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Volcanoes & Climate

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  • npat1@juno.com
    Consequently, the sulfur compounds have a greater short-term effect, and cooling dominates. However, over long periods of time (thousands or millions of
    Message 1 of 1 , Jan 3 4:18 AM
      ' Consequently, the sulfur compounds have a greater
      short-term effect, and cooling dominates. However,
      over long periods of time (thousands or millions of years),
      multiple eruptions of giant volcanoes, such as the
      flood basalt volcanoes, can raise the carbon dioxide
      levels enough to cause significant global warming.'

      http://www.cotf.edu/ete/modules/volcanoes/vclimate.html

      Volcanoes & Climate

      Volcanic eruptions can alter the climate of the earth for both short and
      long periods of time. For example, average global temperatures dropped
      about a degree Fahrenheit for about two years after the eruption of Mount
      Pinatubo in 1991, and very cold temperatures caused crop failures and
      famine in North America and Europe for two years following the eruption
      of Tambora in 1815. Volcanologists believe that the balance of the
      earth's mild climate over periods of millions of years is maintained by
      ongoing volcanism. Volcanoes affect the climate through the gases and
      dust particles thrown into the atmosphere during eruptions. The effect of
      the volcanic gases and dust may warm or cool the earth's surface,
      depending on how sunlight interacts with the volcanic material.

      Volcanic dust blasted into the atmosphere causes temporary cooling. The
      amount of cooling depends on the amount of dust put into the air, and the
      duration of the cooling depends on the size of the dust particles.
      Particles the size of sand grains fall out of the air in a matter of a
      few minutes and stay close to the volcano. These particles have little
      effect on the climate. Tiny dust-size ash particles thrown into the lower
      atmosphere will float around for hours or days, causing darkness and
      cooling directly beneath the ash cloud, but these particles are quickly
      washed out of the air by the abundant water and rain present in the lower
      atmosphere. However, dust tossed into the dry upper atmosphere, the
      stratosphere, can remain for weeks to months before they finally settle.
      These particles block sunlight and cause some cooling over large areas of
      the earth.

      Volcanoes that release large amounts of sulfur compounds like sulfur
      oxide or sulfur dioxide affect the climate more strongly than those that
      eject just dust. The sulfur compounds are gases that rise easily into the
      stratosphere. Once there, they combine with the (limited) water available
      to form a haze of tiny droplets of sulfuric acid. These tiny droplets are
      very light in color and reflect a great deal of sunlight for their size.
      Although the droplets eventually grow large enough to fall to the earth,
      the stratosphere is so dry that it takes time, months or even years to
      happen. Consequently, reflective hazes of sulfur droplets can cause
      significant cooling of the earth for as long as two years after a major
      sulfur-bearing eruption. Sulfur hazes are believed to have been the
      primary cause of the global cooling that occurred after the Pinatubo and
      Tambora eruptions. For many months, a satellite tracked the sulfur cloud
      produced by Pinatubo. The image shows the cloud about three months after
      the eruption. It is already a continuous band of haze encircling the
      entire globe. You can learn more about the cooling effects of sulfur
      hazes by clicking here.

      Volcanoes also release large amounts of water and carbon dioxide. When
      these two compounds are in the form of gases in the atmosphere, they
      absorb heat radiation (infrared) emitted by the ground and hold it in the
      atmosphere. This causes the air below to get warmer. Therefore, you might
      think that a major eruption would cause a temporary warming of the
      atmosphere rather than a cooling. However, there are very large amounts
      of water and carbon dioxide in the atmosphere already, and even a large
      eruption doesn't change the global amounts very much. In addition, the
      water generally condenses out of the atmosphere as rain in a few hours to
      a few days, and the carbon dioxide quickly dissolves in the ocean or is
      absorbed by plants. Consequently, the sulfur compounds have a greater
      short-term effect, and cooling dominates. However, over long periods of
      time (thousands or millions of years), multiple eruptions of giant
      volcanoes, such as the flood basalt volcanoes, can raise the carbon
      dioxide levels enough to cause significant global warming.
      HTML code by Chris Kreger
      Maintained by ETE Team
      Last updated May 16, 2003

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