1. CHAPTER 5 HONORS EARTH SCIENCE
GLACIERS
CHAPTER 5
HONORS EARTH SCIENCE

2. a thick mass of moving ice
What is a glacier?
a thick mass of moving ice

3. Step 1: Snow accumulates.
How do glaciers form?
Step 1: Snow accumulates.
More snow falls during the winter than melts in the summer.

4. Trans Labrador Highway

5. Step 2: Snow changes to firn.
As snow accumulates, its weight compress the individual snowflakes to form firn.
FIRN

6. Firn

7. Step 3: Firn is compressed to form solid glacial ice.

8. http://www.asf.alaska.edu:2222/img/firn_diagram.gif http://207.239.98.44/IcelandI%20232.jpg

9. Step 4: The ice begins to move.
Plastic flow- weight of glacier moves out like pancake batter

10. When the climate cooled…
Ice advanced over the land, moving southward from Canada over the Great Lakes Region.

11. Glaciar Perito Moreno, in Santa Cruz province, Argentina
Glaciar Perito Moreno, in Santa Cruz province, Argentina. It hasn’t happened since 1988 and it is said to be one of the most extraordinary natural events in the world.
- Roberto Cerrudo

12. Glacier terms Zone of Ablation- melting
Zone of Accumulation- snow accumulates
Crevasse- cracks
Advance- more accumulation than melting
Retreat- more melting than accumulation

13. VALLEY GLACIER

14. How do glaciers erode the surface?
Plucking –freeze/thaw process lifts particles into ice
Striations- parallel scratches made from rocks in ice scraping against bedrock

15. Glaciers pick up lots of sediment as they advance over the land.

16. TYPES OF GLACIERS
Alpine (Valley)Glaciers – glaciers that form at high elevation in mountain valleys
Ice sheets or Continental Glaciers form in polar regions such as Greenland and Antarctica.

18. Cirque
A bowl-shaped depression located where a glacier begins to form

20. Horn A tall, pointed rock peak left at the top of a mountain
Kinnerly Peak - Glacier National Park
A tall, pointed rock peak left at the top of a mountain

21. The most famous horn in the Alps… The Matterhorn
Located on the boundary between Switzerland and Italy, the Matterhorn’s summit is 4478 m above sea level.

22. Arete – spines or ridges of rock that separate glacial valleys

23. U-shaped Valley - Yosemite National Park

24. V-shaped valleys become U-shaped valleys as glaciers move through them…
Step 2
Step 1
A typical river valley
Over time, running water cuts a deeper V-shape.
Step 3
Glacier fills valley, widening and straightening the channel
Step 4
Glaciers melt leaving a U-shaped valley

25. Hanging Valley
a small valley that has not eroded as deep as the main valley that it is connected to
Waterfalls often form at hanging valleys.

26. TYPES OF GLACIAL DRIFT (Sediments)
TILL- unsorted; deposited by ice
STRATIFIED DRIFT- layered; deposited by meltwater streams
OUTWASH- sorted sand; deposited by meltwater

27. Erratics Boulders carried great distance by the glacier
Don’t match surrounding rock

28. Erratics along Lake Michigan Shoreline

29. TYPES OF GLACIERS
Alpine (Valley)Glaciers – glaciers that form at high elevation in mountain valleys
Ice sheets or Continental Glaciers form in polar regions such as Greenland and Antarctica.

30. MORAINES Deposited along edge of glacier during melting
Terminal- very end of glacier
Lateral- side of glacier
Recessional- progresses behind terminal

31. MORAINES MADE OF TILL- unsorted sediment
MADE OF TILL- unsorted sediment

32. terminal moraine – unsorted sediments deposited at the edge of the melting glacier

33. Ground Moraine- flat till deposits between recessional moraines

35. Kettle Lakes
Made from ice blocks

36. Kettle Lakes
Kettle lakes form when blocks of ice break off the front edge of a glacier, become buried by sediment. The ice melts leaving a hole which fills with water creating a lake.

37. Drumlins
Hills of sediment deposited by the glacier- till

38. ESKERS Winding ridges of stratified drift
Deposited by meltwater streams
Mined for gravel

39. KAMES Cone shaped deposits Deposited at end of meltwater streams
Stratified drift

40. Why do scientists believe that glaciers once covered Michigan?

42. Moraine Deposits = unsorted sediments
Moraines are made of unsorted sediments. Only mass movements and glaciers deposit unsorted sediments.
Since there are no large hills or mountains in Michigan for this sediment to fall down, it must have been deposited by the glaciers.

43. Moraine Deposits have the same shape as the Great Lakes.
Michigan moraines run parallel to the shoreline.
The same process that formed the moraines formed the Great Lakes.

44. Each of the Great Lakes began as a river.
Image from Earth Science, Tarbuck and Lutgens, 2003

45. As the climate cooled… The rivers froze.
Glaciers moved through them – widening and deepening them to form today’s lake bottoms.

46. The sediment removed from the river valleys was deposited in the moraines covering our state. This is why the moraines run parallel to the shorelines of the Great Lakes.

47. When the climate began to warm, the glaciers began to melt and retreat.

48. The fresh water from the melting glaciers filled in the deep U-shaped valleys that they had carved and turned them into the lakes we have today.

49. What other evidence do we have that glaciers once covered our state?
Depositional features such as drumlins and kettle lakes.
Kalkaska, Michigan

50. Kettle Lakes

51. Why do scientists believe that glaciers once covered Michigan?
Michigan is covered with unsorted moraine deposits.
The moraine deposits follow the outline of Great Lakes..
Erratics
striations

53. Kelly’s Island, Ohio

54. Kelly’s Island Glacial grooves

56. Glacial Striations Granite Island, Lake Superior MI Calumet, MI
N47°14’77’’ W88°26’82’’

58. Resources http://cse.cosm.sc.edu/erth_sci/Erosion/plucking.jpg