1. Earth Science and M.E.A.P
The benchmarks and you!

2. EG. Geosphere Benchmark 1
Explain the surface features
of the Great Lakes region
using Ice Age theory.
Michigan Geography

3. Key concepts: Glacial processes snow changing to ice pressure
climate change
snow changing to ice
pressure
moving (advance, retreat)
melting
deposits
features—hills, lakes, Great Lakes

4. Tools:
Elevation map

5. Tools:
Relief map

6. Topographic map
Tools:

7. Real-world contexts: Examples in Michigan of… glacial formations..
such as moraines,
kettles,
drumlins

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

9. Step 1: Snow accumulates.
How do glaciers form?
Step 1: Snow accumulates.
More snow falls during the winter than melts in the summer.
Over the years, a thick accumulation of snow develops.

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

11. Firn

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

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

14. Step 4: The ice begins to move.
Once the ice becomes 50m thick, the pressure on the bottom of the glacier is so great that it becomes plastic-like and flows like silly putty out from its thickest point.

15. How do glaciers erode the surface?
Plucking – as a glacier flows over the ground, it loosens and lifts blocks of rock into the bottom of the glacier.
As the glacier moves, these rocks scrape deep grooves, called striations, into the rock below.

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

17. Melting Glaciers
As glaciers move over the land (advance), they carry sediment with them. As they melt (retreat), the sediment that they were carrying is dropped into unsorted piles called moraines.

18. How do glaciers leave their mark on the earth’s surface as they retreat?
Melting glaciers deposit moraine (piles of unsorted sediment that they were carrying) all along the front edge of the glacier

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

20. 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.

21. 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.

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

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

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

25. 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.

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

27. 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.

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

29. 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.

30. Kettle Lakes

31. Drumlins
Hills of sediment deposited by the glacier

32. 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.
Other depositional features such as drumlins and kettle lakes are found throughout Michigan.

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