Glacier deposition and Hydrology Flashcards
What are glaciers?
Glaciers are blocks of ice that flow under their own weight.
How are glaciers connected to people’s livelihoods?
Though irrigation, HEP, and glacial hazards
Transportation
– Supraglacial- Moraines
– Englacial
– Subglacial
Erosion
– Abrasion
– Plucking
– Meltwater
Erosional Landforms
– Striations
– Roche Moutonnées
– Cirques
– U-Shaped valleys
What are moraines?
Accumulations of dirt and rocks that have fallen onto the glacier surface or have been pushed along by glacier as it moves.
Lateral moraines
Forms along the edges of glacier material from valley walls are broken up by frost shattering and fall onto ice surface to be then carried along the sides of the glacier..
When ice melts it forms a ridge of material along the valley side.
Recessional moraines
Form at the end of the glacier, so they are found across the valley, not along it.
Same as terminal moraine but they occur where retreating ice pauses rather than furthest extent.
Terminal moraines
Forms at the start of the glacier- marks the furthest extent of ice, pushes lots of earth as it advances and forms across the valley floor.
Supraglacial moraine
Material at the surface of the glacier including lateral and medial moraine, loose rock debris and dust settling out from the atmosphere.
Push moraine
Formed by glaciers that have retreated and then advanced again.
Moraine formation processes
Supraglacial melt
Push moraines
Moraine formation processes
Supraglacial melt
As debris and rocks fall to the bottom of glacier, the ice is melting at lower altitude.
Moraine formation processes
Push moraines
The ice pushes everything up in this formation.
Formed by glaciers that have retreated and then advanced again.
Subglacial Landforms form…
beneath the glacier.
E.g Flutes, Drumlins
What are flutes?
Small, elongated features, oriented in the ice direction found in large groups and composed of till
How are flutes formed?
Ice flowing over the boulder and it’ll get to a sticky spot and the sediment has a lot of water in it and is very walk and it squeezes around the rock and settles behind it.
When the ice melts away, we’re left by the boulder and the flute of sediment protected by the boulder.
What are drumlins?
Larger, less elongated features, oriented in the ice direction that may or may not have a proximal core and are found in large groups.
How are drumlins formed?
Deformable bed theory
Drumlins form associated with obstacles in the deforming bed
Fluvial theory
Result of meltwater erosion and deposition as a consequence of large floods beneath the ice.
Glacier hydrology: Supraglacial flow
Surface melt during the summer.
Effective transportation…and thermal erosion.
Can lead to the formation of cut and closure channels – englacial streams cut downwards, creep closes the “roof” on them.
Moulins
Glacier pot holes filled with water that keeps on eroding down and down.
Link supraglacial system to englacial and
subglacial systems
Formed from crevasses- stress on a glacier causes ice to stretch.
Englacial flow is
flow within the ice
What two ways does englacial flow happen?
Veins- very slow flow through ice crystals in glacier
Conduits- (tunnels) water from moulins, fast flow
Subglacial flow is
flow at the bottom of the ice
What two ways does englacial flow happen?
Sheet flow- film of water more or less evenly distributed across the bed of glacier (very slow).
Conduits- (tunnels) within ice and at bed of glacier
Cavities- pocket of water distributed on the bed, little channels of water flowing between these.
What two different types of conduits in subglacial flow?
R-channel- water is flowing within the ice.
N-channel- water is flowing through the ice and the rock
Glaciofluvial Landforms formed from having water
Kame Terrace
Esker
Outwash Plain (Sandur)
Glaciofluvial Landforms
Kame Terrace
Terrace formed between the glacier and the valley walls
by sedimentation of a former glacial lake or river
Glaciofluvial Landforms
Eskers
Long sinuous ridges of sand and gravel
Formed from water pathways within the glacier
Best preserved, subglacial eskers
Glaciofluvial Landforms
Outwash Plains (Sandur)
Proglacial rivers that build up outwash
plains (sandurs) flow at very high velocity.
- Proximal sediments - coarse grained, sheet
flow
- Distal sediments - finer grained - braided
rivers
