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43 terms

Glaciation

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Where do glaciers originate?
mountainous areas and they originate at the headwaters of stream tributaries, it is a land based mass of highly compacted ice that moves downward and outward under its own weight due to gravity
ex. Alps, Rockies, Coastal mountains, Scandinavian Knollen, Andes, Himalayas, Caucasus
What do glaciers do?
They are agents of erosion, so they erode, transport, and deposit eroded material.
zone of accumulation
snow accumulates to a great thickness (more snowfall occurs than the melting)
zone of ablation
the area where eroded material is deposited, more loss and wastage than accumulation
abrasion
work on glacier floor and valley sides (sand-paper effect). Produces smooth gently sloping landforms
frost-shattering
loose material falls from the valley sides onto the edges of the glacier to form a lateral moraine or the materials fall down crevasses to be transported a englacial debris
plucking (quarrying)
a glacier freezes onto rock outcrops, when the ice moves it pulls away the mass of rock and creates a jagged landscape
cirque glacier
small, semi-circular or triangular glaciers that form on the sides of the mountains
How does a cirque form?
Snow collects in the hollows, freeze-thaw action produces disintegration of rocks, this debris is moved by meltwater and the hollow is enlarged.
Cirque
a Glacially eroded rock basin with a steep head wall and steep sides surrounding an armchair shaped depression
horn
the sharpened peak of a mountain
arete
A sharp ridge that forms between two glacial cirques
(pyramidal peak is a ridge formed between three glacial cirques
U-shaped Valley
Former narrow V-shaped valleys that are deepened by erosion to create U-shaped valleys (flat bottom)
continental glaciers (ice sheets)
unconfined by topography
- covering >50,000km squared of land, flows outward in all directions
Greenland and Antarctica
hanging valley
Results from a main glacier eroding at a different rate than its tributary glaciers. A tributary glacier valley whose floor is at a higher level than that of the main glacial valley
ice cap
a large glacier forming on an extensive area of relatively level land, flowing outward from its center
covers <50,000 km squared of land
Baffin Island, Alask and Iceland
valley glaciers (alpine)
- confined to mountain valleys where they flow from higher to lower elevations
- shape is controlled by the valley it flows in
- valley glaciers flow into the ocean
- North America, Andes, Alps, and the Himalayas
zone of accumulation
an area of a glacier where additions of snow exceed losses of ice from melting, evaporation and sublimation
zone of ablation
an area of a glacier where losses of ice from melting, evaporation and sublimation exceed additions of snow annually
What is transportation by glaciers?
eroded material is transported within the glaciers, under, and on top of glaciers. Some material is also transported by meltwater
striations
a series of parallel scratches and grooves
moraine
type of landform that develops when the debris carried by a glacier is deposited
lateral moraine
Ridge of till along edge of a valley glacier. Composed largely of material fallen to the glacier from valley walls
englacial moraine
a lateral moraine that has been covered with snow which is then added to the material in the ground and it becomes a ground moraine
Terminal moraine
marks the maximum limit of a glacier lobe (snout) (the end and final accumulation of debris)
medial moraine
a linear accumulation of material extending down the centre of a glacier; it is caused by merging of two lateral moraines from the point at which the glaciers unite
recessional moraines
marks a recessional phase or still-stand in the overall decline of a glacier - the glacier sits long enough to leave a mound of material (usually parallel to the terminal moraine)
striations
scratches left on rocks and bedrock by glacier movement
glacial erratics
boulders picked up and carried by ice often for many kilometers and deposited on the area of completely different lithology (bedrock)
till
unstratified soil deposited by a glacier
outwash deposits
are formed when sand is eroded, transported, and deposited by meltwater streams from the glacier's snout and nearby till deposits to nearby areas in front of the glacier
outwash plain
develops when there is a great number of meltwater streams depositing material ahead of the glacier
kame
where sediment rich water flows into a crevasse or depression in the ice, a conical shaped pile of sand and gravel forms a kame
Features associated with alpine glaciation
drift
the collective name for all the glacial boulders, gravel,sand and clay deposited under glacial conditions
two types of glacial drift
till - unsorted material (eg. moraines, erratics)
fluvioglacial material - sorted by meltwater (eg. varve)
valley glacier
- larger masses of ice which move down from either an icefield or a cirque basin
-usually follow former river courses and are bound by steep sides
kame terrace
A deposit, often sloping down valley more steeply than the valley floor, formed where a glacial stream ran along the glacier margin
basil slip
the movement of ice along the interface between the glacier and the bedrock by slippage
plastic flow
A type of glacial movement that occurs within the glacier, below a depth of approximately 40 meters, in which the ice is not fractured.
glacier surge
the rapid, lurching, unexpected forward movement of glacier
sublimation
a change directly from the solid to the gaseous state without becoming liquid
glacial retreat
the movement of a glacier's toe back toward the glacier's origin; occurs if the rate of ablation exceeds rate of supply

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