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
Glacial erosion, transportation and deposition
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
supraglacial; material carried on top of a glacier
englacial; material carried whithin the glacier
subglacial; material carried at the base/bottom of the glacier
TILL: unsorted material showing the direction of flow of the glacier, oftenly deposited as moraine
Here are three glacial landforms you should learn for a potential 15 marker...
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
desc: steep-sided ridge
exp: formed when two glaciers flow parralell erode against each other; creating a sharp ridge inbetween the two
desc: steep-sides valleys with flat bottoms
exp: V-shaped valley erodes into a U shape
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
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
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
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