Geology

Toba Timing

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Science  30 Nov 2012:
Vol. 338, Issue 6111, pp. 1128
DOI: 10.1126/science.338.6111.1128-a
CREDIT: MAX GRABERT

Toba in Sumatra is thought to have been the largest volcanic eruption in the past tens of millions of years—larger than the main eruption at Yellowstone—and it formed a huge lake about 30 km wide and 100 km long. Signals of the eruption are thought to be preserved in both Greenland and Antarctic ice cores. The event has been proposed to have led to a population bottleneck in early Homo sapiens that is recorded in our genetic history. The exact age of the eruption, however, has been uncertain, complicating efforts at global correlation of climatic and environmental events. Storey et al. have now obtained a precise 40Ar/39Ar radiometric age on crystals from Toba deposits in Malaysia. The age, supported by astronomical calibrations, is 73.88 ± 0.32 thousand years ago, close to the presumed age of about 74 ka. The date helps calibrate the signals and thus correlates the age of ice cores in separate hemispheres, and the eruption timing just precedes an abrupt cooling of about 10°C recorded in the Greenland ice.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1208178109 (2012).

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