International scientists probe unsolved puzzles of the Earth and beyond at "Earth System Proc...( ddress the geological debate about whet...)

ddress the geological debate about whether or not the early Earth behaved the same way as at present, with plate tectonics. Using evidence from Venus, Ghail will explain that the early Earth did not have modern plate tectonics, but did have something that looked similar to it, which explains the confusing evidence from the geological record. He will further argue that since this situation is unstable on Venus today (i.e., every so often Venus undergoes a cataclysmic resurfacing), early Earth did the same.

Grant M. Young, Department of Earth Sciences at the University of Western Ontario, explores the role of plate tectonics in bringing about dramatic climate oscillations, changes in the atmosphere and hydrosphere, and setting the stage for the "explosive" evolution of life in the Cambrian. The Proterozoic eon began and ended with unbelievable climatic changes--ancient sedimentary rocks bear silent testimony to severe glaciations on every continent. The cause of these glaciations remains one of the great unanswered questions of science, but one possibility is that they were induced by plate tectonic processes. Following continental collisions, enhanced physical and chemical breakdown of minerals from resulting mountainous land-masses would have resulted in removal of CO2 from the atmosphere, and climatic cooling. The glaciations appear to be interspersed with warm climatic episodes, when atmospheric CO2 (from volcanic eruptions) built up again because during glaciations, weathering processes are inhibited.

James C. Zachos, of the Earth Sciences Department at UCLA, notes that the current warming of global climate may not be unprecedented in terms of rate and magnitude. Some 55 mya, Earth's atmosphere and oceans warmed by more than 6C in a period of less than 20 kyrs. Geochemical evidence suggests that the warming was caused by the release of a massive quantity of methane from the destabilization of marine clathrates (frozen water and methane) in several short
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Contact: Ann Cairns
acairns@geosociety.org
303-447-2020 x 1156
Geological Society of America
24-May-2001

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