Glacial erosion is a physical process where glaciers erode and form landscapes through glacial activity, leaving behind landforms such as valleys, fjords, or mountain peaks as evidence of their passage.
Glaciers scrape rocks of various shapes and sizes against mountainside as they travel, leaving stunning landforms that stand out in any landscape.
1. Long periods of time
Ice can erode bedrock at very slow rates; even in the most vigorous glaciers, bedrock erosion is balanced by till deformation; till erosion rates depend on rock type, lithologic contrasts and geologic feedbacks that limit sediment flux (Zoet and Iverson 2018).
Landforms can be created through erosion due to glaciation. Examples include glacial lakes, peaks and other features that stand out on an otherwise glaciated landscape.
Glacial abrasion can create many different features on glaciated landscapes, including striations and moraine formation. Other forms of erosion may result from freeze-thaw cycles or subglacial avalanches.
Erosion by glaciers occurs most rapidly in areas with highly permeable rock that allows water to seep through cracks and pores, creating stress changes which promote fracture growth and quarrying of bedrock. Lithologic factors play a critical role in controlling basal sliding rate; these lithologies can even result in adverse bed slopes on downglacier sides of overdeepenings (Gilbert1906b). Slope formation can occur for different reasons.
2. Remote locations
Ice is a powerful force and through erosion can shape landscapes in ways never imagined before. Erosion occurs when rocks are scraped along by something (ice) causing it to wear away at the landscape causing corries, aretes, pyramidal peaks, U-shaped valleys hanging valleys truncated spurs ribbon lakes and even mountain ranges to form.
Cosmogenic nuclide exposure dating indicates that many Quaternary sediments were covered by glacial ice, suggesting their subglacial erosion was far more significant than previously understood; rates may have varied according to ice sheet flow dynamics and zonation of cold and warm-based erosion (EIS).
Due to slow rates of erosion and difficulty accessing sites, this evidence can be challenging to document. Abrasion and quarrying activities often ‘catch up’ with fluvial incision and overwrite any evidence for EIS erosive power; this phenomenon may become especially prominent if terminal reach flattening occurs, diminishing excess transport capacity and thus the chance for incision.
3. Slow pace of erosion
Glaciers move slowly over a rock surface, slowly grinding over it with their teeth to produce what is known as abrasion and also freezing around weak sections of bedrock to pluck them away – this process is known as plucking.
Glaciers’ immense power to shape landforms is evidenced in their remarkable landforms, creating unique geological features such as U-shaped valleys, fjords, moraines and even mountain horns in mountainous regions as well as bowl-shaped depressions and amphitheater-like valleys.
Glacial erosion leaves behind striations and grooves in rocks, as well as a finely polished surface known as rock flour, that are difficult to reconcile with contemporary sediment fluxes; suggesting they could be related to climate-induced conditions – for instance low erosion rates across Platform and Younger Basement provinces are correlated with cold-based temperatures that prevent melting43 while at the same time slow abrasion and plucking processes are to blame43
4. Subtle effects
Glacial erosion leaves behind some striking landforms when it happens, including ribbon lakes, ridges with jagged tops, and landforms with intriguing names like aretes. Abrasion is the main mechanism through which glaciers erode rock by dragging pieces of jagged rock behind their glacier to be ground against other rocks until eventually worn away over time.
Glacial erosion produces striations and grooves in rocks, while also producing fine powdery substances known as rock flour and creating glacial pavements that make valleys appear smoother.
However, erosion is not always easy to spot; you need only be in an area with glacier activity to see it at work! Glacial erosion may not seem noticeable at first glance but you will know when you see it happen; when it does, however, it will definitely become evident! Glacial erosion is subtle but important and can help you learn about a place’s history so be on the lookout! It’s definitely something worth keeping an eye out for!