lecture 7 - landforms and landscapes of glacial erosion

Question 1

Bennett and Glasser (2009)

Answer 1

(all features in the lecture)

Question 2

Sudden and John (1976)

Answer 2

general textbook

Question 3

Greenwood et al (2007)

Answer 3

British ice sheet mapping of MW channels is patchy

• marginal, sub marginal and subG channels all found in conjunction with each other
• info about ice sheet retreat patterns

MW channels = valuable paleo-glaciological information, previous extent of a G

can calculate the ice surface slope

Question 4

Boulton (1979)

Answer 4

beneath G either deformable bed sediments or rigid bed rock surfaces
- unlithified, unfrozen sediments deform beneath Gs

erosional landforms (e.g. RMs) indicate presence of abrasion and plucking

plucking provides tools for abrasion

two priniciple styles of erosion

• where substratum is resistant compared with G ice and composed of cohesive material (eroded by fragments then incorporated)
• where substratum is deformable (eroded as a result of deformation beneath G)

Question 5

Boulton and Hindmarsh (1987)

Answer 5

experiments beneath Briedmerkujokull, Iceland

flow laws for subG till - relates strain rate to shear stress and effective pressure

subG zones composed of soft, unlithified or poorly lithified sediments
- evidence they underwent strong shear deformation

different horizons (noticed using tunnels and strain markers

• A = deformation by continuous deformation of the whole sediment mass
• B = deformation by discontinuous movement