. Also created atop this cone may be a crater where the main vent is located. Commonly there are two types of volcanoes, one of which is known as a shield volcano. Shield volcanoes are usually much larger in diameter than they are in height. They form when lava is extruded in a gentle, non violent manner because it is mostly liquified and fluid like. The other type is a composite volcano. Composite volcanoes, unlike shield volcanoes are very steep-sided and they erupt with a massive explosion sending lava, pumice, and hot volcanic ash flying in all directions. Today there are about 500 known active volcanoes, most of which lie on a plate boundary.

Adam's Home Page

Class Home Page