Home Object Activities Contact Who's who How to join NSF How to support NSF What's on Nature and Society Book review: Under a Green Sky by Peter D Ward, Smithsonian Books, 2007 Peter Ward has spent his working life studying the rocks that contain the evidence for the mass extinctions that have punctuated the story of life on earth. Along the way he was one of the geologists who helped to find proof for the Alvarez hypothesis that a meteorite impact caused the demise of the dinosaurs at the end of the Cretaceous period, the mass extinction that really resonates with the public. When this hypothesis was resoundingly confirmed in rocks all around the globe, geologists and others wondered whether similar impacts had caused all or most of the other extinctions also recorded in the rocks. This book provides an interesting view of the working life of a geologist, in a chatty and readable style. It also reveals the changes in geological thinking which have been forced on geologists by the evidence available to them in the rocks. In Ward’s own case, he did not stop with the rocks, but also dived in tropical waters, to link the evidence in the rocks with the evidence in today’s oceans. The conclusion Ward and his colleagues have reached is striking, and a matter of no mere academic interest but of tremendous importance for us today. Their conclusion is that the famous K-T extinction of the dinosaurs is the only one that was caused by meteorite impact. Their evidence shows that the other extinctions, including the most deadly of all at the end of the Permian, but also the late Cambrian, Ordovician, Devonian, Triassic and other minor ones, were all caused by rapid greenhouse events. Geologists had postulated that the great flood basalts that coincided with many extinctions had indeed caused them. Ward and others have shown that it was the massive outpourings of carbon dioxide and methane by the volcanic events that triggered the extinctions. As the world warmed so did the oceans, causing a shut down or at least major change in the oceanic conveyor belts. This allowed the ocean to become anoxic and the atmosphere poisonous. Ward has written this book because he has seen the clear parallels between what vulcanism has accomplished in the past, and what humans are doing now. As he says, it does not matter whether the greenhouse gases are released by vulcanism or by cars and other human activity. Already we can see the temperature rising, oceanic circulation shifting and possibly shutting down, even large dead patches in the ocean. It is ominously like the conditions that triggered almost all of the mass extinctions of the past. This book is Ward’s cry to his fellow humans to take notice and take action. Jenny Wanless December 2007 - January 2008 edition accessible here Back to top ________________________________________________________________
|