13.8.4 What processes shape desert landforms? Sand covers about 20 per cent of the world’s deserts. This sand is the result of millions of years of erosion of rocks and plateaus by extremes of temperature, wind and water. Several natural processes have combined to create desert landforms and patterns. Unprotected surfaces are prone to erosion, especially after heavy rain, which may lead to significant erosion of ancient river channels. Extreme temperatures, strong winds and rushing water after desert rainstorms cause rocks to break down into smaller fragments through the process of weathering. Materials carried by water and wind are eventually deposited in new locations. Over time these materials build up, forming different shapes and patterns in the desert.
FIGURE5 A variety of landforms are found in the desert. They result from the actions of wind and water. Can you pick the landforms created by erosion and those created by deposition?
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1 Abutte is the remaining solid core of what was once a mesa. It is often shaped like a castle or a tower. 2 Crescent-shaped barchan dunes are produced when sand cover is fairly light. 3 An arch, or window, is an opening in a rocky wall that has been carved out over millions of years by erosion. 4 An alluvial fan is the semicircular build-up of material that collects at the base of slopes and at the end of wadis after being deposited there by water and wind. 5 A playa lake may cover a wide area, but it is never deep. Most water in it evaporates, leaving a layer of salt on the surface. These salt-covered stretches are called salt pans. 6 Claypans are low-lying sections of ground that may remain wet and muddy for some time. 7 Transverse dunes have a rippled surface, due to gentle breezes consistently blowing in one direction. 8 Anoasis is a fertile spot in a desert. It receives water from underground supplies. 9 Amesa is a plateau-like section of higher land with a flat top and steep sides. The flat surface was once the ground level, before weathering and erosion took their toll. 10 Sanddunes often start as small mounds of sand that collect around an object such as a rock. As they grow larger, they are moved and shaped by wind. 11 An inselberg is a solid rock formation that was once below ground level. As the softer land around it erodes, it becomes more and more prominent. Uluru is an inselberg. 12 A chimney rock is the pillar-like remains of a butte.
13 Star dunes are produced by wind gusts that swirl in from all directions. 14 Longitudinal dunes form when strong winds blow in one direction.
324 Jacaranda Humanities Alive 8 Victorian Curriculum Third Edition
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