Glaciers: Glacial Processes

Question 1

What are the 3 types of weathering?

Answer 1

1. Freeze-thaw weathering (frost shattering/action)
2. Carbonation
3. Nivation

Question 2

What is freeze-thaw weathering (or frost shattering/action)?

Answer 2

• occurs where the temp regularly rises and falls above and falls below freezing
• Precip collects in cracks, freezes overnight and expands by 9-10%
• This puts pressure of the sides of the cracks
• During the day, the ice thaws and contracts releasing the pressure
• Repeated cycles, cracks get bigger —> eventually the rock cracks open. The rocks that then break off are jagged and angular (scree)

Question 3

What is carbonation?

Answer 3

carbon dioxide dissolved in water forms a weak carbonic acid. This reacts with and dissolves calcium carbonate in some rocks (particularly limestone) to form calcium bicarbonate. A process of chemical weathering. CO2 is more soluable at low temps, meaning water can dissolve more CO2 when cold.

Question 4

What is nivation?

Answer 4

• compacted snow gathers in a small depression and eventually erodes into a full hollow of snow - called nivation hollows, enlarged by nivation processes.
• Common in south-facing slopes in the northern hemisphere.
• The freeze thaw cycle leads to weathering of the rock under and around the edges of the snow patches

Question 5

What are the Erosional processes?

Answer 5

• plucking
• abrasion

Question 6

What is plucking?

Answer 6

meltwater at the bottom of the glacier freezes onto rock on the valley base
• As the glacier moves, the rock is pulled away from the valley base - leaving a jagged surface. Mainly occurs when the rock is well-jointed

Question 7

What is abrasion?

Answer 7

as the glacier slides over its bed, it picks up rock fragments that act like sandpaper, on a giant scale, rubbing against and wearing away the sides and floor of the valley. This leads to the valley getting steeper, deeper and wider.

Question 8

How do glaciers transport sediment (transportation)?

Answer 8

• a glacier is capable of transporting large amounts of debris. Some of this may be derived form rockfalls on the valley side
• This debris is on the surface of the glacier (superglacial debris) or buried within the ice (englacial). Material found at the base of the glacier is known as subglacial.

Question 9

What is glacial deposition?

Answer 9

• deposition of sediment transported by the ice takes place when the ice melts, which is primarily in the ablation zone close to the glaciers snout.
• Here the sediment on and in the ice simply melts out in much the same way as the items used to decorate a snowman are left in the ground.

Question 10

What are the periglacial processes?

Answer 10

• active layer
• frost heave
• solifluction

Question 11

What is the active layer?

Answer 11

the top layer of permafrost that thaws over the summer

Question 12

What is frost heave?

Answer 12

Water underneath rocks or ground freezes, expands and thus forces the mass upwards

Question 13

What is solifluction?

Answer 13

Mass movement of soil that becomes waterlogged when water is trapped between the active layer and the frozen permafrost. Waterlogged soil flows easily when gravity acts upon it (usually on a gradient)

Question 14

What are the fluvioglacial processes (water)?

Answer 14

involve erosion, transport and deposition by meltwater.
- When glaciers melt, huge quantities of meltwater are produced which has the capacity to transport much debris - meltwater streams. They have a high velocity and turbulent flow, meaning they can pick up and transport a larger amount of material than normal rivers of a smaller size. They are highly erosive due to the amount of material, and therefore create deep channel. When meltwater discharge decrease, the loss of energy results in material to be deposited.