Glacial erosion is a complex process that produces unique landforms such as corries, aretes, ribbon lakes, roche moutonnee, paternoster lakes and glacial striations. How does it work?
Glaciers are powerful agents of erosion. Their movements disrupt the surface by means of abrasion and plowing; additionally, they leave behind distinctive geomorphic features like U-shaped valleys and cirques that stand as monuments to their power.
It’s hard to see
Glaciers can have an astounding effect on landscapes. Through processes like erosion and plucking, glaciers sculpt landforms such as striations lines, cirques, U-shaped valleys, horns and moraines into existence.
Abrasion: As glaciers slide down mountains, their base materials, including rocks and sediments deposited therein, rub against bedrock causing it to erode and create striations on its surface.
As glaciers move across their respective territories, they transport debris in the form of boulders known as erratics as well as smaller rock particles known as glacial till.
These features are visible on the ground as depressions called troughs, which may fill with water to form ribbon lakes. Glaciers can also erode river valleys by widening them out and steepening their walls, producing what’s known as cirques.
It’s hard to understand
Glaciers carry vast amounts of ice, which erodes the land as they move across it, creating beautiful landscapes like U-shaped valleys, horns, moraine and ribbon lakes as they pass over it. But their cause can be difficult to comprehend; two main processes by which glaciers erode are: abrasion and plucking.
Abrasion occurs when glaciers move across bedrock that has differing strengths; for instance, moving over softer rocks will erode it more than harder rock types. Abrasion may also occur when glaciers float on top of sediment layers.
Striation occurs when glaciers melt, depositing sediment at different places in its wake. Glacial striations is a beautiful phenomenon found throughout glaciated regions today and is frequently seen creating stunning landscapes.
It’s hard to measure
Glaciers’ erosional power is profound and all-pervasive, yet its mechanics remain unclear and difficult to comprehend. What knowledge we do possess of subglacial erosion stems largely from inferences drawn from studying landforms left behind when glaciers receded from deglaciated settings.
These landforms include striated rock formations, made up of grooved-surface rocks that were abraded by glaciers. Cirques and rock basins, some up to kilometers in length and breadth, also are notable landforms that result from glacial erosion.
However, glacier abrasion is only effective when its base ice is moving freely, creating an issue when cold-based glaciers become attached to bedrock and cannot effectively drag tools across their landscape. Once used up, an automatic mechanism must replenish it at the glacier base in order for abrasion to continue.
It’s hard to predict
Glaciers move across land they occupy and tend to erode it in unpredictable patterns, making erosion hard to predict.
Glacial erosion can create dramatic landscapes. When rock contains sections which are harder to erode than others, protrusions (known as roche moutonnees) and tails (crags) form due to glacial action.
As glaciers melt, spectacular landforms such as ribbon lakes can emerge – creating stunning scenes. However, as climates warm, erosion rates will likely increase as melting glaciers can erode land faster than non-melting ones and may change landforms created by melting glaciers such as cirques, troughs and rock basins. Erosion rates also depend on slope of landscape; typically steeper landscapes tend to be less vulnerable to erosion compared to flatter ones but this may not always be true.