[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.87,0:00:05.70,Default,,0000,0000,0000,,>[NICOLE KJERSTEN] So for us \Nto understand the landscape
Dialogue: 0,0:00:05.70,0:00:08.27,Default,,0000,0000,0000,,of Minnesota as we know it today,
Dialogue: 0,0:00:08.27,0:00:10.98,Default,,0000,0000,0000,,we need to understand where it came from.
Dialogue: 0,0:00:10.98,0:00:14.38,Default,,0000,0000,0000,,And to understand that, \Nwe have to look back
Dialogue: 0,0:00:14.38,0:00:19.63,Default,,0000,0000,0000,,to what's happened in this space \Nsince the beginning of Earth.
Dialogue: 0,0:00:19.63,0:00:26.13,Default,,0000,0000,0000,,Earth was formed about 4.6 billion\N(that's billion with a B) years ago,
Dialogue: 0,0:00:26.13,0:00:29.58,Default,,0000,0000,0000,,and a lot has happened since then.
Dialogue: 0,0:00:29.58,0:00:36.75,Default,,0000,0000,0000,,And so we will briefly go over \Nthe geological history of Minnesota.
Dialogue: 0,0:00:36.75,0:00:39.75,Default,,0000,0000,0000,,If you're interested \Nin this topic in depth,
Dialogue: 0,0:00:39.75,0:00:42.93,Default,,0000,0000,0000,,I would encourage you \Nto take a geology course.
Dialogue: 0,0:00:42.93,0:00:45.05,Default,,0000,0000,0000,,All we need to know is some context
Dialogue: 0,0:00:45.05,0:00:49.62,Default,,0000,0000,0000,,for how Minnesota got to be \Nwhat Minnesota is today
Dialogue: 0,0:00:49.62,0:00:53.63,Default,,0000,0000,0000,,because we know the landscape \Nis so tightly connected
Dialogue: 0,0:00:53.63,0:00:58.37,Default,,0000,0000,0000,,to the life that lives in Minnesota.
Dialogue: 0,0:00:58.37,0:01:03.56,Default,,0000,0000,0000,,Okay, so the Earth, the Earth crust --
Dialogue: 0,0:01:03.56,0:01:08.48,Default,,0000,0000,0000,,so that's the outer layer of Earth \Nthat's made of rock and dirt and such --
Dialogue: 0,0:01:08.48,0:01:10.68,Default,,0000,0000,0000,,it has many, many layers,
Dialogue: 0,0:01:10.68,0:01:14.35,Default,,0000,0000,0000,,with the oldest layers being \Nat the bottom of the crust
Dialogue: 0,0:01:14.35,0:01:17.27,Default,,0000,0000,0000,,and the youngest layers being at the top.
Dialogue: 0,0:01:17.27,0:01:20.56,Default,,0000,0000,0000,,And the observation \Nthat Earth has these layers
Dialogue: 0,0:01:20.56,0:01:26.16,Default,,0000,0000,0000,,and that we find different types \Nof fossils within these layers,
Dialogue: 0,0:01:26.16,0:01:31.22,Default,,0000,0000,0000,,and that there are different \Nelements within those fossils
Dialogue: 0,0:01:31.22,0:01:35.46,Default,,0000,0000,0000,,or within those rocks \Nthat change over time --
Dialogue: 0,0:01:35.46,0:01:40.32,Default,,0000,0000,0000,,the isotopic ratios change over time --
Dialogue: 0,0:01:40.32,0:01:45.23,Default,,0000,0000,0000,,from all of that information, \Nwe can date the Earth.
Dialogue: 0,0:01:45.23,0:01:47.97,Default,,0000,0000,0000,,And we've been able to date the Earth
Dialogue: 0,0:01:47.97,0:01:55.02,Default,,0000,0000,0000,,such that we hypothesize that it was \Nformed about 4.6 billion years ago.
Dialogue: 0,0:01:55.02,0:02:00.18,Default,,0000,0000,0000,,And by looking at these different layers \Nand dating these different layers,
Dialogue: 0,0:02:00.18,0:02:06.18,Default,,0000,0000,0000,,we have divided the Earth \Ninto four major time periods.
Dialogue: 0,0:02:06.18,0:02:07.40,Default,,0000,0000,0000,,And what I want to do is,
Dialogue: 0,0:02:07.40,0:02:09.98,Default,,0000,0000,0000,,I just want to walk through \Neach of those time periods
Dialogue: 0,0:02:09.98,0:02:13.33,Default,,0000,0000,0000,,and provide a little bit more context \Nfor what was happening
Dialogue: 0,0:02:13.33,0:02:19.56,Default,,0000,0000,0000,,in the landscape that we know of \Nas Minnesota during those different times.
Dialogue: 0,0:02:19.56,0:02:22.73,Default,,0000,0000,0000,,So we're going to start\Nin the Precambrian era.
Dialogue: 0,0:02:22.73,0:02:29.60,Default,,0000,0000,0000,,So this is the oldest and longest\Nperiod of geological time.
Dialogue: 0,0:02:29.60,0:02:35.97,Default,,0000,0000,0000,,It went from when the Earth \Nwas formed 4.6 billion years ago
Dialogue: 0,0:02:35.97,0:02:41.78,Default,,0000,0000,0000,,to about 600 million \N(million, with an M) years ago.
Dialogue: 0,0:02:41.78,0:02:45.48,Default,,0000,0000,0000,,And during this time across the globe
Dialogue: 0,0:02:45.48,0:02:49.12,Default,,0000,0000,0000,,is when we saw the formation \Nof oceans and continents.
Dialogue: 0,0:02:49.12,0:02:52.42,Default,,0000,0000,0000,,And I should say, at this point, \Nwhen we're talking about continents,
Dialogue: 0,0:02:52.42,0:02:55.09,Default,,0000,0000,0000,,we're talking about \None giant conglomeration
Dialogue: 0,0:02:55.09,0:02:57.83,Default,,0000,0000,0000,,of all the continents \Nthat we know today
Dialogue: 0,0:02:57.83,0:03:03.67,Default,,0000,0000,0000,,that was called Pangea, \Njust one giant landmass.
Dialogue: 0,0:03:05.05,0:03:08.30,Default,,0000,0000,0000,,During this time, there was \Nlots of volcanic activity,
Dialogue: 0,0:03:08.30,0:03:12.95,Default,,0000,0000,0000,,so that's putting a lot of different\Nelements into the atmosphere,
Dialogue: 0,0:03:12.95,0:03:17.19,Default,,0000,0000,0000,,and volcanoes are responsible \Nfor forming bedrock
Dialogue: 0,0:03:17.19,0:03:22.36,Default,,0000,0000,0000,,and the different types \Nof rocks that we see on Earth.
Dialogue: 0,0:03:22.36,0:03:25.38,Default,,0000,0000,0000,,Not all of them, but a good deal of them.
Dialogue: 0,0:03:25.38,0:03:29.13,Default,,0000,0000,0000,,And we know that at this point in time,
Dialogue: 0,0:03:29.13,0:03:33.15,Default,,0000,0000,0000,,Minnesota actually --or what \Nwe know of today as Minnesota --
Dialogue: 0,0:03:33.15,0:03:35.50,Default,,0000,0000,0000,,was covered by shallow seas.
Dialogue: 0,0:03:35.50,0:03:42.38,Default,,0000,0000,0000,,So that is the reason we have a lot of \Niron deposits in northeastern Minnesota
Dialogue: 0,0:03:42.38,0:03:48.42,Default,,0000,0000,0000,,and why we mine for iron in that area.
Dialogue: 0,0:03:48.42,0:03:53.60,Default,,0000,0000,0000,,This is a time period when we also \Nstart to see the earliest life form,
Dialogue: 0,0:03:53.60,0:03:57.51,Default,,0000,0000,0000,,even though if we look at \Nthis figure here, the fossil record,
Dialogue: 0,0:03:57.51,0:04:04.32,Default,,0000,0000,0000,,there's not many fossils \Nthat were preserved from that time.
Dialogue: 0,0:04:04.32,0:04:10.96,Default,,0000,0000,0000,,Okay. But there are rocks and there \Nare two types of rock formations
Dialogue: 0,0:04:10.96,0:04:15.51,Default,,0000,0000,0000,,that I want you to know about\Nthat are present here in Minnesota
Dialogue: 0,0:04:15.51,0:04:19.18,Default,,0000,0000,0000,,that originated during \Nthis Precambrian period.
Dialogue: 0,0:04:19.18,0:04:24.56,Default,,0000,0000,0000,,The first is the Morton Gneiss and \Nthen the second is the Canadian Shield.
Dialogue: 0,0:04:24.56,0:04:27.19,Default,,0000,0000,0000,,Let's talk about the Morton Gneiss first.
Dialogue: 0,0:04:27.19,0:04:30.38,Default,,0000,0000,0000,,This is the oldest type of rock \Nthat is found in Minnesota
Dialogue: 0,0:04:30.38,0:04:34.63,Default,,0000,0000,0000,,and it is located along \Nthe Minnesota River Valley
Dialogue: 0,0:04:34.63,0:04:38.16,Default,,0000,0000,0000,,kind of near Granite Falls, \Nif you know where that is.
Dialogue: 0,0:04:38.16,0:04:40.34,Default,,0000,0000,0000,,So here's a map of Minnesota,
Dialogue: 0,0:04:40.34,0:04:43.70,Default,,0000,0000,0000,,and this orange rusty color
Dialogue: 0,0:04:43.70,0:04:49.86,Default,,0000,0000,0000,,is shading in the areas where you \Ncan find Morton Gneiss type of rock.
Dialogue: 0,0:04:49.86,0:04:53.12,Default,,0000,0000,0000,,[pronounced] "Neese"? "Ness"?\NI think I'm pronouncing that correctly.
Dialogue: 0,0:04:53.12,0:04:56.26,Default,,0000,0000,0000,,(One of those ways is correct, at least.)
Dialogue: 0,0:04:56.26,0:05:00.90,Default,,0000,0000,0000,,The second type of rock\Nis the Canadian Shield,
Dialogue: 0,0:05:00.90,0:05:03.80,Default,,0000,0000,0000,,and this is really just \Na massive layer of rock
Dialogue: 0,0:05:03.80,0:05:10.36,Default,,0000,0000,0000,,that is present not only in Minnesota, \Nbut also a good portion of Canada.
Dialogue: 0,0:05:10.36,0:05:15.13,Default,,0000,0000,0000,,And so here's a map of the \Nnorthern portion of North America,
Dialogue: 0,0:05:15.13,0:05:18.58,Default,,0000,0000,0000,,and all of this area shaded in purple
Dialogue: 0,0:05:18.58,0:05:24.22,Default,,0000,0000,0000,,represents the rock that makes up \Nthe Canadian Shield.
Dialogue: 0,0:05:24.22,0:05:30.37,Default,,0000,0000,0000,,And if you've gone into central northern \NMinnesota or northeastern Minnesota,
Dialogue: 0,0:05:30.37,0:05:32.94,Default,,0000,0000,0000,,you can see this exposed rock
Dialogue: 0,0:05:32.94,0:05:37.18,Default,,0000,0000,0000,,in various areas such as \Nthe Boundary Waters Canoe Area.
Dialogue: 0,0:05:37.18,0:05:45.47,Default,,0000,0000,0000,,These exposed rocks are actually have been\Naround for millions to billions of years.
Dialogue: 0,0:05:45.47,0:05:51.72,Default,,0000,0000,0000,,And you can also see it along \Nthese cliffs in the North Shore.
Dialogue: 0,0:05:51.72,0:05:54.67,Default,,0000,0000,0000,,Okay, so back to our timeline,
Dialogue: 0,0:05:54.67,0:05:58.25,Default,,0000,0000,0000,,we're now going to move \Nto the Paleozoic era.
Dialogue: 0,0:05:58.25,0:06:04.94,Default,,0000,0000,0000,,And this was a time period \N600 to 225 million years ago.
Dialogue: 0,0:06:04.94,0:06:08.55,Default,,0000,0000,0000,,And believe it or not, \Nat this point in time,
Dialogue: 0,0:06:08.55,0:06:13.64,Default,,0000,0000,0000,,Minnesota is actually thought \Nto be located near the equator.
Dialogue: 0,0:06:13.64,0:06:18.67,Default,,0000,0000,0000,,So remember, when all the continents\Nare mushed together in Pangea
Dialogue: 0,0:06:18.67,0:06:26.18,Default,,0000,0000,0000,,before plate tectonic separated them \Ninto the locations that they are today,
Dialogue: 0,0:06:26.18,0:06:28.54,Default,,0000,0000,0000,,not everything is in \Nthe place that it is today
Dialogue: 0,0:06:28.54,0:06:31.67,Default,,0000,0000,0000,,[corrects self] Not everything \Nwas in the place that it is today.
Dialogue: 0,0:06:31.67,0:06:35.15,Default,,0000,0000,0000,,And so Minnesota is actually \Nlocated near the equator,
Dialogue: 0,0:06:35.15,0:06:43.78,Default,,0000,0000,0000,,which means that there was a lot warmer\Ntemperatures, maybe more moisture.
Dialogue: 0,0:06:43.78,0:06:48.03,Default,,0000,0000,0000,,And that is one of the reasons \Nwhy in the fossil record,
Dialogue: 0,0:06:48.03,0:06:51.96,Default,,0000,0000,0000,,we see evidence of tropical \Nand subtropical plants.
Dialogue: 0,0:06:51.96,0:06:56.19,Default,,0000,0000,0000,,It's also important to note \Nthat there were continental seas
Dialogue: 0,0:06:56.19,0:06:58.52,Default,,0000,0000,0000,,that were present in Minnesota at this time,
Dialogue: 0,0:06:58.52,0:07:00.74,Default,,0000,0000,0000,,which is why in the fossil record,
Dialogue: 0,0:07:00.74,0:07:05.92,Default,,0000,0000,0000,,we can see evidence of marine \Norganisms being present in Minnesota,
Dialogue: 0,0:07:05.92,0:07:09.50,Default,,0000,0000,0000,,despite the fact that we \Ndon't have an ocean today.
Dialogue: 0,0:07:09.50,0:07:13.14,Default,,0000,0000,0000,,Okay, so the next time period \Nis the Mesozoic period.
Dialogue: 0,0:07:13.14,0:07:18.81,Default,,0000,0000,0000,,This was between 225 \Nand 65 million years ago.
Dialogue: 0,0:07:18.81,0:07:21.31,Default,,0000,0000,0000,,Again, we're still under water.
Dialogue: 0,0:07:21.31,0:07:26.89,Default,,0000,0000,0000,,There's still continental seas \Ncovering at least portions of the state.
Dialogue: 0,0:07:26.89,0:07:29.94,Default,,0000,0000,0000,,It's also when we see \Nthe first flowering plants,
Dialogue: 0,0:07:29.94,0:07:32.00,Default,,0000,0000,0000,,the first birds, the first mammals,
Dialogue: 0,0:07:32.00,0:07:37.79,Default,,0000,0000,0000,,even though this is sometimes referred to\Nas the period as the age of the dinosaurs.
Dialogue: 0,0:07:37.79,0:07:42.15,Default,,0000,0000,0000,,So dinosaurs tend to be more \Nprevalent than mammals at this point.
Dialogue: 0,0:07:44.45,0:07:46.98,Default,,0000,0000,0000,,And it's also what's happening
Dialogue: 0,0:07:46.98,0:07:49.51,Default,,0000,0000,0000,,with where Minnesota \Nis located on the globe is,
Dialogue: 0,0:07:49.51,0:07:52.97,Default,,0000,0000,0000,,it is starting to get pulled\Nmore northwards,
Dialogue: 0,0:07:52.97,0:07:56.24,Default,,0000,0000,0000,,and so it's getting pulled towards the poles,
Dialogue: 0,0:07:56.24,0:08:01.74,Default,,0000,0000,0000,,and it's starting to experience \Na cooler and somewhat drier climate
Dialogue: 0,0:08:01.74,0:08:05.11,Default,,0000,0000,0000,,than what it did when it was near the equator.
Dialogue: 0,0:08:05.11,0:08:08.61,Default,,0000,0000,0000,,And here's just an example of some \Nof the fossils that have been found
Dialogue: 0,0:08:08.61,0:08:11.09,Default,,0000,0000,0000,,in Minnesota during this time period
Dialogue: 0,0:08:11.09,0:08:15.83,Default,,0000,0000,0000,,such as small, small vertebrate \Nanimals and flowering plants
Dialogue: 0,0:08:15.83,0:08:20.69,Default,,0000,0000,0000,,that have been preserved \Nin the different layers of rocks
Dialogue: 0,0:08:20.69,0:08:24.54,Default,,0000,0000,0000,,that have been dated to the Mesozoic.
Dialogue: 0,0:08:24.54,0:08:27.90,Default,,0000,0000,0000,,Okay, and then our final \Ntime period is the Cenozoic.
Dialogue: 0,0:08:27.90,0:08:32.16,Default,,0000,0000,0000,,That is from 65 million years ago to present.
Dialogue: 0,0:08:32.16,0:08:35.28,Default,,0000,0000,0000,,And this is known as the age of mammals,
Dialogue: 0,0:08:35.28,0:08:42.31,Default,,0000,0000,0000,,where we see the dinosaurs have died out \Nand the mammals are starting to rule.
Dialogue: 0,0:08:42.31,0:08:46.40,Default,,0000,0000,0000,,It's also a period where \Nthere's intense glaciation,
Dialogue: 0,0:08:46.40,0:08:53.94,Default,,0000,0000,0000,,and so Minnesota has made it to where \Nit presently is located on the globe.
Dialogue: 0,0:08:53.94,0:08:59.58,Default,,0000,0000,0000,,And not only did Minnesota \Nsee a cooling period,
Dialogue: 0,0:08:59.58,0:09:03.33,Default,,0000,0000,0000,,but there was just a large \Ncooling period across the globe,
Dialogue: 0,0:09:03.33,0:09:06.25,Default,,0000,0000,0000,,which resulted in glacier formations.
Dialogue: 0,0:09:06.25,0:09:12.09,Default,,0000,0000,0000,,And glaciers had a huge impact \Non the present landscape,
Dialogue: 0,0:09:12.09,0:09:15.32,Default,,0000,0000,0000,,which we'll learn more\Nabout in the next lecture.
Dialogue: 0,0:09:15.32,0:09:23.32,Default,,0000,0000,0000,,Which we will get to after I wrap this up \Nand say thank you for your attention.
Dialogue: 0,0:09:23.32,0:09:28.65,Default,,0000,0000,0000,,And like I've already previewed, \Nwe will talk about glaciers next.\N