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What Defines a Continent? Distinguished Speaker Dr. Cin-Ty- Lee Explains This Week

The EES Distinguished Speaker this week is Dr. Cin-Ty Lee, Professor and Chair of the Earth, Environmental and Planetary Sciences at Rice University. His talk is titiled:

"The Making of a Continent"

What defines a continent? Is it its elevation or its composition?  Here I show that continents are ultimately defined by their thick crusts, which allows them to ride high above the seafloor, though not necessarily always above sea level. I show that continents are born through magmatic mountain building, which results in the generation of thick crust.  And as the crust thickens, magmas undergo more extensive differentiation at higher pressures, resulting in garnet fractionation, which drives the formation of a silicic crust. The garnet-rich cumulates eventually founder back into the mantle.  Thus, the key to making continental crust is magmatic thickening, with the generation of silicic crust being merely a by product of the thickening process.  After magmatism and tectonism end, erosion and thermal subsidence causes elevations to decrease, such that mountains eventually invert into basins.  The resting state of a stabilized continent, however, depends on the thermal state of the Earth's mantle and the nature of the underlying continental lithospheric mantle.  In the Proterozoic, stable continents may reside below sea level, only to rise above sea level as the Earth cools.  Continents, born through mountains, eventually become basins, but with the march of time, they rise again. The implications of Earth transitioning from a water type world to a more terrestrial world will be

Lee is a geologist/petrologist/geochemist who investigates how our planet has evolved with time, from the deepest parts of the Earth's mantle to the continental crust and to the atmosphere.  He combines field mapping and sampling with state of the art analytical tools (mass spectrometry, x-ray spectrometry, electron probe microanalysis) and simple analytical and numerical modeling.  Lee has worked on continent formation and destruction, redox evolution of the Earth's interior, the origin of various ore deposits, the petrological structure of volcanic margins, and the origin of granites.  He is now working on the geochemical interactions between the deep Earth and oceans/atmospheres in order to better understand what controls long term climate evolution.

Join us as we step through the making of a continent on Friday, September 14, 2018 at 12:30 in Room 204, Natural Science Building on the East Lansing Campus.

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