Glaciers are nature's bulldozers, carving and shaping landscapes with incredible force. Through abrasion and plucking , they create unique landforms like cirques, U-shaped valleys, and glacial horns. These processes transform entire mountain ranges and leave lasting impacts on the Earth's surface.
Subglacial meltwater plays a crucial role in glacial erosion, enhancing the glacier's ability to sculpt the land. It creates features like potholes and eskers, and forms subglacial lakes. The combined action of ice and water results in dramatic landscape modifications that continue to influence modern environments.
Glacial Erosion Processes
Mechanical and Chemical Processes
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TC - Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann ... View original
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16.3 Glacial Erosion – Physical Geology – 2nd Edition View original
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TC - Formation of ribbed bedforms below shear margins and lobes of palaeo-ice streams View original
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Top images from around the web for Mechanical and Chemical Processes TC - Formation of ribbed bedforms below shear margins and lobes of palaeo-ice streams View original
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TC - Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann ... View original
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16.3 Glacial Erosion – Physical Geology – 2nd Edition View original
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TC - Formation of ribbed bedforms below shear margins and lobes of palaeo-ice streams View original
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TC - Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann ... View original
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Glacial erosion wears away and reshapes underlying bedrock and sediment through mechanical and chemical processes
Effectiveness depends on factors
Ice velocity
Ice thickness
Ice temperature
Properties of underlying bedrock
Erosion rates vary significantly
Cold-based glaciers: less than 0.1 mm/year
Warm-based, fast-flowing glaciers: over 10 mm/year
Abrasion and Plucking
Abrasion scours glacier bed with rock fragments embedded in ice base
Results in striations and polished surfaces (glacial polish)
Plucking removes rock fragments frozen to glacier bed as ice moves
Creates jagged surface (roche moutonnée)
Quarrying removes large bedrock blocks facilitated by pre-existing fractures
Forms steep cliff faces (headwalls)
Cirques and Arêtes
Cirques form bowl-shaped depressions carved into mountainsides
Shaped by combination of plucking and abrasion
Involve nivation process where snow accumulates in pre-existing depressions
Arêtes create sharp, knife-edge ridges between adjacent cirques
Form when two cirques erode headward into a mountain
Examples include Crib Goch in Snowdonia, Wales
Glacial Valleys and Associated Features
U-shaped valleys (glacial troughs) form by widening and deepening pre-existing river valleys
Ice erodes both valley floor and walls, unlike rivers which primarily erode downward
Examples include Yosemite Valley, California
Hanging valleys suspend smaller tributary valleys above main U-shaped valley floor
Result from differential erosion rates between main and tributary glaciers
Create waterfalls where tributary streams flow into main valley (Bridalveil Fall, Yosemite)
Glacial horns form sharp, pyramidal peaks when three or more cirques erode headward
Famous example (Matterhorn, Swiss Alps)
Subglacial Meltwater's Role
Erosional Processes and Features
Subglacial meltwater enhances glacial erosion
Facilitates sediment transport
Increases effectiveness of abrasion and plucking
Creates distinctive erosional features
Potholes: cylindrical holes drilled by swirling water and sediment
Flutes: elongated ridges parallel to ice flow
P-forms: smooth, undulating rock surfaces sculpted by pressurized water flow
Tunnel valleys form long, overdeepened troughs beneath ice sheets
Carved by pressurized subglacial meltwater
Often follow pre-existing bedrock weaknesses
Examples found in northern Europe and North America
Depositional Features and Hydrological Impacts
Eskers create sinuous ridges of glaciofluvial sediment
Deposited by meltwater streams within or beneath glaciers
Represent preserved subglacial drainage channels
Examples found in Finland and Canada
Subglacial lakes form by meltwater accumulation beneath ice sheets
Influence ice dynamics and erosional processes at glacier bed
Lake Vostok in Antarctica largest known subglacial lake
Interaction between meltwater and sediment forms streamlined subglacial bedforms
Drumlins: elongated hills aligned parallel to ice flow
Mega-scale glacial lineations: extremely long parallel ridges
Glacial Erosion's Impact on Landscapes
Landscape Modification and Denudation
Glacial erosion primarily shapes alpine and high-latitude landscapes
Creates distinctive landforms not found in non-glaciated regions
Alters pre-existing fluvial drainage patterns
Develops new watershed boundaries and river systems
Examples include the Great Lakes basin in North America
Contributes to mountain range denudation
Glaciers erode mountains up to 10 times faster than other erosional processes
Varies with latitude, elevation, and climate
Most pronounced in high mountain ranges (Himalayas) and polar regions (Greenland)
Long-term Landscape Evolution
Creates overdeepened basins becoming lakes after glacier retreat
Influences hydrology and ecology of deglaciated landscapes
Examples include the lakes of the European Alps and Patagonia
Interacts with other geomorphic agents to shape complex landscape systems
Mass wasting (landslides, rockfalls)
Fluvial erosion (river incision, sediment transport)
Legacy of past glacial erosion continues to influence modern landscapes
Affects sediment supply to rivers and coasts
Impacts slope stability in mountainous regions
Influences ecosystem development and biodiversity patterns