When a volcano erupts with a great explosion, a powerful pyroclastic flow travels downward to wreak havoc. This combination of ash, gas and mineral fragments is so hot that it can burn and destroy almost anything that gets in its way. Volcanic ash can travel at speeds of almost 125 mph (200 kph) as it covers vast areas with a thick layer of hot, toxic dust. Ash fall can be carried thousands of miles by strong winds, threatening plant and animal life along the way.
Aside from the heat of the initial pyroclastic flow, continuing downfalls of volcanic ash can threaten ecosystems. Plants smothered by dust and debris will eventually die because they can't get enough sunlight or access to air. Microorganisms in the soil are also at risk. Branches of trees can break from the weight of heavy dust layers. The ash also carries toxic chemicals and dangerous levels of acidity. This can make it impossible for plant life to survive when the ashes become mixed with the topsoil. Animals don't escape the devastation. They can develop skin and eye irritations, and smaller insects can be rendered immobile by heavy particles in the air. Inhalation of ash particles can cause respiratory problems, and chemicals can poison supplies of food and water.
The ash from a volcanic eruption is a short-term death sentence for nearby plants and animals, but the long-term effects on the environment can be positive. Volcanic soil holds more water than most other soils, which helps irrigate plant life. It may take weeks or even thousands of years, but eventually, the ash particles ejected from a volcano actually provide the very plants they helped destroy with the vital nutrients organic carbon and nitrogen.
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