Have you seen glacial landforms such as ribbon lakes and mountain peaks before? Have you ever pondered which term best describes glacial erosion rates?
Glaciers erode and deposit material at different places on land around them, creating characteristic landforms easily recognized even after just a few geography classes.
Plucking
Plucked rocks refers to a process of glacier erosion where large pieces are removed by flowing glaciers in chunks, known as plucking. This occurs as glacier ice scrapes against embedded rocks which rub together as it moves downward, leaving behind scratches called striations scars on them as it moves downhill and eroding them away – leaving behind grooves called striations scars on their surfaces eroding further and leaving behind scarring called striations scars on them and their surfaces scratched for long enough and carried off into space by flowing glaciers which leave behind scratches known as striations scars where this happens.
Ice by itself isn’t very efficient at erosion, but when combined with rock fragments adhering to it, its erosion becomes comparable to rubbing sandpaper against wood – creating long striations lines running along with its movement.
The same process that removes large rocks also breaks apart and collects smaller particles, creating what is known as moraine deposits. Moraines are one of the main features of glaciated environments – this material often fills fjord basins.
Abrasion
Glaciers can be powerful tools of erosion when encountered with soft enough rocks (Mohs hardness of 1.5 at 0degC). Here, the glacier itself rubs and abrades away at the underlying surface to leave unique landforms like ribbon lakes as it slowly advances forward.
Due to basal sliding and reduced erosion rates in cold-based glaciers, direct measurements of subglacial erosion rates are rare; hence they have mostly been calculated using theoretical models3-6.
Abrasion in glacial streams can be hard to measure due to the dispersed nature of sediment deposition by moving glaciers, as its particles tend to disperse into layers as it travels downstream. If long-term records can be kept with closely spaced observations, however, abrasion serves as an accurate proxy for erosion rates in glaciated rivers as its abrasive action can combine with processes like plucking and freeze-thaw weathering to produce meaningful results.
Freeze-thaw weathering
The freeze-thaw cycle releases minerals and nutrients stored in rocks, which then cycle back through soil organisms and organisms as food sources to support ecosystems. This phenomenon is especially prominent in areas with strongly continental-style climates like those found in high mountain regions like Himalayas, Karakoram, and Tibet.
As it moves across the landscape, a glacier gathers rocks in its path and transports them, picking them up to carry. As it travels it scrapes against them causing erosion known as abrasion while its massive weight grinds away at them into smaller particles called plucking; producing another form of erosion known as striations.
As glaciers recede into warmer seasons, their meltwater may refreeze over surface cracks and crevices it has formed in rock surfaces, cracking it further. This form of physical/mechanical weathering known as freeze-thaw creates microhabitats suitable for plant and animal life that has adapted to these harsh environments.
Landforms
Erosion may be destructive, but it also creates landforms. A butte is an eroded rock formation with tall, flat-topped rocks shaped by both plucking and abrasion processes; another example are sand dunes in areas where wind erosion is predominant.
Glaciers are powerful erosion agents. They scrape across the ground surface, erode rocks into particles called till, then deposit these pieces as till. Rock sizes range from giant boulders to silt, while any non-bedded rocks known as glacial erratics.
Erosion rates of glacial erosion can be difficult to ascertain because they include both abrasion and plucking as well as fluvial erosion processes. To accurately gauge this process, scientists need to collect worldwide data over long periods at widely spaced locations – this task being made difficult due to differing local conditions like elevation or geological history which affect erosion rates differently in different locations.