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20 MARKS: With Reference to one or more hot deserts that you have studied,…
20 MARKS: With Reference to one or more hot deserts that you have studied, assess potential impacts of climate change on the development of landforms.
INTRO
Climate Change: refers to long-term shifts in temperatures and weather patterns. Human climate change (anthropogenic)- due to human activities
countries can implement carbon budgets, which affects their carbon footprint
landform development- critical for the formation of desert environments and their features (fluvial and aeolian)
AEOLIAN LANDFORMS
Two types of erosion: Deflation- removal of loose material on the desert floor (eg deflation hollows and desert pavements). Abrasion- wind-blown sand driven against rock surfaces, carving/sculpting them (eg yardangs, ventifacts, zeugens)
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case study: Mojave desert- one of the western deserts of the USA; spanning parts of California, Nevada, Utah, and Arizona, known for its arid climate, varied landscape, and diverse ecosystem
Changing climatic conditions within the last 20,000 years have had a particularly strong effect on the physical appearance of the Mojave desert landscape today
PARAGRAPH ONE
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Increased aridity, leading to drier soils, enhances wind erosion by reducing soil cohesion and increasing soil erodibility. This effect is further amplified by the loss of vegetation cover, which is a natural protector against wind erosion
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Development of yardangs, ventifacts, deflation hollows, sand dunes and desert pavements accelerate
Ventifacts: small-scale features found on desert pavements. Individual rocks, usually the size of pebbles that have a clear eroded face (facet) that is aligned with prevailing winds. one well-developed side (unidirectional wind), three well-developed facets (dreikanter)
Yardangs: elongated ridges separated by deep grooves cut into the desert surface. The rocks are vertical to the ground surface. (vertical rock layers)- the weaker rocks are eroded by abrasion to form deep troughs, whereas the tougher rocks are left upstanding. Only form in unidirectional wind areas.
Desert Pavements: a desert surface covered with rock fragments; formed when the wind blows away finer sand particles and leaves behind the larger stones, over time becoming more concentrated
Deflation hollows: s depression caused by strong, gusty winds that erode loose material from the desert surface. Sand, temporarily stored on the ground surface is whisked up by the wind (source of energy) to be transferred and deposited elsewhere.
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EVALUATE: depends on the sediment supply + vegetation cover (but could decrease with increased temperatures + more drought seasons)
PARAGRAPH TWO
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Accelerated formations of wadis, alluvial fans, bajadas and pediment
Alluvial fans: at the edge of a mountain range, the sediment washed out through a wadi or canyon is deposited to form an alluvial fan. As the water spreads from the mountain front, energy is lost and sediment is deposited rapidly. Over time, as water reworks this vast store of sediment, the alluvial fan displays clear stratification (layering) and sorting. Coarser sediment is more concentrated closer to the mountain range and the finer sediment is washed onto the desert plain. Can extend for several km and be 300m thick
Wadis: a dry riverbed that can take the form of a distinct channel in a lowland plain or an incised hully or valley cut into a plateau. Features: steep edges that are the result of severe erosion during periods of high water flow, flat bottoms infilled with sediment
Bajadas: extensive alluvial fans emerging from an upland area can coalesce (merge) to form a continuous apron of sediment extending for many km across a mountain front. Similar characteristics to alluvial fans (layering and sorting). Playas (salt lakes) may form on lower bajadas where they become extensive flat deposits.
pediment: a pediment is a gently sloping, straight erosional rock surface at the foot of a mountain range. A common characteristic is a distinct break in slope between the mountain front and the top of the pediment. A pediment is often partly or completely blanketed by sediment (such as alluvial fans) washed down by rivers from the mountains. The formation (not simple): as they do not have distinctive carved channels, they may be formed by intensive sheet-wash erosion, combined with extensive surface and subsurface weathering. At the edge of a mountain range, water builds up within the ground resulting in more concentrated weathering. Periodic sheet-wash then removes the loose material- creating a smooth rock surface.
MOJAVE DESERT: Death valley experiences flooding (this could be increased? or shows what would happen to the desert if this was widespread). DV can experience flash flooding (Intense rainfall can quickly overwhelm the drainage systems), especially during the summer monsoon season. In 2022, the Furnace Creek weather station recorded its rainiest day ever, with 1.70 inches of rain. can create a temporary lake in Badwater Basin
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EVALUATE: increased erosion (pediment and wadis- formation VS bajadas and alluvial fans- diminished (and by mass movement of water)- decreased deposition. But Aeolian more important (link back to question) ephermal streams!!
CONCLUSION
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in addition, changing temperatures can affect weathering processes (thermal fracture), leading to granular disintegration and exfoliation of the crystalline rocks
aeolian processes shape the landscape more BUT Fluvial changes from climate change have the biggest impact because this will in turn cause more Aeolian change with dryer soils and less vegetation (eg increased barchan and seif dunes)