Approximately 73,000 years ago, an Indonesian volcano known as Toba
erupted with enough force to send more than 600 cubic miles of
volcanic material into the atmosphere. Detected on this graph, which
displays volcanic sulfate levels between 20,000 and 110,000 years
ago, Toba was the largest eruption of the past 500,000 years. (The
seemingly larger spike at about 53,000 years ago involved a series
of smaller eruptions on Iceland, which is far closer than Toba is to
Greenland, where this core was taken.) Such violent, so-called
caldera eruptions can drastically alter global climate, by spewing
so much ash and sulfur compounds into the atmosphere as to block
sunlight and lower temperatures worldwide. Ice cores offer
scientists the best means available to learn how past eruptions have
affected climate—and thus to predict the impact that future
ones might have. If an eruption on the order of Toba, which
climatologists believe may have led to as much as several centuries
of cold climatic conditions, were to occur today, it could seriously
disrupt life on Earth.Graph modified from:
Zielinski, G.A., P.A. Mayewski, L.D. Meeker, S. Whitlow, and M. Twickler, 1996a, A 110,000-year record of explosive volcanism from the GISP2 (Greenland) ice core, Quaternary Research, 45, 109-118.