GEO 103 Lecture 16: Archean Eon
Document Summary
Major question about precambrian geology is history of plate tectonic processes. Modern-style plate tectonic activity at least since early proterozoic and likely since late archean. Common view is that plate tectonics occurred during earlier archean but it differed in detail from today. Earth was hotter due to greater radioactivity and more heat needed to be liberated at surface. Heat needs to released or else everything will become melted. If there are more breaks and faults on continental plates, there are more places for heat to escape. Little if any stable continental curst (cratons) existed at the beginning of archean. As plate tectonics developed, rapid amalgamation of granite-gneiss-greenstone belts into stable cratons through subduction processes that evolved over time. During late archean - early proterozoic, sedimentary evidence records widespread development of continental shelves, that were rarely present during early archean. By end of archean, ~50% or more of present continental crust volume was in place.
