1. Glaciers

2. Glacier
a thick ice mass that originates on land from the accumulation, compaction, and recrystallization of snow.
Agents of erosion – acquire, transport and deposit sediment
Occupy ~10% of land area
“Interrupts” hydrologic cycle by “locking up” water

3. Glacier Types 1. Valley (Alpine) Found in mountainous areas
Smaller than ice sheets
Lengths greater than widths
Only cover a small region
Transform V-shaped valleys into U -shaped valleys

4. Alpine Glaciers

5. 2. Ice sheets (Continental glacier)
Glacier Types
2. Ice sheets (Continental glacier)
Large scale – cover 10% of Earth’s land
Found in polar regions
Greenland – 1.7 million km2
Antarctica – 13.9 million km2

6. Continental Glaciers

7. Daily Questions Upslope
The images were taken at the same location but with 59 years between the photos.
Which direction is the ice moving (upslope or downslope)?
Which direction is the glacier moving (upslope or downslope)?
Is there a difference between the directions – explain.
Downslope
Upslope
Downslope
Fig. 16.3

8. Glacier movement Gravity primary force
Entire ice sheet moves 5 to 50 m/yr
Plastic flow – flowing solid
Basal slip – movement over bedrock
Fastest movement within the center
Friction Slows down the sides

9. Glacier movement
20 meters
100 meters

10. Glacier movement

11. Glacier Budget In - Zone of accumulation Out – Zone of wastage
Snow accumulates and forms ice
Outer limit is the snowline
Out – Zone of wastage
ablation – general term for loss of ice or snow from a glacier
Sublimation
Melting
Evaporation
Calving - icebergs

12. Glacier budget
Zone of Accumulation
Zone of Wastage
If ice formation is greater than ice loss – glacier advances downslope
If ice formation is less than ice loss – glacier retreats upslope
If ice formation is = ice loss – glacier position is stationary

14. Glacier Erosion and Deposition
Plucking – loosen and lift blocks of rock (mechanical weathering)
Abrasion – sediment in ice acts as giant “sandpaper”
Creates Rock flour – very fine-grained material
Creates Striations – grooves scratched in bedrock that indicate direction of ice movement

25. Causes of Glaciation Full Reasoning is not known
Theory of Glaciation needs to include:
Interglacial periods – periods of warm climate separating periods of glacial advancements.

27. Causes of Glaciation Full Reasoning is not known
Theory of Glaciation needs to include:
Interglacial periods – periods of warm climate separating periods of glacial advancements.
Glacial episodes in the Paleozoic ( mya) and Precambrian time (700 mya).

29. Causes of Glaciation Full Reasoning is not known
Theory of Glaciation needs to include:
Interglacial periods – periods of warm climate separating periods of glacial advancements.
Glacial episodes in the Paleozoic ( mya) and Precambrian time (700 mya).
Earth’s average global is 14oC, in the geologic past it was 22oC – Glaciation requires a temp. of about 10oC.
Continental glaciers originate in polar or elevated land.
Sufficient precipitation needs to occur.

30. Milankovitch cycles Earth’s orbital changes controls its climate
Eccentricity
Measure of the nooncircularity of Earth's orbit
Cycle is about 100,000 years

32. Milankovitch cycles Eccentricity Inclination
The changes in the axial tilt (22o to 24.5o) of the Earth
The greater the tilt the greater the contrast between summer and winter temperatures
Cycle is about 41,000 years

34. Milankovitch cycles Eccentricity Inclination Precession
The wobble of the Earth as it spins on its axis
Cycle is about 26,000 years

36. Milankovitch cycles
Main effect of cycles is to change the contrast in the temperature of the summer and winter.
Glaciation would occur when the summer temperature is closer to the winter temperature, but winter temperature are not colder than usual.
Rather the mild summers melt less ice than is received in the winter.