Dr. George Shaw (from Union College), "Earth's Early Atmosphere: A New (Old) Approach that Solves Many Problems"
Time: 4-6 p.m.
Sponsored By: School of Science and Engineering
Location: Coykendall Science Building Auditorium
Contact: Dr. Julio J. Gonzalez, x3724, firstname.lastname@example.org
The idea that Earth's early atmosphere strongly resembled modern volcanic emissions (mostly water and carbon dioxide) has dominated geological thinking for more than 50 years. Although there were good reasons to adopt this view, it is almost certainly incorrect, and in serious conflict with several lines of geological evidence collected over the past several decades. There are problems with 1) how to produce a warm climate (liquid oceans) when the sun was 25% less luminous during the Archean, 2) the generation of pre-biotic molecules and the emergence of life, 3) the absence of carbonate sediments among the oldest rocks, 4) the carbon isotope record of organic and carbonate sedimentary rocks, and 5) the delay in oxidation of Earth's surface following the development of bacterial oxygenic photosynthesis. All of these problems disappear if one adopts a model with an originally highly reduced surface environment, with most of the carbon as dissolved, floating and precipitating organic compounds in a global ocean. The surface gradually becomes oxidized (over 2 billion years or so) as a consequence of global tectonic production and emission of magmagenic carbon dioxide. Such a slow, evolutionary model solves all of the above problems and even provides an explanation for the climate transition known to have taken place on Mars. George Shaw is the John & Jane Wold Professor of Geology at Union College.