Natural Disasters

Volcanoes

A volcano is a vent through which molten rock escapes to the earth's surface. When pressure from gases within the molten rock becomes too great, an eruption occurs.

Some eruptions are relatively quiet, producing lava flows that creep across the land at 2 to 10 miles per hour.

Explosive eruptions can shoot columns of gases and rock fragments tens of miles into the atmosphere, spreading ash hundreds of miles downwind. Lateral blasts can flatten trees for miles. Hot, sometimes poisonous, gases may flow down the sides of the of the volcano.

Lava flows are streams of molten rock that either pour from a vent quietly through lava tubes or by lava fountains. Because of their intense heat, lava flows are also great fire hazards. Lava flows destroy everything in their path, but most move slowly enough that people can move out of the way.

Fresh volcanic ash, made of pulverized rock, can be harsh, acidic, gritty, glassy and odorous. While not immediately dangerous to most adults, the combination of acidic gas and ash could cause lung damage to small infants, very old people or those suffering from severe respiratory illnesses. Volcanic ash can also damage machinery, including engines and electrical equipment. Ash accumulations mixed with water become heavy and can collapse roofs. Volcanic eruptions can be accompanied by other natural hazards: earthquakes, mudflows and flash floods, rock falls and landslides, acid rain, fire, and (under special conditions) tsunamis. Active volcanoes in the

U.S. are found mainly in Hawaii, Alaska and the Pacific Northwest.

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