The Great Lakes

1. The Great Lakes Introduction

2. The 5 Great Lakes • Huron • Ontario • Michigan • Erie • Superior

3. An Important Coastline • 1/10th of the population of the USA • 1/4th of the Canadian population • 25% of the Canadian Agriculture and 7% of the USA

4. Lake Superior • Largest volume • Deepest and coldest • Fewest people living on it • Least amount of pollution • Forested basin

5. Lake Michigan • 2nd Largest • only Great Lake entirely in the USA • Northern = less populated, fishing industry, and paper mills • Southern = densely populated (8 mill.) with Chicago and Milwaukee

6. Lake Huron • 3rd Largest by volume • vacation location on Georgian Bay and Northern Michigan • high population in the Saginaw River Basin • Fishing in the Saginaw Bay

7. Lake Erie • Smallest in Volume • Warm and Shallow • Freezes in winter • Land around it is farmland = lots of pollution • 17 urban centers of over 50,000 people

8. Lake Ontario • Smaller in area than Lake Erie, but deeper • Canadian Shore = densely populated (Toronto) and used for industry and farming • US Shore = mostly unused; one large city (Rochester), some farming and industry

9. Great Lake Exploitation • The Great Lakes were heavily used from the point European settlers moved in • killing fur-bearing animals • clear-cut forests for agriculture and logging • over-fishing

10. Industrialization of the Great Lakes • Early Settlement Times = untreated waste released into rivers (bacteria and disease) • 1920’s = PCB’s = carcinogen in plastic and fertilizers • 1940’s = DDT = bio-magnifying pesticide

11. Great Lakes Water Quality Agreement (1972) • Growing concern for deteriorating water quality in the Great Lakes • included the US and Canada • agreement limited the amount of pollutants that were discharged into the Lakes

12. Toxic Contaminates • Accumulate up the food chain • egg thinning in bird fish-eating bird eggs • Cormorants, Ospreys, Herring Gulls • Human health risks • mercury contamination • PCB’s • Birth defects, reproductive health, immune system

13. Great Lakes Water Quality Agreement Revisions (1978) • Manage Lakes with an ecosystem approach • Actions Plans (RAPs) for Areas of Concerns (AOCs) • health of lakes determined by ecological indicators (specific bird and fish populations)

14. The Problem of Management • Several Governments control the lakes and make individual decisions on them • 2 Sovereign Nations (US and Canada) • 1 Province (Ontario) • 8 States (MN, WI, IL, IN, PA, MI, OH, NY) • Thousands of local governments

15. Great Lakes Formation • 3 Billion yrs ago = volcanic activity and folding creates the Great Lakes basin • 600 million yrs ago = most of N. America covered by a salt water sea (salt deposits, petosky stones)

16. Great Lakes Formation • 1 million yrs ago = continental glaciers up to 6,500 ft thick advanced over Michigan • leveled hills • altered ecosystems • created large rivers that became the lakes

17. Great Lakes Formation • 14,000 – 10,000 years ago = climate warms up and continental glaciers shrink • sand, silt, clay, and boulders deposited by glacier • meltwater fills in the depression left from the weight of the glacier • uplift occurs and shapes the current great lakes Link

18. The Great Lakes Natural Processes

19. Climate • Summer • North = cool, dry air from Canada • South = tropical air from the Gulf of Mexico • Areas directly near the lakes have cooler temperatures because the lakes cool the air

20. Climate • Winter • cool arctic air flows over the Great Lakes and picks up moisture, then drops it on the land • Lake-effect snow creates snowbelts on the Eastern side of all the lakes

21. Global Warming Effects • More evaporation from lakes = lower lake levels • increased weather disturbances • changes in crops and food production • problems with shipping

22. Lake Levels • Day-to-Day Changes = caused by winds • Annual = winter (low levels) and summer (high levels) • Long-term cycles = cyclic changes caused by changes in climate

23. Lake Stratification • Layering of lake water based on temperature differences • caused by density differences • cold water = more dense = sinks to bottom

24. Lake Layers • Epilimnion = warm layer on surface and near shore, most life lives here, sunlight • Thermocline = thin middle layer separating warm and cold layers • Hypolimnion = cool, dense lower layer, not much sunlight, not much life

25. Fall Turnover 1. Cold fall air cools the surface of the water 2. Cold, dense surface water drops to the bottom of the lake 3. Entire lake mixes as water drops

26. Spring Turnover • 1. Ice freezes over the surface in the winter • 2. Ice melts and cools the water near the surface • 3. Water at surface is cooler than on the bottom • 4. Water from the bottom rises and mixes the lake

27. Importance of Turnover • Mixes oxygen through all layers so life can exist in most of the lake • mixes and dilutes pollutants • fishing industry

29. Great Lake Invertebrates • Phytoplankton = sun-catching plankton, (algae, euglena) • Zooplankton = eat other types of plankton (copepod, spiny water flea, daphnia)

30. Great Lake Fishes • Smallmouth and largemouth bass • northern pike • lake trout • lake herring • whitefish • salmon

31. Great Lakes Birds • Eagle = population is on the come back after their habitat was destroyed and DDT affected their reproduction • Herring Gull = often know as sea gulls, eat fish, mice, garbage, and anything else they can find • Cormorant = eat large amounts of fish and are not liked by fishermen