A volcano could be a mountain that opens downward to a reservoir of molten rock beneath the surface of the world. Unlike most mountains, the area is pushed up from below, volcanoes have vents through which molten rock escapes to the earth's surface. When the gas pressure in the molten rock becomes excessive, an associated eruption occurs. Eruptions can be silent or explosive. There may also be volcanic rock flows, two-dimensional landscapes, toxic gases and rocks, and fly ash that can generally travel many miles downwind. Due to their intense heat, volcanic rock flows pose significant fire risks. Volcanic rock flows destroy everything in their path, but most are large enough for people to move away from the area. Fresh volcanic ash, composed of small-grained rock, can be abrasive, acidic, grainy, gaseous and odorous. Although not immediately dangerous to most adults, the acid gas and ash will cause damage to the respiratory organs of young children, the elderly and those suffering from serious metabolic diseases. Volcanic ash can also damage machinery, as can en...