Geology of the Great Basin area - Essay Example

Geology of the great basin area The great basin has been rightly described as a “mountain-studded, sand-and sage-filled bowl” (Fiero, 4). It comprises of the state of Nevada, almost half of Utah, and parts of California, Oregon, Idaho, and Wyoming (Fiero, 7). On western and eastern sides, mountain walls protect and geographically isolate the great basin from the outside world (Fiero, 7). On the Western side, there are the great mountains of Sierra Nevada and on western side, Wasatch mountains and the high plateaus of southern Utah (Fiero, 7).

The floor of the valleys of great basin is four or five thousand feet above sea level (Fiero, 9). Surface water is removed from the basin not by drainage but by evaporation alone (Fiero, 9). There are many streams flowing through the basin like tributaries of the Deschutes, John Day, Owyhee, and snake river (Fiero, 8). The tributaries of Colorado have created deep canyons in the southern part of the great basin. But the most important feature of Great Basin is “interior drainage of rivers and streams into remnant pleistocene lakes or playas” (Sturtevant and D’Azevedo, 6).

The geological character of the great basin comes under the category, ‘Basin and Range’, which is a geological region with “uplifted and tilted ranges separated by broad elongated basins” (Fiero, 9). Great basin, is geologically, a part of the Basin and range that spreads over Nevada, Utah, Oregone, Idaho, Wyoming and also New Mexico and Arizona (Sturtevant and D’Azevedo, 6). There are geological evidences showing the existence of “deep lakes and rushing rivers” in pre-historical period, in the Great Basin (Sturtevant and D’Azevedo, 33).

In the northern part, the basin has volcanic lava covers amounting to thousands of feet depth (Fiero, 9). Around 2000 and 1000 B.C., the Mount Mazama had erupted and this was the source of lava and volcanic ash spread over the north of Great Basin (Sturtevant and D’Azevedo, 35). The lakes in this region are found to have shown great fluctuations in their water wealth through history, which is supposed to have caused by climatic changes (Sturtevant and D’Azevedo, 34). The pleistocene lakes shrank while Holocene lakes and marshes surived and developed (Sturtevant and D’Azevedo, 34).

There is found to be a “lateral continuity” of geological features throughout the Great Basin (Fiero, 30). Fiero describes the geological history of this region as “great uplifts, collisions of continental masses, fiery volcanoes and burial beneath oceans” which in turn has determined the mineral composition of this region (13). The rock types in the region are, igneous rocks, bearing silica, iron and magnesium, clastic sedimentary rocks (shales, sandstones and conglomerates etc.), non-clastic sedimentary rocks (Halite, Gypsum etc.), organic sedimentary rocks (Fossiliferous limestone, peat, coal etc.) and metamorphic rocks (slate, quartzite, marble etc.) (Fiero, 14-23).

Dunes are another conspicuous feature of the Great Basin. These dunes are found to “act as sponges, rapidly absorbing occasional rain but releasing it slowly (Sturtevant and D’Azevedo, 34). Paleontologic studies have revealed. “the rocks of the Great Basin reflect life-forms that may date back more than two billion years” (Fiero, 43). The Great Basin fossil types include, foraminifera, sponges, corals, trilobites, bryozoa, brachiopods, pelecypods, gastropods, cephalopods, crinoids, graptolites and plant fossils (Fiero, 44-49).

The geological diversity of Great Basin has been an unending treasure trove of pre-history for archeologists and the explorations are still continuing. Works Cited Fiero, Bill, Geology of the Great Basin, Nevada: University of Nevada Press, 2009.Print. Sturtevant, W.C. and D’Azevedo, W.L., Great Basin, Washington D.C: Government Printing Office, 1986.Print.