1. An Introduction to a Powerful Force That Has Shaped the Earth.
Glaciers
An Introduction to a Powerful Force That Has Shaped the Earth.

2. Glaciers Have Sculpted the Earth Around You….

3. How Do Glaciers Shape the Earth?

4. What Is a Glacier?
A mass of moving ice created from accumulation of snow over many years that compresses into large, thickened ice masses
A glacier moves like a very slow river eroding and shaping the land beneath it

5. What’s important about Glaciers?
Glaciers are the second largest reservoir of water on earth.
A 5o C increase in global average temperature would likely cause all glaciers to melt, raising sea level by m.
Glaciers represent permanent ice (does not melt each summer) - so they reflect climatic conditions, not variations in weather.

6. What’s important about Glaciers?
Glaciers are an important agent of erosion and formed much of the landscape of Michigan.
Form deposits of sediment that have distinctive characteristics (drift and till).
Most recent glacial period culminated at the end of the Pleistocene, about 15,000-20,000 years ago.

7. How do Glaciers form?
Starts with abundant winter snowfall that doesn’t melt away (snowline - altitude above which snow is permanent)
Snow is converted to glacial ice under overlying weight of accumulating snow
2 Major requirements:
Low Temperatures
Adequate amounts of snow

8. FIRN
Grainy ice created from the partial melting and refreezing of snow crystals.

9. Requirements for Glacier Formation:
Temperatures low enough to retain snow year round (High Altitude and High Latitude).
Sufficient Snow: Some polar climates are very dry, so glaciers do not
develop.

10. A Brief Overview of Glacier Formation
Select this button to access the story of a Glacier….
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11. Types of Glaciers Categorized by: Size Where they formed Two Types:
Valley Glacier
Continental Glacier or Ice Sheet

12. VALLEY GLACIER
A Glacier formed in mountainous areas when ice moves down a valley. It produces a long, narrow, wedge-shaped mass of ice.

13. Continental Glacier Ice Sheets
A Glacier covering a large land mass (millions of square kilometers). The type of Glacier occurring during the ice age and in present day Greenland and Antarctica.

14. Movement of Glaciers
When ice accumulation is thick enough it will begin to flow.
Speed and Amount of flow depends on slope and weight.
Two Movement Types:
Basal Slip
Internal Plastic Flow

15. Basal Slip
The weight of overlying ice exerts enough pressure to melt some ice at the base of the glacier.
The melting ice creates a slippery surface for the overlying glacier to slide over.

16. Internal Plastic Flow
Solid ice crystals throughout the glacier slipping over each other
Creates a slow forward motion
Like a river, not all parts of the glacier flows at the same speed. Where would it flow fastest? Slowest? And Why?

17. Valley Glacier Landforms

18. Cirque and Aretes Cirque A bowl shaped depression Aretes ‘Spine’
Sharp, jagged ridges between cirque
The glacial processes that change the shape of a mountain begin in the upper end of the valley where a valley glacier forms. As a glacier wedges its way through a narrow valley, it breaks off rock from the valley walls, causing the walls to become steeper. The moving glacier also pulls blocks of rocks from the floor of the upper valley creating the bowl shaped depressions (cirque).

19. Horn
Several Aretes joined to form a sharp, pyramid peak

20. Hanging Valley
A small tributary glacial valley suspended on a higher portion of a mountain.
Ice melt flows over the cliff as a waterfall.

21. U-Shaped Valley
As the valley walls and floor are scraped away by a glacier, the original V-shape valley is changed into a U-shape.

22. Moraine Landforms made from glacial till
Photo depicts a ground moraine.
Ridges of unsorted rock material on the ground or on the glacier

23. Lateral Moraines
Strips of dirt and rock that flow with the ice along the sides of valley glaciers.

24. Medial Moraines
When a segment of the glacier merges into a larger ice mass, the lateral moraines create debris in the middle of the larger flow.

25. Continental Glacier Landforms
Erode by leveling existing landforms, producing relatively smooth, rounded landscapes.
Features are exposed as the glacier retreats.

26. Moraine Landforms made from glacial till
Photo depicts a ground moraine.
Ridges of unsorted rock material on the ground or on the glacier

27. Ground Moraine A mantle of till deposited underneath the ice
Often very rocky

28. Ground Moraine
Farmers and people putting in a new yard uncover the many rocks deposited from the last ice age.
The soil of Ohio west to Montana and North to Canada is ground moraine

29. Terminal Moraine
Hilly ridges composed of a mixture of rock, sand, and clay
Marks the farthest advance of the ice.
Cape Cod and Long Island are examples of Terminal Moraines

30. Till The result of glacial drift
Contain various sizes of sediment that is not sorted or layered

31. Outwash
Glacial till that has been transported, sorted and deposited by glacial meltwater

32. Kame
Small hills of sand and gravel
Formed from outwash.

33. Esker
Long, narrow ridges of sand and gravel in the middle of ground moraine
They wind for kilometers roughly parallel to the direction the ice moved.
Form from melt water streams flowing in tunnels along the bottom of the melting glacier.

34. Gravel Pits
Today, Kames and Eskers created during the last ice age are frequently exploited as gravel pits.

35. Erratic A large boulder deposited by a glacier.
Typically a different rock type than the material in which it is deposited.

36. Kettle
The result of a very large block of ice being left behind as a glacier recedes. The melting ice forms potholes which are sometimes filled with water in a glacier, till, or outwash plain. Vegetation may grow up around kettles.
A Kettle Lake

37. Drumlins Long, low, tear shaped mounds of till
The long axes of the drumlins are parallel to the direction of glacial movement
Drumlins have the shape of an inverted spoon

38. Roches Moutonnees Rounded knobs of rock created by a glacier
The glacier polishes and smooths out the top of existing rock as it passes over
The glacier plucks chunks of the rock out as it passes by creating a rough surface on the side

39. Dangers of Glaciers
Icebergs
Crevasses

40. Iceberg Pieces of ice that break off of a glacier.
The ice sheet on Greenland is the primary source of icebergs in the North Atlantic.
Create a hazard for ships.

41. Crevasses Large cracks formed in the surface of a glacier
Often covered with snow and extending 30 m downward
Crevasses – May be more than 30 m deep and can be hidden by a thin crust of snow that breaks under the slightest weight. Traveling over the top of a glacier is very dangerous.

42. The Ice Age
A long period of climatic cooling during which continental ice sheets cover large areas of the earth’s surface.

43. The Ice Age
It is believed that the world has gone through several periods of glacial ice age advancement and retreat.
It will occur again….

44. Causes for an Ice Age Milankovitch Theory
Small, regular changes in earth’s orbit and tilt which cause changes in the amount of solar energy reaching earth’s surface

45. Causes for an Ice Age Milankovitch Theory 3 Periodic Changes
A more elliptical orbit
Tilt ranging from
Circular motion of precession

46. Useful web sites for Glaciers