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Glacial plucking is most significant where the rock surface is well jointed or fractured or where it contains exposed bed planes, as this allows meltwater and clasts to penetrate more easily. [2] Plucking of bedrock also occurs in steep upland rivers, and shares a number of similarities with glacial examples.
While plucking has generally been thought of as a greater force of geomorphological change, there is evidence that in softer rocks with wide joint spacing that abrasion can be just as efficient. [9] A smooth, polished surface is left behind by glacial abrasion, sometimes with glacial striations , which provide information about the mechanics of ...
The following affect the rate of abrasion: [1] The amount of rock debris embedded in the basal surface of the ice. If there is no rock in the basal surface of the ice there will be no abrasion, but if there is too much rock in the basal surface of the ice the motion of the glacier will be affected, thus affecting abrasion rates.
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 ...
Kolks cause extreme local erosion, plucking bedrock and creating pothole-type geographical features called rock-cut basins. Examples can be seen in the flood regions result from glacial Lake Missoula , which created the channeled scablands in the Columbia Basin region of eastern Washington .
In Switzerland, alpine terminal moraines can be found, one striking example being the moraine at the end of the valley of the Forno Glacier in the south-eastern canton of Graubünden near St. Moritz and the Italian border. In New Zealand the Franz Josef Glacier on the West Coast has created the terminal moraine called the Waiho Loop.
Drumlins occur in various shapes and sizes, [6] including symmetrical (about the long axis), spindle, parabolic forms, and transverse asymmetrical forms. Generally, they are elongated, oval-shaped hills, with a long axis parallel to the orientation of ice flow and with an up-ice (stoss) face that is generally steeper than the down-ice (lee) face.
A valley glacier cannot avoid the interlocking spurs as a river can. As the valley glacier moves, abrasion and plucking erode the protruding tips of the spurs, leaving steep cliff-like truncated spurs. Hanging valleys are found in between truncated spurs as they join the main glacial valley from the side. It is common for waterfalls to form ...