Glacial surface features

Question 1

Marginal crevasses

Answer 1

• Crevasses form because of frictional drag between ice and rock of valley sides
  = Margins to move more slowly than middle of the glacier
• Crevasses open at angle to the margin of the glacier

Question 2

Transverse crevasses

Answer 2

• Crevasses form when the glacier’s gradient steepens and the glacier surface extends itself = extending flow
• Transverse crevasses open as glacier ‘extends’ at steepening of gradient

Question 3

Longitudinal crevasses

Answer 3

• Valley becomes wider and ice surface widens to fill the valley
• Glacier spreads out laterally
• Stress acts on the glacier at right angles to the margins and crevasses open up parallel to the glacier margins

Question 4

Di-Radial splaying crevasses

Answer 4

• Radial crevasses splay out in the region of the glacier snout
• In the case of longitudinal crevasses, result from the spreading out of ice into a lobe
• Open at right angles to the direction of stresses

Question 5

Bergschrund

Answer 5

• Large crevasse caused by the tension from the ice pulling away from the ice attached to the back wall
• Produces a big semi-circular crevasses at the back of the glacier

Question 6

Types of crevasses

Answer 6

1. Marginal
2. Transverse
3. Longitudinal
4. Di-Radial splaying crevasses
5. Bergschrund