Erosion can be hard to see as its effects unfold slowly over long periods of time and ice moves slowly, yet glaciers can be powerful forces which erode landscapes in unique ways, leaving stunning landscape features like ribbon lakes and aretes behind.
Erosion occurs mainly through two forms of erosion: plucking and abrasion. Abrasion works like rubbing sandpaper against wood surfaces, leaving grooves, striations or glacial pavements behind on rocks.
Observing Erosion in the Field
Glacial erosion has not been studied extensively due to its difficulty and numerous variables involved.
Erosion rates can range across orders of magnitude. Quarrying (pulling rocks from beneath a glacier and quarrying them out again) accounts for most erosion; cobble-sized sediment is produced primarily by this process while silt is generated less dramatically through abrasion; both processes result in U-shaped valleys, horns and moraine being formed from this activity.
Temperature also has an effect on erosion rates; warm-based glaciers tend to be more erosive than their Antarctic counterparts because the ice in warm-based glaciers is freer to move compared with Antarctic ones that are “glued” to bedrock, leading to basal slippage and basal slip causing basal slipage resulting in basal slipage and basal slip abrasion – although retreating glaciers in Patagonia do not typically exhibit signs of this process.
Observing Erosion in the Laboratory
Students can observe glacial erosion by working through various stations in their classroom with a teacher and recording their observations on an Erosion Worksheet. This allows them to gain an understanding of how erosion is influenced by various variables while giving them practice writing conclusions.
Researchers have utilized both measurements and laboratory experiments to establish that several factors impact the rate at which ice erodes. Precipitation type and glacier temperature play key roles; additional influences include rock being picked up by glaciers; however, these tend to have less of an effect on overall erosion rates than movements within them.
Observing Erosion in the Air
As glaciers traverse environments of differing strength, they leave behind several distinctive landforms. Abrasion scratches known as striations mar the bedrock surface; glaciers also scrape rocks they pass over with scrapers known as plucking; this causes plucked boulders to remain attached to them until further wear-and-tear wear them away; finally being transported downstream as rock debris.
Climate cycling plays a substantial role in driving long-range erosion rates, evidenced by high sediment yields that surpass long-term averages and glaciers’ ability to remobilize proglacial sediment in headwall regions by advancing glaciers. Moulins migrating inland over till-mantled regions as subglacial erosion continues, providing ample scope for further research; similarly, tracking streams that dominate sediment transport provides further leads of inquiry while studying how preexisting weaknesses interact with glacial erosion is another area worth investigation – these questions merit thorough examination by those interested.
Observing Erosion in the Water
Subglacial erosion is essential to glacial processes because it helps control sediment output from regions while shaping glacial valley morphologies. Subglacial erosion mainly takes place via quarrying, abrasion and moulin-fed stream action but may also depend on basal sliding rates, climate forcing conditions or thermal regime.
Subglacial erosion measurements can be difficult due to various variables affecting its location and climate in a region; such information is typically inaccessible in remote areas, making direct measurements extremely unlikely.
Glacial erosion is a complex process. Ice itself does not play an effective role in this erosion process as its Mohs hardness (at 0degC) is only 1.5, however rock fragments embedded within glacier bases and then dragged along an underlying surface are what really cause erosion; their friction causes long scratches known as striations scars in the rock’s surface that contribute significantly.