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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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