EESA06H3 Lecture Notes - Lecture 4: Mantle Plume, East African Rift, Continental Crust
Document Summary
Asthenosphere: the weak layer that the tectonic plates move over. Types of plate margins: divergent, convergent and transform. Life cycle of ocean basins: embryonic, mature and dying. Acidic (silica-rich such as granitegranitic crust/continental crust) vs basic(iron-rich, silica poor such as basalt) igneous rocks. Rocks of different chemistries tells us about different environments. Basic flows very easily (higher density 2. 9g/cm3) oceanic crust. Failed rift - started to break up but didn"t. Oceans are widening - about 7-8 cm a year. Crust above plume head is warmed and stretched. Plume head - crust is warmed and stretched which results in the breakup of plates. Cold mantle of old oceanic crust is subducted. Slab avalanching: accumulate at the boundary and then suddenly fall down into lower levels of the mantle. Continents are made out of silica rich crustlightlow density. Mantle is stratified both chemically and physically - not homogenous (key figure) Descending slabs of old oceanic crust don"t go down willingly.
