GGR201H1 Chapter Notes - Chapter 3-4: Abyssal Plain, Isostasy, Oceanic Crust
21 Feb 2017
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Convergent plate boundaries: occurs at mountain belts, subduction zones, and volcanic arcs, volcanism is explosive, where some of the largest earthquakes occur. Divergent plate boundaries: occurs at rift valleys, volcanism is effusive, abyssal plains. Tectonic setting determines the rock types, which determines resistance to erosion: depositional basins have loose sedimentary rock which erodes easily, mountain rages have metamorphic and igneous rocks which are strong. Isostasy: a state of gravitational equilibrium between the crust, and the mantle, which it sits on top of, allows different elevations to exist because the pressure exerted by overlaying rock columns is be equal. Example: continents sit higher than oceanic crust because they are less dense: creates isostatic compensation, or uplift. If material is eroded away, it is displaced by material underneath moving upward. Mountains which formed a long time ago are still present because they are isostatically compensated at a rate like the one at which they are eroded.
