Hallam T. Catastrophes and lesser calamities The causes of mass extinctions

New York, Oxford University Press, 2004, 226 p.When I accepted an invitation from the Oxford University Press to write a popular account of mass extinctions, I had two things primarily in mind. Firstly, I had become somewhat exasperated over the years, as had many of my colleagues, by the unbalanced and over-sensationalized treatment of the subject of mass extinctions by the media, including respectable broadsheet newspapers and television channels. This was of course the direct consequence of the remarkable discoveries of an iridium anomaly and shocked quartz at the Cretaceous– Tertiary boundary, apparently coinciding with the extinction of the dinosaurs. This led to the interpretation of a spectacular deterioration of the global environment as a consequence of the impact of an asteroid about 10 kilometres in diameter. The combination of dinosaur extinction and asteroid impact has proved irresistible to science journalists, who are always under pressure from their editors to produce sensational material that will interest the general public. As a direct consequence of this research on Cretaceous– Tertiary boundary strata, there has been a tendency among some very able scientists, both within and outside the Earth-science community, to ascribe many or even all catastrophic mass-extinction events to the impact of asteroids or comets, and much attention has been given to the prospect of future Armageddon induced by phenomena from outer space. All this has meant that events produced by changes solely confined to our own planet have been underplayed by both the public and many otherwise well-informed scientists. This book is intended to redress the balance and put impacts within the context of a number of purely Earth-bound events that have evidently affected the biosphere severely on a number of occasions in the geological past.In search of possible causes of mass extinctions
Historical background
Evidence for catastrophic organic changes in the geological record
Impact by comets and asteroids
Sea-level changes
Oxygen deficiency in the oceans
Climate change
Volcanic activity
Pulling the strands together
The evolutionary significance of mass extinctions
The influence of humans