Improving Ocean Literacy By Teaching the Geology of the Great Lakes
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Transcript of Improving Ocean Literacy By Teaching the Geology of the Great Lakes
Michigan State University
David P. Lusch, Ph.D, [email protected]
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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David P. Lusch, Ph.D, [email protected]
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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
depth: 282 m max, 85 m avg
area: 193,700 km2
depth: 229 m max, 59 m avg
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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Great Lakes Structural Geology
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Great Lakes Structural Geology
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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The EndThe Endhttp://www.rsgis.msu.edu/http://www.rsgis.msu.edu/