Mass extinctions of life with up to > 90% loss of species have been an important driving force for the evolution of life on the Earth, but their causes are still debated. The 12 documented extinction episodes of the last 260 My are significantly correlated with the 4 largest (≥ 100 km in diameter) impact craters at 36, 66, 145, and 215 Ma (with coeval layers of distal impact debris) and with 8 massive flood-basalt eruptions at 66, 94, ~120, 134, 184, 201, 252 and 260 Ma. The 8 coeval flood-basalts/mass extinctions are all correlated with times of ocean anoxia, suggesting that gases released by the volcanism led to hyperthermal conditions, ocean hypoxia, acidification, and resulting mass extinctions.

On a longer timescale, the 6 “major” mass extinctions of the last 541 My (at 66, 201, 252, 260, 372, and 443 Ma) all seem to be correlated with concurrent flood-basalt episodes (and volcanogenic Hg anomalies) and hypoxic oceans. These highly significant correlations argue that mass extinctions are caused almost exclusively by severe environmental crises produced by pulses of massive flood-basalt volcanism, and by the largest asteroid/comet impacts. There is little room for strictly biological causes.

Spectral analysis has revealed evidence for an apparent underlying ~26 to 36-My cycle in extinctions, cosmic impacts, volcanism and other geological events. These cyclical events are most likely related to pulses of plate-tectonic/hotspot activity, possibly paced by the astrophysical dynamics of the Galaxy.

About the Speaker:

Michael R. Rampino is a Professor in the Biology and Environmental Studies Departments at New York University. He received his Ph.D. from Columbia University. Connections with NASA go back to 1978, when he was a post-doc and then worked for several years as a Research Associate at the Goddard institute for Space Studies in New York City. His fields of interest include volcanology, impact studies, mass extinctions, paleoclimatology and most recently potential connections between terrestrial geology and astrophysical cycles. 
                   
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