The Physical Make-up of Volcanoes.

VOLCANOES AND MOUNTAINS Volcanoes are mountains but they are very different from other mountains; they are not formed by folding and crumpling or by uplift and erosion. Instead, volcanoes are built by the accumulation of their own eruptive products lava, bombs (crusted over ash flows, and tephra (airborne ash and dust). A volcano is most commonly a conical hill or mountain built around a vent that connects with reservoirs of molten rock below the surface …

…sm. They must continue to improve the capability for predicting eruptions and to provide decision makers and the general public with the best possible information on high-risk volcanoes for sound decisions on land-use planning and public safety. Geoscientists still do not fully understand how volcanoes really work, but considerable advances have been made in recent decades. An improved understanding of volcanic phenomena provides important clues to the Earth's past, present, and possibly its future.