2.A9 Glacial meltwater plays a significant role in creating distinctive landforms and contributes to glaciated landscapes. Flashcards
The processes of water movement within the glacial system is defined by three types -
Supraglacial, englacial and sub-glacial flows.
Glacial and fluvioglacial deposits have different characteristics - in terms of features which can be
Ice contact features or proglacial features -
Ice contact features may include:
Kames, eskers and kame terraces
Proglacial features include:
Sandurs, pro-glacial lakes, meltwater channels and kettleholes.
Characteristics of fluvio-glacial deposits -
- Generally smaller than glacial till as meltwater streams, still have less energy than valley glaciers.
- Generally smoother and rounder through water contact and attrition
- Deposition varies with largest material found up valley or nearest the glacier snout and finer material down the valley.
Glacial and fluvioglacial deposits have different characteristics -
Glacier travel with outlet streams and behave normally to other normal streams it is varied due to vegetation, discharge and vegetation. Fluvioglacial streams operate very differently because of the high pressure and viscosity flow this causes erosion of underlying bedrock by abrasion. Ablation rates are high during deglaciation and high meltwater leads to powerful erosion. Fluvioglacial material is deposited at or beyond the ice margin, by streams coming out of the ice margin known as an outwash plain.
Ice contact feature ( Delta) Kames - formation -
Occur at the edge of the glacier and carry lateral moraine and is formed by deposition of material in ice in either depressions or crevasses, can be known as Delta Kames from occurring at the side of the glacier, show some evidence of stratification.
Ice contact features - Kame terraces - formation
Form relatively bench like features along the side of the glacier, where a gap or lake between the valley side is filled with fluvio-glacial deposits
What does fluvioglacial mean?
“Fluvioglacial” or “glaciofluvial” means erosion or deposition caused by flowing meltwater, from melting glaciers, ice sheets and ice caps.
Ice contact features - Eskers - formation
Result from subglacial meltwater deposition. Deposition occurs sand and gravel being deposited by flowing through underground tunnels, Eskers are thought to form when sub/englacial channels become obstructed leading to the deposition of material. The ice need to be stagnant (having no current or flow) to form englacial eskers.
Proglacial features - Sandurs/Outwash plain - formation
When an en/subglacial stream exists the snout of the glacier. Decrease in water pressure and velocity causing the deposition. The stream carry debris in braided channels which leave the largest deposits near the ice front and carry the finer particles further across the plain.
The deposits appear in layers showing the larger deposits at each spring. The glacial material that was spread out by the braided river system forms a gently sloping surface made up of sorted and stratified sand and gravel which gets progressively smaller the more it moves away from the ice front.
Proglacial features - proglacial lakes - formation
Can be known as ice margin lakes formed in front of an ice mass from meltwater, they are dependant on the rapidity of the deglaciation. Where meltwater from the glacier becomes impounded within a depression and is blocked by high ground.
Proglacial features - meltwater channels - formation
When proglacial lakes overflow their confines, these form an open V shape and are caused by intense fluvial erosion along the flow path, in the present day these channels are mostly dry with a small stream lead to diversions of preglacial drainage systems.
Proglacial features - Kettleholes - formation
Small, circular lakes formed by the melting of ice blocks left by the retreating glacier. After the ice melted the ground above it subsided leading to a depression filled with water. Many dry as to this day are only filled with rainwater and may have vegetation affecting their depths.
