|MadSci Network: Earth Sciences|
How do volcanoes affect the atmosphere?
That's a good question Amanda and the answer is very important since volcanic eruptions can significantly alter the earth's climate. Volcanoes affect the Earth's atmosphere by pumping dust and various types of gases into the air when they erupt.
While larger dust particles may stay in the lower atmosphere for a few hours or days, they quickly settle out and are removed by rainfall. Smaller dust particles may be blasted up into the dry upper atmosphere (the stratosphere), however, where they will stay for several weeks or months before they finally settle out. These particles affect the earth's climate by blocking the sunlight and cooling large areas of the earth. A large number of volcanic eruptions over a short period of time may cool the earth enough to cause real problems.
Important gases ejected by erupting volcanoes are water vapor, carbon dioxide, and sulfur compounds like sulfur dioxide. Since the earth's atmosphere already contains a lot of water vapor and carbon dioxide, these gases usually don't have much of an effect globally. If there were a large number of volcanic eruptions over a short period of time, however, the carbon dioxide levels may contribute to global warming (just the opposite effect of the dust I just wrote about!).
Sulfur compounds from volcanoes can cause real problems, on the other hand. They rise easily into the stratosphere where they combine with small amounts of water vapor to form tiny droplets of sulfuric acid (sometimes called "battery acid" since it's found in your car's battery). These droplets reflect large amounts of sunlight back into space for several months and may significantly cool the earth.
For more general information about volcanoes, check out the wonderful world-wide web Volcano World. For more information about volcanoes and climate, read the essay Volcanoes and Global Climate Change from NASA or the essay Volcanic Emissions and Global Change from the United States Geological Survey.
Try the links in the MadSci Library for more information on Earth Sciences.