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Unformatted text preview: NOTES FROM READING Handout Most of the Earths surface lies between two broad ranges of elevation: the continental level (above sea level) and the oceanic level (below sea level). Oceanic crust is more abundant than continental crust. DIVISIONS OF THE CONTINENTS CRATONS- a generally low lying area of relatively low relief (few ups and downs) composed of two parts that form sort of the core of a continent o Craton- the segment of the Earths continents that have remained tectonically stable and relatively earthquake-free for a vast period of time. The craton is composed of the continental shield and the surrounding continental platform. SHIELD- low lying areas a few hundred meters above sea level composed of very old igneous and metamorphic rocks that form under conditions characterized by very high temperatures and pressures. These conditions are found deep in the earth. o Example = Canadian Shield of N. America, includes northern Michigan and the Adirondack Mountains in northern New York. Also includes much of central Africa and much of the Amazon River basin in South America COVERED SHIELD or the STABLE PLATFORM- low lying area where the shield is covered by a relatively thin veneer or horizontal sedimentary rocks that were deposited on the continent during periods when seal level was higher. o Example= interior of the U.S. from the Appalachians to the Rockies. Includes Middle Tennessee (note the horizontal layers of rocklimestoneexposed along roads in Nashville; this is typical of the covered shield) FOLDED MOUNTAINS- long linear belts where the earths crust has been folded because of compression. Erosion typically has removed the upper parts of the folds so that the highest parts of the mountains are those parts composed of the most resistant rock types. o Examples= Appalachians, Andes, Himalayas, Rockies, Alps o squiggly // force ~~~ force RIFT SYSTEMS- zones where portions of the Earths crust have been dropped down commonly below sea level. The down dropping is caused by tensional (pulling apart) forces; if they operate for long enough, these forces can cause a continent to split. o Examples= The Dead Sea rift, the Basin and Range of western U.S. (the Great Basin), the east African rift system o Force ~~~ Force CONTINENTAL SHELF- This is the nearly flat portion of the continent that currently is below sea level. It is underlain by continental crust, and thus is part of the continent. During periods of low sea level, such as when a lot of water is tied up in glaciers, the...
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This note was uploaded on 04/21/2008 for the course EES 101 taught by Professor Miller during the Spring '08 term at Vanderbilt.
- Spring '08