Video review 6: Desert Landforms Watch the video by Wendy Van Norden below, or i
ID: 106641 • Letter: V
Question
Video review 6: Desert Landforms
Watch the video by Wendy Van Norden below, or in the extra materials section. Another excellent video, this one describing some features common in deserts.
Write a brief review of this video. Using the video and your text, address these questions in your review:
Describe how a basin and range forms. What processes are involved?
What is a "normal fault"? Why is it discussed along with basin and range (horst and graben) topology?
What types of erosional features are often associated with basin and range?
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Please watch the youtube video to help address these questions. https://www.youtube.com/watch?v=XPAASmrteKg the video is called Desert Landforms by Wendy Van Norden.
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The Colorado Plateau is largely made up of high desert, with scattered areas of forests. In the southwest corner of the Colorado Plateau lies the Grand Canyon of the Colorado River. Much of the Plateau's landscape is related, in both appearance and geologic history, to the Grand Canyon. The province is bounded by the Rocky Mountains in Colorado, and by the Uinta Mountains and Wasatch Mountains branches of the Rockies in northern and central Utah. It is also bounded by the Rio Grande Rift, Mogollon Rim and the Basin and Range Province. Isolated ranges of the Southern Rocky Mountains such as the San Juan Mountains in Colorado and the La Sal Mountains in Utah intermix into the central and southern parts of the Colorado Plateau. The region actually consists of a system of massive plateaus separated by faults. Its landforms range from high mountains to fantastically carved canyons, the focus of a great density of protected public lands. Deep, incised river gorges are common in the Colorado Plateau. Most famous of all is the Grand Canyon, one of the largest and most well-known in the world. This massive cleft of the Colorado River reveals a stunning spectrum of geologic time in its multicolored rock layers; the oldest beds exposed at the bottom of the Inner Gorge are Precambrian in age.
The erosive scouring of moving water, ice and wind have carved fantastic formations throughout the plateau's beds of sandstone, shale and limestone. Arches and natural bridges derive from freeze-thaw cycles of ice and stream cutting. Ice, along with chemical weathering, also explains the intricate hoodoos and badlands of the misleadingly named Bryce Canyon. Water creeping into crevices of rock freezes at night, then thaws during the day. The pressure exerted by expanding ice, according to the National Park Service, ranges from around 2,000 to 20,000 lbs per square inch. Such relentless force, over time, wedges apart rocks.
The varying resistance of different layers of rock to the forces of erosion and weathering explains much of the topographic splendor of the Colorado Plateau, including the mesas and buttes studding its plains. On display in the canyon lands and hoodoos, this phenomenon also explains the isolate mesas and buttes that stud the region's broad plains. These flat-topped outcrops result from more resistant caps of rock left behind as surrounding layers wear away. Isolate mountain ranges rise to impressive elevation on the Colorado Plateau. Many are domes swelled around intrusions of igneous rock.
The largest of the provinces in Utah is the Colorado Plateau. It has been described as a land of layered, flat-lying sedimentary rock. Water is the most important agent for change within the Colorado Plateau. The Utah section of the plateau is drained by the Colorado and Green rivers and their tributaries. The plateau's varied exposed surface materials can be spectacular in appearance. Utah's portion of the Colorado Plateau can be further divided into the Uinta Basin, Canyon lands, and High Plateaus sub-provinces. Although the Colorado Plateau region is characterized by a variety of landforms composed of flat-lying sedimentary rocks, the Canyon lands section has some exceptions. Within the Canyon lands section, a series of steep, rugged, and isolated mountains occur.
A large portion of the Great Basin in Utah is called the Bonneville Basin. The Bonneville Basin and associated Bonneville Salt Flats were formed through the recession and evaporation of the Pleistocene-era Lake Bonneville. The lowest elevation within the Great Basin occurs within the Bonneville Basin and is covered by the Great Salt Lake.
Q - Describe how a basin and range forms. What processes are involved?
A - Tectonic activity is the movement of large pieces of the Earth's crust, called tectonic plates. Tectonic activity is responsible for such phenomena as earthquakes and volcanoes. The natural processes of weathering and erosion also contribute to forming structural basins. Structural basins form as tectonic plates shift.
Q - What is a "normal fault"? Why is it discussed along with basin and range (horst and graben) topology?
A – A normal or geological fault in which the hanging wall has moved downward relative to the footwall. Normal faults occur where two blocks of rock are pulled apart, as by tension. Normal dip-slip faults are produced by vertical compression as the Earth's crust lengthens. The hanging wall slides down relative to the footwall. Normal faults are common; they bound many of the mountain ranges of the world and many of the rift valleys found along spreading margins of tectonic plates. Whereas Horst and graben are formed when normal fault of opposite dip occur in pair with parallel strike lines. Horst and graben are always formed together. Graben are usually represented by low-lying areas such as rifts and river valleys whereas horsts represent the ridges between or on either side of these valleys.
Q - What types of erosional features are often associated with basin and range?
A – The common feature to note in the world's basins and ranges is the extreme amount of erosion that occurs on the peaks of the ranges. As they rise, they are immediately subject to weathering and erosion. The rocks are eroded by water, ice, and wind and particles are quickly stripped and washed down the mountain sides. This eroded material then fills the faults and collects as sediment in the valleys.
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