Glacial erosion refers to the process by which glaciers erode bedrock and other rocks they carry, both through mechanical weathering and chemical attack.
Some effects of abrasion include rock flour (powdered bits of rock), striations patterns, and glacial pavements.
Other effects include bowl-shaped cirques and high altitude lakes known as tarns.
Glacier erodes leave behind grooves and scratches known as striations in rocks, known as grooves or scratches. Rocks frozen into glaciers serve as sandpaper; as large rocks scrape away other rocks leaving these marks. These grooves typically run along a straight path in which the glacier moved.
Glacial erosion forms cirques and troughs from glacier erosion. Cirques are bowl-shaped depressions carved by glaciers which flow into V-shaped valleys formerly created by rivers. A low spot between two cirques, called an arete, connects two of them. Horned mountains form when glaciers erode away rock around their summits by plucking it away with them as the glaciers advance along their journey transforming landscapes over many thousands of years.
As rocks frozen into a glacier scour over bedrock, they leave behind long scratches called striations or grooving that run parallel with its movement. When quartz striations on shale is exposed to glacial movement or there is constant access to abrading material (rock flour referred to by geologists as “glacial sand”) for abrading purposes, abrade-ment speeds up even further.
Abrasion also causes bedrock erosion by creating curved lines and depressions, known as chatter marks or curved fractures, which have an undulating surface with irregular edges that form what are known as chatter marks or curved fractures. They can consist of closely spaced crescent-shaped gouges or cracks; or sinuous lines sculpted into what are called sichelwannen erosional features whose longer axes typically slope upward towards glaciers.
Glacial erosion creates some of the most spectacular landforms on Earth, including cirques, troughs, rock basins and fjords. Larger glaciers may even erode valley walls to form glacial valleys.
Cirques are bowl-shaped depressions at the heads of mountain glaciers caused by frost wedging, abrasion and ice plucking, with circular lakes often known as tarns forming at their bases. Two adjacent cirques carved together can form an arete ridge; when three or more are combined they may create sharp spiked peaks known as horns.
Glacial erosion can create an array of landforms, from mountains and valleys to valleys and even lakes! Erosion occurs primarily through plucking and abrasion; however, freeze-thaw weathering also has an influence.
A trough is a U-shaped valley carved by rivers. Over time, glaciers flowed through these valleys and gradually eroded away at their sides and bottom, widening and deepening them over time.
Aretes are pointed-shaped mountains formed when two corries develop on each side of a mountain peak, producing an arete-shaped mountain. When formed from hard rock, an arete may include crag and tail formation – where hard rocks protect softer parts of the mountain (the tail). Edinburgh is an example of such formation.
As glaciers erode, they leave behind many landforms. These landforms include striations lines, grooves, and rock flour (formed by rocks that have been ground down by abrasion) as well as various deposits like varves – dark fine-grained layers that alternate each year with lighter colored sands.
Other forms of glacial landforms include cirques, ribbon lakes, corries, troughs and mountain ridges – many formed from processes including erosion and plucking.
A cirque is an amphitheater-shaped valley formed by glaciers eroding into mountains, often leaving behind features such as aretes, horns, troughs and hanging valleys. As glaciers retreat further, their crests become steeper while summit height decreases; some may even include a resistant residual cliff that forms what’s known as a “roches moutonnee.”