1. Glaciers

2. “RIVERS OF ICE” Mass movement of frozen ice on land
Form at high latitude or high elevation
Last extension of ice here began 20,000 years ago and receded about 10,000 years ago.
Today only covers 10% of land surface

3. Ice Flow Glaciers are not static they are dynamic Formation:
A steady accumulation of snow piles up and compresses layers beneath – these compressed layers turn into ice
Force of gravity continuously pulls ice downward
Movement:
Fastest ice is found on the surface at center of valley
Rate varies from a few cm to meters per day.

4. There are 3 Categories of Glaciers
1. Valley (Alpine) Glaciers
found in mountainous regions
high altitudes
Ex. Alps (New Zealand and Europe), Rockies
Fanz Joseph Glacier – New Zealand

5. Valley or Alpine Glacier
It occupies a valley in the mountains. The mountains are alpine, that is bare and jagged due to glaciation.
Outlet glacier of Juneau icefield in Alaska.
Dark stripes are medial moraines.

6. Ice Sheets (Continental Glaciers)
Much larger
Flow direction is from an area of thick ice to thin ice
Ex. Greenland, Antarctica
Ellesmere Island, Canada

7. 3. Tidewater Glacier Flow far enough to reach out into the ocean
Create icebergs
Vertical calving base and small bergs floating in the sea
Hubbard glacier, Alaska

8. Ice calving

9. Glacial Retreat Kilimanjaro, 1993 top, 2000 bottom – glacial retreat
Alaska's Glacial Retreat Alaska's glaciers are receding at twice the rate previously thought, according to a study published in the July 19, 2002, issue of the journal Science. These two images show Portage Glacier, near Anchorage, Alaska, in about 1950 and in July The ice has pulled back nearly out of sight, leaving behind a glacial lake.

10. Glacial advance and retreat

11. Budget of a Glacier
Glacier accummulation = snow adds to the weight of a glacier
Glacier Wastage (ablation) = melting and calving.
When accummulation is greater than wastage = glacier advances
When accummulation is less than wastage = glacier retreats
If accummulation = Wastage = glacier remains stationary
Calving = breakage of ice forming icebergs

12. Glacial Erosion – Two Key Methods Plucking and Abrasion
Features of Glacial Erosion:
U-shaped valleys, sharp ridges (Aretes), pyramid peaks (Horns), water-filled valleys (Fjiords), and bowl shaped valleys (Cirques).

13. Glacial Erosion Sharp ridges and pyramid peaks
Deep glacial carved fjord valleys

14. Striations and Grooves
Indicate orientation but not direction

15. Depositional Features of Glaciers aka Glacial Dump
Drift = any sediment deposited by moving ice
2 Types:
Stratified Drift = well-sorted sediments deposited by streams (meltwater)
Till = unsorted sediment, deposited by moving ice

16. Deposits of Till lateral moraines form along valley walls
medial moraines form where 2 lateral moraines meet
end moraine left at terminus of glacier where it retreats
This photo shows two medial moraines (blue arrows) as seen from the air. The black arrows point to lateral moraines that have formed along the sides of the valley wall. Where the two main glaciers shown in the photo flow together, their lateral moraines join to form a medial moraine. The medial moraine on the right formed in the same way, however we can't see where the glaciers flow together to form the moraine.

17. Drumlins A drumlin is tear-shaped ridge showing direction of ice flow
Low smoothly rounded elongated hill, of compact glacial till.
Built under the margin of the ice and shaped by its flow., or carved out of an older moraine by readvancing ice.
Its longer axis is parallel to the direction of the movement of ice.
Blunt nose points in the direction from which the ice approached. Gentler slope tapering in the other direction.
Height 8-60 m, average is 30 m, length 400 – 2000 m, average 1500m.

18. Drumlins
Typical drumlin on a farm in Wisconsin, shows the direction of the glacier

19. Glacial Erratics Large boulder left behind by the glacier
Rock fragment carried by glacial ice, deposited at some distance from the outcrop from which it was derived. Generally resting on bedrock of different lithology (color, composition …)
Glacial erratic near Calgary, Canada
Central Park, besides being a world-class urban resource, is a showcase of New York City geology. The beautifully exposed outcrops of schist and gneiss bear traces of the ice ages, when continental glaciers scraped their way across the region leaving grooves and polish on the tough bedrock. When the glaciers melted, they dropped whatever they were carrying, including some large boulders like this. The rock has a different composition from the ground it sits on and clearly comes from elsewhere. Boulders like this are called erratics.

20. Deposits of Stratified Drift
Kame : a small hill forms where sediments accumulate beneath ice. Esker: forms from under-glacial streams Kettle: a depression that can be water-filled
Kames and kettles
Kame is a mound, knob or short irregular ridge.
Composed of stratified sand and gravel, deposited by subglacial stream as a fan or delta at the margin of a melting glacier, by a superglacial stream in a low place or hole on the surface of the glacier.
Esker: serpentine ridge of roughly stratified gravel and sand deposited by a stream flowing in or beneath the ice.
Kettle: depression in the glacial drift formed by the melting of a detached block of stagnant ice buried in the drift – common in kame fields

21. Kames

22. Eskers
One of many eskers running across the northwest of Canada

23. Muir Glacier 1941 and 2004

24. Massive melting – Holgate glacier, Alaska 1909 and 2004