Improving Ocean Literacy By Teaching the Geology of the Great Lakes

Michigan State University

David P. Lusch, Ph.D, [email protected]


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Improving Ocean Literacy By Teaching the

Geology of the Great Lakes

Improving Ocean Literacy By Teaching the

Geology of the Great Lakes

David P. Lusch, Ph.D., GISP

Dept. of GeographyMichigan State University

Online Workshop through the College of ExplorationJanuary-February, 2008

David P. Lusch, Ph.D., GISP

Dept. of GeographyMichigan State University

Online Workshop through the College of ExplorationJanuary-February, 2008




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OCEAN LITERACY - ESSENTIAL PRINCIPLES The Earth has one big ocean with many features

The ocean and life in the ocean shape the features of the Earth

The ocean is a major influence on weather and climate

The ocean makes Earth habitable

The ocean supports a great diversity of life and ecosystems

The ocean and humans are inextricably interconnected

The ocean is largely unexplored




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OCEAN LITERACY – FUNDAMENTAL CONCEPTS

2. The ocean and life in the ocean shape the features of the earth

2.1 Some landforms we see today were once underwater

2.1.1 Forces underneath landmasses and the sea floor (tectonics) can change the shape of the

earth’s surface

2.1.2 Changes in sea level shape the earth’s surface

2.1.3 Some rocks found on land were formed in the ocean

2.2 Movement of water erodes and deposits materials (sediments)

2.2.1 Rivers carry sediments downstream to the oceans (clastic

sediments)

2.2.2 The facies concept explains lateral variations in the

lithologic characteristics of sediments of the same geological age




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Largest: 209,800 km2

Deepest: 406 m max, 147 m avg

Smallest: 82,990 km2

depth: 244 m max, 86 m avg

area: 103,700 km2

Shallowest: 64 m max, 19 m avg

area: 175,800 km2


area: 193,700 km2


One lake,

surface elev: 176 m

20% of all the freshwateron Earth!




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Everything yellow, brown, red or black is below sea level! (except in Lake Erie)




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191 years

2.6 years

Retention Times

6 years

99 years

22 years




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Origin of the Great Lakes Distal causes

For Lake Superior - plate tectonics and rifting

For the lower Great Lakes - development of the Michigan sedimentary basin

Proximal causes Glacial sculpting of bedrock, mediated by differences in resistance to erosion

Isostatic uplift of the region shifting the watershed outlet




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Rock Types in the Great Lakes Region

MichiganSedimentary

Basin

Canadian Shield

Mid-continent

rift




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Extends > 2000 km; trough >150 km wide

Rift occurred about 1.1 Ga (billion years ago). The rift filled with lavas which became basalts

Along the rift edges, non-volcanic sediments were deposited, perhaps by rivers flowing into the rift

Likely cause of the rift was a geophysical hot spot that domed the crust and cracked it

A "triple junction" plate break occurred under what is now Lake Superior

The Mid-continent Rift of North America




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The Mid-continent Rift of North America




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Lower Great Lake Basins




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Great Lakes Structural Geology




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Wisconsin

Dome

Thornton, IL

Marblehead

Freemont

Kelleys Is

Pelee Is

Toledo




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Michigan Structural Basin Michigan Basin was inundated numerous

times by oceans during the Paleozoic Period, which eventually filled it with thick sedimentary deposits.

Four general sedimentary rock types fill the Michigan Basin:

Sandstones

Carbonates (limestone and dolostone)

Shales

Evaporites (halite and gypsum)




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Michigan Structural Basin

Younger rocks (542 – 145 million years old)

All sedimentary (mostly marine deposits)

Variably resistant to physical erosion Sandstone and carbonates resist physical erosion

Shale is soft, thinly bedded and easily eroded




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Cambrian 500 Ma

Equator

N

X




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Mississippian 345 Ma

Equator

N

Mississippian 325 Ma

Equator

N

What a difference 20 million years makes!




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Facies Concept Lateral variations in the lithologic characteristics of a volume of sediments of the same geologic age

Off-shorenon-clastic

zone

Near-shorezone

Off-shoreclastic zone

Wave energy keeps fine clastic

sediments in suspension

No wave energy - fine clastic

sediments settle out

No wave energy - no clastics

non-clastic sediments settle out

Becomessandstone

Becomesshale

Becomes limestone/dolostone




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Michigan Sedimentary Basin

Structural basin – like nested bowls

Oldest rocks at the bottom, youngest at the top




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Differential erosion Sedimentary rock types are of unequal

resistance to physical erosion: Sandstones and Carbonates are stronger and tend to support highlands

Shales are weaker and tend to underlie lowlands




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Michigan Sedimentary Basin




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Niagaran Escarpment The major resistant-rock (dolomite) landform in the Michigan Structural Basin




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Niagaran EscarpmentRock Island ,

Wisconsin




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Niagaran EscarpmentFayette State Park, Michigan




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Niagaran EscarpmentBruce Peninsula, Ontario

N

Dip slopeScarpslope




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Niagaran Escarpment

Hwy 401

Kelso & Hilton Falls Conservation Areas, Ontario

N




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Niagaran Escarpment

Hwy 401

Niagara Falls

Lewiston, NY




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Bathymetry of the Lake Huron Basin




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The whole of the Great Lakes Watershed was covered by continental glaciers as recently as 17,800 years ago.




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Beginning about 14,300 years ago, the melting Ice Sheet began uncovering

portions of the Great Lakes Basin that sloped toward the ice margins.

Trapped between the glacier and the higher deglaciated terrain, meltwaters formed a series of proglacial lakes that occupied parts of the basins of every Great Lake. Proglacial Lake

Ice Sheet

The Glacial Great Lakes




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The earliest proglacial lakes to form were Glacial Lake Chicago (Lake Michigan basin) and Glacial Lake Maumee (Lake Erie basin).

Over the next 4,300 years, glacial lake levels in the Great Lakes Basin progressively fell as the ice margin waxed and waned and as new drainage outlets were uncovered and down-cut by flowing water.

Eventually, the water levels in the Michigan - Huron Basin reached their lowest elevation when drainage shifted to the final outlet at North Bay, Ontario, which flowed eastward along the Ottawa River Valley.

The Glacial Great Lakes




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Glacial Lake Stages




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Glacial Lake Stages

Mau

mee

Arko

na

Yp

silanti L

ow

-Water P

hase

Whittlesey

Warren

Grassm

ereL

un

dy (E

lkton

)

Ear

ly A

lgon

quin

Kirkfield

Lo

w-W

ater Ph

ase

Main

Alg

on

qu

in

Pos

t-A

lgon

quin

Sta

nley

and

Hou

gh

Nip

piss

ing

Alg

oma

Mod

ern

Gre

atl

akean

Sta

de

Mack

inaw

Inte

rsta

de

Tw

ocr

eekan

Inte

rsta

de

Port

Bru

ceSta

de

Port

Huro

nSta

de

Glacial Lakes in the Huron and Erie

Basins




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ISOSTATIC REBOUND With glacial melting, the tremendous weight of the ice was lifted from the North American Plate and the land surface, noticeably depressed during the glacial maximum, begins to rebound upward. This process continues today at a rate of about 7.5 cm per century.




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Isostatic rebound evidence

Nipissing wave cliff

Algonquin 11,000 C14 yrs184.4 m

Nipissing 4500 C14 yrs184.4 m

Algonquin 11,000 C14 yrs184.4 m

Nipissing 4500 C14 yrs184.4 m

51.8 m rise in 6500 yrs.

Nipissing wave cliff

Algonquin wave cliffs




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Improving Ocean Literacy By Teaching the Geology of the Great Lakes