Chapter 14: Glacial Geology and Climate Change

Question 1

Glaciers

Answer 1

Perennial, flowing ice
-plastic layer/zone
-brittle layer/zone at surface (crevasses)
Some glaciers (warm-based) also slide)

Question 2

Conversion of snow to ice

Answer 2

Compaction
Recrystallization
-Solid state (no melting)
-Melting and refreezing

Question 3

Classification and Flow Pattern (size)

Answer 3

Continental glaciers: radical flow (unconstrained)

Mountain glaciers: linear flow (constrained)

Question 4

Budget (Mass Balance)

Answer 4

• Accumulation: additions (mainly snow)
• Ablations: losses (mainly melting)
• Ice flows from accumulation to ablation area
• When ablation exceeds accumulation, glacier recedes
• When accumulation exceeds ablation, glacier advances
• Equilibrium: neither advance nor retreat

Question 5

Accumulation area

Answer 5

Portion of glacier where annual additions exceed annual losses

Question 6

Ablation area

Answer 6

Portion of glacier where annual losses exceed annual additions

Question 7

Equilibrium/Firn line

Answer 7

Boundary between accumulation and ablation areas

Question 8

Erosion by Abrasion (subglacial)

Answer 8

Grinding

• Finely ground rock (flour)
• Polish and striations

Question 9

Erosion by plucking (subglacial)

Answer 9

Freezing on

• Pressure melting on upstream side of bump
• Re-freezing on downstream (reduced pressure) side
• Roche Mountonnee: Abraded and plucked
• Large erosional landforms: U-shaped trough, fiord, hanging valley, cirque, horn

Question 10

Deposition

Answer 10

subglacial and marginal (ablation area)
-Till
-Stratified drift
Glacial lake sediment

Question 11

Till

Answer 11

Unsorted, unstratified; deposited by ice

• Erratic
• Moraines (marginal)
• Drumlin (subglacial)

Question 12

Stratified Drift

Answer 12

Sorted, stratified (sand and gravel); deposited by meltwater streams
-Outwash, plain, kame (kettle), esker

Question 13

Glacial Lake Sediment

Answer 13

Varves (annual couplets)

-Thin horizontal layers

Question 14

Climate Change

Answer 14

Continental Drift- millions of years
Mountain Building (orogenesis)- millions of years
Milankovitch (1913)(orbital or astronomical) theory of glacial/interglacial climate cycles

Question 15

Milankovitch theory of glacial/interglacial climate cycle

Answer 15

-Eccentricity (orbit shape): 100,000 year cycle
-Obliquity (axial tilt): 40,000 year cycle
Precession (changing position in orbit at particular season): 20,000 year cycle