1. Geology of Great Lakes
How the lakes formed

3. Ice age

5. Shale and sandstone – soft stones
Bedrock – hard stone
Valleys soft
Lake bottoms hard
Volcanoe – OK and Lake Superior
Mountains from lava
Retreating rerouted Lake chicago to miss
Huron to Geo bay to niagra
Erie to ohio river
Erie to Michigan

6. Glaciers and Erosion Chapter 15
15.1 Glaciers: Moving Ice
15.2 Landforms Created by Glaciers
15. 3 Ice Ages

7. 15.1 Glaciers: Moving Ice
Glacier - Soft snowflakes become compacted and pressure forms moving mass of ice
A. Formation
B. Types
C. Movement

8. Formation Moisture usually runs off to rivers
High elevations make ice and snow
Snowline – elevation that snow and ice stay all year (about 1 mile up)
Snowfield - motionless mass of ice/snow
Firn – small grains of ice from melting and refreezing
Turns steel blue and flattens with pressure and starts to slowly slide (move) downhill

11. Types of Glaciers Size and where they are formed:
1. Valley – mountainous area, narrow wedge shape
2. Continental – large land mass
Greenland and Anarctica
If melted, would raise sea level 60 m

14. Valley

15. Continental

16. Movement of Glaciers River of ice Moves 100 m per year
1. Basal slip – base of ice melts because of the pressure so acts to lubricate
2. Internal plastic flow – slow surface movement, fastest in center, slower on sides

18. Features of Glaciers Crevasses – large cracks, danger for climbers
Icebergs – ¾ under water, danger for ships

21. 15.2 Landforms Created by Glaciers
Glacial erosion
Glacial deposition
Till deposits
Stratified drift deposition
Glacial lakes
History of the Great Lakes
Salt Lakes

22. Glacial erosion Drag a rock behind a tractor?
Cirque – bowl shaped depression (from where the block break off) circus tent
Aretes – sawtooth ridges (spines)
Horn – pyramid-like peak (several aretes)
Ice picks up material and scrapes, gouges, polishes
Roches moutonnees – round knobs, sheep rocks
Hanging valley – melted water forms draining to the big valley

24. Glacial deposition Drift – material left when melts
Large boulders – erratics
Till – unsorted sediments
Stratified drift – sorted and deposited in layers
meltwater- melting glacier moving sediments

26. Till deposits Moraines – land forms from till
Lateral moraine – long ridge on the side of valley
Medial moraine – where to valley merge, dark striped usually
Ground moraine – unsorted material becoming soil
Drumlins – tear-shaped mounds of till
Terminal moraine – till at front of glacier

28. till

30. morraine

31. Stratified drift deposition
Outwash plain – melt in front of glacier of drift
Kettles – depressions from ice buried in till
Eskers – ridges of long windy deposits

33. Glacial lakes Minn. Land of 10,000 lakes Kettle holes
History of the Great Lakes erosion and deposition by continental ice sheets
1st toward the Miss. River
Hudson valley to Atlantic Ocean
Salt Lakes
Southwestern U.S.
No stream outlets
Evaporation
Salt Lake
Mojave Desert deposits of borax

38. 15. 3 Ice Ages Ice age – long period of climate cooling
Interglacial periods – during warming temp
1st – 600 million years ago
Last – 114,000 years ago started and finished 11,000 years ago
Climate during ice ages
Glacial periods
Causes of ice ages

39. Climate during ice ages
Drop in ave. temp of 5’C
^ snowfall
Advance of continental ice sheets

40. Glacial periods 1/3 of land covered with ice
Most in N. America and Europe
So much water is locked up in ice, the seal level is 140 m lower than today
Continental ice sheet over Hudson Bay and down to Ohio
Mile of ice over Muskegon?

43. Causes of ice ages
Milankovitch theory – changes in orbit and tilt of earth
Orbit became more elongated every 100,000 years
Over 41,000 yrs tilt goes from 21.5’ to 24.5’
Change in axis over time
Evidence in shells of dead marine life

47. Other theories Solar – sunlight
Plate motion interferred with ocean currents
Volcanoe eruptions
meteorite