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Wednesday Nite at the Lab. >> Tom Zinnen: Welcome to
tonight. I appreciate you all being here
is Tom Hooyer. Our presenter for tonight
Geological and Natural History He works both for the Wisconsin
appointment with the UW-Madison Department of Geologyn
and Geophysics. This is his second presentation
to Wednesday Nite at the Lab, and I appreciate him coming
back. Tonight, he'll be talking about
"Once Upon A Lake: The History
Wisconsin." Please join me in welcoming Tom
to Wednesday Nite at the Lab. ( applause )
Tom Hooyer: Many of you that
period of our climate in the we are actually in the warmest
And I'm secretly hoping that past 125,000 years.
because as a glacial geologist, I want the ice ages to return.
Tonight, I want to talk about the great glacial lakes here in
Wisconsin.
lakes here, a lot of you might When I mention glacial great
were in the Michigan and think about the old lakes that
However, I don't want to talk about those lakes, those old
lakes.
glacial lakes that were within I want to talk about the great
Now, as many of you might know, we recently experienced a large
glaciation called the North American Ice Sheet.
It occurred about 21,000 years
A lot of you, when you think ago.
probably think about Lake abWinnebago being the thirdou
largest inland lake, I think, in North America.
You think, well there were
at one time. certainly were bigger lakes here
I guess the question is, why I'm here to tell you there were.
Well the reason why is that in aren't those lakes here today.
to dam up a river, usually. ordAnd how do you do that?need
If you're an engineer, you build
Well, how we do it during the ice age, is we build a big ice
sheet, and we advance an ice
damming up surface water sheet across the landscape,
That map I just showed you, the first person to sort of draw the
last great ice sheet was this gentleman here, T.C. Chamberlin,
who was actually a faculty
Wisconsin. member here at the University of
he came here, and he was one of the first people to refute that
a lot of deposits that we have
flood deposits from a Biblical in the Midwest were actually not
result of continental flood, butglaciations.ually the
He was one of the pioneers here who sort of started off the work
on glacial geology and
sheets. We had many others, a long line
of famous glacial geologists in the state.
One of the most prominent ones
the department and at the isGeological Survey for aboutat
50 years. He pretty much mapped the entire
state.
know today about the glacial And what we know, 90% of what we
attributed to him. history of the state can be
large glacier that actually So anentered Wisconsin.ce a
And what we do, as geologists,
What we've done here, there's we five different lobes.up.
The biggest lobe being the Green
And all these ice lobes actually Bay lobe.
Ice Sheet, which had it's center originated from the Laurentide
What I want to point out here tonight is one of the large
glacial lakes that formed is
Wisconsin. this one called Glacial Lake
minutes. I'll talk about that in a few
his horse, or in his buggy, eventually in his car, how did
he know that the state had been glaciated?
How did people know?
How do you know the state's been Anyone have any ideas?
( inaudible ) Yeah, okay.
I heard moraines and debris.
actually looked at those Certainly, when a lot of people
where that was actually from. But one thing, if you go out and
you kick away the soil in some
these things called striations. And how striations form is whene
the debris in the bottom of the ice, which is moving, scrapes
across the bedrock. It gives us a good indication
that there was a glacier here once, and the direction that it
actually flowed.
( inaudible ) Flat sided rocks is a good one.
How about, here's another one.
They're called drumlins. We have a beautiful land form.
from Jefferson and Dodge And here's a relief map
Here's Highway 94 cutting across Counties.
toward Fond du Lac. What we see is these big drumlin
fields here, or a swarm of
These are basically glacial landforms.
But initially, people thought,
formed in a large flood. well, maybe these could be
when people discovered Well, it wasn't until the '50s,
They could go out and they could radiocarbon dating.
wood. In northeast Wisconsin, we have
have a famous layer called the
buried beneath glacial deposits. Two Creeks Forest Bed, that's
a forest, a glacier came and A lot of these trees, there was
I'll talk more about this later. just mowed down the forest.
out and we can cut pieces off So what wthese trees.we can go
And there's a big stump sticking
right there. out of some glacial sediment
They'll come back and they're about, I don't know, 13,000
years ago.
13,000 years ago. WeBut how about prior to that?re
Do we have any other records of climate change here in
Wisconsin?
Well, we really don't. Anybody know?
record. So back in the '80s, I believe
the late '70s, early '80s, to understand what the climate was
here in North America, they said, well, we can do two
things. We can go up onto the ice caps
and we can collect ice cores, with the hopes of getting us a
long-term history of climate
And we can go to the ocean and change in the world.
middle of the ocean, where we we cknow it's a fairly quietthe
depositional environment. We can look at those ocean cores
and see if there's a record of
When we do that, maybe we can get a long-term view of what the
climate has done, at least in North America, or else around
the world.
One of the most complete climate So I just wanted to show this.
Ice Sheet. records comes from the Greenland
right up to the middle of the ice sheet there, the summit, and
they set up a big drill rig under a large dome there.
They basically collect these ice
your right. cIf you slice one of these iceon
cores open, what happens, is
bubbles in this ice here. If you take a very detailed, or
a little piece of that and look at it in detail, you can see
that it contains little air bubbles.
And ice, because it's a crystalline material, you can
see the structure of the ice. Those are air bubbles.
So you can go in there and you
You can determine what the can extract that air.
atmosphere, or the methane content of what CO2 was in the
But what you can also do is you can chemically analyze the ice
as well, and get a good record
I'll talk about that in a little of climate change.
Here's a portion of that bit.
Greenland. climate record that we have from
Down here, we have, this is It's quipresent.esting.
There's 100,000 ago on the far
From the analysis of the ice right.
on this axis. What we see is climate changing
dramatically, the squiggly black
10,000 years ago, when we see linethis abrupt warming.bout
Now things are very warm. So we're in the warmest period
that we've been in for the past 125,000 years.
So what happens if you even out this climate change, what we see
is these periods of long
abrupt warming. So in the past ten years or so,
they've been going down to the
Sheet. South Pole, to the Antarctic Ice
and doing the same sort of They've been drilling ice cores
The graph on the X-axis here is aflipped.
So zero down there is today.
or 150,000 years ago. AndOnce again, we have thisgo,
temperature from the isotopes of
But we see the same thing here. We get long periods of gradual
cooling, punctuated by very abrupt warming.
So the question is, how many
glaciated. times has Wisconsin been
here 13,000 years ago because we We know that there were glaciers
But do you know how many ice see trees that were mowed down.
Has there been one? sheets hFive?een here?
Ten?
( inaudible ) Three? Four?
It's probably more than that, and I'll show you why.
The ice sheet cores go back about 800,000 years now with the
Antarctic Ice Sheet and the data
But we have a longer-term record that's coming out of there.
What happens here is you take a ship out into the middle of the
ocean.
overboard. You dump a big piece of pipe
It's quite simple. It's called a piston core.
the bottom of the ocean and you collect these cores of sediment.
Then you basically crack open those cores and you examine
them. In these cores are these little
creatures, little plankton
Here's a picture of one Rosalina called foraminifera.
We probably have a foraminifera expert here in this crowd?
No, all right.
core and you can look at various What happens is that you get the
And you can get a climate record species of these forams.
I'm going to show you that. I'll explain this in a little
bit more detail.
ocean core. And on this axis, we have depth
from the top of the core to the bottom.
It's about an 11 meter core.
oxygen-isotope ratio. What happens is, what's
important for this slide, and I'll explain oxygen-isotopes in
a minute. What's important to note is that
as you move to the right, you have warmer climate.
And to the left is colder.
have also age or time on this You canY-axis right here.op, we
We can see at present, we're
climate. actually in a fairly warm
event right here. YWe had a long cooling over the
past 100,000 years. We have an abrupt warming event.
What's interesting is when you
and you take a look at these go down into the sediment cores
You see an abrupt warming, forams here, you see the signal.
long periods of cooling, a long cooling, abrupt warming,
cooling, warming, cooling, warming, and whatnot.
So if we look at the ocean
data set right here from a core rthat was analyzed back in theld
late '60s.
least, what, one, two, three, four, five, six major periods of
climate warming and cooling.
There's at least ten major They have extended this record.
over the past million years. glaciations that have occurred
ice sheets here in Wisconsin ten So the question is, have we had
I don't have the answer to that. times, or not.
deposits from the last We know that we have extensive
And we have deposits from some glaciation.
we're unable to date them. glaciation before that, but
about oxygen isotopes. I want to talk a little bit
guys to sleep. Hopefully this won't put you
slide, this is how we're getting If you remember on the previous
temperature. these old records of
that oxygen has three different isotopes, O-18, O-17 and O-16.
We know that there's a lot of O-18 in that ocean.
I think it's like 99% that's
One percent is maybe oxygen 16. There's a very minor amount of
oxygen 17.
is that the mass of O-18, Soobviously, has got an extrare
neutron in the atom.
a balance here, it'd be heavier If ythan let's say, water8s on
made up of O-16.
Extra neutrons. So we know that in warm
climates, when we're evaporating
proportion of O-16 to O-18 this water, we get sort of a
warm periods. So when the climate was cold, we
tend to fractionate the oxygen
What happened is that precipitation actually contains
more oxygen 16. So what we expect, and I'll try
to show that in this diagram
when it's cold, we have hevaporation precipitation.s
What happens is that you get
the ice sheet on land. more oxygen 16 stored up here in
oxygen 18-enriched ocean. What's interesting, you
remember those bugs I was telling you about?
The forams, what we do is we
We actually look at the ratio. analyze them for O-16 and O-18.
here at a series of bugs that were living right here over a
long period of time, what we
glaciations, we would see-- These bugs are composed of
calcium carbonate shells. What we would see is that
there's a higher ratio of O-18
Unlike during interglacial to O-16, right?
relatively depleted compared to timthis situation here.is
And what happens is precipitation now contains a
similar amount of O-18 to O-16. So during periods, these bugs
here, during warm periods,
ratio of O-16 to O-18. they're going to have a higher
that we can look at the oxygen So what's interesting here is
those foraminifera in that sea isotope ratio of O-16 to O-18 in
That's how we can extract that core.
Here, I just wanted to show you that climate record once again.
This is one specific little foram that these oxygen isotope
ratios is from. That gives you an idea of what a
climate record that we've had,
As geologists, we love to show probably in this world.
going back to, that would be geologic time sections here,
And the most recent ice age occurred in this period
that we call the Quaternary.
1.8 million years old. It's about
for the past million years, but Sohow about the 800,000 yearsds
prior to that.
there? How many more glaciations were
try to figure out what's So a lot of climate scientists
Quaternary. It turns out in Wisconsin, large
parts of our geological record
period here in the Mesozoic, are actually missing, like a
We have some very old rocks where the here.aurs lived.
We have a good Quaternary record
difficult to tell what the age in this state, although it's
I just wanted to show you here, this is the extent of the state
that's been glaciated.
driftless area here. We have this area called the
non-glaciated area. As far as we know, there's never
been any ice sheets that have covered this area.
That's quite strange, because if
Midwestern states, it's surrounded by glacial deposits,
like I showed you, striations,
whatnot. glacial sediments, drumlins,
that's not glaciated. A lot of people speculate as to
why that is.
anything tonight about that. I'm not going to speculate
Wisconsin, a relief, you can Anyway, if you look at a map of
here. actualIt's quite obvious.ss area
It has a very different pattern.
outline of the last glaciation, Yowhere the glaciers reached.the
It kind of stretches across the state.
If you use your imagination on
there. this map, you can draw it across
glaciers. Hopefully, everyone believes me
now that Wisconsin was
glaciers did come from the glaciated, and that these
They dammed up our drainage ways, forming these large
glacial lakes.
about tonight is this one, The first one I want to talk
Many of you know of it as the central sand plain today.
What happened here is that the
Fox River Valley and actually terminated at something we calle
a Johnstown moraine, right
As many of you drive up north, here.
out on the central sand plain you come pasthere. and you drive
It turns out that right in this area, this is where Glacial Lake
Wisconsin was located.
advanced down here, it pinned up What happened is that as the ice
here. aYou can see the actual moraine
actually wraps around like that and comes down to Madison.
The Wisconsin River comes here, across the Wisconsin Dells, and
down around Portage.
blocked off that drainage way, What happened was that you
glacial lake that's sitting and thenright here. a large
And here's a photograph of the
Wisconsin. northern part of Glacial Lake
there. Many of you have driven across
And here is just a better relief It's a very unexciting drive.
Here you can once again see the lake plain of Glacial Lake
Wisconsin, here at the central
But one thing I want to point out now, and I'll talk about it
later on is this Glacial Lake Oshkosh.
It occupied many of these lower areas right here.
So when the ice sheet came down and pinned up against the
Baraboo Hills right here this lake formed.
People ask, where did all this
Well, actually, it went up here, water go.
River to the Mississippi River. This lake was quite large, maybe
about ten to 12 times the size
We know that once the ice sheet ostarted to retreat as climate.
warmed, the lake filled in back here in an area we call the
Lewiston Basin. An outlet formed right here.
We call that the Alloa Outlet.
catastrophically down the lower TWisconsin River.
Here's a cross section. I want to back up, but next I'm
going to show you a cross section that runs from the
outlet all the way down to the
Hills. eastern end of the Baraboo
looked like. This is what the lake probably
east fork of the Black River. IIt contained two main basins,he
here. And as soon as the ice sheet
backed off of here, this basin, or both basins drained
catastrophically down to the
So here's a little detail of Wisconsin River.
I just want to show you this. Here we have the Green Bay lobe
at its maximum extent.
here. Many of you can picture Devil's
Lake. It sits right in that gorge
right there.
was draining out the east fork And here we have the lake that
As soon as the ice sheet of the Black River.
forms. retreats, this Lewiston Basin
here, all the way down here. And it ultimately drains over
forms called Glacial Lake And we haveOshkosh. lake that
I want to talk about that drainage.
Many of you have been to the
And if you take a look, when the Wisconsin Dells.
the soft Cambrian bedrock. lake drained, it cut down into
this unique system of gullies or As it was draining, it formed
And there's a picture from dells, as people call them.
early turn of the last century. HYou can see the water cut downe
through the sandstone.
Gulch up there. It's a very narrow passageway.
Some people have done calculations of the volume of
water in the lake, and have looked at other geologic
features, and sort of determined
of about seven to ten days. thAnd some people speculate--od
Here's a picture of the lower Wisconsin River--
Is that a lot of the sand that's
actually transported there from the discharge event from Glacial
Lake Wisconsin. Certainly, the existing river
now is transporting a lot of
plain. sediment from the central sand
several hundred feet thick in But a lthe valley.sand is
So the source of that may have
event. been from this large flooding
It's of the central sand plain, the former lake bed of Glacial
Lake Wisconsin. It is a prime area for growing
cranberries, which Wisconsin is one of the major producers.
The conditions are right because
it's very poorly drained. theTwo conditions that are and
necessary.
myself for the past six years since I've been at the Geologic
Survey is that as soon as the ice sheet retreated up into the
Fox River Valley, we have this
formed, call Glacial Lake other lakeOshkosh. actually
This green circle here
It turns out that, obviously, the Fox River, which now drains
out Green Bay, couldn't drain out there, so this lake filled
up in the lowlands and drained
Wisconsin River. out here at Portage to the lower
simply the extent of the Green The black dashed line here is
maximum around 20,000 years ago. Bay lobe at the last glacial
shaded relief. I want to show you another
Wisconsin Dells, and the river Remember I talked about the
This blue area that you can see up here, most of that was
occupied by Glacial Lake
This area shows a large area of Green Lake and Marquette
Counties, not to mention
This is kind of what the lake northerlooked like.ounty.
This is where its outlets were. We have this outlet here down
through Portage.
up, it cut, it drained out into As sthe Lake Michigan Basin.ked
As the ice sheet retreated, more
cut across the Door peninsula. and more of these outlets were
up quite dramatically are in Two of these outlets that show
One of these major outlets Manitowoc and Kewaunee Counties.
right here. A lot of this is through really
solid bedrock.
northward, another lower outlet opened here called the Kewaunee.
Now if you go up there today, the rivers that occupy these
valleys are very small. So you know that these valleys
could not have been cut by
the past 10,000 years. drainage during the Holocene, or
drainage events from a glacial They're actually remnants of big
This schematic actually shows that drainage sequence.
Here we have the Green Bay lobe.
northward. It's actually receding
Michigan Basin. The lake becomes smaller, lower
outlets open and the lake becomes smaller.
Smaller yet.
recedes out of Wisconsin and all And then eventually the ice
Winnebago, Lake Butte des Morts and Lake Poygan, which are
actually rather shallow.
( inaudible ) I wantedSure.how this.
( inaudible ) Sure, we know we have some good
dates from the bottom of some geologic cores that show that
it started to recede back about 18,000 years ago.
And receded out of Wisconsin
It was relatively quickly. about 15,000 years ago.
story that I'll get to is that But the interesting part of the
re-advances of the Green Bay there were two sort of major
The ice sheet must have been lobe.
the climate. responding to oscillations in
bit. I'll talk about that in a little
those outlets. Here I just want to show you
surface, across from left to This is a section of a land
You can see here is where the Manitowoc outlet is, the
Neshota, the Kewaunee, and the
this glacial lake. Ahnapee that were used to drain
Well, if you go up there, you'll What's the evidence for a lake?
relatively grim place, because find the Fox River Valley a
topography. People up there might disagree
with me, because I guess it all depends where you live.
But it's pretty flat. The Fox River Valley is not as
flat as some places of northern Illinois.
So you go up there and you say, what's the evidence for a lake?
Well one thing we can see here
here. iThere are a lot of boulderst
sitting up here.
lake sediment. This turns out to be a lot of
soil right here. Same here, you can see the sandy
right here. ThYou come down, the more deepce
water, clear lake sediments.
you go up there. It's not very convincing when
lake there. You'At least I had problemsas a
believing it when I first drove my car across there.
But as I went and visited some
can see such a sequence as this. quarries and gravel pits, you
about 30 feet high. TYou can see these laminatedh,
sediments right here. You see there's a dark layer,
light layer, dark layer,
So there might be 100 such whatnot.
What these are is couplets. These each dark layer and each
light layer represent one year
lake. of So if you go up there and the
there's of course some sandy
interpret this as lake sediment. material on top, I would
have coarser sediment at the top This lake is shallowing, so you
It's quite impressive. with finer grain sequence.
once was a large lake there. That's a good indication there
love to go out and drill bore Of holes into this stuff. we
It's what we do to learn about
We've done so. the geology.
holes we've drilled recently. There's the drill rig that we
hire to go do this sort of work.
we've actually recovered. It's about one foot across and
about 106 feet in depth.
layers. It's actually a clay layer, silt
layer, clay layer, silt layer.
counted over 1200 of these bars, In some of the cores, we've
through at least 1200 years. which means the lake existed
or log of one such bore that we What we can drilled.re's a core
Here's that sample, that
What's interesting is the squiggly line, here we have core
depth, or elevation above sea level, but we have a measure of
something called natural gamma
What's important to notice here is that we notice there's three
different ages of Glacial Lake
So basically what happens, is that we know Glacial Lake
Oshkosh was reactivated twice after the initial recession of
the ice sheet here. And these white lines here
actually show the extent of those re-advances back into
Wisconsin.
occurred, reaches its maximum extent about 15,000 years ago.
It sort of extended down around Fond du Lac, up onto the
escarpment and out into Lake
Then the ice sheet totally Michigan Basin.
our forest here. receded and we had the growth of
rapidly. So climate was warming very
re-advanced to this margin right When the ice sheet actually
northern tip of Lake Winnebago here, which reached just the
It actually buried this forest. If you go out, you can actually
find it.
beaver-chewed wood that we This is actually a piece of
So a beaver was, you know, found.
And you can actually see a operating in that forest.
six-inch thick layer of organic thick, itmaterial.ly about a
So we're very confident of the
So the ice sheets are not the sort of stagnant things that we
all think about.
but in over sort of a 100 year Glaciers do move quite slowly,
actually move quite rapidly. to 1,000 year time period, they
15,000 years ago, the ice sheet retreated out and actually
re-advanced into Wisconsin. So in a period of 2,000 years,
we've seen a major re-advance, a
again. recession, and a re-advance once
sort of like a beating heart. They sort of advance and recede,
you know, unless the climate
disappear. warms and they actually
I apologize, I know this is This iquite boring here.tion.
Here we just have elevation.
up to Green Bay. This is a distance from Portage
this thick sequence of lake Wsediment and things we callt
glacial till, which means that
directly. That's what the landscape is
dominated by, is glacial
One thing I'd mentioned earlier is that, what is the record of
climate change here in
It's not that great. Wisconsin.
I talked a little bit about isotopes earlier collected from.
the ice cores and the ocean core.
But in one of our cores, which
actually consists of all lake sediment and tills that I talked
about earlier.
extracted the water from the We went in there and we
We analyzed it for oxygen 18 and sediment.
It turns out what we're after is oxygen 16.
here in this state? thaThat's the question we'reater
asking. And the thing is that when we
pump from the aquifers, the bedrock aquifers we have in the
state, are we actually mining ground water?
That is, are we taking a
limited resource, or is actually resource that's ultimately a
precipitation? recharging from water and
were asking ourselves here. It turns out that you can see we
have this bow-shaped curve here.
18 here sort of represent that And what this values of oxygen
within this very thick clay we have vesequence.ound water
So the question remains is that is the water in the aquifers,
which are mainly in the bedrock down here?
Is that real old water? Is that fairly young water?
Are we pumping a source that's
That's a real interesting question that I won't get into
much tonight, simply because
would add another ten minutes to it's not my expertise, and it
But one question that people this talk, at least.
this thing called isostatic depression will have affected
lake levels in Glacial Lake Wisconsin and Glacial Lake
Oshkosh.
think about the earth as a Now, if you think about this,
That's really what it is. We have the earth's crust, which
is very rigid.
mantle, which is actually not And very rigid at all.e a
That's mainly molten rock.
filled with Jell-O, if you push or apply a force on one side of
the balloon, you're going to
going to pop out elsewhere, displace tharight?-O and it's
If you think about this, if you take water out of the oceans and
we load them up on land, we're
We cause something called liisostatic depression.n.
When we load these big ice
depress the crust of the earth. Now of course, how much of this
depression actually occurs here depends upon how jelly-like, or
I should say how viscous that Jell-O is in side.
It also depends upon the
here. So if you can imagine, if we
load Wisconsin with a big ice sheet like this, we're going to
actually depress the land surface.
Actually, this depression is
of the ice sheet, as well, maybe actually felt out way in front
It's like, you know, this is by 50 to 100 miles.
The material is squeezed out something called a forebulge.
So here's a graph with a lot of undernelines on it.sheet.
But what's important here is
what I call isostatic rebound or this represents the amount of
years. depression over the last 13,000
these are a bunch of old glacial If you take a look at this,
Midwest. great lakes throughout the
We have a big one here in the This Lake Michigan Basin.osh.
We had other ones in the Great
As you can see here, in Wisconsin, we have seen 20
meters, which is about 70 feet, of rebound.
The earth's surface is actually coming up over the past 13,000
years.
northern Canada. You can see that way up in
about 500 meters of rebound. They've seen on the order of
What we do, is that this is actually the result of numeric
models that have been calibrated
So we're fairly confident in to fit geologic data.
these numbers are fairly right this project we've doing that
So if we take a look at Wisconsin a bit closer, here we
have Glacial Lake Oshkosh in
Here's a lake that was in the front Michigan Basin.y lobe.
You can see that at right about Portage, which is right here,
basically there's been zero isostatic rebound or actual
depression. If you go to the northern part
of Glacial Lake Oshkosh, there's
years ago. about 50 meters since 18,000
the shoreline that we find here Sof Glacial Lake Oshkosh, if we
go all the way up into Oconto County, we should find that at
50 meters higher than it is down
We would expect to see over 150 feet of difference between their
shorelines. Does that make sense?
A lot of people ask, well, is Wisconsin still coming up today?
Does anyone know that?
of the glaciers? Are we still feeling the effects
Maybe because it doesn't matter, Does anyone know that?
Because this rebound is such a right?
timescale. slow thing, it's on a geologic
we make from year to year. It doesn't affect any decisions
from, let's say Portage, all the But if we take a transect going
peninsula, and that's that way up to the tip of the door
X-axis, and we take this, what I distance right here on the
present. call deformation relative to
the ice sheets advance. WhatWell, we'll start here.e, is
The ice sheets advance. We actually depress the crust,
right?
ice sheets advance, we're Here depressing the crust.o, the
Here's 15,000, 13,000, 11,000,
So what happened is that we've and so forth.
surface. been depressing the land
years, this land surface has In the past, probably 10,000
You can see as it comes up actually been on the rebound.
about 9,000, all the way up to during the Halocene period from
If you recall, I showed you a picture of this thing called a
forebulge in front of the ice sheet.
That's what's happening in
We had depression and uplift, so Wisconsin today.
The question is that there's it's doing this sort of motion.
years, is probably have modified probably over the past 10,000
How drastically, I really don't drainage sysknow.in our state.
A lot of people spend time
from Lake Michigan to try to get looking at modern gauge records
This is significant in some areas, especially if you're
along an ocean coastline. This rebound can have an effect
over say, a couple hundred
It can be enough to raise sea level over engineered barriers
and whatnot.
Will those ideas account for Question?
was the bulge ahead of it? the driftless area, like if that
I mean, when we modeled the ice sheet here, when we calibrate
this model using our lakeshore
that we have, actually, they say lines and whatnot, it turns out
thick in the state. So 400 meters is, you know,
1,300 feet, something like that.
higher than anything in the So the driftless area.ch, much
So you can imagine with a giant ice sheet that's much higher,
just back from the margin, than anything in the driftless area.
So no, that forebulge wouldn't
Even if it was 50 meters high out in front, it wouldn't have
provided enough topographic relief to divert the glacier
south.
The reason why the driftless That's a good question.
have an answer. aSo anyway, I just kind of't
wanted to end up the talk today.
occurring, Tom? Whe( inaudible )ar eclipse
Anyway, I just want to say
on a cold night. thanks for coming out tonight
little bit about the natural Thanks for letting me talk a
Wisconsin, and also this one, Glacial Lake Oshkosh up along
the Fox River Valley. Thanks.
( applause )
Sure. >> I live in Middleton, and we
have two kettle, which means an old source of water.
And they just fill up, then they
drain them out into Lake become silted and we have to
The water levels in those kettles are simply an expression
of the water table. So they're recharged by the
ground water. Yeah, there's a lot of those in
Wisconsin, especially up in northern Wisconsin, there's a
lot of small, little kettle lakes that don't have an outlet.
So those are glacial lakes, but they certainly aren't on the
scale of the lakes I've been
were much larger, ten or 15 talkintimes the size., which
We still like them. >> Oh, yeah, they're very nice.
Question? >> Going back to Glacial Lake
Wisconsin and the land form of
something that drained in seven Wisconto ten days?s this
Or was it that quickly? >> It was.
And once the ice sheet quit impinging on the eastern side of
the Baraboo Hills, what happens,
little bit, the water breaks you back that ice off just a
effective at melting that ice. through and the water is very
you're asking is, one it takes So there's geologic evidence
like that, to actually cut down quiteto that sandstone.drock
But they find good size boulders
Valley. In order to transport good size
boulders, you have to have a
So that's some of the geologic large stream with lots of power.
It would be difficult to cut evidence.
believe, and transport these through that sandstone, I
flow event that occurred over a bouldlong period of time. low
There's certainly a lot of
those calculations. But it's pretty convincing when
you take a look at some of the
I put on here, the volume, if you can wrap your mind around
it, was about 87 cubic
compared to Lake Winnebago with kiloa volume of three cubicbig,
kilometers. So this is orders of magnitude,
almost two orders of magnitude
And to give you an idea, that lake was about 4,000 square
kilometers compared to Lake Winnebago that was 600 square
kilometers. The average depth of Glacial
Lake Wisconsin, I'm not sure of that.
I wasn't involved in making those calculations.
But it's probably about, I would
like that. imagine 20 meters, or something
that. MayGlacial Lake Oshkosh, theact
average was about 17 feet, about
Glacial Lake Wisconsin was quite five meters deep.
meters. So if I compare the two lakes,
the volume of Glacial Lake
kilometers, compared to 87 for Oshkosh, about 111 cubic
They have done calculations of Glacial Lake Wisconsin.
been out to the Wisconsin River and across the Door Peninsula
for Glacial Lake Oshkosh. They've come up with values of
one times ten to the fifth cubic
I don't know how this compares, and I meant to check this on the
Web, compared to the floods along the Mississippi River that
occurred back in the early '90s.
numbers? Does anyone know those discharge
I think it might be something comparable, like that.
If you can imagine these lakes
days, something like that. draining in a period of seven
It would take about 15 years to fill Glacial Lake Wisconsin back
again.
Your relief maps that you showed, the topographical relief
pictures, where are those from? >> It turns out that the United
States Geological Survey makes
elevation models. And if you have the software,
you can download that data right
make those. offOf course, you have tocan
manipulate them, color them, and
topographic features and whatnot, and add, you know,
They're neat. >> They are neat.
They're fun to show, because it gives you an idea from space.
Are they from space?
off their topographic maps. >>I think most of the data isken
taken off of the topographic
maps. That's the source of the data.
( inaudible ) ( laughter )
In the future, what do
Well, maybe I go to another state.
( laughter )
Wisconsin has such a long history starting with
T.C. Chamberlin back in the 1800s, of studying
glacial deposits here.
When I came here, I thought, The thing that's really--
Right, that these giants in this what am I going to add?
years. business haven't known for 100
they didn't have these digital And it turns out that back then,
looking at here. elevation models that we're
detailed information. It becomes more important when
we're looking for something for sand and gravel resources, or
we're trying to understand
We need to know the geology grounquite well.urces.
It turns out that there's plenty
do. of wo>> You might find oil.l to
I wish. ( laughter )
Question? >> Did you say that there is
or is not glacial water,
There is. There is glacial water in those
thick clay lake sediments up in the Fox River Valley.
The question is that beneath
what we call a Cambrian bedrock those glaciasystem.ents, we have
And there's a big, thick layer, and I'll call it the Mt. Simon
sandstone, that comprises the major aquifer for southeast
Wisconsin, but also for Madison,
Tom asked me to talk about as well.
tonight. this, but I didn't do it
have heard that Waukesha wants The question is that many of you
Michigan. One of the things is that a good
portion of Waukesha County is outside the surface water
drainage basin. That's what determines whether
you can extract water out of
So Waukesha has been pumping Lake Michigan or not.
many decades now, especially as thWaukesha County has boomed.or
What's happened is that they're depleting the aquifer somewhat.
They've lowered the water table.
quality as an issue there as But they're also getting water
They're starting to draw off well.
problems in their water. some brines, and have radium
this aquifer. To give you an idea, they pump
30 million gallons a day in Waukesha.
I think Madison pumps 50 million
So the question that you're ggetting at, is that old water,.
pumping glacial water, are we mining a resource that's not
renewable.
Some people would say the Andaquifer is being charged.to.
Some people think Lake Mendota, for example, is a recharge for
that deep sandstone aquifer.
into Lake Michigan Basin, maybe, But as that aquifer slopes down
impermeable, or less permeable you know, there's more sort of
actually prohibit water, you units up in the section that
infiltrating and getting down and recharging that aquifer.
Some people would say that some areas of that aquifer contain
very old water, and that we're
we're using it. noYou know, of course, I woulds
say that our water qualities are
maybe the western states, where notthey're struggling now ind to
drought conditions. But it is an issue, because if
we let Waukesha County extract
Lakes, then we start to sestablish, supplement whatt
they're drawing out of the
establish a precedent that ground water system, we
outside their "surface water anyone can take water that's
That' causes all sorts of draiissues.sin."
Chamberlin discovered this
But was that like a general glaciatitheory?isconsin.
You know, people thought there
places. I was wondering, nobody thoughtr
of continental glaciation before.
Well, you know, no one
I mean, if you go back to the 1800s, Louis Agassi is sort of
the main man. He came from Europe.
He was looking at big erratics, what we call erratics.
There's one that sits right up
There's a big boulder that's an on Baserratic. now.
Basically, it's a piece of
There's no granite readily granite.
So it had to come from far away. available in the Madison area.
those erratics were carried by The reason, people thought all
And so, what we've seen, and it wasn't until after Agassi and
other folks, took a lot of heat from this back in the early
1800s.
other folks around North And Chamberlin, along with some
Agassi, and said, look, there's no way that these boulders are
from this big flood.
spread. Where did the flood come from?
And all these other land forms, they went and saw these till
sequences.
from a glacier, they went to the In the Midwest, we see deposits
that looks like the deposit from modern glaciers and said, oh,
What's interesting is that a modern glacier.
of named these tills. ChThere was the Wisconsin, thet
Illinoian, the Kansan, and the
It turns out that Chamberlin Iowan.
big glacier here. sAnd then he started to look a
around. This is huge.
It wasn't here, it had to be up in Canada.
And he was actually the first one that made that big map
showing the extent of a continental glacier.
That's what Chamberlin's really well known for, is that he sort
of took that idea.
called the Late Wisconsin. In fact, the last glaciation is
Chamberlin named it such. It was the upper most till unit
that he was looking at, and he
Anything, the lower ones, for calledthose other states.onsin.
So those have sort of gone by the wayside, but the Late
Wisconsin has stuck.
throughout the world today. So, I guess our state's quite
honored to have the last
Chamberlin really was sort of a glacipioneer, really.r us.
Agassi was sort of the real pioneer and took a lot of heat,
but Chamberlin hopped on that boat quite quickly when he
realized, when he sort of correctly evaluated the data.
So hats off to him. He certainly, I'm sure, took a
lot of heat from people back in the 1800s.
Back to the idea about
Isn't there a compact among the states surrounding the Great
Lakes about those kinds of
There is. And I don't know much about that
compact.
sure, who know much more about There's others in this room, I'm
But what's happening is that it.
surface water divide. WaYou know, in the groundwatere
flow system, we also have sort
say systems. of groundwater, I don't want to
that crosses further to the There's a gwest.water divide
So Waukesha's argument is that
groundwater basin, it discharges the groundwater, within that
So we're saying that this artificial line, this surface
water drainage divide has really
ground water. goAm I not making sense?he
But they're saying that a divide
groundwater divide, not the surface water divide.e
Because you know, when you put
let's say if you spread it on the land, it actually soaks in.
It goes back into and recharges the aquifer.
The aquifer discharges into Lake
That's their argument. Michigan.
compact based upon that logic, So they're challenging that
ground water divides, not the that surface water divides.n the
Does that make sense? >> Is the Laurentide Ice Sheet
below the North American Ice
No, that's an old map I put up there.
The Laurentide Ice Sheet was the
covered North America. last great ice sheet that
stuck up there. It was initially just called the
North American Ice Sheet, because no one knew anything
about it. So there was really nothing
called the North American Ice Sheet.
That's sort of a general term that was used very early on.
I don't know where the term Laurentide came from, who named
it that.
I think Chamberlin called it the I have no idea.
start with, but it's North American Ice Sheet to
Laurentide. We certainly had many of those
ice sheets. And probably many of them came
into Wisconsin over the past two
Yes? million years.
that as oil is extracted from >>the ground, the space getsng
filled by water?
Is that true? That's>> It depends.tion.
( laughter )
A lot of times, you pump the oil It depends where you are.
takes a while for any sort of anwater or fluids to recharge.t
But a lot of times, oil companies, what I know, they
will actually put up two wells. They'll pump oil out of one.
They'll inject water down one and they'll try to push the oil
out the other one.
what the geologic situation is. >> In so far as that happens, is
there an issue about that water being locked in the earth and
not be evaporated, and does that
climate? affect our water supply and our
there. >> Well, a lot of questions
ground water, it exists in The water, if you think about
right. porous spaces between grains,
those pore spaces or those voids So what happens is that how well
or not you'll be successful in are connected determines whether
The question is that ground water doesn't evaporate, because
it's not exposed to air.
evaporation in the groundwater. So the question is with climate
change. If we have a reduction in
precipitation, let's say, that's
reduction in recharge to our going to possibly mean a
That's possibly what it means. aquifers.
are in the world. So once again, that's sort of a
site specific question. Did I answer your questions?
Some of them, yes.
Thank you all very much. ( inaudible )
Thank you. ( applause ) ek.