Alpine Glaciers
Continental (Ice Sheet)
Ice Cap

Glacial Ice = recrystallized -(firn)

Glacial Movement = plastic flow + basal slip
Economy (Budget) of Glacier = balance between accumulation and ablation

Glacial Erosion
-abrasion
-plucking

Glacier Erosional Features:
arete (Alpine)
roches moutonnees (Continental)
horn (A)
paternoster lakes (A)
cirque (A)
U-shaped valleys (A,C)
tarn (A)
fiord (A,C)
bergschrund (A)
truncated spur (A)
col (A)
hanging valley (A)
groove (A,C)
chatter marks (A,C)
striations (A,C)
col (A)

Glacial Deposits -- Drift
Stratified drift
till

Glacial Depositional Features:
Till
Stratified Drift
erratics (C,A)
outwash plain (C)
moraines (C,A)
-lateral (A)
-medial (A) )
-end (terminal) (C,A)
-recessional (C,A)
-ground (C,A)
valley train (A)
drumlin (C)
kettle (C)
drumlin fields (C)
crevasse fillings (C,A)
Ice-contact deposits (C)
-kame
-kame terrace
-esker
-glacial delta

Alpine glaciation enhances the relief whereas continental glaciation subdues the relief.
Pleistocene = Ice Age
-15 to 20 major ice advances
-30% of Earth's surface imprinted
-N. Hemisphere 2x more ice than S. hemisphere
-Little Ice Age: 1550 - 1850
7 Prepleistocene glaciations

Cause of Glaciation
-no universally accepted theory
-lower T -require higher precipitation
-landmass @ high latitude
-need "triggers" to operate
-Volcanism
-Variations in sun's energy production

on 3 time scales

1. 106 years -plate tectonics
2. 105 years -Milankovitch Cycles
a) eccentricity of Earth's orbit (105,000 yrs.)
b) tilt of Earth's axis (41,000 yrs.)
c) precession of Earth's axis (23,000 yrs.)
-Major changes in oceanic circulation
3. 102 or 103 yrs.

1. Explain how glacial ice is formed and why it flows. Explain why all of the ice in an alpine glacier does not flow at the same rate.
2. Briefly explain how the "economy" or "budget" of an alpine glacier affects the position of the ice front. (Hint: Use a completely labeled diagram to illustrate your discussion).
3. Compare and contrast the affects of alpine glaciation and continental glaciation on the topography of mountainous area.
4. Explain how the difference between till and stratified drift arises. What general effect do glacial deposits have on the landscape?
5. Compare and contrast a drumlin and a roches moutonnees. Explain how these features re used to judge the direction of ice flow.
6. Explain how glaciers erode bedrock. Why are fjords deep?
7. Explain how a terminal moraine and a ground moraine are formed.
8. Explain how eskers form.
9. What conditions must be satisfied before an "ice age" is initiated?
10. Provide an explanation for the alternation between glacial and interglacial periods during the Pleistocene.

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