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
What are drumlins?
-there made up of glacial till
-sediment gets deposited when glacier is overcome with sediment
-the steeper end faces the direction uphill and the gently sloping end faces the direction of the ice flow- 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
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
What are till plains?
when a large section of ice detaches from the main body of the glacier and melts, the suspended debris will be deposited and form a large plain of unsorted till.
What are moulins?
They are meltwater channels within glaciers.
-lots of melting in summer- meltwater can flow on top, within or under a glacier.
-They can cause pressure melting and hydraulic action of rock.
What is an esker?
- A sub-glacier meltwater channel
-deposits of fluvio glacial sediment under the ice - The stream carries sorted sediment by meltwater
-post-glacier it melts and leaves Eskers, which are long ridges of material running in the direction of ice advance
Example: Thelon esker, Canada
What is permafrost
Permently frozen ground for atleast 2 years.
Covers 25% of land in North Hemisphere
Contains 1.5 trillion tonnes of Co2
What is a periglacial landscape and what happens in the development of them?
-Landscape that is not glaciated but exposed to very cold conditions
-frost action takes place
-development of permafrost
-Tundra environment
-Found in Alaska and Canada
What is a kame terrace
They are frequently found along the side of a glacial valley and are stratified deposits of meltwater streams flowing between the ice and the adjacent valley side. They are made up of gravel and sand.These kame terraces tend to look like long, flat benches, with many pits on the surface made by kettles.- fluvioglacial
What is an outwash plain
Outwash plains are formed in front of a glacier and are where material is deposited over a wide area, carried out from the glacier by meltwater. Discharge occurs from both the melting snout of the glacier and the emergence of meltwater streams from within the body of the glacier. -sorted sediment
What are terracettes
-They form when vegetation interupts soil moving down a slope due to frost heave and frost action. A flatter area builds up behind the obstruction, which leads to a series of step-like terraces.
Example: Pen-y-ghent, North Yorkshire
What are solifuction lobes
Where slopes have a steeper gradient of 10-20° then solifluction lobes will form. These have a tongue-like
appearance that extends downslope and can be up to 50 m in width and 5 m high.
-Form by solifuction- flow of water down a steep slope during the summer. Permafrost is impermable to water, soil above gets oversaturated and slides downslope by gravity.
What is a thermokarst?
-Ice in the ground melts, causing the ground to collapse and holes form. The holes become filled with water, creating an uneven marshy landscape- Canada, North-West British Columbia
What is patterned ground
-Stones that are on the surface- arranged in polygons, circles or stripes formed by frost heave or frost contraction.
What is frost heave?
-Water underneath stones freezes and expands forcing the stones upwards. They can reach the surface and roll down to the edges of the mounds that have formed, forming circles around them. If the mounds are on a slope the stones roll downhill and form lines.
What is frost contraction?
-Causes ground to crack in polygon shapes. The cracks fill with stones, forming polygon patterns on the surface.
What are block fields?
Example: Schiehallian, Scottland
- A field of loose rocks. They are formed in place by frost shattering of the bedrock layer due to repeated thawing and freezing- frost action.
what is plucking
meltwater flowing along the base of the glacier freezes to the bedrock, fragments of which are ripped out by the moving glacier.
What is abrasion
-Sandpaper effect of rocks eroding a surface, repeated rock erosion.
How open-system pingos form
- There is discontinuous permafrost. Groundwater is forced upwards through gaps in the permafrost. The water collects together and freezes, forming a core of ice that pushes ground above it upwards.
How closed-system pingos form
- Forms where there is continuous permafrost, with a lake at the surface. The lake insulates the ground so ground below is not frozen. The lake dries up, the ground isn’t insulated anymore and the permafrost advances around the area of unfrozen ground, this causes water to collect in the centre of the unfrozen ground. Water freezes and creates a core of ice that pushes the ground above it upwards.
For example: Mckenzie River, Canada
What are kettle holes
small depressions filled with lakes/marshes. Formed when blocks of ice, washed onto plain melts and leaves a gap in the sediments. These holes fill with water to form small lakes- plants can grow-marshy.
What is an ice wedge
- When temps are low, the ground contracts and creates cracks- frost contraction
-Spring-temps increase and active layer thaws and meltwater seeps into cracks
-permafrost=still frozen so water freezes in cracks- ice wedges
-next winter, cracks can re-open, splitting the ice wedge and more water seeps in and freezes, widening the wedge.
What is continuous permafrost
found in coldest reigons- reaches 1500m below ground
what is discontinuous permafrost
warmer reigons-20-45m below surface
moraine
Lateral:
material deposited on the sides of
a glacier, leaving a ridge when the ice melts.
Medial: formed from two lateral moraines meeting in the middle of a glacier and depositing material.
Ground: carried under the glacier and
abraded between the glacier and valley
floor. Ground moraine is the only sorted
moraine as all of it is abraded underneath
the glacier, whereas all other types of
moraine is unsorted.
Terminal:
Material deposited at the snout of
a glacier on the valley floor.
glacial trough
A u-shaped valley
bulldozing
formed by a glacier
and eroding through a river
(v-shaped) valley.
