Outline:

The kinematic evoloution of tectonic plate boundaries can have a profound impact on regional geology.  The kinematic evolution of the western U.S. is an excellent example.  Prior to 37 m.a. (million years ago), the west coast of North America was the site of a subduction zone.  Since that time the plate west coast has been a mix of subduction and transform tectonics.  To decipher this history, geologists need to know how to infer kinematics, the subject of our lecture.
 
 

Plate Tectonics on a Plane and Releative Plate Motions

• Three types of plate boundaries
• Divergent (ridges and rifts)
• Convergent (subduction zones)
• Strike-slip (slip between two plates parallel to plate boundary)
• Releative Motion:
• The motion of a fixed point on one plate with respect to another plate
• Absolute Motion:
• Motion of plates with respect to Earth's spin axis.
• Sometimes with respect to the "Fixed hotspot reference frame", which may not be all that fixed
• Good indicators or relative motion (see figure below):
• Mid-ocean ridges
• Transform faults
• Inaccurate indicators of relative motion
• subduction zones