What rivers can tell us about the earth's history | Liz Hajek

翻译人员: Lipeng Chen 校对人员: Hongmeng Yang

All right, let's get up our picture of the earth.

好的，我们来看看地球的照片。

The earth is pretty awesome.

地球确实令人惊叹。

I'm a geologist, so I get pretty psyched about this,

我是名地质学家，所以对这很着迷，

but the earth is great.

地球很伟大。

It's powerful, it's dynamic, it's constantly changing.

它充满力量，充满活力， 时时刻刻都在变化。

It's a pretty exciting place to live.

确实是个令人兴奋的居住地。

But I want to share with you guys today my perspective as a geologist

但我今天想从一个地质学家的视角

in how understanding earth's past

和你们分享，了解地球的过去

can help inform and guide decisions that we make today

将如何帮助并指导我们在地球上

about how to sustainably live on earth's surface.

可持续的生存下去。

So there's a lot of exciting things that go on on the surface of the earth.

地球表面有着许多令人兴奋的事物。

If we zoom in here a little bit,

如果我们在这里放大一点，

I want to talk to you guys a little bit about one of the things that happens.

我想和你们谈谈一个现象。

物质在地球的表面不断被冲刷，

Material get shuffled around earth's surface all the time,

其中一个重要的影响是， 高山上的东西也会被冲刷掉，

and one of the big thing that happens is material from high mountains

gets eroded and transported and deposited in the sea.

被搬运并最终沉淀于海底。

And this process is ongoing all the time,

这一过程一直发生着，

并且深刻的影响了地形的形成。

and it has huge effects on how the landscape works.

So this example here in south India --

举个例子，在印度南部

we have some of the biggest mountains in the world,

有着世界上最高的山峰，

and you can see in this satellite photo

你可以从这张卫星图像上看到，

rivers transporting material from those mountains out to the sea.

河流运输着这些山上的东西直至海洋。

You can think of these rivers like bulldozers.

你可以把这些河流想象成推土机。

They're basically taking these mountains and pushing them down towards the sea.

它们基本上就是在拽着这些山峰， 将它们向海的方向推移。

We'll give you guys an example here.

给你们举个例子。

So we zoom in a little bit.

我们放大一点。

I want to talk to you guys specifically about a river.

我想和你们具体谈谈其中一条河。

我们可以看到河流 运输物质到海洋的过程中，

We can see these beautiful patterns that the rivers make

as they're pushing material down to the sea,

描绘出的美丽图案，

but these patterns aren't static.

但是这些图案不是一成不变的。

These rivers are wiggling and jumping around quite a bit,

这些河流这里绕一绕，那里绕一绕，

就会对我们的生活产生很大的影响。

and it can have big impacts on our lives.

So an example of this is this is the Kosi River.

其中一个例子是戈西河。

So the Kosi River has this nice c-shaped pathway,

戈西河有着漂亮的C形河道，

and it exits the big mountains of Nepal

它从尼泊尔的高山流出，

carrying with it a ton of material,

带着成吨的矿物，

a lot of sediments that's being eroded from the high mountains,

通过侵蚀高山得到的沉积物，

and it spreads out across India

穿过印度，

and moves this material.

并且运输着它们。

So we're going to zoom in to this area

我们将放大这一块区域，

and I'm going to tell you a little bit about what happened with the Kosi.

而我将告诉你们戈西河发生的事情。

It's an example of how dynamic these systems can be.

这个例子告诉了我们 这些系统的动态程度。

So this is a satellite image from August of 2008,

这是2008年八月的一张卫星图像，

and this satellite image is colored

已经被着色了，

所以植物或植被都是绿色的，

so that vegetations or plants show up as green

and water shows up as blue.

水是蓝色的。

So here again you can see that c-shaped pathway

你可以看到当它离开尼泊尔时

that this river takes as it exits Nepal.

是呈C形的河道。

And now this is monsoon season.

现在是季风季节。

August is monsoon season in this region of the world,

八月是这个地区的季风季节，

and anyone that lives near a river is no stranger to flooding

任何住在河流旁边的人都对洪水

and the hazards and inconveniences at minimum that are associated with that.

以及洪水带来的危害 和不便不感到陌生。

But something interesting happened in 2008,

但是2008年发生了有趣的事情，

and this river moved in a way that's very different.

这条河流以十分不同的方式变化了。

It flooded in a way that's very different than it normally does.

它以与平常不同的方式造成了洪水。

So the Kosi River is flowing down here,

戈西河流到这里，

but sometimes as these rivers are bulldozing sediment,

但是有时随着这些河流 运输的沉积物越来越多，

they kind of get clogged,

河道开始堵塞了，

and these clogs can actually cause the rivers

而这些堵塞实际上可以

导致河流走向的巨大变动。

to shift their course dramatically.

这是仅仅两周后的卫星图像。

So this satellite image is from just two weeks later.

Here's the previous pathway,

这是之前的河道，

that c-shaped pathway,

那C形的河道，

and you notice it's not blue anymore.

你会发现它不再是蓝的了。

But now what we have is this blue pathway

现在蓝色的河道，

that cuts down the middle of the field of view here.

在图中央纵切了一刀。

现实中，戈西河漫上了它的河堤，

What happened is the Kosi River jumped its banks,

and for reference, the scale bar here is 40 miles.

还有这里的比例尺是40英里。

This river moved over 30 miles very abruptly.

这条河十分突然的 移动了超过30英里。

So this river got clogged and it jumped its banks.

这条河堵住了，然后漫过了河堤。

Here's an image from about a week later,

这是一周后的一张图片，

and you can see these are the previous pathways,

你可以看到这些是之前的河道，

and you can see this process of river-jumping continues

而且漫堤的过程仍在继续，

as this river moves farther away from its major course.

这条河离它的主道越来越远。

So you can imagine in landscapes like this,

所以你可以想象，

where rivers move around frequently,

在这种河流经常改道的地形里，

it's really important to understand when, where and how they're going to jump.

理解河流何时、何地以及 如何改道是十分重要的。

But these kinds of processes also happen a lot closer to home as well.

但是这种过程同样也发生在我们身边。

So in the United States,

在美国，

we have the Mississippi River that drains most of the continental US.

密西西比河流经大部分的美洲大陆。

It pushes material from the Rocky Mountains

它推动着来自落基山脉

and from the Great Plains.

和大平原的物质。

It drains it and moves it all the way across America

它夹带着这些物质贯穿美国，

and dumps it out in the Gulf of Mexico.

然后把它们倒入墨西哥湾。

So this is the course of the Mississippi that we're familiar with today,

这是我们今天熟悉的密西西比河河道，

but it didn't always flow in this direction.

但是它并非一直是按这个方向流动的。

If we use the geologic record,

如果我们利用地质记录，

we can reconstruct where it went in the past.

就可以重建它过去的走向。

So for example, this red area here

举个例子，这里红色的区域

is where we know the Mississippi River flowed and deposited material

据我们目前所知，是大约 4600年前密西西比河流过

about 4,600 years ago.

并且沉积物质的地方。

Then about 3,500 years ago it moved

然后大约在3500年前，

to follow the course outlined here in orange.

它移动到了橘色标注的河道流动。

And it kept moving and it keeps moving.

它一直移动，不停移动。

So here's about 2,000 years ago,

这是约2000年前，

a thousand years ago,

1000年前，

700 years ago.

700年前。

And it was only as recently as 500 years ago

直到500年前，

that it occupied the pathway that we're familiar with today.

它才移动到了我们今天熟悉的河道。

So these processes are really important,

这些过程十分重要，

and especially here, this delta area,

特别是这里，这个三角洲，

where these river-jumping events in the Mississippi

在这个三角洲里密西西比河 不断漫堤和改道，

are building land at the interface of the land and the sea.

于是在陆地和海洋的交界处 形成了（新的）陆地。

This is really valuable real estate,

这是非常宝贵的资产，

and deltas like this are some of the most densely populated areas on our planet.

像这样的三角洲是我们星球上 人口最稠密的地区。

So understanding the dynamics of these landscapes,

所以了解这些地形的动态变化，

how they formed and how they will continue to change in the future

它们如何形成，在未来将如何继续演化

is really important for the people that live there.

对于生活在那里的人们十分重要。

So rivers also wiggle.

河流也会轻微摆动。

These are sort of bigger jumps that we've been talking about.

我们刚才谈到的是更大的漫堤过程。

I want to show you guys some river wiggles here.

我想向你们展示这里的一些河流摆动。

我们转移到亚马逊河流域，

So we're going to fly down to the Amazon River basin,

and here again we have a big river system

类似的，这里有一个巨大的河流系统，

that is draining and moving and plowing material from the Andean Mountains,

不断冲刷，转移着 安第斯山脉上的物质，

transporting it across South America

携带着它们穿越南美大陆，

and dumping it out into the Atlantic Ocean.

最终它们被倾入大西洋。

So if we zoom in here, you guys can see these nice, curvy river pathways.

如果我们在这里放大， 你们可以看到这些蜿蜒曲折的河道。

Again, they're really beautiful, but again, they're not static.

同样的，它们十分美丽，但又不稳定。

These rivers wiggle around.

这些河流的走向不停扭曲变动。

We can use satellite imagery over the last 30 or so years

我们可以利用最近30年的卫星图像

to actually monitor how these change.

来实际观察这是如何变化的。

So take a minute and just watch any bend or curve in this river,

花点时间看看这条河 任何地方的弯曲，

and you'll see it doesn't stay in the same place for very long.

你会发现它并不会在一个地方呆很久。

它会不断变化，演变，改变图案。

It changes and evolves and warps its pattern.

If you look in this area in particular,

如果你再仔细看看这块区域，

I want you guys to notice there's a sort of a loop in the river

我想让你们关注到河流中 有一个类似圆圈的地方，

完完全全的被分隔开来了。

that gets completely cut off.

It's almost like a whip cracking

它就像个马鞭，

and snaps off the pathway of the river at a certain spot.

从河流的某个位置被分开了。

So just for reference, again,

方便大家参考，

in this location, that river changed its course over four miles

在这个地方，河流在一到两个季节里

over the course of a season or two.

将它的河道移动了将近四英里。

So the landscapes that we live in on earth,

所以我们所居住的这个地球上的 地形其实是不断在变化的：

as this material is being eroded from the mountains

随着高山上的物质被不断侵蚀，

and transported to the sea,

不断被运输到海洋，

are wiggling around all the time.

地形也在不断地发生变化，

它们时时刻刻都在变化着，

They're changing all the time,

而我们需要理解这些过程

and we need to be able to understand these processes

以便于可持续的生存在这些地形之中。

so we can manage and live sustainably on these landscapes.

But it's hard to do if the only information we have

但如果仅仅知道地表发生了什么，

is what's going on today at earth's surface.

仍不足以为可持续的生存指明方向。

Right? We don't have a lot of observations.

我们的观测还不够。

We only have 30 years' worth of satellite photos, for example.

例如，我们只有近30年的卫星数据。

We need more observations to understand these processes more.

我们需要更多的观测来 更加深入地了解这些过程。

And additionally, we need to know

此外，我们需要了解

how these landscapes are going to respond to changing climate

随着人类不断占据和改造地表，

and to changing land use

这些地形对气候的变化和

as we continue to occupy and modify earth's surface.

人类对土地的使用将会呈现怎样的反应。

So this is where the rocks come in.

这就是为什么我们接下来会提到岩石。

So as rivers flow,

随着河流流动，

as they're bulldozing material from the mountains to the sea,

随着它们不断将物质 从高山运送到海洋，

sometimes bits of sand and clay and rock get stuck in the ground.

有的时候一些泥沙和石块会滞留在地面。

And that stuff that gets stuck in the ground gets buried,

这些留在地面的沙石逐渐被掩埋，

and through time, we get big, thick accumulations of sediments

随着时间的流逝， 便形成了又大又厚的堆积，

that eventually turn into rocks.

最终变成了岩石。

What this means is that we can go to places like this,

这意味着，我们可以去到

where we see big, thick stacks of sedimentary rocks,

拥有大量沉积岩的地方，

and go back in time

回到过去，

and see what the landscapes looked like in the past.

了解过去的地形是什么样子的。

We can do this to help reconstruct

从而我们可以重构

and understand how earth landscapes evolve.

并理解地球的地形演化过程。

This is pretty convenient, too,

这也非常方便，

because the earth has had sort of an epic history. Right?

因为地球有着宏伟的历史，对吧？

So this video here is a reconstruction of paleogeography

这个视频重构的是地球历史中

for just the first 600 million years of earth's history.

最开始的那6亿年的地表演变。

So just a little bit of time here.

我们花了短短几秒就看完了（笑）。

So as the plates move around,

随着板块移动，

we know climate has changed, sea level has changed,

我们知道气候变化了， 海平面变化了，

不同的地形和环境形成了，

we have a lot of different types of landscapes

and different types of environments that we can go back --

我们可以回到过去——

if we have a time machine --

如果有时间机器的话——

we can go back and look at,

我们可以回到过去进行观察，

and we do indeed have a time machine

而我们确实拥有一台时间机器，

because we can look at the rocks that were deposited at these times.

我们可以观察这段时间内堆积的岩石。

So I'm going to give you an example of this

举个例子，带你们到

地球历史上的一个特殊时期。

and take you to a special time in earth's past.

大约5500万年前，地球骤暖。

About 55 million years ago, there was a really abrupt warming event,

and what happened was a whole bunch of carbon dioxide

当时大量的二氧化碳

被释放到了地球的大气中，

was released into earth's atmosphere,

这导致了快速并且极端的全球变暖。

and it caused a rapid and pretty extreme global warming event.

And when I say warm, I mean pretty warm,

我说的“暖和”是指超级暖和，

that there were things like crocodiles and palm trees

那时北至加拿大，南至巴塔哥尼亚，

as far north as Canada and as far south as Patagonia.

都能找到鳄鱼和棕榈树。

So this was a pretty warm time and it happened really abruptly.

所以这的确是非常暖和的时期， 而且发生得非常突然。

我们能做的，

So what we can do

就是回到过去，找到当时沉积的岩石，

is we can go back and find rocks that were deposited at this time

并且重构这些地形是 如何随全球变暖变化的。

and reconstruct how the landscape changed in response to this warming event.

So here, yay, rocks.

这里，太好了，有岩石。

(Laughter)

（笑声）

Here's a pile of rocks.

这是一堆岩石。

This yellow blob here,

这里黄色圈出的一片，

this is actually a fossil river,

其实是一条古河道，

so just like this cartoon I showed,

就像我刚才展示的卡通一样，

these are deposits that were laid down 55 million years ago.

这些是5500万年前留下的沉积物。

As geologists, we can go and look at these up close

作为地质学家， 我们可以近距离的观测它们，

and reconstruct the landscape.

并且重构地形。

So here's another example.

还有一个例子。

The yellow blob here is a fossil river.

这黄色范围内的一片是古河道。

Here's another one above it.

在它上面还有一片。

We can go and look in detail and make measurements and observations,

我们可以到实地仔细考察、测量，

and we can measure features.

还可以观测它们的特征。

For example, the features I just highlighted there

例如，我刚刚标注的地方

tell us that this particular river was probably about three feet deep.

告诉我们这条河大约3英尺深。

You could wade across this cute little stream

如果你生活在5500万年前，

if you were walking around 55 million years ago.

你可以涉水通过这条萌萌的小溪。

The reddish stuff that's above and below those channels,

在这些渠道之上和之下的红色物质，

those are ancient soil deposits.

是古代的土壤沉积。

我们可以通过它们知道在这片土地 生活和生长着什么样的生物，

So we can look at those to tell us what lived and grew on the landscape

and to understand how these rivers were interacting with their floodplains.

并且了解这些河流是如何和 冲积平原相互影响的。

So we can look in detail and reconstruct with some specificity

我们可以仔细的观测，准确的重构

how these rivers flowed and what the landscapes looked like.

这些河流的走向，以及地形的样貌。

So when we do this for this particular place

现在当我们为这个地区重构过去的

at this time,

地形时，

如果我们看看 在这次突然变暖之前发生了什么，

if we look what happened before this abrupt warming event,

the rivers kind of carved their way down from the mountains to the sea,

这些河流从高山到海洋开辟了一条道路，

and they looked maybe similar to what I showed you in the Amazon River basin.

看上去和我向你们展示的 亚马逊流域很像。

But right at the onset of this climate change event,

但是气候变化刚一开始，

the rivers change dramatically.

这些河流就发生了剧变。

All of a sudden they got much broader,

首先它们一下子就变宽了许多，

and they started to slide back and forth across the landscape more readily.

其次它们在地表上的 改道活动更加频繁。

Eventually, the rivers reverted back to a state that was more similar

最终，这些河流变回了

to what they would have looked like before this climate event,

气候变暖之前的样子，

but it took a long, long time.

但这花了很长很长的时间。

So we can go back in earth's time and do these kinds of reconstructions

我们可以回到地球的过去， 做类似的重构，

and understand how earth's landscape has changed

了解地表是如何随着气候变化， 如之前提到的地球骤暖

in response to a climate event like this or a land use event.

或土地使用的变化而变化的。

So some of the ways that rivers change

河流产生变化一些方式，

or the reasons that rivers change their pattern and their movements

或是改变走向和水文活动的原因，

is because of things like with extra water falling on the land's surface

有一些是因为当地表有了更多的水，

when climate is hotter,

再加上气候变暖，

we can move more sediment and erode more sediment,

沉积物会被更加频繁地被运送或侵蚀，

and that changes how rivers behave.

这些都会对河流产生影响。

So ultimately,

总而言之，

as long as earth's surface is our home,

只要地球是我们的家园，

we need to carefully manage the resources and risks

我们就需要小心的管理资源，

associated with living in dynamic environments.

警惕生活在这种动态环境中的风险。

And I think the only way we can really do that sustainably

我认为我们能真正持续 这么做的唯一途径

is if we include information

是充分考虑在地球历史的

about how landscapes evolved and behaved in earth's past.

慢慢长河中，地形的演变和走向。

Thank you.

谢谢。

(Applause)

（掌声）