1 00:00:00,984 --> 00:00:04,240 All right, let's get up our picture of the earth. 2 00:00:04,560 --> 00:00:05,976 The earth is pretty awesome. 3 00:00:06,000 --> 00:00:08,429 I'm a geologist, so I get pretty psyched about this, 4 00:00:08,453 --> 00:00:09,816 but the earth is great. 5 00:00:09,840 --> 00:00:13,296 It's powerful, it's dynamic, it's constantly changing. 6 00:00:13,320 --> 00:00:15,120 It's a pretty exciting place to live. 7 00:00:16,280 --> 00:00:19,976 But I want to share with you guys today my perspective as a geologist 8 00:00:20,000 --> 00:00:22,216 in how understanding earth's past 9 00:00:22,240 --> 00:00:25,736 can help inform and guide decisions that we make today 10 00:00:25,760 --> 00:00:28,840 about how to sustainably live on earth's surface. 11 00:00:29,520 --> 00:00:33,256 So there's a lot of exciting things that go on on the surface of the earth. 12 00:00:33,280 --> 00:00:34,840 If we zoom in here a little bit, 13 00:00:35,360 --> 00:00:39,016 I want to talk to you guys a little bit about one of the things that happens. 14 00:00:39,040 --> 00:00:41,786 Material get shuffled around earth's surface all the time, 15 00:00:41,800 --> 00:00:45,036 and one of the big thing that happens is material from high mountains 16 00:00:45,060 --> 00:00:47,536 gets eroded and transported and deposited in the sea. 17 00:00:47,560 --> 00:00:49,516 And this process is ongoing all the time, 18 00:00:49,550 --> 00:00:51,936 and it has huge effects on how the landscape works. 19 00:00:51,960 --> 00:00:53,856 So this example here in south India -- 20 00:00:53,880 --> 00:00:56,376 we have some of the biggest mountains in the world, 21 00:00:56,400 --> 00:00:58,376 and you can see in this satellite photo 22 00:00:58,400 --> 00:01:02,576 rivers transporting material from those mountains out to the sea. 23 00:01:02,600 --> 00:01:04,775 You can think of these rivers like bulldozers. 24 00:01:04,800 --> 00:01:08,520 They're basically taking these mountains and pushing them down towards the sea. 25 00:01:09,440 --> 00:01:11,256 We'll give you guys an example here. 26 00:01:11,280 --> 00:01:12,616 So we zoom in a little bit. 27 00:01:12,640 --> 00:01:15,176 I want to talk to you guys specifically about a river. 28 00:01:15,200 --> 00:01:17,856 We can see these beautiful patterns that the rivers make 29 00:01:17,880 --> 00:01:19,976 as they're pushing material down to the sea, 30 00:01:20,000 --> 00:01:21,616 but these patterns aren't static. 31 00:01:21,640 --> 00:01:24,326 These rivers are wiggling and jumping around quite a bit, 32 00:01:24,350 --> 00:01:26,316 and it can have big impacts on our lives. 33 00:01:26,340 --> 00:01:28,736 So an example of this is this is the Kosi River. 34 00:01:28,760 --> 00:01:31,416 So the Kosi River has this nice c-shaped pathway, 35 00:01:31,440 --> 00:01:33,896 and it exits the big mountains of Nepal 36 00:01:33,920 --> 00:01:36,056 carrying with it a ton of material, 37 00:01:36,080 --> 00:01:39,046 a lot of sediments that's being eroded from the high mountains, 38 00:01:39,070 --> 00:01:40,926 and it spreads out across India 39 00:01:40,950 --> 00:01:42,270 and moves this material. 40 00:01:42,560 --> 00:01:44,856 So we're going to zoom in to this area 41 00:01:44,880 --> 00:01:48,309 and I'm going to tell you a little bit about what happened with the Kosi. 42 00:01:48,333 --> 00:01:50,896 It's an example of how dynamic these systems can be. 43 00:01:50,920 --> 00:01:54,496 So this is a satellite image from August of 2008, 44 00:01:54,520 --> 00:01:56,216 and this satellite image is colored 45 00:01:56,240 --> 00:01:58,416 so that vegetations or plants show up as green 46 00:01:58,440 --> 00:02:00,096 and water shows up as blue. 47 00:02:00,120 --> 00:02:03,656 So here again you can see that c-shaped pathway 48 00:02:03,680 --> 00:02:05,600 that this river takes as it exits Nepal. 49 00:02:06,120 --> 00:02:08,136 And now this is monsoon season. 50 00:02:08,160 --> 00:02:10,656 August is monsoon season in this region of the world, 51 00:02:10,680 --> 00:02:13,576 and anyone that lives near a river is no stranger to flooding 52 00:02:13,600 --> 00:02:17,172 and the hazards and inconveniences at minimum that are associated with that. 53 00:02:17,440 --> 00:02:19,696 But something interesting happened in 2008, 54 00:02:19,720 --> 00:02:22,616 and this river moved in a way that's very different. 55 00:02:22,640 --> 00:02:25,640 It flooded in a way that's very different than it normally does. 56 00:02:25,664 --> 00:02:28,416 So the Kosi River is flowing down here, 57 00:02:28,440 --> 00:02:31,016 but sometimes as these rivers are bulldozing sediment, 58 00:02:31,040 --> 00:02:32,296 they kind of get clogged, 59 00:02:32,320 --> 00:02:34,456 and these clogs can actually cause the rivers 60 00:02:34,480 --> 00:02:36,176 to shift their course dramatically. 61 00:02:36,200 --> 00:02:39,056 So this satellite image is from just two weeks later. 62 00:02:39,080 --> 00:02:41,016 Here's the previous pathway, 63 00:02:41,040 --> 00:02:42,656 that c-shaped pathway, 64 00:02:42,680 --> 00:02:44,776 and you notice it's not blue anymore. 65 00:02:44,800 --> 00:02:46,776 But now what we have is this blue pathway 66 00:02:46,800 --> 00:02:49,256 that cuts down the middle of the field of view here. 67 00:02:49,280 --> 00:02:51,616 What happened is the Kosi River jumped its banks, 68 00:02:51,640 --> 00:02:54,336 and for reference, the scale bar here is 40 miles. 69 00:02:54,360 --> 00:02:57,880 This river moved over 30 miles very abruptly. 70 00:02:58,560 --> 00:03:01,736 So this river got clogged and it jumped its banks. 71 00:03:01,760 --> 00:03:03,856 Here's an image from about a week later, 72 00:03:03,880 --> 00:03:06,136 and you can see these are the previous pathways, 73 00:03:06,160 --> 00:03:08,816 and you can see this process of river-jumping continues 74 00:03:08,840 --> 00:03:11,412 as this river moves farther away from its major course. 75 00:03:11,920 --> 00:03:13,976 So you can imagine in landscapes like this, 76 00:03:14,000 --> 00:03:16,616 where rivers move around frequently, 77 00:03:16,640 --> 00:03:21,136 it's really important to understand when, where and how they're going to jump. 78 00:03:21,160 --> 00:03:25,040 But these kinds of processes also happen a lot closer to home as well. 79 00:03:25,640 --> 00:03:27,456 So in the United States, 80 00:03:27,480 --> 00:03:31,536 we have the Mississippi River that drains most of the continental US. 81 00:03:31,560 --> 00:03:33,936 It pushes material from the Rocky Mountains 82 00:03:33,960 --> 00:03:35,496 and from the Great Plains. 83 00:03:35,520 --> 00:03:38,736 It drains it and moves it all the way across America 84 00:03:38,760 --> 00:03:40,680 and dumps it out in the Gulf of Mexico. 85 00:03:41,320 --> 00:03:44,776 So this is the course of the Mississippi that we're familiar with today, 86 00:03:44,800 --> 00:03:46,896 but it didn't always flow in this direction. 87 00:03:46,920 --> 00:03:48,576 If we use the geologic record, 88 00:03:48,600 --> 00:03:51,320 we can reconstruct where it went in the past. 89 00:03:52,120 --> 00:03:54,416 So for example, this red area here 90 00:03:54,440 --> 00:03:57,976 is where we know the Mississippi River flowed and deposited material 91 00:03:58,000 --> 00:03:59,640 about 4,600 years ago. 92 00:04:00,240 --> 00:04:02,336 Then about 3,500 years ago it moved 93 00:04:02,360 --> 00:04:04,736 to follow the course outlined here in orange. 94 00:04:04,760 --> 00:04:06,776 And it kept moving and it keeps moving. 95 00:04:06,800 --> 00:04:08,696 So here's about 2,000 years ago, 96 00:04:08,720 --> 00:04:10,416 a thousand years ago, 97 00:04:10,440 --> 00:04:11,656 700 years ago. 98 00:04:11,680 --> 00:04:14,096 And it was only as recently as 500 years ago 99 00:04:14,120 --> 00:04:16,959 that it occupied the pathway that we're familiar with today. 100 00:04:18,079 --> 00:04:20,016 So these processes are really important, 101 00:04:20,040 --> 00:04:22,896 and especially here, this delta area, 102 00:04:22,920 --> 00:04:26,736 where these river-jumping events in the Mississippi 103 00:04:26,760 --> 00:04:29,576 are building land at the interface of the land and the sea. 104 00:04:29,600 --> 00:04:31,336 This is really valuable real estate, 105 00:04:31,360 --> 00:04:36,616 and deltas like this are some of the most densely populated areas on our planet. 106 00:04:36,640 --> 00:04:39,096 So understanding the dynamics of these landscapes, 107 00:04:39,120 --> 00:04:42,256 how they formed and how they will continue to change in the future 108 00:04:42,280 --> 00:04:44,680 is really important for the people that live there. 109 00:04:45,480 --> 00:04:47,016 So rivers also wiggle. 110 00:04:47,040 --> 00:04:49,936 These are sort of bigger jumps that we've been talking about. 111 00:04:49,960 --> 00:04:52,216 I want to show you guys some river wiggles here. 112 00:04:52,240 --> 00:04:54,776 So we're going to fly down to the Amazon River basin, 113 00:04:54,800 --> 00:04:56,816 and here again we have a big river system 114 00:04:56,840 --> 00:05:01,216 that is draining and moving and plowing material from the Andean Mountains, 115 00:05:01,240 --> 00:05:03,056 transporting it across South America 116 00:05:03,080 --> 00:05:05,760 and dumping it out into the Atlantic Ocean. 117 00:05:06,560 --> 00:05:11,256 So if we zoom in here, you guys can see these nice, curvy river pathways. 118 00:05:11,280 --> 00:05:14,256 Again, they're really beautiful, but again, they're not static. 119 00:05:14,280 --> 00:05:16,016 These rivers wiggle around. 120 00:05:16,040 --> 00:05:19,656 We can use satellite imagery over the last 30 or so years 121 00:05:19,680 --> 00:05:21,816 to actually monitor how these change. 122 00:05:21,840 --> 00:05:26,016 So take a minute and just watch any bend or curve in this river, 123 00:05:26,040 --> 00:05:29,016 and you'll see it doesn't stay in the same place for very long. 124 00:05:29,040 --> 00:05:31,320 It changes and evolves and warps its pattern. 125 00:05:32,840 --> 00:05:35,216 If you look in this area in particular, 126 00:05:35,240 --> 00:05:38,216 I want you guys to notice there's a sort of a loop in the river 127 00:05:38,240 --> 00:05:39,656 that gets completely cut off. 128 00:05:39,680 --> 00:05:41,256 It's almost like a whip cracking 129 00:05:41,280 --> 00:05:43,960 and snaps off the pathway of the river at a certain spot. 130 00:05:44,360 --> 00:05:45,976 So just for reference, again, 131 00:05:46,000 --> 00:05:50,936 in this location, that river changed its course over four miles 132 00:05:50,960 --> 00:05:52,640 over the course of a season or two. 133 00:05:53,080 --> 00:05:55,976 So the landscapes that we live in on earth, 134 00:05:56,000 --> 00:05:58,416 as this material is being eroded from the mountains 135 00:05:58,440 --> 00:05:59,776 and transported to the sea, 136 00:05:59,800 --> 00:06:01,416 are wiggling around all the time. 137 00:06:01,440 --> 00:06:02,896 They're changing all the time, 138 00:06:02,920 --> 00:06:05,376 and we need to be able to understand these processes 139 00:06:05,400 --> 00:06:08,136 so we can manage and live sustainably on these landscapes. 140 00:06:08,160 --> 00:06:11,216 But it's hard to do if the only information we have 141 00:06:11,240 --> 00:06:13,576 is what's going on today at earth's surface. 142 00:06:13,600 --> 00:06:15,656 Right? We don't have a lot of observations. 143 00:06:15,680 --> 00:06:20,496 We only have 30 years' worth of satellite photos, for example. 144 00:06:20,520 --> 00:06:23,416 We need more observations to understand these processes more. 145 00:06:23,440 --> 00:06:25,056 And additionally, we need to know 146 00:06:25,080 --> 00:06:28,296 how these landscapes are going to respond to changing climate 147 00:06:28,320 --> 00:06:29,576 and to changing land use 148 00:06:29,600 --> 00:06:32,440 as we continue to occupy and modify earth's surface. 149 00:06:33,160 --> 00:06:35,696 So this is where the rocks come in. 150 00:06:35,720 --> 00:06:38,216 So as rivers flow, 151 00:06:38,240 --> 00:06:41,136 as they're bulldozing material from the mountains to the sea, 152 00:06:41,160 --> 00:06:44,616 sometimes bits of sand and clay and rock get stuck in the ground. 153 00:06:44,640 --> 00:06:47,336 And that stuff that gets stuck in the ground gets buried, 154 00:06:47,360 --> 00:06:51,096 and through time, we get big, thick accumulations of sediments 155 00:06:51,120 --> 00:06:53,136 that eventually turn into rocks. 156 00:06:53,160 --> 00:06:55,736 What this means is that we can go to places like this, 157 00:06:55,760 --> 00:06:58,456 where we see big, thick stacks of sedimentary rocks, 158 00:06:58,480 --> 00:06:59,976 and go back in time 159 00:07:00,000 --> 00:07:02,736 and see what the landscapes looked like in the past. 160 00:07:02,760 --> 00:07:04,896 We can do this to help reconstruct 161 00:07:04,920 --> 00:07:09,240 and understand how earth landscapes evolve. 162 00:07:10,160 --> 00:07:11,776 This is pretty convenient, too, 163 00:07:11,800 --> 00:07:14,776 because the earth has had sort of an epic history. Right? 164 00:07:14,800 --> 00:07:19,616 So this video here is a reconstruction of paleogeography 165 00:07:19,640 --> 00:07:23,256 for just the first 600 million years of earth's history. 166 00:07:23,280 --> 00:07:25,256 So just a little bit of time here. 167 00:07:25,280 --> 00:07:28,016 So as the plates move around, 168 00:07:28,040 --> 00:07:31,176 we know climate has changed, sea level has changed, 169 00:07:31,200 --> 00:07:34,856 we have a lot of different types of landscapes 170 00:07:34,880 --> 00:07:37,616 and different types of environments that we can go back -- 171 00:07:37,640 --> 00:07:39,016 if we have a time machine -- 172 00:07:39,040 --> 00:07:40,376 we can go back and look at, 173 00:07:40,400 --> 00:07:42,136 and we do indeed have a time machine 174 00:07:42,160 --> 00:07:45,496 because we can look at the rocks that were deposited at these times. 175 00:07:45,520 --> 00:07:47,536 So I'm going to give you an example of this 176 00:07:47,560 --> 00:07:49,776 and take you to a special time in earth's past. 177 00:07:49,800 --> 00:07:53,016 About 55 million years ago, there was a really abrupt warming event, 178 00:07:53,040 --> 00:07:55,536 and what happened was a whole bunch of carbon dioxide 179 00:07:55,560 --> 00:07:57,376 was released into earth's atmosphere, 180 00:07:57,400 --> 00:08:01,256 and it caused a rapid and pretty extreme global warming event. 181 00:08:01,280 --> 00:08:03,936 And when I say warm, I mean pretty warm, 182 00:08:03,960 --> 00:08:06,936 that there were things like crocodiles and palm trees 183 00:08:06,960 --> 00:08:09,976 as far north as Canada and as far south as Patagonia. 184 00:08:10,000 --> 00:08:13,176 So this was a pretty warm time and it happened really abruptly. 185 00:08:13,200 --> 00:08:14,416 So what we can do 186 00:08:14,440 --> 00:08:17,496 is we can go back and find rocks that were deposited at this time 187 00:08:17,520 --> 00:08:21,120 and reconstruct how the landscape changed in response to this warming event. 188 00:08:21,560 --> 00:08:23,456 So here, yay, rocks. 189 00:08:23,480 --> 00:08:25,816 (Laughter) 190 00:08:25,840 --> 00:08:27,576 Here's a pile of rocks. 191 00:08:27,600 --> 00:08:29,216 This yellow blob here, 192 00:08:29,240 --> 00:08:30,976 this is actually a fossil river, 193 00:08:31,000 --> 00:08:32,667 so just like this cartoon I showed, 194 00:08:32,691 --> 00:08:35,976 these are deposits that were laid down 55 million years ago. 195 00:08:36,000 --> 00:08:39,096 As geologists, we can go and look at these up close 196 00:08:39,120 --> 00:08:40,549 and reconstruct the landscape. 197 00:08:41,240 --> 00:08:42,736 So here's another example. 198 00:08:42,760 --> 00:08:45,216 The yellow blob here is a fossil river. 199 00:08:45,240 --> 00:08:46,776 Here's another one above it. 200 00:08:46,800 --> 00:08:50,096 We can go and look in detail and make measurements and observations, 201 00:08:50,120 --> 00:08:51,496 and we can measure features. 202 00:08:51,520 --> 00:08:53,896 For example, the features I just highlighted there 203 00:08:53,920 --> 00:08:57,376 tell us that this particular river was probably about three feet deep. 204 00:08:57,400 --> 00:08:59,496 You could wade across this cute little stream 205 00:08:59,520 --> 00:09:01,760 if you were walking around 55 million years ago. 206 00:09:02,480 --> 00:09:05,376 The reddish stuff that's above and below those channels, 207 00:09:05,400 --> 00:09:07,176 those are ancient soil deposits. 208 00:09:07,200 --> 00:09:11,056 So we can look at those to tell us what lived and grew on the landscape 209 00:09:11,080 --> 00:09:14,640 and to understand how these rivers were interacting with their floodplains. 210 00:09:15,680 --> 00:09:20,056 So we can look in detail and reconstruct with some specificity 211 00:09:20,080 --> 00:09:22,936 how these rivers flowed and what the landscapes looked like. 212 00:09:22,960 --> 00:09:25,440 So when we do this for this particular place 213 00:09:26,160 --> 00:09:27,376 at this time, 214 00:09:27,400 --> 00:09:30,136 if we look what happened before this abrupt warming event, 215 00:09:30,160 --> 00:09:33,776 the rivers kind of carved their way down from the mountains to the sea, 216 00:09:33,800 --> 00:09:38,936 and they looked maybe similar to what I showed you in the Amazon River basin. 217 00:09:38,960 --> 00:09:41,416 But right at the onset of this climate change event, 218 00:09:41,440 --> 00:09:42,920 the rivers change dramatically. 219 00:09:43,480 --> 00:09:45,336 All of a sudden they got much broader, 220 00:09:45,360 --> 00:09:48,920 and they started to slide back and forth across the landscape more readily. 221 00:09:49,880 --> 00:09:53,776 Eventually, the rivers reverted back to a state that was more similar 222 00:09:53,800 --> 00:09:57,616 to what they would have looked like before this climate event, 223 00:09:57,640 --> 00:09:59,280 but it took a long, long time. 224 00:10:00,240 --> 00:10:04,096 So we can go back in earth's time and do these kinds of reconstructions 225 00:10:04,120 --> 00:10:06,736 and understand how earth's landscape has changed 226 00:10:06,760 --> 00:10:10,536 in response to a climate event like this or a land use event. 227 00:10:10,560 --> 00:10:12,656 So some of the ways that rivers change 228 00:10:12,680 --> 00:10:17,456 or the reasons that rivers change their pattern and their movements 229 00:10:17,480 --> 00:10:21,416 is because of things like with extra water falling on the land's surface 230 00:10:21,440 --> 00:10:23,376 when climate is hotter, 231 00:10:23,400 --> 00:10:25,936 we can move more sediment and erode more sediment, 232 00:10:25,960 --> 00:10:27,800 and that changes how rivers behave. 233 00:10:28,680 --> 00:10:30,776 So ultimately, 234 00:10:30,800 --> 00:10:33,416 as long as earth's surface is our home, 235 00:10:33,440 --> 00:10:36,816 we need to carefully manage the resources and risks 236 00:10:36,840 --> 00:10:39,816 associated with living in dynamic environments. 237 00:10:39,840 --> 00:10:43,776 And I think the only way we can really do that sustainably 238 00:10:43,800 --> 00:10:46,016 is if we include information 239 00:10:46,040 --> 00:10:50,136 about how landscapes evolved and behaved in earth's past. 240 00:10:50,160 --> 00:10:51,376 Thank you. 241 00:10:51,400 --> 00:10:55,840 (Applause)