- Good afternoon, I'd like to introduce Dr. Tom Fitz,
Associate Professor of Geoscience
at Northland College in Ashland, Wisconsin,
who delights in the Earth's story
and sharing that story
and why it matters in all of our lives.
Dr. Fitz is a dedicated professor for over 20 years
and has received many awards for his teaching and research
while at Northland College.
When asked what drew him to Wisconsin from Massachusetts,
he replied, "To teach and study rocks."
Wisconsin is a wonderful geologic setting
to learn and teach students.
Living near the Penokee Range
has enabled Dr. Fitz to study the unique setting
that makes up the range for the past 16 years.
He loves to take students on field trips
and share the natural beauty of the area.
At this time, it gives me great pleasure
to welcome Dr. Tom Fitz to present
Geology of the Penokee Range in Wisconsin.
[audience applauds]
[converses indistinctly]
- All right, welcome, thank you for coming.
It's a pleasure to share the fascinating story
of the geology of the Penokee Range, yes.
Okay, my career has really been dedicated to
teaching people about the Earth and their relationship to it
and also why that matters.
Why should we care about the geology of a place, okay?
And I've been leading geology field trips
through the Penokees for about 15 years,
and it never ceases to amaze me
what I see there in the rocks.
So this is what we're gonna do today, okay.
I'm gonna take you to the Penokees the best I can.
And so first I'm gonna tell you just a little bit
about the geography and the general geology of the Penokees.
Then we'll look at the rocks,
and we'll travel back in time billions of years
and read the story in the rocks
and figure out how those rocks have formed.
And then we'll spend some time
thinking about why that matters.
Why does the geology of the Penokees matter
and the geology of any place?
This is why geology matters to society.
One is the resources, okay.
Minerals, energy, and water.
Those are the geological resources that we all need,
that we all rely on,
and are used in large quantities by society.
Okay, we'll also talk about hazards.
The environmental hazards associated with resource use
and also the human health hazards
because we live on a crazy, dynamic planet,
and it's got a lot of hazards,
and we need to understand those
so we can protect ourselves.
Okay, and then also just the,
how it enriches our lives to understand our surroundings.
And that's definitely true,
and that's true of the geological stories
under our feet as well.
So we'll finish with that.
Okay, so first just a little bit about the Penokees.
Okay, the Penokee Range,
this is a landscape map of northern Wisconsin.
And the Penokee Range is over here, all right.
And it is basically these double ridge
right along there like that.
It is, it stands about 400 feet.
The two ridges stand about 400 feet
above the surrounding landscape.
It's about 50 miles long,
and then it also extends over into Michigan
and goes about 50 miles into Michigan
where it's called the Gogebic Range.
So together we call it the Gogebic/Penokee Range, okay.
It is there because of the hard bedrock underneath, okay.
The area is sparsely populated.
It's really quite beautiful.
It receives about 33 inches of rain per year,
and the average annual temperature is about 43 degrees,
important numbers when we're considering
what will grow there.
All right, what is the ecosystem of the area?
It is mantled by a thin veneer of soil,
mostly loamy soils derived from the till,
the glacial till that is underneath it.
And that together, the soils and the water,
support a pretty dense forest,
and it's quite a pristine area.
Okay, I should mention, this photograph,
which was taken from Corrigan's Bluff,
sort of in the middle of the Penokees,
was taken by my friend Megan, who's a great photographer.
I give credit to
people whose photographs I have borrowed
or diagrams I have borrowed
in the lower right of each slide.
And the rest of them,
the cartoons and the photos that aren't so good,
the rest are mine, okay.
So, as I mentioned, the Penokee Range
really owes its existence to the hard bedrock.
And this is a geologic map,
a bedrock geologic map, of the area,
and you can see the different layers.
And, basically, in the Penokee Range,
there are layers and layers of rocks that are stacked up
and that have been tipped to the north.
So, basically, what we see on the stripes,
those are the edges of rock, bedrock units.
All right, and there are two layers in there
that are especially hard that stand up.
And so that's really what this story is about.
It's taking a look at those,
the rocks within those two edges, okay.
So this is a geologic cross-section.
Okay, if we go back,
if we were to draw a geologic cross-section
across the Penokee Range,
going like that, from north to south,
and take a slice of the Earth,
that's what we'd be looking at.
From south on the left
to north on the right, okay.
So this is my cartoon drawing of it.
And what we can see down here
is this is the bedrock underneath.
Okay, the hard bedrock.
And we can see the two ridges there.
Okay, so there are two layers within the rock,
within the bedrock, that's especially hard,
the southern ridge and then the northern ridge here.
All right, and then overlying that
are the surficial deposits that are of glacial age,
and we'll mention those as well.
That mantles the hard bedrock ridges,
and as I mentioned the soils have actually formed
in that glacial material, those glacial deposits.
Okay, so what we're gonna do
is we're gonna take a look at the story
within the bedrock going from this oldest stuff.
There are basically three packages of bedrock
within the ridges here.
Okay, on the south, that's the oldest one,
the middle one, and then the northernmost one.
All right, and we're gonna travel back in time
and look at how those things have formed.
Okay, so there it is.
There's some hard bedrock sticking out.
And around it is soil, the glacial deposits around it.
Okay, so that's some hard basalt sticking up.
Basalt volcanic rock sticking up in the woods
in the Penokees.
Okay, so before we get going on the details of the story,
one of the things I have to mention
is that when we're talking about geologic stories,
we have to extend our thinking of time
into deep time.
Okay, and that's really one of the really fun things,
and I think important things,
about understanding the geology
and what geology brings to us,
you know, as a science, any historical sciences,
to stretch our minds outside of the human time frame.
All right, and that's an important thing to do, I think,
to be able to see processes, natural processes,
on very long time scales.
So what we're gonna do is
we're gonna travel way back in time,
way back down that spiral of geologic time
to about halfway back to the beginning of Earth's history,
okay, to about 2 1/2 billion years ago,
and then move our way forward.
Okay, so this is a geologic time scale not drawn to scale.
But the olds, the beginning of the Earth,
4.6 billion years ago to today up here.
All right, it's not drawn to scale,
but the major geologic time periods are shown here.
And basically the bedrock
was created in three episodes,
okay, spanning many hundreds of millions of years each,
but three episodes of rock-forming processes
are represented in the Penokees,
okay, from 2.7 billion years ago to 1.1 billion years ago.
And that's the old story
that we're gonna look at in the bedrock.
And then there's the more recent story,
relatively recent in geologic terms,
of the glacial story and the glaciation of that
and the deposition of the glacial deposits
and the development of the soils
that support the forests today.
Okay, so let's go back to 2.7 billion years ago, okay.
And one of the really interesting things about the Penokees
is that since it was tipped up like that,
it is such a complete, it's a really remarkable story there.
I mean, these are some of the oldest rocks
in Wisconsin right here.
And 2.7 billion years ago, it was a time
when the continents were just first starting to develop.
So when we're thinking about this far back in time,
we can't think about it as like the Penokees are today.
We have to think about it almost like
this is taking place on Venus or something, you know,
and it evolves through all these billions of years
of constant geologic change to be what it is today.
Okay, so 2.7 billion years ago, very few continents,
and the rocks that were created and preserved there
were created on the ocean floor from submarine volcanoes.
And this is actually the oldest,
some of the oldest rock to be preserved.
All right, so there was certainly rock there before this,
but the rock cycle was moving so fast,
rocks were being constantly recycled,
and so these are the oldest things to get preserved,
okay, some of the oldest stuff in Wisconsin, all right.
Yeah, a remarkable story, okay, there it is.
These rocks are all scrambled in together.
They've had a complex history long ago.
They got very hot.
They got deformed like Silly Putty.
And the rock is a gneiss, okay, G-N-E-I-S-S.
Complicated stuff, some really beautiful stuff there.
Okay, and then what happened after a long complex history
recorded in that rock itself is a long time of erosion,
all right, and much of it was stripped away.
So we lost quite a bit of record there.
So it was a long period, like hundreds of millions
of years of erosion, and then sea level rising.
Sea level rises and falls a lot,
okay, when we're talking about
these long periods of geologic time.
So, sea level will rise across the continents
and deposit marine rocks across all the continents,
and it'll go back down.
Much of that will be eroded,
and then it will rise back up again.
And that has happened many times in this region,
and most regions of most continents
have marine sedimentary rocks preserved on them.
Okay, so sea level rises.
This is going back to about 1.9 billion years ago.
And sediment is deposited upon that surface.
So those old volcanic rocks are eroded down
to a flat surface.
This stuff was deposited on top of it,
and we call that gap in time right there,
we call that an unconformity.
So across this gap there is, you know,
700 million years of time missing, all right, right there.
Okay, and deposited on that, above the unconformity,
was lots of layers of sand and mud,
okay, in this shallow, off-shore basin.
Layers and layers of sand and mud
that later were compressed and heated
and turned into slate and quartzite.
And then the deposition continued
where another layer laid down,
but this is a little bit different.
This took place, the deposition of the next layer up
called the Tyler, no, called the ironwood formation.
The ironwood formation was deposited at a time
when there was a lot of change taking place
in Earth's atmosphere.
The first photosynthesis on a large scale
was putting oxygen into the atmosphere
in high enough abundance, still low quantities,
but high enough abundance
that the chemistry of the atmosphere was changing,
and some of that oxygen was dissolving into the oceans.
The oceans at that time were quite rich in iron.
So we had oxygen, the first free oxygen in the atmosphere,
in what we call the great oxygenation event, all right,
which was a really big change on Earth.
Oxygen dissolved in the water.
The ocean was richer in iron at that time.
The oxygen and the iron combined
and were deposited on the ocean floor
as big layers of iron oxide.
And that time period,
about 1.9, 1.8 billion years ago,
is when all of the big iron formations on Earth
were deposited because of this chemical reaction
that was taking place because of
just the correct geochemical situation.
And it created these,
the big, beautiful banded iron formations.
And that's it right there.
That's the ironwood iron formation.
It has layers of iron oxide in here.
In this case, it's the mineral magnetite
and layers of quartz, like that.
The ironwood iron formation is about 700 feet thick,
and it's mostly like this.
Some places it's more quartz;
some places it's more magnetite.
But it's really a remarkable rock.
I mean, there is, [laughs]
it's crazy, all right,
because of all of the magnetism, for one thing.
It's also a really beautiful rock.
I mean, it's like this stripes.
It's like tiger-striped in red and white
and black in some places, really remarkable stuff.
And you can see right there, that's my magnet.
You can see the, whoops, I didn't mean to do that.
Okay, you can see my magnet stuck right there on the rock.
There aren't many places in the world
where you can go up to a rock
and throw a magnet and it sticks.
And the Penokee Range is one of those places,
one of the few places on Earth.
It's also one of the few places on Earth
where your compass doesn't necessarily point north,
which can make navigation in those woods very challenging,
you know, because you don't know whether you can,
well, sometimes you don't know
whether you can trust your compass
because it's not doing the right thing.
Sometimes it's pointing east, west
along the length of the range,
and sometimes it doesn't spin at all.
It's like it pegged down, it wants to be on the rock,
and the compass needle doesn't change at all.
So, anyway, just a really remarkable rock.
Now, this is a fairly recent discovery.
At the top of the ironwood iron formation,
there is a very interesting layer of broken rock.
So I've represented it there by that dotted red line.
And there it is, this one isn't actually in the Penokees
because this layer, it's about 10 feet thick,
this crazy, broken rock that we call breccia.
It sits on top of all of the rocks,
all of the iron formations in the Lake Superior region.
It actually isn't exposed in any outcrops in the Penokees,
but we know it's in there
because there have been so many drill holes
penetrated through that so we know this rock exists.
This particular outcrop in this photograph,
I took this photograph in Thunder Bay, Ontario,
in the same stratigraphic position.
So a similar thing exists in the Penokee Range,
Thunder Bay, Ontario.
And you can see that that rock is just broken.
I mean, it's just made of broken pieces.
And it wasn't really understood what this breccia,
what formed this breccia, all these broken pieces?
They're all sedimentary rocks.
You can see the layering in them,
but they're all spread around like that.
Well, interesting story is that,
Oh, and then it also has,
some places it has the broken pieces,
but then it also has these spherules
and some perfect spherical spherules in there.
Very interesting stuff.
And the discovery came in 2005
by Bill Addison, who was a science teacher
in Thunder Bay, Ontario, and one of the outcrops
was right up the road from his house,
and he'd been studying that for a while.
He had a microscope in his basement,
and he found some of these, okay.
And these are quartz grains, so these ones right here.
That, that, and that, those three, those are quartz grains,
and they have planar fractures in them,
and quartz doesn't have planar fractures in it.
Quartz does not have anything what we call cleavage,
which is a weakness in the crystal structure.
It doesn't have that.
There's only one way that quartz can have a fracture,
a planar fracture like that,
and that is if it gets hit really hard, all right,
harder than anything on Earth.
Actually, it has to get hit by a meteorite.
So this is the story and this evolved.
That was 2005 that Bill made that discovery,
and the story has been sort of evolving since then.
And the United States Geological Survey
has done some really interesting studies on this as well.
And it's now been tied to the impact crater
that was known for a long time in Sudbury, Ontario,
which is the third biggest known impact crater on Earth.
And what we see in this breccia layer
at the top of the ironwood iron formation
represents an absolutely catastrophic meteorite impact.
A rock about six miles in diameter slammed into the Earth,
and, basically, what we see in this rock, okay,
those are pieces of the ocean floor
that were torn up by a great big tsunami.
It's estimated that that tsunami
may have been about a kilometer tall.
So 0.6 mile tall wave that went around the Earth
and tore up the ocean floor.
This was basically a global event.
And the spherules here,
the round, the funny, round spherule pieces in there,
those are pieces of melted Sudbury, Ontario.
Sudbury, Ontario was vaporized,
what is now Sudbury, Ontario,
and the rock went into the atmosphere
and then condensed into these lapilli we call them.
And these lapilli came down,
raining down into the ocean floor
after it'd been all torn up by this meteorite impact.
[laughs] That's a crazy story, okay.
And that layer, okay, exists at the top of
all of the iron formations in the Lake Superior region.
Okay, so that layer has now been found
in about 10 places around the Lake Superior basin.
There's the Sudbury impact crater right there.
So this is a remarkable story
that this layer is actually preserved.
Okay, the other interesting thing about this
is that it's at the top of all of the iron formations,
and it ended iron formation deposition,
at least in this part of the world.
So this was a global event.
It was such a big event
that it changed the chemistry of the oceans in such a way
that iron formations were no longer deposited
on this big scale.
There were small ones later on,
but this changed the world, this meteorite impact.
And the United States Geological Survey is continuing
studies on that with drill core from the Penokees.
Okay, so that layer is very nicely dated.
We have a nice date from the Sudbury layer
at 1.85 billion years ago.
So we've got the 2.7 billion year old package,
and we've got the 1.85 billion year old package.
And then there was more rock deposited on top of that layer,
and these rocks were deeply buried
and heated up enough that they will change a little bit
in a process we call metamorphism.
So there was some recrystallization
in an event called the Penokee orogeny, okay,
at about 1,830 million, 1.83 million years ago.
And then, another period of erosion.
So we lost some of that geologic record.
And then the next event that created rock
was another few hundred million years later.
Oh, so we have the development
of another unconformity there.
And then a big gap in time,
many hundreds of millions of years go by,
and then the next event
is the third in our formation of bedrock units here,
and that is huge eruptions.
All right, and this is what we call the Midcontinent Rift.
So, North America, the small North American continent
that was growing at the time
actually started to split open
in this great big split of volcanoes
that we call the Midcontinent Rift,
and it was about a 20 million year period or so
of lots of volcanic eruptions.
It was estimated that three million cubic kilometers
of magma was produced along the Midcontinent Rift.
That's a lot of magma.
At times, the lava flows spread out across the Earth
and basically repaved the Earth's surface with black lava,
the rock that became the rock basalt.
And this is well-preserved
in the western Lake Superior region
in Wisconsin and Michigan and Minnesota.
So lots and lots, miles and miles thickness of
basalt lava flows.
You can see that is actually those ropes right there.
We call those pahoehoe ropes,
beautiful Hawaiian name for these ropey lava flow tops.
So that's a lava flow,
and then this is the base of the next lava flow up,
so lava flows piled up and piled up, miles thick.
And that event is also very nicely dated,
and then it crystallized to make the basalt.
This took place 1.1 billion years ago,
the Midcontinent Rift.
So then we've got the 1.85 and the 2.7 billion year,
those are the three, basically, the three packages
of rocks within the Penokee Range.
But when the Midcontinent Rift,
when the volcanoes died down,
then what happened is the volcanoes were eroded,
and they were basically buried in their own debris.
So we have gravel, and there's the,
what's called the Copper Harbor Conglomerate
is a layer that sits right above the lava flows,
and you can see the gravel in there.
This is a really very photogenic rock as well
because it's like rock within rock, right, conglomerate.
So you get these rounded pieces,
and those are all volcanic pieces, which is interesting.
So, clearly, it had to be deposited on the side of a volcano
because all of the pieces are volcanic.
Yeah, and you know what?
When that rock is now getting eroded,
those pieces will pop out, right,
and now it's a pebble with the shape that it had
attained a billion years ago,
which is kind of an interesting thing to inherit.
The conglomerates were buried in sandstone,
and these are the great big sheets of sandstone
that exist in the Bayfield Peninsula
and the Apostle Islands if you've been up there.
And the sea caves have,
the ice caves have recently become discovered
and become very popular.
And those are in the sandstone.
That's Lake Superior, [clears throat] excuse me,
frozen Lake Superior.
And those are the sandstones
that sit above the Midcontinent Rift rocks.
Okay, so there it is, there's the sandstone,
and that's our package of the rocks, okay.
The resistant layers,
the part that's gonna be important here,
is that the resistant layers are the ironwood iron formation
and then those lava flows.
So, in recent time, when we bring this to the recent,
those are gonna end up being the Penokee Ridge.
So then, right after the Midcontinent Rift,
the whole area got compressed in a great big tectonic vice
as continents ran into North America and closed that rift,
and the whole thing got tipped and folded
into a great big U shape like this,
and basically the U shape is Wisconsin on the south side
and Minnesota on the north side.
So the western Lake Superior region is basically a canoe.
It's like the gunnels of the canoe
are the hard edges of Wisconsin and Minnesota like that.
So this is the southern edge of that canoe.
Okay, those are the bedrock units,
and then we have an even bigger gap in time
when there is a long period of erosion.
Probably there were,
sea level rose and deposited rock upon it,
but it has also been, those have also been eroded away.
So we skip to relatively recent geologic time,
and this is what it looked like
probably a few million years ago, not billion,
a few million years ago when the climate started to change,
and ice advanced out of the north
and overrode the Penokee Range
and scraped off any soft rock off of the top.
And then, when it melted back,
left a mantle draped over there of rock,
I mean, of sediment, okay,
all kinds of glacial deposits laid in there,
on top of it, a relatively thin veneer,
some places a few hundred feet thick.
But on the Penokee Ridge itself, the two ridges,
this right here is the ironwood ridge,
the hard ironwood ridge,
and that is the basalt ridge of the Midcontinent Rift.
So those are the two hard ridges,
and the glacial deposits are relatively thin
up there, thin soils.
There's a lot of rock exposed
right along the top of those two ridges.
Okay, so there's the glacial till.
That's the stuff that is just dumped
by a glacier when it melts.
So there's a mantle of till, and then at the very top,
you can see the soils that have developed on top of that.
There's one more, okay, and there it is,
the hummocky topography of classic [clears throat]
glacial deposits that surround the Penokee Ridge.
Okay, one more event, and that was
as the glaciers were melting out of the Penokee region
for the last time,
there was a large lake there.
That was in the western Lake Superior basin.
We call it Glacial Lake Duluth, right,
and the water level was about 500 feet
above the current Lake Superior water level,
and it deposited lots of clay.
So the north part of the Penokees,
going towards Lake Superior,
is the Lake Superior clay plain we call it.
Lots of red clay deposited in that glacial lake there,
which, of course, controls the soil
and the way the water moves off the landscape today.
So there it is.
There's the geologic cross-section of the Penokee Range.
We did our quick tour through geologic time,
and you can see in the south, these are the old rocks,
the 2.7 billion year old package,
the ironwood package here.
The 1.85, that meteorite impact layer, would be in there.
This is the Midcontinent Rift volcanic rocks.
And then we've got the whole, oh, these are the sandstones.
And then we've got the whole thing
draped in glacial deposits like that,
with the two hard ridges standing up,
making the Penokee Range.
So that's the story.
Now, why does it matter?
Why do we care about this?
Why do we care what the geology is under our feet?
And the first thing is resources.
As I mentioned, minerals, energy, water, we all use that.
Our society uses lots of it,
and we need to understand those resources.
Another thing is the hazards,
and hazards associated with resource use,
but also the hazards that come from
just living on this crazy dynamic planet.
And then, the last thing, as I mentioned, is understanding,
And it enriches your life to understand your surroundings.
And I'm gonna show you some of the reasons why.
First is resources.
Metals, particularly.
If you're gonna talk about the Penokee Range,
you need to talk about metals.
And that's my kitchen stove, all right,
with a lot of iron and there's a lot of iron there.
There's stainless steel,
there's high carbon steel, there's cast iron,
and I also turned all the burners on
so you can see I'm using more natural resources there.
We've got some propane under the steel there.
Okay, and all of that comes out of the Earth, right.
All of our mineral resources, most of our energy,
all of our water is somehow related to geologic processes.
So first let's take a look at the Penokee Range,
what's in there, okay, the ancient gneiss.
That's our friend the ancient gneiss there,
the 2.7 billion year old rock.
There is a small amount of gold here and there,
and people have been looking for gold
in those rocks for a long time.
Nobody's made a lot of money at it,
but people continue to look.
And I'm sure that they'll be looking for a long time
because there's just enough to keep people interested.
Maybe more, okay, who knows?
And then, of course, we have the banded iron formation,
the ironwood iron formation,
which is, as I mentioned, 700 feet thick
with lots of magnetite in there.
There is a lot of iron there.
It is estimated that the ironwood iron formation
contains about 2.7 billion tons of economic,
depending upon what the economics are, of ore, of iron ore.
That's a huge deposit.
Okay, it is part of the iron ranges.
It's one of the eight iron ranges
in the western Lake Superior region.
And most of the iron used in the United States
has been mined out of the Lake Superior iron formations.
The Mesabi is the big one.
That's like 60% of all the iron used in the United States
has come out of the Mesabi Range.
Here's the Gogebic/Penokee Range down here,
which is inactive now.
And then there are two mines
still operating over in the Marquette Range.
All of these rocks are related.
They were all deposited in that shallow basin
that I talked about, and they all have that,
or most of them anyway,
have that impact layer right at the top.
So there has been mining
in the Gogebic-Penokee in the past.
There was, between 1880s and the 1960s,
there was 325 million tons of iron ore removed,
mostly from underground mines,
mostly high-grade, soft, natural ores,
okay, which was mostly,
the big pieces of it anyway were mined out,
and what remains is the hard rock,
okay, which is called the taconite.
Taconite is banded iron formation
that has an especially large amount of iron in it.
So, less quartz and more of the magnetite
or the mineral hematite.
And there's still a lot of it there.
So there is still interest
in mining in the Penokee Range, as you know.
There was a company interested in mining it in the past,
and the price of iron ore is low now,
but who knows what will happen in the future?
There's still a lot of iron in the ground there,
and there may continue to be interest in mining
in the Penokees for the iron ore.
And if we're gonna talk about that,
then we also need to talk about
the hazards associated with potentially mining
or the mining that has gone on there in the past.
Hazards and environmental issues, okay,
because all resource extraction and use
has some environmental impact.
We need to understand the resource.
We need to understand the mining,
We need to understand the extraction
so that we can minimize the amount
of environmental impact that we have.
Okay, remember this one,
going back 1.1 billion years ago
when we had the Midcontinent Rift and that
three million cubic kilometers of magma
coming up through the Earth?
Well, when it did, it came up through
all these preexisting layers.
So there's the ironwood iron formation,
and we've got lots of lava coming up through it
and it heated it.
So, in some places, the iron formation
and all the other preexisting rocks got very hot
and hot enough to change,
and new minerals actually grew during this
what we call a metamorphic process,
a recrystallization because of the heat.
So what we need to do
is we need to take a look at these places where,
this is the ironwood,
where the ironwood was heated up by
being in contact with the magma, or close contact,
and what we see are some different minerals.
In certain places, where the conditions were correct
and the previous mineralogy was such
that it could make these new minerals when it got heated,
we have that brown layer in there.
Okay, that brown layer right there
has got a different mineral in it.
It's not all quartz, okay.
You can see it here, this brown mineral.
This is just taken under a stereo microscope.
And what I have here is that, right there, is my 0.5
millimeter pencil lead for scale.
So that's my pencil.
And you can see this vein right here of this brown mineral.
It's elongate brown mineral.
It's an amphibole mineral.
It's a group of minerals, all right.
And the concern here is that,
well, there are lots of long, skinny minerals, okay.
The concern is, if they're a certain
size and a certain shape and a certain composition, okay,
they can be very big hazards if inhaled,
okay, or ingested,
and basically what we're talking about here is asbestos.
And so we need to understand this mineral right here.
So, next what we're gonna do
is we're gonna take a look down the petrographic microscope.
And that means that we're gonna shine light
through the rock, a very thin slice of the rock,
and look at that through the microscope,
and that's what we see, okay.
First, let me see here, I want to show you,
we're gonna be talking about scale,
geology, we talk about different time scales.
We gotta stretch our mind into different time scales.
We also need to think about different scales of geography.
So we have to think about different spatial scales as well.
All right, and this, right here,
and we're about to zoom in on this mineral.
So I want to talk a little bit about scale.
There's my pencil lead right there.
So that's a 0.5 millimeter pencil lead
under my optical microscope.
And that is
a 250 micron bar.
500 microns is 0.5 millimeters.
So that's 250 microns.
And what I'm gonna do in these next slides
is I'm gonna take that scale bar
and stretch it out appropriately
or skinny it down appropriate to scale.
So, there's the,
the 250 micron scale right there,
and this is the microscopic view looking through the rock.
The black here is the mineral magnetite.
That's the one that the magnet sticks on.
A lot of this is the mineral quartz.
And then you see these little, brown,
grayish-brown fibers in there.
That's the amphibole,
and you can see that they are long and skinny
little needles of stuff.
And so let us go, okay, there's for scale.
For comparison, a human hair,
typical human hair from your head, is about a 100 microns.
So a 100 microns would be like that.
Okay, so there's our 250 micron bar.
All right, and in some places,
the rock is mostly this mineral,
this amphibole mineral here.
And you can see the pattern.
It's this crazy pattern.
We've been calling them bow ties
It's like a three-dimensional bow tie,
this fan of crystals that comes out like this.
And in some places, we get fans
going all different directions,
bow ties in all different directions,
and the rock is mostly, you know,
the majority of the rock is this amphibole mineral.
There it is,
same view but on the right, what I have here
is I've got the polarizing filter in there
so that helps us identify the mineral.
It is definitely one of the amphibole minerals, okay.
There is, okay, one more view of it here.
All right, what we're gonna do next
is we're gonna zoom in on the end of this,
these fibrous ends of that little bow tie right there.
Okay, and that's about as the highest magnification
I can go with my optical microscope.
Okay, there's our 250 micron bar scale,
and you can see that these things are really very thin.
So the concern here is that if these things
get lodged in your lungs,
if they become airborne and they get lodged in your lungs,
they stay there indefinitely
and eventually in some people they cause disease.
And what we're talking about here is mesothelioma,
which is a type of lung cancer that's very specific to,
it seems to be very specific to exposure
to these amphibole minerals,
these little skinny fibers of the amphibole minerals.
So there it is.
It's clearly a long, skinny amphibole there,
but to measure them
accurately, we need to use electrons.
So I put some of these rocks under electron beams
in the Microbeam Laboratory at the
US Geological Survey in Denver.
Okay, so that's one of the rocks
in the scanning electron microscope.
And, okay, so the scanning electron microscope
is an amazing tool, all right,
because you can just zoom in and in and in
and just see a whole another universe
as you go into things.
So that's what we're about to do.
Here's our bar scale, you see the bar scale down here?
That's 200 microns.
And we'll zoom in to this.
Okay, that's one of the bow ties there you can see.
And we'll zoom in, there's a 50 micron.
We'll zoom in again, like this, 20 micron.
We'll zoom in again, like that, 10 microns.
And you can still see that it's the skinny fibers,
and you can start to see the cross-section,
typical cross-section of the amphibole minerals as well.
One more, like that, five microns.
Okay, so,
I mentioned that it has to be a certain size
and shape and composition.
All right, so next we need to compare this
to what does it mean to be asbestiform.
Abestiform is the shape that is especially dangerous.
Okay, 20 to one aspect ratio.
In other words, it has to be 20 times
longer than it is wide.
All right, it has to be less than 5.5 microns wide.
It has to have two of the following,
parallel fibers, splayed ends,
matted, curved masses,
I mean, matted masses and curved fibers,
and we have all of those things.
So the next question is what mineral is it?
Most asbestos, asbestos is a commercial term,
okay, so it describes a commercial product, all right.
So, most asbestos
is the mineral serpentine,
and that's most commercial grade asbestos
into that it appears to be less dangerous.
The dangerous ones are the amphibole asbestos.
And these are the amphibole minerals
that are commonly asbestiform
and have been used as commercial asbestos products.
What we're talking about here is the mineral grunerite.
So this is asbestiform grunerite
in quite large quantities.
And it is known to be a very serious health hazard
when it is this composition and it is this shape.
All right, just one more, I'm gonna show you these.
This is an especially photogenic one.
Just amazing stuff, we're gonna zoom into this,
50 microns, 10 microns, and then we'll zoom in.
The 10-micron scale, is that it?
Okay, yeah, that's it.
Okay, so, this is a serious hazard.
Every place where rocks rich in this mineral
have been mined, people have died of mesothelioma.
So this is a serious hazard here.
And in some places in the Penokee Range,
there's quite a lot of it.
There are also places where there isn't any
because it didn't get hot enough.
So, that stuff, it's not soluble.
It stays in the rock, okay, unless that rock is disturbed.
And, yeah, so there it is.
It's in the rock.
But a more immediate question,
all right, so that has, you know, big,
it has to be considered if we're gonna
start mining that rock, okay.
But a more immediate concern is, is it in the soil?
Is places where the rock is at the surface
and it has been disturbed.
So, I took some place on that layer
that I knew was rich in the grunerite,
the asbestiform grunerite.
I took just some rubble there
sitting on the road, all right,
and I put that in the electron beam.
And this is a sand grain right back here.
It's actually a magnetite sand grain,
and you can see sitting on there is a curved fiber.
And we'll zoom in on that.
So, yes, indeed, there is some loose at the surface.
In at least one place in the Penokee Range
there is asbestos, okay,
or asbestiform grunerite, all right, in the rock.
So the United States Geological Survey is continuing
to do studies there on the bedrock, which is very important.
That study is going on right now.
And I've given them all of my information,
and then I am also continuing,
actually just starting,
a study on the soils to see how widespread is it,
and is it a health concern just like being out there
on some of those dusty roads.
Okay, so that's something we need to know.
All right, okay, the amphibole,
the asbestiform amphibole is certainly a concern,
but there are also other concerns
when it comes to mining in the Penokees
in the ironwood iron formation.
And that is, okay, this is ironwood.
There's magnetite right there.
There's some quartz,
and that right there, that's the mineral pyrite
And pyrite is iron sulfide,
which isn't a problem when it's in the rock, like that.
But when that gets ground up
and comes in contact with water and oxygen,
it can make acid rock drainage, okay,
which if done on a large scale
can become acid mine drainage.
And it's, again, it's one of these things
where we need to understand the resource.
We need to understand the rock to see
and understand what would happen to it if it were dug up,
and would it create acid mine drainage or not?
And it's a complicated question.
I mean, it's like the geochemistry of waste rock piles
is a complicated thing.
But there certainly is pyrite there,
and so that's another thing that needs to be understood.
Okay, and iron isn't the only resource in the Penokees.
There are also other resources.
It's a water-rich region,
33 inches of rain a year, shallow bedrock, lots of run-off.
So we've got some beautiful rivers.
This is actually at Copper Falls State Park,
where, basically, the Bad River
and the Tyler Forks River meet head on
right there in Copper Falls State Park.
It's a beautiful beautiful spot.
Okay, and then another resource up there
is just the vast wilderness, okay,
lots of forested land,
okay, wide open land,
which is an important resource in itself.
And then downstream at the end of the Bad River,
is the great big Bad River Slough and Kakagon Slough,
which is some of the richest wild rice beds
in the world, probably,
certainly in the Lake Superior region.
Okay, so other resources.
So here we have it.
We have resource, you know, we all depend on resources.
We all use resources, and we have these competing needs.
Right, we need iron.
We need clean water.
We need clean air.
We need wilderness space.
We need forest products.
We have all of these competing demands,
and we have an increasing population, all right,
and a population of people
that is using more and more resources
as the standard of living changes, okay.
So these are complicated issues, all right.
And so many aspects of our society
come together around resource issues, all right
And more and more they're becoming global,
complicated global issues, okay.
And we need to do this right, all right.
We need to supply resources,
and we need to protect human health,
and we need to protect the environment
for future generations, okay.
So one of the things that needs to be done
is we need to understand it, right.
We need to understand the resources.
We now have good enough science that we can understand
what is going on in those ecosystems,
what's going on with those rock systems
and the geochemistry of the system, you know,
and we need to understand that
and base our decisions about resource use on sound science.
And we need to have the guts to do it right, you know.
If we're going to extract these resources,
we need to have the regulations and we need to have,
and we need to enforce those regulations and do it right.
And then we also need to, in some places, say,
you know what, this is an environment
that is too susceptible, okay, to damage.
And it's like no matter what the resource is,
the other resources other than the metal
are actually more important, okay.
And so we're gonna balance our resource use
and make wise decisions.
That's what we need to do, okay.
Okay, and then we come to the last part,
and that is why it's important
to understand the geology of any region,
including the Penokees,
and that is to understand our surroundings.
And this is probably my favorite part
of studying geology and sharing it with people,
and that is to,
just the enrichment that comes from
understanding the rocks
and understanding your relationship to them, all right.
And, I mean, just think about what we have looked
and what we have seen in the rocks today, okay.
Submarine volcanic eruptions.
The evolution of the ocean and atmosphere system.
Meteorite impact that changed the world.
Volcanic eruptions that repaved the Earth's surface.
Glaciation that scraped off and
buried the whole landscape in a mile of ice.
You know, it all happened right there.
You know, it's like, that's great.
You couldn't even make that stuff up, you know.
It's such a great story.
And, you know, there it is.
You just, you read it in the rock, you know,
and that's a beautiful thing right there, okay.
It is also beautiful in itself, okay, just to see it.
And what I like to say is that
the more you understand something, the more you see in it,
and the more you see in it, the more beautiful it becomes.
These are kind of some kyanite crystals,
the mineral kyanite, not really common but
great geologic story in the kyanite
that I pulled out of some rocks
just a little bit to the east of the Penokee Range,
sort of at the end,
the east end of the Penokee/Gogebic Range.
Okay, some beautiful kyanite crystals
under the microscope, yeah.
Okay, and then another thing is about the connections, okay,
the connections between different parts of an ecosystem,
different parts of the natural systems.
You know, there it is.
That's the
loamy tilled soil of the Penokees.
And you think about what that, what its history is.
You know, it was derived from this long history, you know,
and here it is at Earth's surface in a different role.
You know, it is now part of the Earth.
It's part of the atmosphere.
It's part of the hydrosphere,
It's part of the biosphere, you know.
It all comes together there in soils, okay.
And we are connected to all of this through the soil,
right, because, I mean, we eat the food,
and we basically come from the Earth
through the soil and water,
and that's a cool thing to understand right there,
right, where you come from, all right
And then also that everything, you know,
this is this whole story, you know.
You look at the geology of a place,
you look at what's going on in any ecosystem,
and basically what's going on there
has to do with the geologic history.
What are the materials that were left there
by this long history of change through billions of years?
What is the current climate?
You know, the 33 inches of rain
and the 43 degree annual temperature, you know.
And what is recent disturbance?
So, the history, the
current climate, and the disturbance,
pretty much everything comes back to that, right.
And, yeah, so this is what we get in the Penokee Range,
and this is just sort of the last part of the story,
starting from billions of years ago.
And it is an ongoing story.
So we think about geology just in the past, right,
but really the past sort of spiraling up to today,
you know, it's a continuing story.
So what we have right now is like one glimpse,
one short little glimpse of geologic time, but it continues.
It goes on and on.
And you know what?
It's fun to see that story.
It's fun to know your place in that.
And, you know, it's an honor
to be able to read the rock and to share it.
Thanks.
[applause]