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

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of Minnesota as we know it today,

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we need to understand where it came from.

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And to understand that, [br]we have to look back

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

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

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and a lot has happened since then.

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

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If you're interested in this topic in depth,

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I would encourage you [br]to take a geology course.

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All we need to know is some context

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for how Minnesota got to be [br]what Minnesota is today

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because we know the landscape [br]is so tightly connected

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to the life that lives in Minnesota.

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Okay, so the Earth, the Earth crust,

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so that's the outer layer of Earth [br]that's made of rock and dirt and such.

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It has many, many layers,

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with the oldest layers being [br]at the bottom of the crust

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and the youngest layers being at the top.

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And the observation [br]that Earth has these layers

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

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and that there are different [br]elements within those fossils

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or within those rocks [br]that change over time.

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The isotopic ratios change over time.

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From all of that information, [br]we can date the Earth.

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And we've been able to date the Earth

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

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And by looking at these different layers [br]and dating these different layers,

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we have divided the Earth [br]into four major time periods.

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And what I want to do is,

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I just want to walk through [br]each of those time periods

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and provide a little bit more context [br]for what was happening

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

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

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

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

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

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And during this time across the globe

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is when we saw the formation [br]of oceans and continents.

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

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we're talking about one giant conglomeration[br]of all the continents that we know today

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that was called Pangea, [br]just one giant landmass.

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During this time, there was [br]lots of volcanic activity,

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

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and volcanoes are responsible [br]for forming bedrock

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

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

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And we know that at this point in time,

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Minnesota actually --or what [br]we know of today as Minnesota --

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was covered by shallow seas.

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

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and why we mine for iron in that area.

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

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

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

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

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

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that originated during [br]this Precambrian period.

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The first is the Morten gneiss and [br]then the second is the Canadian Shield.

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Let's talk about the Morton Gneiss first.

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This is the oldest type of rock [br]that is found in Minnesota

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and it is located along [br]the Minnesota River Valley

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

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So here's a map of Minnesota,

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and this orange rusty color

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

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Nes Nest I think I'm pronouncing that correctly.

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One of those ways is correct, at least.

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The second type of rock[br]is the Canadian Shield.

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And this is really just [br]a massive layer of rock

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

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

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and all of this area shaded in purple

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represents the rock that makes up [br]the Canadian Shield.

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

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you can see this exposed rock

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in various areas such as [br]the Boundary Waters Canoe Area.

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

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

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Okay, so back to our timeline,

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we're now going to move [br]to the Paleozoic era.

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And this was a time period [br]600-225 million years ago.

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And believe it or not, [br]at this point in time,

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Minnesota is actually thought [br]to be located near the equator.

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

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

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um, No everything is in the place that it is today.

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

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And so Minnesota is actually [br]located near the equator,

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

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

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we see evidence of tropical [br]and subtropical plants.

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

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that were present in Minnesota at this time,

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which is why in the fossil record,

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

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

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Okay, so the next time period [br]is the Mesozoic period.

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This was 225 to 265 million years ago.

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Again, we're still underwater.

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

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

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the first birds, the first mammals,

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

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

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And it's also what's happening with [br]where Minnesota is located on the globe is,

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it is starting to get pulled[br]more northwards,

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and so it's getting pulled towards the poles,

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

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than what it did when it was near the equator.

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

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in Minnesota during this time period

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such as small, small vertebrate [br]animals and flowering plants

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that have been preserved [br]in the different layers of rocks

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that have been dated to the Mesozoic.

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

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That is from 65 million years ago to present.

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And this is known as the age of mammals,

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

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It's also a period where [br]there's intense glaciation,

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

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And not only did Minnesota [br]see a cooling period,

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but there is just a large [br]cooling period across the globe,

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which resulted in glacier formations.

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And glaciers had a huge impact [br]on the present landscape,

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

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

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