Glacial erosion alters the landscape it travels across, producing notable landforms like horns, aretes, and moraine.
Cook notes that glacial erosion is affected by two forms of precipitation: rainfall and snowfall. Rainwater percolating through to its base can lubricate its interface with bedrock, speeding up sliding, and thus intensifying erosion.
Cirque Stairways
Glacial ice erodes rock by scraping across its surface, leaving distinctive landforms such as horns, drumlins and moraines behind. Glaciers also use powerful abrasers called glaciers to gouge deep holes called hydraulic channels in bedrock; plasticity of flow allows glaciers to “dig” into this layer before freeze-thaw erosion continues to sharpen their gouges over time.
Cirque glaciers often form from snowmelt that accumulates at a hollow on mountain sides called a corrie, resembling an indented bowl with steep sides.
Erosion and weathering caused by glacier abrasion, plucking, quarrying and subglacial fluvial erosion will eventually create an even deeper hollow. Erosion depends on how fast glacial ice slides over bedrock; its speed being determined by its temperature at its base; warm-based ice may rub against bedrock while cold-based ice adheres tightly against bedrock, acting more like glue than an erosion agent and therefore has less of an effect. Colder-based ice may “drag” tools across bedrock during glacial quarrying/plucking operations or subglacial fluvial erosion processes known as subglacial fluvial erosion processes known as glacial plucking/plucking operations or subglacial fluvial erosion.
U-Shape Valleys
Over time, rivers eroded the landscape to form narrow and steep V-shaped valleys; when glaciers intervened they transformed these river valleys into U-shaped ones with flat floors and rounded walls.
Glaciers create mountain valleys through processes like plucking and abrasion, widening, deepening and smoothening their sides. Ribbon lakes may form in hollows that were more deeply eroded by glaciers; additionally, misfit streams or rivers may meander across their wide floor to form U-shaped valleys.
As glaciers retreat and recede, they leave behind mounds of weathered rock called moraines along their paths. Furthermore, glaciers shape the land by carving eskers (long lines of rock that extend out from valley walls), tills (rocks scraped by glaciers) and roche moutonee (a type of cirque where two glaciers meet). Switzerland is home to one such glacial feature – Matter Valley being just one such example.
Rock Drumlins
A drumlin is an elongated feature found behind end moraines that is streamlined at its down-ice end, composed of rock or till (glacial sediment) with possible core structures in some instances. They generally orient parallel to glacier flow.
Glacial erosion creates them through erosion of rocks containing spots of harder material that protrude as knobs from underneath, protecting softer material from further abrasion. They typically take the form of an elongated low ridge or hill.
Drumlin fields have long been recognized, yet their specific patterns, internal composition and timing of formation remain a source of mystery. According to recent research findings, drumlins may be related to net erosion beneath ice sheets; therefore they form as part of interactions between an advancing glacier and its environment.
Rock Basins
Rock basins are circular depressions in bedrock formed when glaciers erode it. Usually containing pools of water and often covered with mineral detritus deposited along their walls or washed into it from higher slopes, they’re often tinted reddened by algal mats.
Glaciers scrape rocks, creating glacial striations scars. If the rock abrades itself at spots harder than surrounding rocks, a knob-and-tail shape forms as soft areas are preferentially eroded away, protecting its harder part while leaving behind its tail that runs alongside its path.
Origin of Rock Basins It can be difficult to trace the source of rock basins due to their difficulty of creation; measuring rates of abrasion is hard; these rates cannot easily be compared with fluvial erosion during interglacial periods and fluvial erosion during glacial times. They probably form in ablation zones located around granitic massifs.