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Plucking is increased where there are preexisting fractures in a rock bed. As the glacier slides down a mountain, energy from friction, pressure or geothermal heat causes glacial meltwater to infiltrate the spaces between rocks. [4] This process, known as frost wedging, puts stress on
This process can make the existing terminal moraine far larger than its previous size. [2] Dump moraines occur when rock, sediment, and debris, which accumulate at the top surface of the glacier, either slide, fall, or flow off of the snout of the glacier. The accumulation of till will form a terminal moraine as the glacier retreats. [2]
Diagram of glacial plucking and abrasion. Glaciers erode terrain through two principal processes: plucking and abrasion. [64] As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands ...
Multiple erratics on the terminal moraine of the Okanogan Lobe. The Cascade Mountains are in the background.. The term "erratic" is commonly used to refer to erratic blocks, which geologist Archibald Geikie describes as: "large masses of rock, often as big as a house, that have been transported by glacier ice, and have been lodged in a prominent position in the glacier valleys or have been ...
The snow-free debris hills around the lagoon are lateral and terminal moraines of a valley glacier in Manang, Nepal.. A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sheet.
Glacial abrasion is the surface wear achieved by individual clasts, or rocks of various sizes, contained within ice or by subglacial sediment as the glacier slides over bedrock. [9] Abrasion can crush smaller grains or particles and remove grains or multigrain fragments, but the removal of larger fragments is classified as plucking (or ...
Glacial plucking is the removal of large blocks from the bed of a glacier. [11] Much of the silt in till is produced by glacial grinding, [4] and the longer the till remains at the ice-bedrock interface, the more thoroughly it is crushed. However, the crushing process appears to stop with fine silt.
Roche moutonnée near Myot Hill, Scotland In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier.The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock, and plucking (i.e. pieces cracked off) on the "lee" (downstream) side.