Frontiers of Science Lecture A Cool Early Earth This event will feature John W. Valley, professor of geology and geophysics at the University of Wisconsin-Madison. His presentation will focus on the climate and geology of the young planet Earth, and how life grasped a beginning on the planet. Date: Wednesday, March 8, 2006 Time: 7:30 p.m. Location: Aline Wilmot Skaggs Biology Auditorium, University of Utah campus 275 South 1430 East Admission: FREE and open to the public! Contact Info: (801) 581-6958 jdegooyer@science.utah.edu www.science.utah.edu Frontiers of Science lecture: A Cool Early Earth with Professor John W. Valley When the Earth was formed, some 4.5 billion years ago, it was an inferno of boiling metals, minerals and gases. Red-hot oceans of molten rock, massive meteorite strikes, and even brimstone in the atmosphere justify calling this time period the Hadean. These extreme conditions had to subside before continents could form, before the dense atmosphere could pool as liquid water, and before the first primitive life could survive and evolve. But when was the end of the hellish Hadean period? Evidence from rocks has placed the Hadean boundary at about 3.8 billion years ago. The oldest sedimentary (low temperature) rocks and hints of life are dated to 3.8 billion years, and the earliest known fossils are 3.5 billion years old. Recently, however, the discovery of crystals of the mineral zircon, as old as 4.4 billion years old, from isolated localities in northwestern Australia has provided evidence that the Hadean ended far sooner than previously thought  perhaps by 400 million years! These zircons are exceptionally robust, and were separated from parent rocks by chemical weathering, dispersed across the Earth as wind-blown dust, and deposited in sand and gravel bars that are now solid rock. They carry chemical clues in the form of mineral inclusions, trace elements, and isotopes of uranium, lead, oxygen, and hafnium. The study of these tiny Âtime-capsules is driving new technology and each new result is avidly debated. While extreme opinions exist on both sides, a moderate suggestion is that small continental land masses existed by 4.4 byr, that oceans hospitable to life existed by 4.2 byr, and thus the Hadean ended before 4.2 byr. This concept of a cool early Earth represents a major departure from traditional ideas of how the Earth evolved. Valley earned M.S. and Ph.D. degrees in geophysics at the University of Michigan , Ann Arbor in 1977 and 1980, respectively. He spent three years at Rice University in Houston as an assistant professor before accepting a faculty position at the University of Wisconsin-Madison in 1983. He was promoted to a full professor in 1989, and is currently the Charles R. Van Hise Professor of Geology and Geophysics at UW-Madison. Professor Valley was elected a Fellow of the Geological Society of America in 1992, and a Fellow of the Mineralogical Society of America in 1993. He is now the President of the Mineralogical Society of America. He has served as Associate Editor of the Journal of Geophysical Research, and Associate Editor of the American Journal of Science. In 2003, Valley received the N.L. Bowen Award, presented by the American Geophysical Union for his work on zircons from early Archean rocks of northwestern Australia. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com