WORLDWIDE DISPERSAL OF ASH AND GASES FROM EARTHS LARGEST KNOWN ERUPTION - TOBA, SUMATRA, 75 KA

The eruption of the Youngest Toba Tuff (YTT) occurred 75 +/- 2 ka in North Sumatra (2-degrees-C 45'N, 98 degrees-C 45'E). The eruption produced at least 2800 km3 of dense rock equivalent (DRE) rhyolite magma (7 x 10(18) g). Much of the volume of magma was preserved as a non-welded outflow sheet covering 20,000-30,000 km2 and a thick, welded intracaldera tuff. At least 800 km3 (2 x 10(18) g) of Toba ash was deposited in an extensive ash blanket over the Indian Ocean and Southern Asia. Detailed studies of the chemistry of minerals and glasses in pumices from the YTT enable estimation of the minimum masses of gaseous components released to earth's atmosphere during the eruption: H2O:. The high eruption rate, with the entire event lasting perhaps 9-14 days make stratospheric venting of a significant fraction of these gases and associated silicate ash and aerosol particles likely. The masses of ash and gases released is nearly two orders of magnitude higher than any known historic eruption.