10 November 2020
(presentation at 7.00pm, Zoom discussion at 7.45pm)
In this talk, Professor John Marshall, from the University of Southampton, will explore how a brief UV-B burst, during a climatic warming interval, collapsed the Devonian-Carboniferous boundary terrestrial ecosystem.
There is an unexplained terrestrial mass extinction at the Devonian-Carboniferous boundary (359 million years ago). The discovery in East Greenland of malformed land plant spores demonstrates that the extinction was coincident with elevated UV-B radiation demonstrating ozone layer reduction. Mercury data through the extinction level proves that, unlike other mass extinctions, there were no planetary scale volcanic eruptions. Significantly, the Devonian-Carboniferous boundary terrestrial mass extinction was coincident with a major climatic warming that ended the intense final glacial cycle of the latest Devonian ice age.
A mechanism for ozone layer reduction during rapid warming is increased convective transport of ClO. In such a situation ozone loss during rapid warming is an inherent Earth System process with the unavoidable conclusion that we should be alert for such an eventuality in the future warming world. Other explanations, often mooted, but never before testable are the ozone being stripped off by a distant supernova explosion and instability of the Earth’s magnetic field.
This event has been organised by the South regional committee.
The presentation will be livestreamed on this page at 7.00pm and available to all. There is no need to book to watch this live stream.
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Featured image: Rich Painting
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