All major crises of life in the past 300 million years coincide with large scale volcanic eruptions.
This includes the two biggest mass extinctions of all time: the end-Cretaceous and end-Permian events.
The reasons behind this coincidence have not been clear but geologists have generally thought that it is related to the effects of two of the principal volcanic gases, carbon dioxide and sulphur dioxide.
These have diametrically opposed climatic effects, the former causes long-term global warming and the latter causes short-term cooling due to formation of clouds of volcanic aerosols.
The talk will look at some of the latest research which shows that some mass extinction events coincide with huge individual eruptions - involving up a thousand cubic kilometres of lava. Event Page: http://www.sciencecafesheffield.org/200911.htm