EESA06H3 Chapter Notes - Chapter 3: Asthenosphere, Radon, Juan De Fuca Plate
Document Summary
Three types of plate boundaries: 1) divergent (away) 2)transform (horizontal)and 3) convergent (toward) Transform boundaries: two plates that move past each other along a transform boundary, earthquakes are shallow, most transform faults= the ocean floor and offset ridge segments, some are found in continental crust. Convergent boundaries: general types collision of two continents or subduction of ocean floor under continent/ sea floor, collision boundaries characterized by broad zones of shallow earthquakes on a complex system of faults. One continent usually overrides the other slightly creating thick crust and mountain r anges: during subduction, earthquakes occur for several different reasons. Horizontal+vertical distribution of earthquakes can be used to determine the angle of subduction of a downgoing plate. Subduction angle is probably controlled by plate density and the rate of plate convergence. Older oceanic lithosphere (southeast pacific) tends to be colder + more dense, therefore subducts at a steeper angle.
