Plate Tectonics
The theory of plate tectonics was developed in the 1960’s and states that the earth is broken into a number of shifting plates. Plate tectonics also provides geology with a comprehensive theory of how the earth’s crust moves. In this essay I will explain the different types of plate movements, how the plates move and how this movement affects earthquakes and volcanoes.
To begin, there are three different types of plate movement; divergent boundaries, convergent boundaries, and transform boundaries. At a divergent boundary the lithosphere breaks apart on parallel faults that move outward from each other. The plates break apart the block between the two faults sink into the asthenosphere creating a rift and pushing magma upward to fill in the crack. With a convergent boundary the plates move toward each other with one plate subducted under another plate. At the location where the plate sinks under another plate is called the subduction zone. Finally, with a transform boundary two plates slide horizontally past each other rubbing (Murck, Skinner, McKenzie).
To follow, each of the different boundaries move in different ways but mostly all move at the same speed. The plates are said to move relative to one another, moving just a few inches per year. The relative motion between the plates can range from three to ten centimeters per year. At five centimeters per year it would add up to thirty miles in one million years and some the earth’s plates have been moving for one hundred million years (Murck, Skinner, McKenzie).
To finish, the different types of plate movements cause different reactions in whether a certain boundary movement will cause a large earthquake or maybe not an earthquake at all. Divergent boundary earthquakes frequently shake the mid-ocean ridge as a result of faults that form as two plates separate. Mostly shallow earthquakes occur at divergent boundaries because at this boundary the asthenosphere is too hot