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Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,CH 1.2: MN Geological History\Nhttps://youtu.be/T5pfp8z2Cqw\N>[NICOLE KJERSTEN] So for us \Nto understand the landscape 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,of Minnesota as we know it today, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,we need to understand where it came from.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And to understand that, \Nwe have to look back 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to what's happened in this space \Nsince the beginning of Earth.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Earth was formed about 4.6 billion\N(that's billion with a B) years ago, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and a lot has happened since then.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And so we will briefly go over \Nthe geological history of Minnesota.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,If you're interested in this topic in depth, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,I would encourage you \Nto take a geology course.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,All we need to know is some context 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,for how Minnesota got to be \Nwhat Minnesota is today 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,because we know the landscape \Nis so tightly connected 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to the life that lives in Minnesota.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, so the Earth, the Earth crust, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,so that's the outer layer of Earth \Nthat's made of rock and dirt and such.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It has many, many layers, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,with the oldest layers being \Nat the bottom of the crust 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and the youngest layers being at the top.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And the observation \Nthat Earth has these layers 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and that we find different types \Nof fossils within these layers, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and that there are different \Nelements within those fossils 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or within those rocks \Nthat change over time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The isotopic ratios change over time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,From all of that information, \Nwe can date the Earth.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And we've been able to date the Earth
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,such that we hypothesize that it was \Nformed about 4.6 billion years ago.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And by looking at these different layers \Nand dating these different layers, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,we have divided the Earth \Ninto four major time periods.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And what I want to do is, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,I just want to walk through \Neach of those time periods 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and provide a little bit more context \Nfor what was happening 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,in the landscape that we know of as Minnesota during those different times.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So we're going to start\Nin the Precambrian era.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So this is the oldest and longest\Nperiod of geological time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It went from when the Earth \Nwas formed 4.6 billion years ago 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to about 600 million \N(million, with an M) years ago.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And during this time across the globe 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is when we saw the formation \Nof oceans and continents.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And I should say, at this point, \Nwhen we're talking about continents, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,we're talking about one giant conglomeration\Nof all the continents that we know today 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that was called Pangea, \Njust one giant landmass.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,During this time, there was \Nlots of volcanic activity, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,so that's putting a lot of different elements into the atmosphere,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and volcanoes are responsible \Nfor forming bedrock 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and the different types \Nof rocks that we see on Earth.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Not all of them, but a good deal of them.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And we know that at this point in time, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Minnesota actually --or what \Nwe know of today as Minnesota  --
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,was covered by shallow seas.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So that is the reason we have a lot of \Niron deposits in northeastern Minnesota 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and why we mine for iron in that area.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This is a time period when we also \Nstart to see the earliest life form, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,even though if we look at \Nthis figure here, the fossil record, \Nthere's not many fossils \Nthat were preserved from that time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay. But there are rocks and there \Nare two types of rock formations 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that I want you to know about\Nthat are present here in Minnesota 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that originated during this Precambrian period.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The first is the Morten gneiss and then the second is the Canadian shield.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Let's talk about the Morton Gneiss first.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This is the oldest type of rock \Nthat is found in Minnesota 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and it is located along \Nthe Minnesota River Valley 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,kind of near Granite Falls, \Nif you know where that is.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So here's a map of Minnesota, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and this orange rusty color 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is shading in the areas where you \Ncan find Morton Gneiss type of rock.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Nes Nest I think I'm pronouncing that correctly.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,One of those ways is correct, at least.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The second type of rock is the Canadian Shield.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And this is really just a massive layer of rock 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that is present not only in Minnesota, \Nbut also a good portion of Canada.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And so here's a map of the northern portion of North America, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and all of this area shaded in purple 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,represents the rock that makes up \Nthe Canadian Shield.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And if you've gone into central northern \NMinnesota or northeastern Minnesota, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you can see this exposed rock in various areas \Nsuch as the Boundary Waters Canoe Area.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,These exposed rocks are actually have been\Naround for millions to billions of years.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And you can also see it along \Nthese cliffs in the North Shore.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, so back to our timeline, \Nwe're now going to move to the Paleozoic era.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And this was a time period \N600-225 million years ago.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And believe it or not, \Nat this point in time, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Minnesota is actually thought \Nto be located near the equator.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So remember, when all the continents are mushed together in Pangea 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,before plate tectonic separated them \Ninto the locations that they are today, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,um, No everything is in the place that it is today.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Not everything was in the place that it is today.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And so Minnesota is actually \Nlocated near the equator, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,which means that there was a lot warmer temperatures, maybe more moisture.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And that is one of the reasons \Nwhy in the fossil record, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,we see evidence of tropical \Nand subtropical plants.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It's also important to note \Nthat there were continental seas 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that were present in Minnesota at this time, \Nwhich is why in the fossil record, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,we can see evidence of marine organisms being present in Minnesota, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,despite the fact that we \Ndon't have an ocean today.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, so the next time period \Nis the Mesozoic period.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This was 225 to 265 million years ago.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Again, we're still underwater.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,There's still continental seas \Ncovering at least portions of the state.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It's also when we see the first flowering plants, the first birds, the first mammals, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,even though this is sometimes referred to\Nas the period as the age of the dinosaurs.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So dinosaurs tend to be more \Nprevalent than mammals at this point.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And it's also what's happening with where Minnesota is located on the globe is, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,it is starting to get pulled\Nmore northwards, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and so it's getting pulled towards the poles, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and it's starting to experience \Na cooler and somewhat drier climate 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,than what it did when it was near the equator.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And here's just an example of some \Nof the fossils that have been found 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,in Minnesota during this time period 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,such as small, small vertebrate \Nanimals and flowering plants 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that have been preserved \Nin the different layers of rocks 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that have been dated to the Mesozoic.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, and then our final \Ntime period is the Cenozoic.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,That is from 65 million years ago to present.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And this is known as the age of mammals, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,where we see the dinosaurs have died out \Nand the mammals are starting to rule.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It's also a period where \Nthere's intense glaciation, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and so Minnesota has made it to where \Nit presently is located on the globe.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And not only did Minnesota \Nsee a cooling period, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,but there is just a large \Ncooling period across the globe, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,which resulted in glacier formations.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And glaciers had a huge impact \Non the present landscape, 
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,which we'll learn more about in the next lecture.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Which we will get to after I wrap this up \Nand say thank you for your attention.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And like I've already previewed, \Nwe will talk about glaciers next.\N