VolcanoesMonday August 07 2000 Volcanoes - 06:53

Volcano, mountain or hill formed by the accumulation of materials erupted through one or more openings (called volcanic vents) in the earth's surface. The term volcano can also refer to the vents themselves. Most volcanoes have steep sides, but some can be gently sloping mountains or even flat tablelands, plateaus, or plains. The volcanoes above sea level are the best known, but the vast majority of the world's volcanoes lie beneath the sea, formed along the global oceanic ridge systems that crisscross the deep ocean floor

Materials erupting from ValcanoesMonday August 07 2000 Volcanoes - 07:53

Three different types of materials may erupt from an active volcano. These materials are lava, tephra (rock fragments), and gases. The type and amount of the material that erupts from an active volcano depends on the composition of the magma inside the volcano.