3.1.4.3 Geomorphological Processes Flashcards

(57 cards)

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

25
When do surges occur
When an excessive build up of meltwater under the glacier leads to ice moving forward rapidly
26
Who are surges a hazard to
People living in the glacial valley below the snout
27
How much can surges move the glacier by in a day
250-300m
28
Where does rotational flow occur
Within the Corrie, the birthplace of many glaciers
29
What happens in rotational flow
Ice moving downhill can pivot about a point producing a rotational movement
30
What combines with pivot water movement in rotational flow | What does this lead to
Pressure | Leads to greater erosion and an over deepening of the Corrie floor
31
What can happen in extending flow due to higher velocity
The surface ice can break and crack
32
Which flow has the most gravitational force
Extending flow
33
Which temperature at he base causes faster ice movement | Why
Warm | More meltwater which lubricates base
34
Why does ice move slower if the base is cold
Ice is frozen to bed rock and there's more friction
35
What bedrock floor gradient causes ice to move faster | Why
Steeper | Greater pull of gravity
36
What time of year do glaciers move fastest at | Why
Summer | More meltwater lubricates ice
37
What thickness of ice causes ice to move faster | Why
Thicker | More potential energy but more force is needed to overcome friction
38
What geology causes ice to move faster | Why
Impermeable rock | As more meltwater stays on rocks base and lubricates it
39
Why do glaciers move slower with permeable rock
As meltwater goes into rocks and doesn't stay on surface so less lubrication
40
How much friction causes ice to move faster
Less friction
41
Why does ice move slower with more friction
As more ice is in contact with bed and valley sides
42
What causes the ice in a glacier to move at different rates as it moves through a valley
The fractional drag between ice and rock
43
What happens as the sides and base of a glacier move slower then the centre surface ice
The ice cracks producing crevasses on the surface
44
2 other ways crevasses form
Where extending flow occurs (ice sped up) | Where the valley widens/ glacier spreads onto a plain
45
Why do crevasses form when there extending flow or widening
As the surface ice is unable to adjust rapidly enough to extra stresses by basal slip/internal flow
46
5 types of crevasses
``` Crevasses at margins (sides) Longitudinal crevasses Transverse crevasses Di radial splaying crevasses Bergschrund (large crevasses) ```
47
Why do crevasses at margins form
As frictional drag between the ice and rock of the valley sides causes the margins to move slower then the centre
48
What angle to crevasses open up at margins compared to old ones
New open up At an angle to the margin | Old ones may be bent/rotated round in direction of the glacial flow
49
When do longitudinal crevasses occur
When the glacier spreads out laterally as the valley widens so there are stresses in the ice
50
How do stresses in the ice act when forming longitudinal crevasses What position do crevasses open up in
At right angles to the margins so crevasses open up parallel to the glacier margins
51
When do transverse crevasses occur
When a glaciers gradient steepens and extending flow occurs
52
What shape are transverse crevasses upglacier | Why
Convex shaped | As the ice moves faster in the centre than the sides
53
When do transverse crevasses close
When compressing flow occurs (gradient reduces)
54
Where do di radial splaying crevasses splay out
In the glacier snout region from the spreading out of ice into a lobe
55
What angles do di radial splaying crevasses also open up at to the direction of stresses
Right angles
56
What's the bergschrund like | We're is it
A big semi circular crevasse | at the back of a glacier
57
How is a bergschrund formed
By the tension caused by ice pulling away from the ice attached to the back wall