Speaker:
Adrian L. Melott, Department of Physics and Astronomy, University of Kansas

Title:
“ Did a Gamma-Ray Burst Initiate the Late Ordovician Extinction?”

Abstract:
Gamma-ray bursts are the most powerful explosions known in the Universe. A GRB within our galaxy could have catastrophic consequences for the Earth. Extrapolations from the global rate suggest an average interval of a few hundred million years for events in which the Earth is irradiated from an event on our side of the Galaxy. The atmosphere would become heavily ionized, resulting in major destruction of the ozone layer, darkened skies and nitric acid rain.
Both the prompt UV and the solar UV resulting from long-term loss of the ozone layer are destructive to living organisms. The attenuation length of UV in water is tens of meters. There is a strong candidate for a GRB based mass extinction in the late Ordovician, 440 My ago. Planktonic organisms and those animals living in shallow water seem to have been particularly hard hit during this mass extinction.

Host:
Bill Hiscock