>[NICOLE KJERSTEN] So for us 
to understand the landscape

of Minnesota as we know it today,

we need to understand where it came from.

And to understand that, 
we have to look back

to what's happened in this space 
since the beginning of Earth.

Earth was formed about 4.6 billion
(that's billion with a B) years ago,

and a lot has happened since then.

And so we will briefly go over 
the geological history of Minnesota.

If you're interested 
in this topic in depth,

I would encourage you 
to take a geology course.

All we need to know is some context

for how Minnesota got to be 
what Minnesota is today

because we know the landscape 
is so tightly connected

to the life that lives in Minnesota.

Okay, so the Earth, the Earth crust --

so that's the outer layer of Earth 
that's made of rock and dirt and such --

it has many, many layers,

with the oldest layers being 
at the bottom of the crust

and the youngest layers being at the top.

And the observation 
that Earth has these layers

and that we find different types 
of fossils within these layers,

and that there are different 
elements within those fossils

or within those rocks 
that change over time --

the isotopic ratios change over time --

from all of that information, 
we can date the Earth.

And we've been able to date the Earth

such that we hypothesize that it was 
formed about 4.6 billion years ago.

And by looking at these different layers 
and dating these different layers,

we have divided the Earth 
into four major time periods.

And what I want to do is,

I just want to walk through 
each of those time periods

and provide a little bit more context 
for what was happening

in the landscape that we know of 
as Minnesota during those different times.

So we're going to start
in the Precambrian era.

So this is the oldest and longest
period of geological time.

It went from when the Earth 
was formed 4.6 billion years ago

to about 600 million 
(million, with an M) years ago.

And during this time across the globe

is when we saw the formation 
of oceans and continents.

And I should say, at this point, 
when we're talking about continents,

we're talking about 
one giant conglomeration

of all the continents 
that we know today

that was called Pangea, 
just one giant landmass.

During this time, there was 
lots of volcanic activity,

so that's putting a lot of different
elements into the atmosphere,

and volcanoes are responsible 
for forming bedrock

and the different types 
of rocks that we see on Earth.

Not all of them, but a good deal of them.

And we know that at this point in time,

Minnesota actually --or what 
we know of today as Minnesota --

was covered by shallow seas.

So that is the reason we have a lot of 
iron deposits in northeastern Minnesota

and why we mine for iron in that area.

This is a time period when we also 
start to see the earliest life form,

even though if we look at 
this figure here, the fossil record,

there's not many fossils 
that were preserved from that time.

Okay. But there are rocks and there 
are two types of rock formations

that I want you to know about
that are present here in Minnesota

that originated during 
this Precambrian period.

The first is the Morton Gneiss and 
then the second is the Canadian Shield.

Let's talk about the Morton Gneiss first.

This is the oldest type of rock 
that is found in Minnesota

and it is located along 
the Minnesota River Valley

kind of near Granite Falls, 
if you know where that is.

So here's a map of Minnesota,

and this orange rusty color

is shading in the areas where you 
can find Morton Gneiss type of rock.

[pronounced] "Neese"? "Ness"?
I think I'm pronouncing that correctly.

(One of those ways is correct, at least.)

The second type of rock
is the Canadian Shield,

and this is really just 
a massive layer of rock

that is present not only in Minnesota, 
but also a good portion of Canada.

And so here's a map of the 
northern portion of North America,

and all of this area shaded in purple

represents the rock that makes up 
the Canadian Shield.

And if you've gone into central northern 
Minnesota or northeastern Minnesota,

you can see this exposed rock

in various areas such as 
the Boundary Waters Canoe Area.

These exposed rocks are actually have been
around for millions to billions of years.

And you can also see it along 
these cliffs in the North Shore.

Okay, so back to our timeline,

we're now going to move 
to the Paleozoic era.

And this was a time period 
600 to 225 million years ago.

And believe it or not, 
at this point in time,

Minnesota is actually thought 
to be located near the equator.

So remember, when all the continents
are mushed together in Pangea

before plate tectonic separated them 
into the locations that they are today,

not everything is in 
the place that it is today

[corrects self] Not everything 
was in the place that it is today.

And so Minnesota is actually 
located near the equator,

which means that there was a lot warmer
temperatures, maybe more moisture.

And that is one of the reasons 
why in the fossil record,

we see evidence of tropical 
and subtropical plants.

It's also important to note 
that there were continental seas

that were present in Minnesota at this time,

which is why in the fossil record,

we can see evidence of marine 
organisms being present in Minnesota,

despite the fact that we 
don't have an ocean today.

Okay, so the next time period 
is the Mesozoic period.

This was between 225 
and 65 million years ago.

Again, we're still under water.

There's still continental seas 
covering at least portions of the state.

It's also when we see 
the first flowering plants,

the first birds, the first mammals,

even though this is sometimes referred to
as the period as the age of the dinosaurs.

So dinosaurs tend to be more 
prevalent than mammals at this point.

And it's also what's happening

with where Minnesota 
is located on the globe is,

it is starting to get pulled
more northwards,

and so it's getting pulled towards the poles,

and it's starting to experience 
a cooler and somewhat drier climate

than what it did when it was near the equator.

And here's just an example of some 
of the fossils that have been found

in Minnesota during this time period

such as small, small vertebrate 
animals and flowering plants

that have been preserved 
in the different layers of rocks

that have been dated to the Mesozoic.

Okay, and then our final 
time period is the Cenozoic.

That is from 65 million years ago to present.

And this is known as the age of mammals,

where we see the dinosaurs have died out 
and the mammals are starting to rule.

It's also a period where 
there's intense glaciation,

and so Minnesota has made it to where 
it presently is located on the globe.

And not only did Minnesota 
see a cooling period,

but there was just a large 
cooling period across the globe,

which resulted in glacier formations.

And glaciers had a huge impact 
on the present landscape,

which we'll learn more
about in the next lecture.

Which we will get to after I wrap this up 
and say thank you for your attention.

And like I've already previewed, 
we will talk about glaciers next.