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Dobbingstone Burn, Scotland—This photo illustrates two different types of erosion affecting the same place. Valley erosion is occurring due to the flow of the stream, and the boulders and stones (and much of the soil) that are lying on the edges are glacial till that was left behind as ice age glaciers flowed over the terrain.
At the interface of the glacier and the underlying land surface, the immense weight of the glacier causes ice to melt and produces subglacial meltwater streams. These streams under immense pressure and at high velocities along with the overlying weight of the glacier itself are able to carve into landscapes and pluck sediment from the ground. [6]
Erosional landforms. As the glaciers expand, due to their accumulating weight of snow and ice they crush, abrade, and scour surfaces such as rocks and bedrock.The resulting erosional landforms include striations, cirques, glacial horns, arêtes, trim lines, U-shaped valleys, roches moutonnées, overdeepenings and hanging valleys.
Definition of Desert – That area of the earth where the sum of rain and snowfall is much less than other areas, where the annual average rainfall is less than 25CM. Definition by UNO (1995) – Land degradation in barren, humid and sub-humid areas due to climate change and human activities is called desertification.
The desert climate or arid climate (in the Köppen climate classification BWh and BWk) is a dry climate sub-type in which there is a severe excess of evaporation over precipitation. The typically bald, rocky, or sandy surfaces in desert climates are dry and hold little moisture, quickly evaporating the already little rainfall they receive.
Glaciers erode and deposit sediment by advancing and retreating. [4] Erosion occurs by abrasion and plucking. [4] These processes are dependent on a variety of factors such as plate tectonic movement, volcanic activity, and changes in atmospheric gas composition. [5] Glacial erosion often causes U-shaped valleys to form. [6]
A desert depression is caused by polygenetic factors such as wind erosion, broad shallow warping and block faulting, stream erosion, karst activity, salt weathering mass wasting, and zoogenic processes; representative examples are the large enclosed basins in Africa, such as Farafra, Baharia, Dakhla, Qattara, Siwa and Kargha. [7]
Deforestation, and conversion of grasslands to desert, may also lead to cooling of the regional climate. This is because of the albedo effect (sunlight reflected by bare ground) during the day, and rapid radiation of heat into space at night, due to the lack of vegetation and atmospheric moisture. [18]