"Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 16–32 kilometers (10–20 mi) above the Earth's surface"
[Edited by SuperSkyline89, 2/22/2008 11:20:27 AM]
Theres one like that here, but its dead now, the last eruption blew it out. Pumice from the explosion reached China. Its now a massive crator lake, called lake Taupo, its dead in the center of the North Island, visible from space so long as you dont go too far away from the atmosphere.
An eruption with the magnitude of 1,000,000,000 nuclear bombs could also trigger massive earthquakes all across the globe. 1 hydrogen bomb leveled a large portion of Hiroshima, killing around 80,000 (check numbers). This eruption would kill almost everybody.