exam 3

(Wikipedia.org)
there are different types of boundaries some of these boundaries include the ones im about to explain.
Transform boundaries: John Wilson saw that because of friction the plates were unable flow past each other. how they move is stress builds up in the plates and when it is to much for the plates potential energy is released as strain. Strain is accumulative and instantaneous the lower crust and mantle accumulates deformation by shearing where the brittle upper crust reacts by fracture or instantaneous stress release to cause motion. The ductile surface of the fault can also release instantaneously when the strain rate is too great. The energy released by instantaneous strain release is the cause of earthquakes.

An example of this plate boundary is the San Andreas Fault which is part of a highly complex system of faults in the area. The Pacific and North American plates move relative to each other such that the Pacific plate is moving northwest with reference to North America.

Divergent boundaries: Two plates that move apart from each other and the space is filled with new crustal material from the molten magma that forms below. The hot spot which may have made the Mid Atlantic Ridge system underlies Iceland which is widening at a rate of a few centimeters per year.
Divergent boundaries are categorized in the lithosphere by rifts on the oceanic ridge including the Mid Atlantic Ridge and the East Pacific Rise. Divergent boundaries can create massive fault zones in the oceanic ridge system. Spreading is not uniform so where spreading rates of adjacent ridge blocks are different massive transform faults occur. These are the fracture zones that are a major source of submarine earthquakes.

http://en.wikipedia.org/wiki/Plate_tectonics Organisation: Wikipedia Title: plate tectonics Date: June 2008
http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html Organisation: J. Louise Title: Plate tectonics the cause of earthquakes Date:may 2001