In the summer of 2008 Mount Kasatoshi in Alaska's Aleutian Islands blew,
sending volcanic minerals, including iron
dust, far to sea and prompting plankton blooms across the Gulf of Alaska.
If
volcanic activity continues to increase, and there is an eruption big enough to
send millions of tons of ash and
dust into the upper layers of the atmosphere, then the Earth's temperature would likely drop at least a degree or two from present levels.