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Physical Geog 3.1.4 Glacial Systems + Landscapes > 3.1.4.3 Geomorphological Processes > Flashcards

3.1.4.3 Geomorphological Processes Flashcards

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1
Q

2 ways the rigid upper layer of ice travels

A

Uniformly

Quickest

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2
Q

2 ways the plastic lower layer ice travels

A

None uniformly

Slowest at base

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3
Q

Why are glaciers slower st valley walls and base

A

Friction

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4
Q

What movement doesn’t exist in cold base glaciers

A

Basal slip

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5
Q

What’s the main movement in cold based glaciers

A

Internal flow

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6
Q

When does internal flow occur

A

Occurs when ice crystals orientate themselves in the direction of the glaciers movement and slide past each other

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7
Q

3 stages to internal flow

A

Jumble of ice crystals

Ice crystals align under pressure

Ice crystals now slide over one another

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8
Q

Why do ice crystals align in internal flow

A

Pressure

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9
Q

7 movements in warm based glaciers

A 
Basal flow/slippage
Regelation slip
Creep
extending flow
Compressing flow
Surges
Rotational flow
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10
Q

When does basal sliding occur

A

When the overlying ice’s weight + friction. With bed and sides cause ice to melt
Encourages ice to move as it isn’t frozen to its base + meltwater acts as lubricant

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11
Q

What causes the ice to melt at the bottom of the glacier for basal flow

A

Pressure and friction

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12
Q

What 2 processes help basal flow

A

Regelation slip

Creep

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13
Q

What happens in regelation slip

A

Obstacles to the ice flow (small<1m) create added pressure on the ice as it begins to move over them ;causing melting which aids the passage of ice over the obstacle

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14
Q

What happens on the upside of the glacier in regelation slip

A

PMP decreases so it’s warmer and ice melts (higher pressure)

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15
Q

What happens on the downside of the glacier in regelation slip

A

PMP increases
So it’s colder
Water refreezes (lower pressure)

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16
Q

What are overcome by creep

A

Larger items

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17
Q

What happens in creep

A

The ice acts like plastic and moulds itself around the obstacle as the ice crystals change shape/deform

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18
Q

What’s creep all due to

A

Stress concentrations around larger obstacles on the bedrock floor

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19
Q

When does compressing flow occur

A

Where there’s a reduction in gradient of valley floor

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20
Q

What happens to the ice in compressing flow

A

Ice decelerates

Thickening of ice mass

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21
Q

What’s at it’s maximum in compressing flow

A

Ice erosion

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22
Q

When does extending flow occur

A

When the valley gradient become steeper

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23
Q

2 things the ice does in extending flow

A

Accelerates

Becomes thinner

24
Q

What’s at it’s minimum in extending flow

A

Erosion

25
Q

When do surges occur

A

When an excessive build up of meltwater under the glacier leads to ice moving forward rapidly

26
Q

Who are surges a hazard to

A

People living in the glacial valley below the snout

27
Q

How much can surges move the glacier by in a day

A

250-300m

28
Q

Where does rotational flow occur

A

Within the Corrie, the birthplace of many glaciers

29
Q

What happens in rotational flow

A

Ice moving downhill can pivot about a point producing a rotational movement

30
Q

What combines with pivot water movement in rotational flow

What does this lead to

A

Pressure

Leads to greater erosion and an over deepening of the Corrie floor

31
Q

What can happen in extending flow due to higher velocity

A

The surface ice can break and crack

32
Q

Which flow has the most gravitational force

A

Extending flow

33
Q

Which temperature at he base causes faster ice movement

Why

A

Warm

More meltwater which lubricates base

34
Q

Why does ice move slower if the base is cold

A

Ice is frozen to bed rock and there’s more friction

35
Q

What bedrock floor gradient causes ice to move faster

Why

A

Steeper

Greater pull of gravity

36
Q

What time of year do glaciers move fastest at

Why

A

Summer

More meltwater lubricates ice

37
Q

What thickness of ice causes ice to move faster

Why

A

Thicker

More potential energy but more force is needed to overcome friction

38
Q

What geology causes ice to move faster

Why

A

Impermeable rock

As more meltwater stays on rocks base and lubricates it

39
Q

Why do glaciers move slower with permeable rock

A

As meltwater goes into rocks and doesn’t stay on surface so less lubrication

40
Q

How much friction causes ice to move faster

A

Less friction

41
Q

Why does ice move slower with more friction

A

As more ice is in contact with bed and valley sides

42
Q

What causes the ice in a glacier to move at different rates as it moves through a valley

A

The fractional drag between ice and rock

43
Q

What happens as the sides and base of a glacier move slower then the centre surface ice

A

The ice cracks producing crevasses on the surface

44
Q

2 other ways crevasses form

A

Where extending flow occurs (ice sped up)

Where the valley widens/ glacier spreads onto a plain

45
Q

Why do crevasses form when there extending flow or widening

A

As the surface ice is unable to adjust rapidly enough to extra stresses by basal slip/internal flow

46
Q

5 types of crevasses

A 
Crevasses at margins (sides)
Longitudinal crevasses
Transverse crevasses
Di radial splaying crevasses
Bergschrund (large crevasses)
47
Q

Why do crevasses at margins form

A

As frictional drag between the ice and rock of the valley sides causes the margins to move slower then the centre

48
Q

What angle to crevasses open up at margins compared to old ones

A

New open up At an angle to the margin

Old ones may be bent/rotated round in direction of the glacial flow

49
Q

When do longitudinal crevasses occur

A

When the glacier spreads out laterally as the valley widens so there are stresses in the ice

50
Q

How do stresses in the ice act when forming longitudinal crevasses
What position do crevasses open up in

A

At right angles to the margins so crevasses open up parallel to the glacier margins

51
Q

When do transverse crevasses occur

A

When a glaciers gradient steepens and extending flow occurs

52
Q

What shape are transverse crevasses upglacier

Why

A

Convex shaped

As the ice moves faster in the centre than the sides

53
Q

When do transverse crevasses close

A

When compressing flow occurs (gradient reduces)

54
Q

Where do di radial splaying crevasses splay out

A

In the glacier snout region from the spreading out of ice into a lobe

55
Q

What angles do di radial splaying crevasses also open up at to the direction of stresses

A

Right angles

56
Q

What’s the bergschrund like

We’re is it

A

A big semi circular crevasse

at the back of a glacier

57
Q

How is a bergschrund formed

A

By the tension caused by ice pulling away from the ice attached to the back wall

Physical Geog 3.1.4 Glacial Systems + Landscapes (14 decks)

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