Ice has many striking effects on the landscape, such as plowing, abrasion and freeze-thaw weathering. Glacial erosion creates landforms like striations lakes and corries which form as it moves around.
Striations is a term referring to undulating grooves cut into glacially abraded bedrock by glacial erosion. They are an ubiquitous feature found across long profiles of glaciated areas.
Plucking
Glaciers that move over bedrock may ‘pluck’ (pick up) rock fragments too large to fit through their ice thickness and deposit them in a till layer underneath their path, creating moraines, roche moutonnees, drumlin fields and glacial polish. This process of pluckeding gives rise to numerous glacial landforms like moraines, roche moutonnees and drumlin fields and glacial polish.
Glacial striations – long parallel lines that appear as scratched rock surfaces – can provide geologists with clues as to whether a rock has been exposed to glacial erosion. Abrasion occurs only if the glacier has warm waters with basal slip.
Ice erosion can easily be overlooked when assessing overall intensity of erosion across a landscape, especially since its rate can vary considerably with time due to factors that cannot easily be restricted using basic environmental proxies – these include climate changes, changes in bedrock size/location/geometry as well as shifts in climate regime.
Abrasion
As glaciers move across a landscape, their movements create frictional wear on its rocks that wear away their surface, leading to features such as striations lines and U-shaped valleys. Abrasion also results in large scars on bedrock known as corries that have to be taken into consideration when considering this form of erosion.
Glaciers can pick up rocks from their surroundings and transport them downhill into a bedrock basin; this process is known as plucking. Erosion caused by this action is hard to quantify because it occurs so rapidly.
One approach is to use the long profiles of preglacial river valleys as a proxy for erosion rates; this requires collecting lots of data from various locations and is difficult to calibrate.
Freeze-thaw weathering
Freeze-thaw weathering occurs when water in rocks freezes and expands, cracking them apart with each expansion cycle. It is particularly prevalent among porous, permeable rock types.
As glaciers move across the landscape, they scrape against rocks beneath it, gradually eroding them through glacial abrasion. This erosion process results in features such as faceted clasts, striations lines and grooves in rock structures; additionally, glacial pavements may form.
Plucking and quarrying are unique forms of erosion unique to glacial conditions, namely plucking and quarrying. Plucking involves detaching large rocks from glacier beds for removal while quarrying involves fractured preexisting bedrock cracks by glacier flow. Basal debris may increase glacial abrasion as friction between bedrock and glacier decreases, speeding its movement over the surface faster. Glacial abrasion creates landforms such as cirques and hanging valleys as it progresses over time.
Moving over the rock
Similar to abrasion or quarrying processes, glaciers use scraping and dragging action of their ice tools across bedrock surfaces to produce rock flour, striations grooves, glacial pavements, trimlines and smooth surfaces known as trimlines. Furthermore, rapid subglacial erosion rates range between 10-4 and 10-2 meters/year-1 due to this rough contact between ice and rock surfaces.
Glaciers are constantly eroding and depositing sediment. They transport rocks of all sizes and types from their surroundings and deposit them elsewhere – these rocks, known as erratics, range in size from giant boulders to silt. Furthermore, glaciers also alter the shape of land they flow over by creating geomorphic features like U-shaped valleys, cirques, moraines or alluvial deposits that change its contours significantly.