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EOS 120 > Glacial Processes and Landforms > Flashcards

Glacial Processes and Landforms Flashcards

1
Q

What percentage of earth’s freshwater is stored in glaciers?

A

around 70%

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2
Q

what percentage of earths surfaces covered in ice?

A

around 10%

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3
Q

where on earth is ice stored?

A 
ice sheets (Antarctica, Greenland)
valley glaciers
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4
Q

What areas were covered by ice sheets during the last ice age?

A

large parts of north america and Europe

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5
Q

glaciers have a strong control on…?

A

average global sea level

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6
Q

what do glacial deposits lead to?

A

construction aggregate

important aquifers

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7
Q

ice flows under its own weight due to …..

A

gravity

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8
Q

If downslope force (shear stress, τ) > resisting force (shear strength), then…

A

ice flows as a plastic

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9
Q

what are some features of glaciers?

A 
zone of accumulation
equilibrium line (line between net gain and net loss)
zone of ablation
crevasses
snowlayers
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10
Q

How does snow become glacial ice?

A

becomes more dense - contains less air

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11
Q

what is the lower limit of the zone of accumulation?

A

the equilibrium line

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12
Q

what is the zone of ablation defined by?

A

net loss by melting

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13
Q

if accumulation > ablation

A

glacier advances

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14
Q

if accumulation < ablation

A

glacier retreats

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15
Q

ice within a glacier always flows in which direction?

A

forwards (even when retreating)

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16
Q

how do glaciers move?

A

creep

basal slip

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17
Q

how fast does the ice in a glacier move?

A

metres/yr to 100 metres/yr

18
Q

what are the different types of glaciers?

A

valley (also tributary/tidewater) glaciers
ice sheets
(they are classified by size/location)

19
Q

how hard is ice?

A

1.5 hardness on mosh scale

can be scratched by a fingernail

20
Q

How do glaciers erode?

A

Glaciers scour & erode rock

21
Q

how do glaciers scour & erode rock?

A

Ice pressure + sediment abrasion

(1) As ice flows, it entrains & ‘pushes’ sediment
- > Abrasion, ‘bulldozing’, & plucking
2) Glacial meltwater
- > Meltwater flow (outwash plains & rivers)
- > Pressurised sub-glacial flow

22
Q

What landforms result from glacial erosion?

A 
cirques
truncated spurs
horns
tarns
arête
hanging valleys
glacial trough (u-shaped)
23
Q

what is a roche moutonnée?

A

Streamlined bedrock mound parallel to ice flow

‘Plucking’ on lee side (freeze/thaw)

24
Q

What deposits do glaciers leave behind?

A

(1) Till
(2) Glaciofluvial deposits
(3) Glaciolacustrine deposits
(4) Glacial erratics

25
Q

what is till?

A

poorly-sorted mixture of many different sediment sizes and striated rocks [material left behind after transport on/in/under ice]

26
Q

what are glaciofluvial deposits?

A

sands/gravels deposited by meltwater channels

27
Q

what are glaciolacustrine deposits?

A

fine-grained sediment, with dropstones. Deposited in lakes.

28
Q

what are glacial erratics?

A

ice-transported boulders, not derived from underlying bedrock

29
Q

What landforms result from glacial deposition

A 
eskers (glaciofluvial feature)
ground moraines
drumlins
kettle lakes
recessional moraine
terminal moraine
outwash plain (glaciofluvial deposition)
30
Q

how are moraines formed?

A

Debris deposited on ice, up-valley (mass wasted)
Transported on surface, down-valley, down-ice
Leaves train of deposits (till) on margins of glacier, and eventually its front (toe)

31
Q

what are lateral moraines?

A

moraines that form along the sides of a glacier

32
Q

how do medial moraines form?

A

lateral moraines become medial moraines when two valley glaciers meet

33
Q

what does a terminal moraine mark?

A

the furthest advance of the glacier

34
Q

when are recessional moraines formed?

A

while terminus of receding glacier remains temporarily stationary

35
Q

during the last glacial maximum which ice sheet covered all of BC?

A

cordilleran ice sheet

36
Q

what is an effect of continental ice sheet on the crust?

A

During glaciation: crust pushed down
After deglaciation: crust rebounds ->uplift [isostatic rebound]
Forms raised beaches (e.g. Hudsons Bay - still rebounding today)

37
Q

rate of isostatic rebound is proportional to…..

A

the viscosity of the underlying mantle (asthenosphere)

38
Q

what is the global average in temperature fluctuations in the past million years?

A

around 10 degrees Celsius

39
Q

what are the milankovitch cycles?

A 
eccentricity
tilt
precession
(variations in earths orbit)
they lead to variations in energy received from the sun
40
Q

what is eccentricity?

A

where earths orbit fluctuates between circular and elliptical over a 100,000 year cycle

41
Q

what is tilt?

A

where earths tilt fluctuates between 22.5 degrees and 24.5 degrees over a 41,000 year cycle

42
Q

what is precession?

A

where earth “wobbles” on its axis over a 26,000 year cycle

EOS 120 (24 decks)

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