Glacial processes and deposits

Question 1

What are the three factors that control the ice age?

Answer 1

1) eccentricity
2)Tilt (obliquity)
3)Precession (wobble)

Question 2

What are the two different types of glaciers? Describe each one

Answer 2

1) Alpine
-follows topography (confined)
-The length of the glacier is much longer than their width
-shapes the valley in a U shape by eroding it when moving

2) Continental (ice sheets)
-overrides topography (unconfined)
-flat
-slow-moving and very thick sheets of ice (~3km)

Question 3

How do glaciers form?

Answer 3

-cold temperature
-consistent precipitation of snow
-snow compacts under pressure and forms glaciers

-would not start moving until the thickness reaches a critical height H, relative to the slope angle B.

H~ 11/sin(B)

Question 4

What are the two mechanics of glacial movement?

Answer 4

1) Internal Visco-Plastic Flow
-the ice in the middle of the glacier moves faster than its surroundings since there is less friction.
-continuous deformation and reformation of ice crystals

2) Basal slip
-meltwater on the bottom of the glacier moves the whole glacier
-moving along the base of the glacier

Question 5

Zone of ablation

Answer 5

Melting of glacier/ snow

Question 6

Zone of accumulation

Answer 6

Accumulating snow

Question 7

Retreating glacier

Answer 7

The rate of ablation is > the rate of accumulation.

Question 8

Advancing glacier

Answer 8

Rate of accumulation > the rate of ablation.

Question 9

What are the two glacial erosion mechanisms?

Answer 9

1) Plunking
- glaciers loosen, lifts, and entrains fractured blocks of rocks (erratics)

2) Abrasion
-Glaciers scrap the bedrock and grind it into powder.
-leaves behind scrape marks (striations) that tell the direction of glacier movement.

Question 10

Erosional landforms: Drumlin formation

Answer 10

-tails point in the direction of ice movement

Question 11

Explain glacial deposits

Answer 11

Sediments are pushed along with the glacier until they melt (unsorted) and/or are transported by meltwater (sorted)

Question 12

What are moraines and what are their four types?

Answer 12

1) end/ terminal moraine
-deposition at the end of the glacier
2)lateral moraine
-deposition on the side of the glacier.
3)medial moraine
-deposition between two glaciers
4)ground moraine
-deposition below the glacier

Question 13

What are the three glacial deposits and explain each one

Answer 13

Kettle
- isolated water pits

Kames
- forms when water transports sediments on top or beside the glacier, and then the glacier melts and drops on the surface.

Eskers

• sinuous tunnel below the ice sheets
  -when glaciers recede, the stream deposits its load into a long ridge-like form
  -good source of sand and gravel

Question 14

Outwash plains

Answer 14

Stratified drift deposited by streams of meltwater in front of the retreating glacier, often composed of sand and gravel.