characterisitics of till and its affects on abrasion rates

Question 1

Angular or sub angular till

Answer 1

embedded till in the ice = no further erosion processes

Question 2

Unsorted

Answer 2

Deposited material, all sizes and masses together.

When water deposits material, it loses energy and deposits in size-based sequence

Question 3

Unstratified

Answer 3

Glacial till is dropped in mounds and ridges rather than in layers

Typical of water-borne deposit

Question 4

Ice thickness

Answer 4

thickness of overlying ice = greater pressure exerted in basal debris

Beyond a certain thickness the pressure is too great = too much friction between debris and bedrock = not much movement

Depends of density and nature of debris - typically 100-200m

Question 5

Why and how does the presence of basal water pressure affect the abrasion rates?

Answer 5

Meltwater at base is vital for abrasion to take place

If water is under pressure the glacier can buoyed up = reduced pressure and erosion

Question 6

Why and how does the presence of sliding go basal ice affect the abrasion rates?

Answer 6

Determines if abrasion can take place

Requires basal sliding to move embedded debris across rock surfaces
Increase of sliding = increase erosion

Question 7

Why and how does the movement of debris on the base affect the abrasion rates?

Answer 7

Abrasion wears away bedrock and basal debris = debris needs to be replenished if abrasion is effective

Replenished through weathering and glacial erosion

Question 8

Why and how does the removal of fine debris affect the abrasion rates

Answer 8

Maintains high rates of abrasion

Fine debris needs to be removed so larger particles can abrade the bedrock (done by meltwater)