1
00:00:12,584 --> 00:00:15,840
All right, let's get up
our picture of the earth.

2
00:00:16,160 --> 00:00:17,576
The earth is pretty awesome.

3
00:00:17,600 --> 00:00:20,029
I'm a geologist, so I get
pretty psyched about this,

4
00:00:20,053 --> 00:00:21,416
but the earth is great.

5
00:00:21,440 --> 00:00:24,896
It's powerful, it's dynamic,
it's constantly changing.

6
00:00:24,920 --> 00:00:26,720
It's a pretty exciting place to live.

7
00:00:27,780 --> 00:00:31,476
But I want to share with you guys today
my perspective as a geologist

8
00:00:31,500 --> 00:00:33,716
in how understanding earth's past

9
00:00:33,740 --> 00:00:37,236
can help inform and guide
decisions that we make today

10
00:00:37,260 --> 00:00:40,340
about how to sustainably live
on earth's surface.

11
00:00:41,020 --> 00:00:44,756
So there's a lot of exciting things
that go on on the surface of the earth.

12
00:00:44,780 --> 00:00:46,340
If we zoom in here a little bit,

13
00:00:46,860 --> 00:00:50,516
I want to talk to you guys a little bit
about one of the things that happens.

14
00:00:50,540 --> 00:00:53,286
Material get shuffled around
earth's surface all the time,

15
00:00:53,311 --> 00:00:56,547
and one of the big thing that happens
is material from high mountains

16
00:00:56,560 --> 00:00:59,036
gets eroded and transported
and deposited in the sea.

17
00:00:59,060 --> 00:01:01,016
And this process is ongoing all the time,

18
00:01:01,050 --> 00:01:03,436
and it has huge effects
on how the landscape works.

19
00:01:03,460 --> 00:01:05,355
So this example here in south India --

20
00:01:05,379 --> 00:01:07,876
we have some of the biggest
mountains in the world,

21
00:01:07,900 --> 00:01:09,876
and you can see in this satellite photo

22
00:01:09,900 --> 00:01:14,076
rivers transporting material
from those mountains out to the sea.

23
00:01:14,100 --> 00:01:16,275
You can think of these rivers
like bulldozers.

24
00:01:16,300 --> 00:01:20,020
They're basically taking these mountains
and pushing them down towards the sea.

25
00:01:20,380 --> 00:01:21,716
We zoom in a little bit.

26
00:01:21,900 --> 00:01:23,641
We can see that -

27
00:01:25,467 --> 00:01:27,197
I'll give you guys an example here.

28
00:01:27,213 --> 00:01:28,558
So we zoom in a little bit,

29
00:01:28,590 --> 00:01:31,180
I want to talk to you guys
specifically about a river -

30
00:01:31,205 --> 00:01:33,955
you can see these beautiful patterns
that the rivers make

31
00:01:33,980 --> 00:01:36,076
as they're pushing material
down to the sea,

32
00:01:36,100 --> 00:01:37,716
but these patterns aren't static.

33
00:01:37,740 --> 00:01:40,426
These rivers are wiggling
and jumping around quite a bit,

34
00:01:40,450 --> 00:01:42,415
and it can have big impacts on our lives.

35
00:01:42,440 --> 00:01:44,836
So an example of this
is this is the Kosi River.

36
00:01:44,860 --> 00:01:47,516
So the Kosi River
has this nice c-shaped pathway,

37
00:01:47,540 --> 00:01:49,996
and it exits the big mountains of Nepal

38
00:01:50,020 --> 00:01:52,156
carrying with it a ton of material,

39
00:01:52,180 --> 00:01:55,146
a lot of sediments that's being
eroded from the high mountains,

40
00:01:55,170 --> 00:01:57,026
and it spreads out across India

41
00:01:57,050 --> 00:01:58,370
and moves this material.

42
00:01:58,660 --> 00:02:00,956
So we're going to zoom in to this area

43
00:02:00,980 --> 00:02:04,409
and I'm going to tell you a little bit
about what happened with the Kosi.

44
00:02:04,433 --> 00:02:06,996
It's an example of how dynamic
these systems can be.

45
00:02:07,020 --> 00:02:10,596
So this is a satellite image
from August of 2008,

46
00:02:10,620 --> 00:02:12,316
and this satellite image is colored

47
00:02:12,340 --> 00:02:14,516
so that vegetations or plants
show up as green

48
00:02:14,540 --> 00:02:16,196
and water shows up as blue.

49
00:02:16,220 --> 00:02:19,756
So here again you can see
that c-shaped pathway

50
00:02:19,780 --> 00:02:21,700
that this river takes as it exits Nepal.

51
00:02:22,220 --> 00:02:24,236
And now this is monsoon season.

52
00:02:24,260 --> 00:02:26,756
August is monsoon season
in this region of the world,

53
00:02:26,780 --> 00:02:29,676
and anyone that lives near a river
is no stranger to flooding

54
00:02:29,700 --> 00:02:33,272
and the hazards and inconveniences
at minimum that are associated with that.

55
00:02:33,540 --> 00:02:35,796
But something interesting
happened in 2008,

56
00:02:35,820 --> 00:02:38,716
and this river moved in a way
that's very different.

57
00:02:38,740 --> 00:02:41,740
It flooded in a way that's very
different than it normally does.

58
00:02:41,764 --> 00:02:44,516
So the Kosi River is flowing down here,

59
00:02:44,540 --> 00:02:47,116
but sometimes as these rivers
are bulldozing sediment,

60
00:02:47,140 --> 00:02:48,396
they kind of get clogged,

61
00:02:48,420 --> 00:02:50,556
and these clogs can
actually cause the rivers

62
00:02:50,580 --> 00:02:52,276
to shift their course dramatically.

63
00:02:52,300 --> 00:02:55,156
So this satellite image
is from just two weeks later.

64
00:02:55,180 --> 00:02:57,116
Here's the previous pathway,

65
00:02:57,140 --> 00:02:58,756
that c-shaped pathway,

66
00:02:58,780 --> 00:03:00,876
and you notice it's not blue anymore.

67
00:03:00,900 --> 00:03:02,876
But now what we have is this blue pathway

68
00:03:02,900 --> 00:03:05,356
that cuts down the middle
of the field of view here.

69
00:03:05,380 --> 00:03:07,716
What happened is
the Kosi River jumped its banks,

70
00:03:07,740 --> 00:03:10,436
and for reference,
the scale bar here is 40 miles.

71
00:03:10,460 --> 00:03:13,980
This river moved
over 30 miles very abruptly.

72
00:03:14,660 --> 00:03:17,836
So this river got clogged
and it jumped its banks.

73
00:03:17,860 --> 00:03:19,956
Here's an image from about a week later,

74
00:03:19,980 --> 00:03:22,236
and you can see
these are the previous pathways,

75
00:03:22,260 --> 00:03:24,916
and you can see this process
of river-jumping continues

76
00:03:24,940 --> 00:03:27,512
as this river moves farther away
from its major course.

77
00:03:28,020 --> 00:03:30,076
So you can imagine
in landscapes like this,

78
00:03:30,100 --> 00:03:32,716
where rivers move around frequently,

79
00:03:32,740 --> 00:03:37,236
it's really important to understand when,
where and how they're going to jump.

80
00:03:37,260 --> 00:03:41,140
But these kinds of processes
also happen a lot closer to home as well.

81
00:03:41,740 --> 00:03:43,556
So in the United States,

82
00:03:43,580 --> 00:03:47,636
we have the Mississippi River
that drains most of the continental US.

83
00:03:47,660 --> 00:03:50,036
It pushes material
from the Rocky Mountains

84
00:03:50,060 --> 00:03:51,596
and from the Great Plains.

85
00:03:51,620 --> 00:03:54,836
It drains it and moves it
all the way across America

86
00:03:54,860 --> 00:03:56,780
and dumps it out in the Gulf of Mexico.

87
00:03:57,420 --> 00:04:00,876
So this is the course of the Mississippi
that we're familiar with today,

88
00:04:00,900 --> 00:04:02,996
but it didn't always flow
in this direction.

89
00:04:03,020 --> 00:04:04,676
If we use the geologic record,

90
00:04:04,700 --> 00:04:07,420
we can reconstruct
where it went in the past.

91
00:04:08,220 --> 00:04:10,516
So for example, this red area here

92
00:04:10,540 --> 00:04:14,076
is where we know the Mississippi River
flowed and deposited material

93
00:04:14,100 --> 00:04:15,740
about 4,600 years ago.

94
00:04:16,339 --> 00:04:18,435
Then about 3,500 years ago it moved

95
00:04:18,459 --> 00:04:20,836
to follow the course
outlined here in orange.

96
00:04:20,860 --> 00:04:22,876
And it kept moving and it keeps moving.

97
00:04:22,900 --> 00:04:24,796
So here's about 2,000 years ago,

98
00:04:24,820 --> 00:04:26,516
a thousand years ago,

99
00:04:26,540 --> 00:04:27,756
700 years ago.

100
00:04:27,780 --> 00:04:30,196
And it was only
as recently as 500 years ago

101
00:04:30,220 --> 00:04:33,059
that it occupied the pathway
that we're familiar with today.

102
00:04:34,179 --> 00:04:36,116
So these processes are really important,

103
00:04:36,140 --> 00:04:38,996
and especially here, this delta area,

104
00:04:39,020 --> 00:04:42,836
where these river-jumping events
in the Mississippi

105
00:04:42,860 --> 00:04:45,676
are building land at the interface
of the land and the sea.

106
00:04:45,700 --> 00:04:47,436
This is really valuable real estate,

107
00:04:47,460 --> 00:04:52,716
and deltas like this are some of the most
densely populated areas on our planet.

108
00:04:52,740 --> 00:04:55,196
So understanding the dynamics
of these landscapes,

109
00:04:55,220 --> 00:04:58,356
how they formed and how they will
continue to change in the future

110
00:04:58,380 --> 00:05:00,780
is really important
for the people that live there.

111
00:05:01,580 --> 00:05:03,116
So rivers also wiggle.

112
00:05:03,140 --> 00:05:06,036
These are sort of bigger jumps
that we've been talking about.

113
00:05:06,060 --> 00:05:08,316
I want to show you guys
some river wiggles here.

114
00:05:08,340 --> 00:05:10,876
So we're going to fly down
to the Amazon River basin,

115
00:05:10,900 --> 00:05:12,916
and here again we have a big river system

116
00:05:12,940 --> 00:05:17,316
that is draining and moving and plowing
material from the Andean Mountains,

117
00:05:17,340 --> 00:05:19,156
transporting it across South America

118
00:05:19,180 --> 00:05:21,860
and dumping it out
into the Atlantic Ocean.

119
00:05:22,660 --> 00:05:27,356
So if we zoom in here, you guys
can see these nice, curvy river pathways.

120
00:05:27,380 --> 00:05:30,356
Again, they're really beautiful,
but again, they're not static.

121
00:05:30,380 --> 00:05:32,116
These rivers wiggle around.

122
00:05:32,140 --> 00:05:35,756
We can use satellite imagery
over the last 30 or so years

123
00:05:35,780 --> 00:05:37,916
to actually monitor how these change.

124
00:05:37,940 --> 00:05:42,116
So take a minute and just watch
any bend or curve in this river,

125
00:05:42,140 --> 00:05:45,116
and you'll see it doesn't stay
in the same place for very long.

126
00:05:45,140 --> 00:05:47,420
It changes and evolves
and warps its pattern.

127
00:05:48,940 --> 00:05:51,316
If you look in this area in particular,

128
00:05:51,340 --> 00:05:54,316
I want you guys to notice
there's a sort of a loop in the river

129
00:05:54,340 --> 00:05:55,756
that gets completely cut off.

130
00:05:55,780 --> 00:05:57,356
It's almost like a whip cracking

131
00:05:57,380 --> 00:06:00,060
and snaps off the pathway
of the river at a certain spot.

132
00:06:00,460 --> 00:06:02,076
So just for reference, again,

133
00:06:02,100 --> 00:06:07,036
in this location, that river
changed its course over four miles

134
00:06:07,060 --> 00:06:08,740
over the course of a season or two.

135
00:06:09,180 --> 00:06:12,076
So the landscapes
that we live in on earth,

136
00:06:12,100 --> 00:06:14,516
as this material
is being eroded from the mountains

137
00:06:14,540 --> 00:06:15,876
and transported to the sea,

138
00:06:15,900 --> 00:06:17,516
are wiggling around all the time.

139
00:06:17,540 --> 00:06:18,996
They're changing all the time,

140
00:06:19,020 --> 00:06:21,476
and we need to be able
to understand these processes

141
00:06:21,500 --> 00:06:24,236
so we can manage and live
sustainably on these landscapes.

142
00:06:24,260 --> 00:06:27,316
But it's hard to do
if the only information we have

143
00:06:27,340 --> 00:06:29,676
is what's going on today
at earth's surface.

144
00:06:29,700 --> 00:06:31,756
Right? We don't have
a lot of observations.

145
00:06:31,780 --> 00:06:36,596
We only have 30 years' worth
of satellite photos, for example.

146
00:06:36,620 --> 00:06:39,516
We need more observations
to understand these processes more.

147
00:06:39,540 --> 00:06:41,156
And additionally, we need to know

148
00:06:41,180 --> 00:06:44,396
how these landscapes are going
to respond to changing climate

149
00:06:44,420 --> 00:06:45,676
and to changing land use

150
00:06:45,700 --> 00:06:48,540
as we continue to occupy
and modify earth's surface.

151
00:06:49,260 --> 00:06:51,796
So this is where the rocks come in.

152
00:06:51,820 --> 00:06:54,316
So as rivers flow,

153
00:06:54,340 --> 00:06:57,236
as they're bulldozing material
from the mountains to the sea,

154
00:06:57,260 --> 00:07:00,716
sometimes bits of sand and clay
and rock get stuck in the ground.

155
00:07:00,740 --> 00:07:03,436
And that stuff that gets stuck
in the ground gets buried,

156
00:07:03,460 --> 00:07:07,196
and through time, we get
big, thick accumulations of sediments

157
00:07:07,220 --> 00:07:09,236
that eventually turn into rocks.

158
00:07:09,260 --> 00:07:11,836
What this means is that we can
go to places like this,

159
00:07:11,860 --> 00:07:14,556
where we see big, thick stacks
of sedimentary rocks,

160
00:07:14,580 --> 00:07:16,076
and go back in time

161
00:07:16,100 --> 00:07:18,836
and see what the landscapes
looked like in the past.

162
00:07:18,860 --> 00:07:20,996
We can do this to help reconstruct

163
00:07:21,020 --> 00:07:25,340
and understand
how earth landscapes evolve.

164
00:07:26,260 --> 00:07:27,876
This is pretty convenient, too,

165
00:07:27,900 --> 00:07:30,876
because the earth has had
sort of an epic history. Right?

166
00:07:30,900 --> 00:07:35,716
So this video here
is a reconstruction of paleogeography

167
00:07:35,740 --> 00:07:39,356
for just the first
600 million years of earth's history.

168
00:07:39,380 --> 00:07:41,356
So just a little bit of time here.

169
00:07:41,380 --> 00:07:44,116
So as the plates move around,

170
00:07:44,140 --> 00:07:47,276
we know climate has changed,
sea level has changed,

171
00:07:47,300 --> 00:07:50,956
we have a lot of different
types of landscapes

172
00:07:50,980 --> 00:07:53,716
and different types of environments
that we can go back --

173
00:07:53,740 --> 00:07:55,116
if we have a time machine --

174
00:07:55,140 --> 00:07:56,476
we can go back and look at,

175
00:07:56,500 --> 00:07:58,236
and we do indeed have a time machine

176
00:07:58,259 --> 00:08:01,595
because we can look at the rocks
that were deposited at these times.

177
00:08:01,620 --> 00:08:03,636
So I'm going to give you
an example of this

178
00:08:03,660 --> 00:08:05,876
and take you to a special
time in earth's past.

179
00:08:05,900 --> 00:08:09,116
About 55 million years ago,
there was a really abrupt warming event,

180
00:08:09,140 --> 00:08:11,636
and what happened was
a whole bunch of carbon dioxide

181
00:08:11,660 --> 00:08:13,476
was released into earth's atmosphere,

182
00:08:13,500 --> 00:08:17,356
and it caused a rapid
and pretty extreme global warming event.

183
00:08:17,380 --> 00:08:20,036
And when I say warm, I mean pretty warm,

184
00:08:20,060 --> 00:08:23,036
that there were things
like crocodiles and palm trees

185
00:08:23,060 --> 00:08:26,076
as far north as Canada
and as far south as Patagonia.

186
00:08:26,100 --> 00:08:29,276
So this was a pretty warm time
and it happened really abruptly.

187
00:08:29,300 --> 00:08:30,516
So what we can do

188
00:08:30,540 --> 00:08:33,596
is we can go back and find rocks
that were deposited at this time

189
00:08:33,620 --> 00:08:37,220
and reconstruct how the landscape changed
in response to this warming event.

190
00:08:37,659 --> 00:08:39,556
So here, yay, rocks.

191
00:08:39,580 --> 00:08:41,916
(Laughter)

192
00:08:41,940 --> 00:08:43,676
Here's a pile of rocks.

193
00:08:43,700 --> 00:08:45,316
This yellow blob here,

194
00:08:45,340 --> 00:08:47,076
this is actually a fossil river,

195
00:08:47,100 --> 00:08:48,767
so just like this cartoon I showed,

196
00:08:48,791 --> 00:08:52,076
these are deposits that were
laid down 55 million years ago.

197
00:08:52,100 --> 00:08:55,196
As geologists, we can go
and look at these up close

198
00:08:55,220 --> 00:08:56,649
and reconstruct the landscape.

199
00:08:57,340 --> 00:08:58,836
So here's another example.

200
00:08:58,860 --> 00:09:01,316
The yellow blob here is a fossil river.

201
00:09:01,340 --> 00:09:02,876
Here's another one above it.

202
00:09:02,900 --> 00:09:06,196
We can go and look in detail
and make measurements and observations,

203
00:09:06,220 --> 00:09:07,596
and we can measure features.

204
00:09:07,620 --> 00:09:09,996
For example, the features
I just highlighted there

205
00:09:10,020 --> 00:09:13,476
tell us that this particular river
was probably about three feet deep.

206
00:09:13,500 --> 00:09:15,596
You could wade
across this cute little stream

207
00:09:15,620 --> 00:09:17,860
if you were walking around
55 million years ago.

208
00:09:18,580 --> 00:09:21,476
The reddish stuff that's above
and below those channels,

209
00:09:21,500 --> 00:09:23,276
those are ancient soil deposits.

210
00:09:23,300 --> 00:09:27,156
So we can look at those to tell us
what lived and grew on the landscape

211
00:09:27,180 --> 00:09:30,740
and to understand how these rivers
were interacting with their floodplains.

212
00:09:31,780 --> 00:09:36,156
So we can look in detail
and reconstruct with some specificity

213
00:09:36,180 --> 00:09:39,036
how these rivers flowed
and what the landscapes looked like.

214
00:09:39,060 --> 00:09:41,540
So when we do this
for this particular place

215
00:09:42,260 --> 00:09:43,476
at this time,

216
00:09:43,500 --> 00:09:46,236
if we look what happened
before this abrupt warming event,

217
00:09:46,260 --> 00:09:49,876
the rivers kind of carved their way
down from the mountains to the sea,

218
00:09:49,900 --> 00:09:55,036
and they looked maybe similar to what
I showed you in the Amazon River basin.

219
00:09:55,060 --> 00:09:57,516
But right at the onset
of this climate change event,

220
00:09:57,540 --> 00:09:59,020
the rivers change dramatically.

221
00:09:59,580 --> 00:10:01,436
All of a sudden they got much broader,

222
00:10:01,460 --> 00:10:05,020
and they started to slide back and forth
across the landscape more readily.

223
00:10:05,980 --> 00:10:09,876
Eventually, the rivers reverted
back to a state that was more similar

224
00:10:09,900 --> 00:10:13,716
to what they would have looked like
before this climate event,

225
00:10:13,740 --> 00:10:15,380
but it took a long, long time.

226
00:10:16,340 --> 00:10:20,196
So we can go back in earth's time
and do these kinds of reconstructions

227
00:10:20,220 --> 00:10:22,836
and understand how
earth's landscape has changed

228
00:10:22,860 --> 00:10:26,636
in response to a climate event like this
or a land use event.

229
00:10:26,660 --> 00:10:28,756
So some of the ways that rivers change

230
00:10:28,780 --> 00:10:33,556
or the reasons that rivers change
their pattern and their movements

231
00:10:33,580 --> 00:10:37,516
is because of things like with extra water
falling on the land's surface

232
00:10:37,540 --> 00:10:39,476
when climate is hotter,

233
00:10:39,500 --> 00:10:42,036
we can move more sediment
and erode more sediment,

234
00:10:42,060 --> 00:10:43,900
and that changes how rivers behave.

235
00:10:44,780 --> 00:10:46,876
So ultimately,

236
00:10:46,900 --> 00:10:49,516
as long as earth's surface is our home,

237
00:10:49,540 --> 00:10:52,916
we need to carefully manage
the resources and risks

238
00:10:52,940 --> 00:10:55,916
associated with living
in dynamic environments.

239
00:10:55,940 --> 00:10:59,876
And I think the only way
we can really do that sustainably

240
00:10:59,900 --> 00:11:02,116
is if we include information

241
00:11:02,140 --> 00:11:06,236
about how landscapes evolved
and behaved in earth's past.

242
00:11:06,260 --> 00:11:07,476
Thank you.

243
00:11:07,500 --> 00:11:11,940
(Applause)