Friday, September 21, 2018
Room 1528 - 1100 North University Building Map
Continents ride high because they are underlain by thick, in contrast to the low riding ocean basins, which have thin crust. The birth of continent is fundamentally controlled by processes that generate thick crust: magmatism and tectonic compression. Continents are born in magmatic orogenies, during which magmatism and thickening feedback on each other to influence the extent and nature of magmatic differentiation. As crust thickens, the depth and extent of differentiation increases, eventually resulting in the fractionation of garnet, which drives residual magmas towards silicic and iron depleted signatures. Eventually, these garnet-rich cumulates, owing to their high densities founder back into the mantle, leaving behind a felsic continental crust. A key component to continent formation processes is erosion. Erosion is highest during magmatism, when the crust is thick and elevations high, resulting in rapid synmagmatic exhumation. As the magmatic and tectonic driving forces wane, continued erosion gradually thins the crust, causing elevations to decrease. With time, thermal relaxation becomes important, resulting in further subsidence. Eventually, the mountain subsides into a continental basin and transitions from erosion to deposition. The final resting state of a continent depends on a number of factors, including the average temperature of the mantle. As the Earth cools, the resting states of stable continents rise, returning them to above sea level.
|Building:||1100 North University Building|
|Event Type:||Lecture / Discussion|
|Source:||Happening @ Michigan from Earth and Environmental Sciences|