Glacial erosion forms distinctive landscape features like aretes, horns, cirques and kettle lakes on earth’s surface.
Which term best characterizes glacial erosion? Here are your answers:
Freeze-thaw weathering
A glacier’s erosion rate depends on its environment and type of rock it travels over, with sedimentary rock being more vulnerable than crystalline bedrock due to less effective quarrying options than abrasion.
Freeze-thaw weathering is a form of mechanical weathering that occurs when water seeps into cracks in rocks during the day and freezes at night, expanding by approximately 9 percent as it freezes to exert pressure against them and gradually weakening them over time.
Rocks disintegrate over time into fragments ranging from coarse gravel to fine silt, helping form soil while also providing shelter for organisms and adding to geological records.
Plucking
As glaciers move down mountains, they erode the rocks they pass over by quarrying and plucking. Furthermore, meltwater seeps into cracks in bedrock beneath, freezes and pushes rocks outward – these “clasts” are later transported along by the glacier.
Erosion processes leave distinctive markings on the landscape known as striations marks – long, wide grooves in bedrock’s surface which provide evidence of once glacier activity. Glacial striations spots also indicate their existence.
Gletscher erosion produces striking landforms such as cirques, aretes, pyramidal peaks, U-shaped valleys, ribbon lakes and roche moutonnee. Glacial erosion also alters mountain tops’ shapes by turning V-shaped valleys into U-shaped ones and flattening out their sides – giving way to distinctive landforms like cirques.
Abrasion
Glaciers move downward scraping rocks under them like sandpaper, creating grooves called striations in the rocks they pass over and wearing away the rock surface over time.
Glaciers carry rocks of various sizes as they erode, from large boulders to silt. When melting glaciers deposit their loads they produce glacial till. Any rocks which differ in type or origin from surrounding bedrock are known as glacial erratics.
These erosion processes have produced incredible landforms that distinguish glaciated landscapes today, from rocks with smoothed-off faces caused by friction against other rocks (faceted clasts) to grooves, striations lines and glacial pavements; glacial polish and glacial polish pavements; larger landforms include cirques, whalebacks and rock drumlins.
Rotational slip
Glaciers are effective erosional agents and have played an essential role in shaping various landforms across the landscape, such as cirques, troughs, rock basins and U-shaped valleys carved by rivers into U-shaped ones, widening and deepening them at both ends. Small bits of rock or sediment entangled within glaciers rub against bedrock until worn away by this abrasive action leaving gouges, striations lines or grooves behind.
Often these grooves do not run parallel with each other but instead form interlocking spurs – an irregular, zigzag pattern known as interlocking spurs – which may become deeper than surrounding rocks through rotational slip. Rotational slip is a type of landslide characterized by movement along a concave failure surface. This process may take millions of years.
Till plains
Till is the sediment left behind by glaciers when they melt, consisting of gravel, small rocks, sand and mud. Once this material has been transported downstream by fast flowing rivers and carried downstream again after melting has occurred; once here it re-sorts and deposits itself as unsorted rock and soil in flat plains across Ohio such as Kalamazoo, Baldwin Cadillac Roscommon counties.
Common features of glacial erosion include striations – grooves on abraded bedrock that range in width from millimeters wide to meters deep and hundreds of meters long – on abraded rock surfaces, as well as glacial lakes which consist of gouged basins filled with water that have been created by glaciers; other forms include eskers and kames created by these lakes that now stand out as long, winding depressions filled with water.