10. Drumlins

Question 1

what is rock flour?

Answer 1

very fine material produced by the scraping and grinding of rock surfaces

Question 2

how are pebble-sized rocks produced?

Answer 2

plucking and freeze-thaw weathering

Question 3

where are drumlins found?

Answer 3

broad lowland regions

long axes parallel to the direction of ice flow

Question 4

describe the gradient of drumlins

Answer 4

the stoss end is high and steep
the lee slope is smooth and tapers gently in the direction of ice movement

Question 5

dimensions of a drumlin

Answer 5

lengths of 1 to 2km
heights of 15 to 30m
widths of 400 to 600m

Question 6

what is a group of drumlins called?

Answer 6

a drumlin swarm or basket of eggs

e.g. Vale of Eden

Question 7

what are drumlins?

Answer 7

elongated hills of glacial deposits

Question 8

drumlin formation: theory 1 (hummocky ground moraine)

Answer 8

during previous glacial advance, hummocky ground moraine was deposited

when the glacier subsequently advances, it goes over the top and moulds the moraine into shape

BUT this does not explain how Roches Moutonnées can exist

Question 9

drumlin formation: theory 2 (nucleus)

Answer 9

a nucleus of frozen till/Roche Moutonnée is rigid under the glacier

material is deposited on/around the nucleus while ice moves over it, moulding it into shape

BUT not all drumlins have a nucleus

Question 10

drumlin formation: theory 3 (fluvioglacial)

Answer 10

fluvioglacial processes deposit sediment in mounds which the ice moves over, moulding into place

explains why some drumlins have sorted material

Question 11

drumlin formation: theory 4 (competence)

Answer 11

ice became overloaded with sediment
when the competence of the glacier was reduced, material was deposited
ice moves over this material, moulding it into shape

this explains all types

Question 12

how can a glacier’s competence be reduced?

Answer 12

small obstacles acting as a trigger point (nucleus)
ice melt
changes to velocity = kinetic energy

Question 13

what can a rose diagram show?

Answer 13

the distribution of glaciers in an area grouped by direction

face north/east as glaciers are formed from nivation hollows