WEBVTT 00:00:00.506 --> 00:00:08.516 [ Music ] 00:00:09.016 --> 00:00:12.000 [ Applause ] 00:00:12.556 --> 00:00:12.766 >> Alright. 00:00:13.456 --> 00:00:15.636 Let's get up our picture of the earth. 00:00:16.146 --> 00:00:17.386 The earth is pretty awesome. 00:00:17.516 --> 00:00:20.176 I'm a geologist, so I get pretty psyched about this, 00:00:20.386 --> 00:00:21.376 but the earth is great. 00:00:21.376 --> 00:00:24.836 It's powerful, it's dynamic, it's constantly changing, 00:00:24.836 --> 00:00:27.446 it's a pretty exciting place to live. 00:00:27.606 --> 00:00:30.596 But I want to share with you guys today my perspective 00:00:30.596 --> 00:00:34.126 as a geologist and how understanding earth's past can help 00:00:34.126 --> 00:00:37.026 inform and guide decisions that we make today, 00:00:37.266 --> 00:00:39.976 about how to sustainably live on earth's surface. 00:00:41.056 --> 00:00:43.056 So, there's a lot of exciting things that go 00:00:43.056 --> 00:00:44.156 on the surface of the earth. 00:00:44.156 --> 00:00:46.276 If we zoom in here a little bit, 00:00:46.366 --> 00:00:48.566 I want to talk to you guys a little bit about one 00:00:48.566 --> 00:00:50.736 of the things that happens is material gets shuffled 00:00:50.736 --> 00:00:52.126 around earth's surface all the time, 00:00:52.126 --> 00:00:53.936 and one of the big things that happens is material 00:00:53.936 --> 00:00:57.326 from high mountains gets eroded and transported 00:00:57.326 --> 00:00:58.436 and deposited in the sea. 00:00:58.776 --> 00:01:00.526 And this process is ongoing all the time 00:01:00.526 --> 00:01:02.696 and it has huge effects on how the landscape works. 00:01:03.506 --> 00:01:05.116 So this example here in South India, 00:01:05.275 --> 00:01:07.646 we have some of the biggest mountains in the world, 00:01:07.646 --> 00:01:09.666 and you can see in this satellite photo, 00:01:09.946 --> 00:01:11.896 rivers transporting material 00:01:11.896 --> 00:01:13.716 from those mountains out to the sea. 00:01:14.146 --> 00:01:15.916 You can think of these rivers like bulldozers. 00:01:15.916 --> 00:01:18.106 They're basically taking these mountains and pushing them 00:01:18.106 --> 00:01:18.876 down towards the sea. 00:01:19.016 --> 00:01:24.086 If we zoom in a little bit, we can see that, 00:01:25.216 --> 00:01:26.976 I'll give you guys an example here, right? 00:01:27.066 --> 00:01:28.176 So if we zoom in a little bit, 00:01:28.176 --> 00:01:30.766 I want to talk to you guys specifically about a river. 00:01:31.036 --> 00:01:33.216 You can see these beautiful patterns that the rivers make 00:01:33.216 --> 00:01:35.136 as they're pushing material down to the sea, 00:01:35.616 --> 00:01:36.796 but these patterns are not static. 00:01:37.086 --> 00:01:39.536 These rivers are wiggling and jumping around quite a bit, 00:01:39.536 --> 00:01:41.516 and it can have big impacts on, on our lives. 00:01:42.236 --> 00:01:44.736 So an example of this is, this is the Kosi River. 00:01:44.826 --> 00:01:47.176 So the Kosi River has this nice C-shaped pathway, 00:01:47.526 --> 00:01:50.306 and it exits the big mountains of Nepal carrying 00:01:50.306 --> 00:01:51.936 with it a ton of material, 00:01:52.176 --> 00:01:53.696 a lot of sediment that's being eroded 00:01:53.696 --> 00:01:56.666 from the high mountains and it spreads out across India 00:01:56.666 --> 00:01:58.036 and moves this material. 00:01:58.696 --> 00:02:00.926 So we're going to zoom in to this area, 00:02:00.926 --> 00:02:02.696 and I'm going to tell you a little bit about what happened 00:02:03.006 --> 00:02:04.076 with the, with the Kosi. 00:02:04.286 --> 00:02:06.476 It's an example of how dynamic these systems can be. 00:02:06.576 --> 00:02:10.246 So this is a satellite image from August of 2008, 00:02:10.306 --> 00:02:12.846 and this is satellite image is colored so that vegetation 00:02:12.846 --> 00:02:15.786 or plants show up as green and water shows up as blue. 00:02:16.266 --> 00:02:19.546 So, here again, you can see that C-shaped pathway 00:02:19.776 --> 00:02:21.536 that this river takes as it exits Nepal, 00:02:22.206 --> 00:02:25.436 and now this is monsoon season, August is monsoon season 00:02:25.436 --> 00:02:26.646 in this region of the world, and, 00:02:26.646 --> 00:02:28.776 and anyone that lives near a river is no stranger 00:02:28.776 --> 00:02:31.926 to flooding and the hazards and inconveniences at minimum 00:02:31.926 --> 00:02:32.956 that are associated with that. 00:02:33.526 --> 00:02:35.766 But something interesting happened in 2008 00:02:35.766 --> 00:02:38.776 and this river moved in a way that's very different, 00:02:38.776 --> 00:02:40.316 it flooded in a way that's very different 00:02:40.396 --> 00:02:41.086 than it normally does. 00:02:41.416 --> 00:02:44.056 So the Kosi River is flowing down here, 00:02:44.526 --> 00:02:47.126 but sometimes as these rivers are bulldozing sediment they 00:02:47.196 --> 00:02:49.816 kind of get clogged, and these clogs can actually cause the 00:02:49.816 --> 00:02:51.636 rivers to shift their course dramatically. 00:02:51.816 --> 00:02:54.746 So this satellite image is from just two weeks later. 00:02:55.146 --> 00:02:58.466 Here's the previous pathway, that C-shaped pathway, 00:02:58.766 --> 00:03:00.126 and you notice it's not blue anymore, 00:03:00.886 --> 00:03:02.946 but now what we have is this blue pathway that cuts 00:03:03.026 --> 00:03:04.426 down the middle of the field of view here. 00:03:04.886 --> 00:03:07.086 What happened is the Kosi River jumped its banks, 00:03:07.746 --> 00:03:10.426 and for reference, this scale bar here is 40 miles. 00:03:10.426 --> 00:03:13.736 This river moved over 30 miles very abruptly. 00:03:14.626 --> 00:03:17.456 So this river got clogged and it jumped its banks. 00:03:17.816 --> 00:03:19.936 Here's an image from an, about a week later, 00:03:19.936 --> 00:03:21.856 and you can see these are the previous pathways, 00:03:21.906 --> 00:03:24.546 and you can see this process of river jumping continues 00:03:24.946 --> 00:03:27.136 as this river moves father away from its major course. 00:03:27.606 --> 00:03:31.316 So you can imagine in landscapes like this where rivers move 00:03:31.386 --> 00:03:34.936 around frequently, it's really important to understand when, 00:03:34.936 --> 00:03:36.356 where, and how they're going to jump. 00:03:37.216 --> 00:03:40.106 But these kinds of processes also happen a lot closer 00:03:40.106 --> 00:03:40.916 to home as well. 00:03:41.736 --> 00:03:44.996 So, in the United States we have the Mississippi River 00:03:44.996 --> 00:03:49.016 that drains most of the Continental U.S. It pushes material 00:03:49.016 --> 00:03:51.136 from the Rocky Mountains and from the Great Plains, 00:03:51.326 --> 00:03:54.616 it drains and it moves it all the way across America 00:03:54.616 --> 00:03:56.606 and dumps it out in the Gulf of Mexico. 00:03:57.306 --> 00:04:00.036 So this is the course of the Mississippi that we're familiar 00:04:00.036 --> 00:04:02.576 with today, but it didn't always flow in this direction. 00:04:02.916 --> 00:04:04.666 If we use the geologic record, 00:04:04.666 --> 00:04:07.706 we can reconstruct where it went in the past. 00:04:08.256 --> 00:04:10.726 So, for example, this red area here is 00:04:10.726 --> 00:04:14.076 where know the Mississippi flowed and deposited material 00:04:14.076 --> 00:04:15.546 about 4,600 years ago. 00:04:16.366 --> 00:04:17.956 Then about 3,500 years ago, 00:04:17.956 --> 00:04:20.396 it moved to follow the course outlined here in orange, 00:04:20.886 --> 00:04:22.886 and it kept moving, and it keeps moving, 00:04:22.936 --> 00:04:27.766 so here's about 2,000 years ago, 1,000 years, 700 years ago, 00:04:27.766 --> 00:04:30.186 and it was only as recently as 500 years ago 00:04:30.186 --> 00:04:32.656 that it occupied the pathway that we're familiar with today. 00:04:34.166 --> 00:04:37.276 So these processes are really important and especially here, 00:04:37.376 --> 00:04:41.356 this delta area, where these river-jumping events 00:04:41.626 --> 00:04:44.736 in the Mississippi are building land at the interface 00:04:44.776 --> 00:04:45.516 of the land and the sea. 00:04:45.516 --> 00:04:47.406 This is really valuable real estate, 00:04:47.406 --> 00:04:49.426 and they're some of the most, deltas, like this, 00:04:49.426 --> 00:04:52.496 are some of the most densely populated areas on our planet. 00:04:52.766 --> 00:04:55.246 So understanding the dynamics of these landscapes, 00:04:55.306 --> 00:04:57.626 how they formed and how they will continue to change 00:04:57.626 --> 00:04:59.106 in the future is really important 00:04:59.106 --> 00:05:01.446 for the people that live there. 00:05:01.686 --> 00:05:03.146 So rivers also wiggle. 00:05:03.146 --> 00:05:04.316 These are sort of bigger jumps 00:05:04.356 --> 00:05:05.216 that we've been talking about, 00:05:05.216 --> 00:05:06.876 I want to show you guys some river wiggles here. 00:05:07.456 --> 00:05:10.336 So we're going to fly down to the Amazon River basin, 00:05:10.616 --> 00:05:13.886 and here, again, we have a big river system that is draining 00:05:13.886 --> 00:05:16.796 and moving and plowing material from the Andes Mountains, 00:05:17.326 --> 00:05:19.086 transporting it across South America, 00:05:19.086 --> 00:05:21.796 and dumping it out into the Atlantic Ocean. 00:05:22.706 --> 00:05:24.726 So if we zoom in here, you guys can see these nice, 00:05:25.286 --> 00:05:27.236 curvy river pathways, right? 00:05:27.326 --> 00:05:28.586 Again, they're really beautiful, but, 00:05:28.586 --> 00:05:29.636 again, they're not static. 00:05:30.206 --> 00:05:31.646 These rivers wiggle around. 00:05:32.146 --> 00:05:35.766 We can use satellite imagery, over the last 30 or so years, 00:05:35.766 --> 00:05:37.496 to actually monitor how these changed. 00:05:37.926 --> 00:05:40.836 So take a minute and just watch any bend 00:05:40.836 --> 00:05:42.996 or curve in this river, and you'll see it doesn't stay 00:05:42.996 --> 00:05:45.726 in the same place for very long, it changes and evolves, 00:05:46.246 --> 00:05:47.286 and warps its pattern. 00:05:48.596 --> 00:05:51.166 If you look in this area, in particular, 00:05:51.256 --> 00:05:53.306 I want you guys to notice there's a sort of a loop 00:05:53.306 --> 00:05:55.546 in the river that gets completely cutoff. 00:05:55.776 --> 00:05:58.536 It's almost like a whip cracking and snaps off the pathway 00:05:58.536 --> 00:05:59.606 of the river at a certain spot. 00:06:00.486 --> 00:06:03.356 So, just for reference, again, so in this location, 00:06:03.546 --> 00:06:06.566 that river changed its course over 4 miles 00:06:07.046 --> 00:06:08.486 over the course of a season or two. 00:06:09.236 --> 00:06:11.876 So, the landscapes that we live in, on earth, 00:06:12.136 --> 00:06:14.196 as this material is being eroded from mountains 00:06:14.196 --> 00:06:16.846 and transported to sea, are wiggling around all the time, 00:06:16.846 --> 00:06:17.796 they're changing all the time, 00:06:17.796 --> 00:06:20.086 and we need to be able to understand these processes 00:06:20.516 --> 00:06:23.616 so we can manage and live sustainably on these landscapes. 00:06:24.096 --> 00:06:27.476 But it's hard to do if the only information we have is 00:06:27.536 --> 00:06:29.126 what's going on today at earth's surface. 00:06:29.626 --> 00:06:32.386 Alright, we don't have a lot of observations, we only hear, 00:06:32.466 --> 00:06:34.016 only have 30, you know, 00:06:34.016 --> 00:06:36.096 30 years' worth of satellite photos for example. 00:06:36.636 --> 00:06:37.746 We need more observations 00:06:37.746 --> 00:06:38.936 to understand these processes more. 00:06:39.326 --> 00:06:40.736 And additionally, we need 00:06:40.736 --> 00:06:43.116 to know how these landscapes are going to respond 00:06:43.246 --> 00:06:46.646 to changing climate and to changing land use as we continue 00:06:46.646 --> 00:06:48.316 to occupy and modify earth's surface. 00:06:49.266 --> 00:06:51.306 So this, this is where the rocks come in. 00:06:51.866 --> 00:06:55.676 So, as rivers flow, as they're bulldozing material 00:06:55.676 --> 00:06:58.526 from the mountains to the sea, sometimes bits of sand 00:06:58.526 --> 00:07:00.296 and clay and rock get stuck in the ground, 00:07:00.756 --> 00:07:02.786 and that stuff that gets stuck in the ground gets buried, 00:07:03.096 --> 00:07:05.436 and through time, we get big, 00:07:05.436 --> 00:07:07.036 thick accumulations of sediments 00:07:07.196 --> 00:07:08.566 that eventually turn into rocks. 00:07:09.256 --> 00:07:11.856 What this means is that we can go to places like this 00:07:11.856 --> 00:07:14.146 where we see big, thick stacks of sedimentary rocks, 00:07:14.546 --> 00:07:17.466 and go back in time and see what the landscapes look 00:07:17.466 --> 00:07:18.706 like in the past. 00:07:18.836 --> 00:07:22.546 We can do this to help reconstruct and understand how, 00:07:23.646 --> 00:07:25.116 how earth landscapes evolve. 00:07:26.236 --> 00:07:28.166 This is pretty convenient too, 00:07:28.206 --> 00:07:30.826 because the earth has had sort of an epic history, right? 00:07:30.896 --> 00:07:35.426 So, this video here is a reconstruction of paleogeography 00:07:35.736 --> 00:07:38.556 for the first, just the first 600 million years 00:07:38.556 --> 00:07:41.066 of earth's history, so, just a little bit of time here. 00:07:41.136 --> 00:07:44.126 So as, as the plates move around, 00:07:44.126 --> 00:07:47.036 we know climate has changed, sea level has changed, 00:07:47.286 --> 00:07:50.936 we have a lot of different types of landscapes 00:07:50.936 --> 00:07:53.116 and different types of environment that we can go back, 00:07:53.406 --> 00:07:55.846 if we have a time machine, we can go back and look at. 00:07:56.116 --> 00:07:57.876 And we do, indeed, have a time machine, 00:07:57.876 --> 00:07:59.616 because we can look at the rocks 00:07:59.616 --> 00:08:00.956 that were deposited at these times. 00:08:01.356 --> 00:08:02.736 So I'm going to give you an example of this, 00:08:02.736 --> 00:08:04.366 I'm going to take you to a special time in earth's past, 00:08:04.736 --> 00:08:06.416 about 55 million years ago, 00:08:06.656 --> 00:08:08.336 there was a really abrupt warming event, 00:08:08.626 --> 00:08:09.966 and what happened was a whole bunch 00:08:09.966 --> 00:08:12.196 of carbon dioxide was released into earth's atmosphere 00:08:12.196 --> 00:08:14.756 and it caused a rapid, and, 00:08:14.756 --> 00:08:17.356 and pretty extreme global warming event, and, 00:08:17.356 --> 00:08:20.076 and when I say warm, I mean pretty warm. 00:08:20.076 --> 00:08:22.736 That there were things like crocodiles and palm trees 00:08:23.056 --> 00:08:25.976 as far north as Canada and as far south as Patagonia. 00:08:26.146 --> 00:08:27.386 So this is a pretty warm time, 00:08:27.436 --> 00:08:28.566 and it happened really abruptly. 00:08:29.326 --> 00:08:31.516 So what we can do is we can go back and find rocks 00:08:31.516 --> 00:08:32.785 that were deposited at this time 00:08:32.785 --> 00:08:35.476 and we reconstruct how the landscape changed in response 00:08:35.476 --> 00:08:36.336 to this warming event. 00:08:37.696 --> 00:08:40.265 So, here, yay, rocks! So [laughter], here, 00:08:40.666 --> 00:08:43.346 here's a pile of rocks. 00:08:43.716 --> 00:08:46.816 This yellow blob here, this is actually a fossil river. 00:08:47.126 --> 00:08:48.646 So just like this cartoon I showed, 00:08:48.756 --> 00:08:51.676 these are deposits that were laid down 55 million years ago. 00:08:52.096 --> 00:08:55.146 As geologists, we can go and look at these up close 00:08:55.226 --> 00:08:56.556 and reconstruct the landscape. 00:08:56.966 --> 00:08:58.806 So here's another example 00:08:58.806 --> 00:09:01.146 of the yellow blob here is a, is a fossil river. 00:09:01.346 --> 00:09:02.316 Here's another one above it. 00:09:02.886 --> 00:09:05.296 We can go and look in detail and make measurements 00:09:05.296 --> 00:09:08.096 and observations, and we can measure features, for example, 00:09:08.096 --> 00:09:10.066 the features I just highlighted there tell us 00:09:10.066 --> 00:09:12.206 that this particular river was probably 00:09:12.266 --> 00:09:13.426 about three feet deep. 00:09:13.546 --> 00:09:15.046 You could wade across this cute, 00:09:15.046 --> 00:09:16.246 little stream if you were walking 00:09:16.246 --> 00:09:18.416 around 55 million years ago. 00:09:18.616 --> 00:09:21.386 The reddish stuff that's above and below those channels, 00:09:21.486 --> 00:09:22.936 those are ancient soil deposits. 00:09:23.306 --> 00:09:25.276 So we can look at those to tell us what lived 00:09:25.386 --> 00:09:26.896 and grew on the landscape, 00:09:27.186 --> 00:09:29.586 and to understand how these rivers were interacting 00:09:29.586 --> 00:09:31.706 with their flood plains. 00:09:31.846 --> 00:09:34.336 So we can look in detail and we can reconstruct with some, 00:09:34.736 --> 00:09:37.416 some specificity how these rivers flowed 00:09:37.416 --> 00:09:38.666 and what the landscapes looked like. 00:09:38.986 --> 00:09:42.966 So when we do this, for this particular place, at this time, 00:09:42.966 --> 00:09:45.706 if we look what happened before this abrupt warming event, 00:09:46.246 --> 00:09:48.936 the rivers kind of carved their way down from the mountains 00:09:48.996 --> 00:09:51.956 to the sea and they did so, they looked maybe similar 00:09:51.956 --> 00:09:54.536 to what we, what I showed you in the Amazon River basin, 00:09:55.036 --> 00:09:57.406 but right at the onset of this climate change event, 00:09:57.466 --> 00:09:58.966 the rivers changed dramatically. 00:09:59.566 --> 00:10:01.176 All of a sudden they got much broader, 00:10:01.456 --> 00:10:02.826 and they started to slide back 00:10:02.916 --> 00:10:04.756 and forth across the landscape more readily. 00:10:05.966 --> 00:10:08.456 Eventually, the rivers reverted back to a state 00:10:08.456 --> 00:10:11.286 that was more similar to what they would have looked 00:10:11.636 --> 00:10:13.026 like before this climate event, 00:10:13.626 --> 00:10:15.266 but it took a long, long time. 00:10:16.326 --> 00:10:19.366 So we can go back in earth's time and do these kinds 00:10:19.366 --> 00:10:22.346 of reconstructions and understand how earth's landscape has 00:10:22.346 --> 00:10:25.106 changed in response to a climate event like this 00:10:25.516 --> 00:10:26.436 or a land use event. 00:10:26.686 --> 00:10:28.786 So some of the ways that rivers that change, 00:10:28.786 --> 00:10:32.016 or the reasons that rivers change their pattern and their, 00:10:32.406 --> 00:10:34.416 and their movements, is because of things 00:10:34.416 --> 00:10:37.806 like with extra water falling on the land's surface, when, 00:10:37.866 --> 00:10:40.916 when climate is hotter, we can move more sediment 00:10:40.916 --> 00:10:43.586 and erode more sediment and that changes how rivers behave. 00:10:44.886 --> 00:10:49.006 So, ultimately, as long as earth's surface is our home, 00:10:49.546 --> 00:10:52.406 we need to carefully manage the resources 00:10:52.406 --> 00:10:55.256 and risks associated with living in dynamic environments. 00:10:55.926 --> 00:10:58.796 And I think the only way we can really do 00:10:58.796 --> 00:11:01.856 that sustainably is if we include information 00:11:02.156 --> 00:11:05.496 about how landscapes evolved and behaved in earth's past. 00:11:06.236 --> 00:11:06.536 Thank you. 00:11:07.516 --> 00:11:10.500 [ Applause ]