Glaciers Flashcards
What are characteristics of tundra soils
-a thin surface organic layer- waterlogged in summer and grey because of lack of oxygen
-permafrost down below that is impermeable
-active layer melts in summer and freezes in winter
Tundra vegetation adapatations
-Shallow roots because of thin organic layer-can’t grow tall
-small,short plants and close together to provide shelter
-protected by hair- traps air acts as an insulator
-dark colour-retain heat
What is the albedo effect?
The reflectivity of surfaces, reflect sun
What effects the distribution of cold environments?
Albedo
Amount of atmosphere travelled through
curvature of the earth- longer length for sun to travel, sun rays dissipate
Altitude- thin less dense air can’t hold as much heat- Mt Everest peak 50% less dense air
Aspect- shaded areas receives less sun
relief-steep relief
What is frost action?
-water gets into crack
-water freezes and expands by 10% causing crack to widen
-ice thaws, contracts and water gets deeper into cracks
-repeated expansion and contraction causes further cracks until rock breaks
When do glaciers advance?
when there is more accumilation than ablation for example mass gained by snowfall.
When do glaciers retreat?
When there is more ablation than accumilation for example mass lost by melting or calving.
Cold based glaciers
little to no melting of ice
Characteristics of warm based glaciers?
-high winter snowfall
-meltwater as lubricant to make it more mobile than cold glaciers
-more likely to erode, transport and deposit material
How long ago was the Pliestocene period?
1.8 million years ago
What is rotational flow?
ice rotates around a point due to abrasion deepening corries.-Warm based glaciers in alpine environments, occurs in hollows.
What is compressional flow?
Happens at a shallow gradient, there is a fast flow of ice initially, near the end of the glacier the ice slows and bunches up.
What is basal sliding?
The melting point of water decreases under pressure; thus water melts at a lower temperature under thicker glaciers. This can then lead to basal sliding, where a glacier ‘floats’ above a layer of meltwater, which acts as a lubricant. Thus, the glacier is able to move faster.
What is extensional flow?
Happens at a steep gradient, at the end of the glacier it gets thinner and thinner which forms cracks called cravases in the ice.
What is internal deformation?
-occurs in cold based glaciers in polar environments.
-little to no meltwater under the glacier
-ice crystals form in middle of the glacier that line up in the direction of flow of the glacier
- mass at the top of the glacier is greater than mass on the bottom, so as it moves it cruses the ice crystals
How do corries form?
plucking-steep back wall
abrasion-hollowed out basin
rotational slip
How do roche moutonee’s form?
-more resistant rock at base of the glacier (bedrock)
-meltwater underneath transports material, abrasion of the side facing the top-sooths the rock causing pressure melting of ice
-side facing downhill- plucking occurs, making it more steep-sided and ice re-freezes due to less pressure
-Example: Easdale- Lake District
What are aretes?
knife-like ridges of rock, formed when 2 corries erode back to back- striding edge (hellvelyn)
What are drumlins?
-there made up of glacial till
-When a glacier hits an obstacle
that cannot be eroded, deposition from
underneath the glacier builds up behind
the obstacle. sediment gets deposited as the glacier is overcome with sediment
-the steeper end faces the direction uphill and the gently sloping end faces the direction of the ice flow (tapered)- they are often in clusters
-Example: Vale of Eden
What are hanging valleys?
-forms when a smaller glacier(tributary glacier) enters a main glacial valley and gets cut off and hangs
-waterfalls often form here
Example: Yosemite, USA
Example of a tarn?
The red tarn, helvellyn
What is a ribbon lake?
am long, narrow lake found in glacial valleys. They are formed in locations where the glacier moved over soft rock. Hard rock is untouched, soft rock is eroded by glacier.
Example: lake windermere
What are truncated spurs
When a valley fills with a glacier, any land in the way (interlocking spurs) is eroded away. Steep sides shows abrasion and plucking.
What are nivation hollows?
Snow falls and is protected in hollows by the wind. The snow is compacted by more snow. Weathering processes like frost action can weaken the soil and rocks underneath the snow. Meltwater washes the sediment out the base of the snow patch. These processes over time form nivation hollows.
There common on south-facing slopes in the northern hemisphere.
Ice —- neve —— firn