Tectonic Plate Boundaries AND Erosion Notes

The most important thing to understand here is that INCREASED GRADIENT increases
erosion.  Remember how erosion increased when you made your streamtables steeper.

Convergent and Divergent Plate Boundaries increase gradient in several ways.

C-OO
  • Makes volcanic islands, which have steep sides.
  • Makes ocean trenches, which are steep underwater.
C-OC
  • Makes tall volcanic mountains (like the Andes), and these have VERY steep sides.
  • Makes ocean trenches, which are steep underwater.
C-CC
  • Makes mountains like the Himalayas, which are, of course, very steep.

D-CC
  • Makes rift valleys, in which grabens form, increasing gradient and causing high areas
    (horsts) to erode down into low areas (grabens).
  • Makes volcanoes like Mt. Tom and Mt. Kilomanjaro, which are moderately steep.
D-OO
  • Makes undersea mountain ranges called mid-oceanic ridges.

ALL OF THE ABOVE BOUNDARIES MAKE STEEPER LANDSCAPES.  Remember:  
Increasing gradient increases erosion!

Transform Plate Boundaries can increase gradient too (as plate get stuck, they can
heave up or drop down parts of themselves temporarily), but are a more minor player.