Volcano
Volcanoes have been called the thermostat of the planet. They wreak havoc, but also spawn far-ranging benefits for soil and air. Some earth scientists now say that the vast swath of destruction from a volcanic eruption can be a source of creation.
Most land volcanoes erupt along plate edges where ocean floors plunge deep under continents and melting rock rises to the surface as magma. The earth's fragmented crust pulls apart and the edges grind past or slide beneath each other at a speed of up to 8 in (20 cm) per year. But just as our blood carries nutrients that feed our body parts, volcanoes do the same for the skin of the earth.
Magma contains elements required for plant growth, such as phosphorus, potassium, magnesium and sulfur. When this volcanic material is blasted out as ash, the fertilization process that moves the nutrients into the soil can occur within months. Java, one of the most volcano-rich spots on the earth, is one of the world's most fertile areas.
Magma also yields energy: it heats the underground water that is tapped by wells to warm most of the homes in Iceland. Natural steam drives turbines that provide 7% of New Zealand's electric power, and it accounts for 1% of the United States' energy needs.
Atmospheric after-effects of a volcanic eruption can last for years, as the eruption of Mount Pinatubo in the Philippines on June 15, 1991, has shown. While water vapor is the main gas in magma, there are smaller amounts of hydrogen chloride, sulfur dioxide, and carbon dioxide. Sulfur dioxide blasted 25 mi (40 km) into the stratosphere after Mount Pinatubo erupted, combined with moisture to create a thin aerosol cloud that girdled the globe in 21 days. Scientists calculated that 2% of the earth's incoming sunlight was deflected, leading to slightly lower temperatures on worldwide average. These light sulfur dioxides can circle the globe for years and possibly damage the ozone layer.
Recently, scientists mapping the sea floor in the South Pacific have found what they call the greatest concentration of active volcanoes on earth. More than 1,000 seamounts and volcanic cones, some as high as 7,000 ft (2,135 m) with peaks 5,000 ft (1,525 m) beneath the ocean surface, are located in an area the size of New York state. One potential benefit of eruptions is that they generate new mineral deposits, including copper, iron, sulfur, and gold. The discovery is likely to intensify debate over whether volcanic activity could change water temperatures enough to affect weather patterns in the Pacific. Scientists speculate that periods of extreme volcanic activity underwater could trigger El Niño, a weather system that alters weather patterns around the world.
Resources
Periodicals
Findley, R. "Mount St. Helens Aftermath: The Mountain That Was and Will Be." National Geographic 180 (December 1991): 713.
Grove, N. "Volcanoes: Crucibles of Creation." National Geographic 182 (December 1992): 5–41.
Powell, C. S. "Greenhouse Gusher." Scientific American 265 (October 1991): 20.
"Volcano Could Cool Climate, Reduce Ozone." Science News 140 (July 6, 1991): 7.
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