1 00:00:00,871 --> 00:00:05,699 >[NICOLE KJERSTEN] So for us to understand the landscape 2 00:00:05,699 --> 00:00:08,266 of Minnesota as we know it today, 3 00:00:08,266 --> 00:00:10,982 we need to understand where it came from. 4 00:00:10,982 --> 00:00:14,383 And to understand that, we have to look back 5 00:00:14,383 --> 00:00:19,633 to what's happened in this space since the beginning of Earth. 6 00:00:19,633 --> 00:00:26,132 Earth was formed about 4.6 billion (that's billion with a B) years ago, 7 00:00:26,132 --> 00:00:29,581 and a lot has happened since then. 8 00:00:29,581 --> 00:00:36,749 And so we will briefly go over the geological history of Minnesota. 9 00:00:36,749 --> 00:00:39,749 If you're interested in this topic in depth, 10 00:00:39,749 --> 00:00:42,932 I would encourage you to take a geology course. 11 00:00:42,932 --> 00:00:45,049 All we need to know is some context 12 00:00:45,049 --> 00:00:49,616 for how Minnesota got to be what Minnesota is today 13 00:00:49,616 --> 00:00:53,632 because we know the landscape is so tightly connected 14 00:00:53,632 --> 00:00:58,366 to the life that lives in Minnesota. 15 00:00:58,366 --> 00:01:03,561 Okay, so the Earth, the Earth crust -- 16 00:01:03,561 --> 00:01:08,482 so that's the outer layer of Earth that's made of rock and dirt and such -- 17 00:01:08,482 --> 00:01:10,682 it has many, many layers, 18 00:01:10,682 --> 00:01:14,349 with the oldest layers being at the bottom of the crust 19 00:01:14,349 --> 00:01:17,273 and the youngest layers being at the top. 20 00:01:17,273 --> 00:01:20,559 And the observation that Earth has these layers 21 00:01:20,559 --> 00:01:26,158 and that we find different types of fossils within these layers, 22 00:01:26,158 --> 00:01:31,225 and that there are different elements within those fossils 23 00:01:31,225 --> 00:01:35,458 or within those rocks that change over time -- 24 00:01:35,458 --> 00:01:40,323 the isotopic ratios change over time -- 25 00:01:40,323 --> 00:01:45,231 from all of that information, we can date the Earth. 26 00:01:45,231 --> 00:01:47,972 And we've been able to date the Earth 27 00:01:47,972 --> 00:01:55,018 such that we hypothesize that it was formed about 4.6 billion years ago. 28 00:01:55,018 --> 00:02:00,184 And by looking at these different layers and dating these different layers, 29 00:02:00,184 --> 00:02:06,183 we have divided the Earth into four major time periods. 30 00:02:06,183 --> 00:02:07,400 And what I want to do is, 31 00:02:07,400 --> 00:02:09,984 I just want to walk through each of those time periods 32 00:02:09,984 --> 00:02:13,326 and provide a little bit more context for what was happening 33 00:02:13,326 --> 00:02:19,565 in the landscape that we know of as Minnesota during those different times. 34 00:02:19,565 --> 00:02:22,733 So we're going to start in the Precambrian era. 35 00:02:22,733 --> 00:02:29,599 So this is the oldest and longest period of geological time. 36 00:02:29,599 --> 00:02:35,966 It went from when the Earth was formed 4.6 billion years ago 37 00:02:35,966 --> 00:02:41,783 to about 600 million (million, with an M) years ago. 38 00:02:41,783 --> 00:02:45,483 And during this time across the globe 39 00:02:45,483 --> 00:02:49,115 is when we saw the formation of oceans and continents. 40 00:02:49,115 --> 00:02:52,416 And I should say, at this point, when we're talking about continents, 41 00:02:52,416 --> 00:02:55,091 we're talking about one giant conglomeration 42 00:02:55,091 --> 00:02:57,826 of all the continents that we know today 43 00:02:57,826 --> 00:03:03,666 that was called Pangea, just one giant landmass. 44 00:03:05,052 --> 00:03:08,298 During this time, there was lots of volcanic activity, 45 00:03:08,298 --> 00:03:12,948 so that's putting a lot of different elements into the atmosphere, 46 00:03:12,948 --> 00:03:17,193 and volcanoes are responsible for forming bedrock 47 00:03:17,193 --> 00:03:22,365 and the different types of rocks that we see on Earth. 48 00:03:22,365 --> 00:03:25,381 Not all of them, but a good deal of them. 49 00:03:25,381 --> 00:03:29,132 And we know that at this point in time, 50 00:03:29,132 --> 00:03:33,149 Minnesota actually --or what we know of today as Minnesota -- 51 00:03:33,149 --> 00:03:35,500 was covered by shallow seas. 52 00:03:35,500 --> 00:03:42,382 So that is the reason we have a lot of iron deposits in northeastern Minnesota 53 00:03:42,382 --> 00:03:48,415 and why we mine for iron in that area. 54 00:03:48,415 --> 00:03:53,598 This is a time period when we also start to see the earliest life form, 55 00:03:53,598 --> 00:03:57,514 even though if we look at this figure here, the fossil record, 56 00:03:57,514 --> 00:04:04,315 there's not many fossils that were preserved from that time. 57 00:04:04,315 --> 00:04:10,964 Okay. But there are rocks and there are two types of rock formations 58 00:04:10,964 --> 00:04:15,514 that I want you to know about that are present here in Minnesota 59 00:04:15,514 --> 00:04:19,180 that originated during this Precambrian period. 60 00:04:19,180 --> 00:04:24,557 The first is the Morton Gneiss and then the second is the Canadian Shield. 61 00:04:24,557 --> 00:04:27,194 Let's talk about the Morton Gneiss first. 62 00:04:27,194 --> 00:04:30,378 This is the oldest type of rock that is found in Minnesota 63 00:04:30,378 --> 00:04:34,628 and it is located along the Minnesota River Valley 64 00:04:34,628 --> 00:04:38,162 kind of near Granite Falls, if you know where that is. 65 00:04:38,162 --> 00:04:40,343 So here's a map of Minnesota, 66 00:04:40,343 --> 00:04:43,695 and this orange rusty color 67 00:04:43,695 --> 00:04:49,864 is shading in the areas where you can find Morton Gneiss type of rock. 68 00:04:49,864 --> 00:04:53,118 [pronounced] "Neese"? "Ness"? I think I'm pronouncing that correctly. 69 00:04:53,118 --> 00:04:56,259 (One of those ways is correct, at least.) 70 00:04:56,259 --> 00:05:00,900 The second type of rock is the Canadian Shield, 71 00:05:00,900 --> 00:05:03,800 and this is really just a massive layer of rock 72 00:05:03,800 --> 00:05:10,365 that is present not only in Minnesota, but also a good portion of Canada. 73 00:05:10,365 --> 00:05:15,132 And so here's a map of the northern portion of North America, 74 00:05:15,132 --> 00:05:18,582 and all of this area shaded in purple 75 00:05:18,582 --> 00:05:24,215 represents the rock that makes up the Canadian Shield. 76 00:05:24,215 --> 00:05:30,369 And if you've gone into central northern Minnesota or northeastern Minnesota, 77 00:05:30,369 --> 00:05:32,936 you can see this exposed rock 78 00:05:32,936 --> 00:05:37,185 in various areas such as the Boundary Waters Canoe Area. 79 00:05:37,185 --> 00:05:45,469 These exposed rocks are actually have been around for millions to billions of years. 80 00:05:45,469 --> 00:05:51,718 And you can also see it along these cliffs in the North Shore. 81 00:05:51,718 --> 00:05:54,668 Okay, so back to our timeline, 82 00:05:54,668 --> 00:05:58,251 we're now going to move to the Paleozoic era. 83 00:05:58,251 --> 00:06:04,936 And this was a time period 600 to 225 million years ago. 84 00:06:04,936 --> 00:06:08,552 And believe it or not, at this point in time, 85 00:06:08,552 --> 00:06:13,636 Minnesota is actually thought to be located near the equator. 86 00:06:13,636 --> 00:06:18,671 So remember, when all the continents are mushed together in Pangea 87 00:06:18,671 --> 00:06:26,176 before plate tectonic separated them into the locations that they are today, 88 00:06:26,176 --> 00:06:28,537 not everything is in the place that it is today 89 00:06:28,537 --> 00:06:31,669 [corrects self] Not everything was in the place that it is today. 90 00:06:31,669 --> 00:06:35,150 And so Minnesota is actually located near the equator, 91 00:06:35,150 --> 00:06:43,781 which means that there was a lot warmer temperatures, maybe more moisture. 92 00:06:43,781 --> 00:06:48,028 And that is one of the reasons why in the fossil record, 93 00:06:48,028 --> 00:06:51,962 we see evidence of tropical and subtropical plants. 94 00:06:51,962 --> 00:06:56,186 It's also important to note that there were continental seas 95 00:06:56,186 --> 00:06:58,521 that were present in Minnesota at this time, 96 00:06:58,521 --> 00:07:00,737 which is why in the fossil record, 97 00:07:00,737 --> 00:07:05,915 we can see evidence of marine organisms being present in Minnesota, 98 00:07:05,915 --> 00:07:09,496 despite the fact that we don't have an ocean today. 99 00:07:09,496 --> 00:07:13,143 Okay, so the next time period is the Mesozoic period. 100 00:07:13,143 --> 00:07:18,808 This was between 225 and 65 million years ago. 101 00:07:18,808 --> 00:07:21,311 Again, we're still under water. 102 00:07:21,311 --> 00:07:26,888 There's still continental seas covering at least portions of the state. 103 00:07:26,888 --> 00:07:29,937 It's also when we see the first flowering plants, 104 00:07:29,937 --> 00:07:32,004 the first birds, the first mammals, 105 00:07:32,004 --> 00:07:37,787 even though this is sometimes referred to as the period as the age of the dinosaurs. 106 00:07:37,787 --> 00:07:42,148 So dinosaurs tend to be more prevalent than mammals at this point. 107 00:07:44,447 --> 00:07:49,513 And it's also what's happening with where Minnesota is located on the globe is, 108 00:07:49,513 --> 00:07:52,968 it is starting to get pulled more northwards, 109 00:07:52,968 --> 00:07:56,245 and so it's getting pulled towards the poles, 110 00:07:56,245 --> 00:08:01,828 and it's starting to experience a cooler and somewhat drier climate 111 00:08:01,828 --> 00:08:05,108 than what it did when it was near the equator. 112 00:08:05,108 --> 00:08:08,611 And here's just an example of some of the fossils that have been found 113 00:08:08,611 --> 00:08:11,093 in Minnesota during this time period 114 00:08:11,093 --> 00:08:15,828 such as small, small vertebrate animals and flowering plants 115 00:08:15,828 --> 00:08:20,694 that have been preserved in the different layers of rocks 116 00:08:20,694 --> 00:08:24,544 that have been dated to the Mesozoic. 117 00:08:24,544 --> 00:08:27,895 Okay, and then our final time period is the Cenozoic. 118 00:08:27,895 --> 00:08:32,157 That is from 65 million years ago to present. 119 00:08:32,157 --> 00:08:35,278 And this is known as the age of mammals, 120 00:08:35,278 --> 00:08:42,307 where we see the dinosaurs have died out and the mammals are starting to rule. 121 00:08:42,307 --> 00:08:46,398 It's also a period where there's intense glaciation, 122 00:08:46,398 --> 00:08:53,945 and so Minnesota has made it to where it presently is located on the globe. 123 00:08:53,945 --> 00:08:59,577 And not only did Minnesota see a cooling period, 124 00:08:59,577 --> 00:09:03,327 but there was just a large cooling period across the globe, 125 00:09:03,327 --> 00:09:06,246 which resulted in glacier formations. 126 00:09:06,246 --> 00:09:12,088 And glaciers had a huge impact on the present landscape, 127 00:09:12,088 --> 00:09:15,321 which we'll learn more about in the next lecture. 128 00:09:15,321 --> 00:09:23,322 Which we will get to after I wrap this up and say thank you for your attention. 129 00:09:23,322 --> 00:09:28,654 And like I've already previewed, we will talk about glaciers next.