Tuesday, September 18, 2012

Plate Tectonics

Although millions of years and a variety of processes have led to today’s view of the Grand Canyon, the process which gave way to its formation is known as plate tectonics.  Before discussing the specifics of plate movements, it is important to give credit to one of the contributors to the plate tectonic theory, Alfred Wegener. Alfred proposed the concept of “continental drift.” He believed at one point, “all continents were one huge super continent” known as Pangea. During his time, there was not enough evidence to convince skeptics, but since his death and the advanced understanding of earth’s structure, his idea is accredited within the paradigm of plate tectonics.

The plates responsible for continental movement are found in the lithosphere, the upper layer of earth’s structure. These plates are thought to float on top of the asthenosphere, a layer capable of movement because of its “plasticity.” The moving plates can be either continental or oceanic crust. Plate movement is classified in one of three categories. Divergence, which pulls plates apart, convergence, the coming together of plates, and transform, the process by which plates move side by side.

By understanding the type of movements made by earth’s plates, it is possible to imagine the convergence of the Pacific Plate (ocean crust) and the North American plate (continental crust) that led the way to the forming of the Grand Canyon. Millions of years ago when these two plates collided, the oceanic crust was subducted, meaning it was forced underneath the continental crust and this upward push of continental crust led to the Rocky Mountains as well as the uplift of the Colorado Plateau. The uplift of the Colorado Plateau allowed the Colorado River “to carve its way downward” about 5 to 6 million years ago commencing the creation of the canyon.




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