Cold Environments

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  • Created by: Aman
  • Created on: 07-05-14 20:52

Glacial processes

Glaciers move in 5 different ways...

1)Basal sliding; meltwater under the ground allows the glacier to slide over the ground

2)Rotational flow; glaciers move in a rotating fashion when in a hollow. 

3)Internal deformation; ice bends and warps to flow downhill like a liquid; how cold glaciers move

4)Extentional flow; strong gravitational force pulls the ice downhill; tension; ice fractures into thick layers while slipping downhill.

5)Compressional flow; glacier moves slowly downhill; less steep gradient; ice from upper glacier pushed towards lower; more ice = more pressure; fracturing 

 N.B crevases are a result of extentional flow 

Speed is determined by: gradient, thickness and temperature of the glacier

steeper valley; faster flow. thicker glacier; faster flow. warmer temperature; faster flow

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Glacial erosion, transportation and deposition

Erosion:

plucking; ice in contact with the rock thaws and refreezes around rock, chiping off rock

abrasion; debris caried in glacier scrapes against valley 

freeze thaw weathering; ice melts and refreezes; weakening and breaking rock

Transport:

supraglacial; material carried on top of a glacier

englacial; material carried whithin the glacier

subglacial; material carried at the base/bottom of the glacier

Deposition:

TILL: unsorted material showing the direction of flow of the glacier, oftenly deposited as moraine 

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Glacial landforms

Here are three glacial landforms you should learn for a potential 15 marker...

CORRIES

desc: an armchair shaped hollow formed in the periglacial periods. can be up to 1.5km X 1.5km

exp: formed on the north-east aspect; least sun and colder wind; more accumulation & less ablation; snow -> ice -> firn; heavy glacier flows downstream with basal sliding; abrasion & plucking deepen hollow(nivation) into a corrie. plucking steepens back wall of corrie 

ARETES

desc: steep-sided ridge

exp: formed when two glaciers flow parralell erode against each other; creating a sharp ridge inbetween the two

GLACIAL TROUGHS

desc: steep-sides valleys with flat bottoms

exp: V-shaped valley erodes into a U shape 

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Glacial deposition

Moraine is different formations of till, with 5 different types of moraine...

1)Medial moraine; deposited moraine in the centre of where two glaciers met/converge

2)Terminal moraine; at the end-point of the glacier

3)Lateral moraine; at the sides of the glacier

4)Push moraine; moraine that was previously deposited being pushed further due to the glacier re-advancing

5)Reccessional moraine; moraine built up as a result of the glacier re-advancing, then retreating, depositing the recessional moraine to a perpendicular(directly in front of) position to the terminal moraine

Drumlins are half egg shaped hills of till; 1500m long and 100m high; stoss end -> tall end, lee end -> short end

Erratics are large boulders that have been carried a great distance by glaciers

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Fluvioglacial process & Landforms

Meltwater streams erode the landscape; similar to rivers but with greater power; pressure of the ice -> water flows much quicker & erodes more 

Melting glaciers deposit...

Outwash plains; a layer of gravel, sand and clay that forms in front of where the snout was; sediment deposited is sorted; gravel(heaviest) deposited first, clay(lightest) deposited last

Kettle holes; hollowes in the outwash plain; formed by ice blocks being broken off by the glacier and buried into the ground -> melting -> holes are left in the outwash plain knowns as KETTLE HOLES

Kames; mounds of sand and gravel found on the valley floor; formed by melting glaciers depositing mounds of material in depressions

Eskers; long winding ridges of sand & gravel; deposited when meltwater streams in a tunnel retreat, leaving eskers

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Periglacial processes & landforms

permafrost is permanently frozen ground; the active layer is the top layer that can melt in the summer; solifluction is where water seeps through the layers of permafrost, and becomes trapped

Ice wedges; wedges of ice that develop in permafrost soil and are formed when the temperature drops to a very low value in winter -> ground contracts and cracks are formed in permafrost(frost contraction) -> temperatures increase in spring -> active layer thaws and meltwater seeps into permafrost -> water freezes in cracks; process repeats and ice wedge icreases in size 

Frost heave; the upwards swelling of stones and is formed from the following process; water freezing on the ground makes humps on the surface -> the active layer freezes in the winter -> ice in the active layer pushes the soil above it upwards -> ice melts around the stones(stones lose heat faster than ice) and reforms underneath the stones -> ice expands and pushes stones upwards towards the surface 

Patterened ground; stones on the surface are arranged in circles/polygons/stripes; can be formed by frost heave or frost contraction

Frost heave = pushed out and rolled to the side via ice in frost heave

Frost contraction = cracks get filled in via the stones 

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Periglacial processes and landforms part 2

Nivation is a process of erosion that makes hollowes deeper by repeated processes of freezing and thawing; periglacial environments have temperatures that fluctuate around 0 degrees -> freezing; ice expands -> frost shattering breaks off bits of rock at hollow; melting; the meltwater carries away debris = this is the result of a nivation hollow & the start of the formation of a corrie

Solifluction is the flow of a waterlogged layer of soil; solifluction lobe is the tounge shaped formation made when one section of soil is soliflucting faster than another   ^

Pingos are ice-filled periglacial hills that can be 80m tall and 500m wide; there are two types of pingos...

Open-system pingo; formed when there is discontinuous permafrost; groundwater is forced up the gaps between the areas of permafrost; water gathers together and refreezes; forming a core of ice that pushes the ground above it upwards (a perimeter of ground covering the ice)

Close-system pingo; formed in areas of continous permafrost, with a lake at the surface; the lake insulates the ground -> area underneath remains frozen; lake dries up -> no more insulation -> permafrost advances around the area of unfrozen ground(that was^); water collects in the are of unfrozen ground -> freezes -> core of ice pushing the ground above it upwards 

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