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

譯者: Lilian Chiu 審譯者: Howard Chuang

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

好，我們先來看一下地球的圖片。

The earth is pretty awesome.

地球是很了不起的。

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

我是地質學家， 所以我對這點十分亢奮。

but the earth is great.

但地球很棒，

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

它很強大、它是動態的、 它不斷在改變，

It's a pretty exciting place to live.

住在地球是很讓人興奮的。

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

但我今天想和大家分享的， 是我身為地質學家的觀點，

in how understanding earth's past

來談談了解地球的過去，

can help inform and guide decisions that we make today

如何能提供我們資訊和導引，

about how to sustainably live on earth's surface.

協助我們在現今做出關於 如何在地球表面永續居住的決策。

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

在地球表面上， 有許多讓人興奮的事物在發生。

If we zoom in here a little bit,

如果我們把這裡放大一點，

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

我想要跟大家談一下， 其中一件正在發生的事：

物質隨時在地球表面上移來移去，

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

其中一件在發生的大事，

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

就是來自高山的物質 會被侵蝕、運送、沉澱到大海中。

gets eroded and transported and deposited in the sea.

And this process is ongoing all the time,

這個過程一直在進行中，

and it has huge effects on how the landscape works.

它對於地景有很大的影響。

So this example here in south India --

這裡的例子是南印度，

we have some of the biggest mountains in the world,

這裡有一些世界最大的山。

and you can see in this satellite photo

從衛星照片可以看見，

rivers transporting material from those mountains out to the sea.

河流將物質從那些山 向外運送到大海。

You can think of these rivers like bulldozers.

你可以把這些河流想像成推土機，

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

基本上，它們是在 將這些山推移向大海。

We'll give you guys an example here.

我會給大家看一個例子。

So we zoom in a little bit.

再放大一點來看。

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

我想要跟你們談的是一條河。

We can see these beautiful patterns that the rivers make

你們可以看見河流 在把物質推向大海的同時，

as they're pushing material down to the sea,

構成了很漂亮的圖案，

but these patterns aren't static.

但這些圖案不是靜態不變的，

These rivers are wiggling and jumping around quite a bit,

這些河流挺會擺動和跳動的，

這對我們的生活有很大的影響。

and it can have big impacts on our lives.

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

這裡是一個例子：戈西河。

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

戈西河有個很完好的 C 形路徑，

and it exits the big mountains of Nepal

它從尼泊爾的大型山岳出海，

carrying with it a ton of material,

帶著一大堆的物質，

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

很多從高山侵蝕下來的沉積物。

and it spreads out across India

它佈及整個印度，

and moves this material.

移動著這些物質。

So we're going to zoom in to this area

我們再把這個區域放大，

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

我要告訴各位戈西河的狀況。

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

這個例子可以說明 這些系統有多動態。

So this is a satellite image from August of 2008,

這是一張衛星影像， 於 2008 年 8 月拍攝。

and this satellite image is colored

這張衛星影像是彩色的，

so that vegetations or plants show up as green

植被和植物會以綠色呈現，

and water shows up as blue.

水會用藍色呈現。

So here again you can see that c-shaped pathway

你可以再次看到 C 形路徑，

that this river takes as it exits Nepal.

這條河流從尼泊爾出海。

And now this is monsoon season.

這時期是季風季，

August is monsoon season in this region of the world,

在這個區域，八月是季風季。

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

住在河流附近的人， 對於洪水絕對不陌生，

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

且肯定也很熟悉洪水 帶來的危險以及不便。

But something interesting happened in 2008,

但在 2008 年發生了 一件很有意思的事，

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

這條河流的移動方式變得非常不同，

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

它泛濫的方式也和平時非常不同。

So the Kosi River is flowing down here,

戈西河在這裡向下流，

but sometimes as these rivers are bulldozing sediment,

但有時，當這些河流 在推動沉積物時，

they kind of get clogged,

它們會像是塞住了。

and these clogs can actually cause the rivers

這些堵塞會造成河流

to shift their course dramatically.

顯著轉變它們的路線。

So this satellite image is from just two weeks later.

這張衛星影像是兩週後拍的，

Here's the previous pathway,

這是先前的路徑，

that c-shaped pathway,

C 形的路徑。

and you notice it's not blue anymore.

你可以注意到，它不再是藍色的了。

But now what we have is this blue pathway

現在我們多了這條藍色路徑，

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

從畫面的中間切下來。

What happened is the Kosi River jumped its banks,

發生的事是： 戈西河躍過了它的堤岸。

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

供大家參考，這條比例尺的 長度是 40 英哩。

This river moved over 30 miles very abruptly.

這條河流非常突然地 移動了超過 30 英哩。

So this river got clogged and it jumped its banks.

這條河流被堵塞， 接著躍過了它的堤岸。

Here's an image from about a week later,

這是大約一週後的影像。

and you can see these are the previous pathways,

可以看見這些是先前的路徑，

and you can see this process of river-jumping continues

且可以看見這個 河流跳躍的過程還在持續著，

as this river moves farther away from its major course.

這條河流離它的主河道越來越遠。

So you can imagine in landscapes like this,

你可以想像，在這種河流

where rivers move around frequently,

常會到處移動的地景中，

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

知道它們何時、在哪兒、 以及如何跳躍是非常重要的。

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

但這類過程也會在離家 更近的地方常常發生，

So in the United States,

在美國，

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

我們有密西西比河， 流過幾乎整個美國大陸，

It pushes material from the Rocky Mountains

它把物質從洛磯山脈，

and from the Great Plains.

以及北美大平原推走。

It drains it and moves it all the way across America

它帶著物質，一路穿越美國，

and dumps it out in the Gulf of Mexico.

然後將物質倒在墨西哥灣。

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

這是我們現今很熟悉的 密西西比河路線，

but it didn't always flow in this direction.

但它之前並非都是流向這個方向的。

If we use the geologic record,

如果我們使用地理記錄，

we can reconstruct where it went in the past.

我們可以重新建造出 它過去流過的路線。

So for example, this red area here

比如，這裡的紅色區域

is where we know the Mississippi River flowed and deposited material

是據我們所知在 4600 年前密西西比河

about 4,600 years ago.

流過並將物質沉積的地方。

Then about 3,500 years ago it moved

接著，約 3500 年前，它移動了，

to follow the course outlined here in orange.

延著這裡用橘色標出的路線流動。

And it kept moving and it keeps moving.

它不斷、不斷地移動。

So here's about 2,000 years ago,

這是約 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

一直要到 500 年前 這麼近期的時候，

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

它才移到了我們現今熟悉的路徑。

So these processes are really important,

這些過程非常重要，

and especially here, this delta area,

特別是這裡，這個三角區域，

where these river-jumping events in the Mississippi

在這裡，這些 密西西比河的跳躍事件

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

在土地和海洋的接介處建立了土地。

This is really valuable real estate,

這是非常珍貴的不動產，

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

地球上有許多人口密度最高的 區域都是像這樣的三角洲。

So understanding the dynamics of these landscapes,

所以，了解這些地景的動態、

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

它們如何形成、 以及它們未來會如何持續改變，

is really important for the people that live there.

對於居住在那兒的人而言， 是非常重要的。

So rivers also wiggle.

所以，河流也會曲行。

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

這些是我們先前談到的大跳躍。

I want to show you guys some river wiggles here.

我想讓大家看一些河流的曲行，

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

所以我們要飛去亞瑪遜河盆地，

and here again we have a big river system

在這裡我們也有很大的河流系統，

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

將物質從安地斯山脈取下，

transporting it across South America

運輸到南美的另一端，

and dumping it out into the Atlantic Ocean.

將它丟在大西洋中。

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

我們把這裡放大， 讓大家能看見這些彎曲的路徑。

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

同樣地，它們也很漂亮， 但也同樣地，它們不是靜態的。

These rivers wiggle around.

這些河流會到處曲行。

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

我們可以用 過去 30 年的衛星影像，

to actually monitor how these change.

來監看這些改變。

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

花一點時間，看著這條河的彎曲處，

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

你會發現它並不會在同一處 停留很長的時間。

It changes and evolves and warps its pattern.

它會改變、會演化、 會扭曲它的路線。

If you look in this area in particular,

我們可以特別看一下這個區域，

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

請大家注意，河流的這裡 有一個像是迴圈的狀況，

that gets completely cut off.

是完全切割開來的。

It's almost like a whip cracking

幾乎就像是鞭子猛擊過去，

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

在某個點把河流的路徑給打斷。

So just for reference, again,

這比例尺同樣也是參考用，

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

在這個地方，河流路徑改變了 4 英哩，

over the course of a season or two.

且只花了一到兩季的時間。

So the landscapes that we live in on earth,

所以在地球上我們所居住的地景，

as this material is being eroded from the mountains

隨著這些物質從山上被侵蝕下來

and transported to the sea,

並運送到海洋，

are wiggling around all the time.

隨時隨地都在移動。

它們無時無刻不在改變，

They're changing all the time,

而我們必須要了解這些過程，

and we need to be able to understand these processes

才能在這些地景中 以永續的方式生活下去。

so we can manage and live sustainably on these landscapes.

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

但是，如果我們手上只有 關於現今地球表面

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

發生什麼狀況的資訊， 就很難做到。

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

對吧？我們並沒有很多觀察資料。

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

比如，我們的衛星照片 就只有近 30 年的。

We need more observations to understand these processes more.

我們需要更多的觀察 才能更了解這些過程。

And additionally, we need to know

此外，我們得要知道

how these landscapes are going to respond to changing climate

這些地景對於氣候變遷、

and to changing land use

以及因我們持續佔領和改變地球表面 而造成的土地使用改變，

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

將會有什麼反應。

So this is where the rocks come in.

這就是要來談岩石的地方了。

So as rivers flow,

隨著河流流動，

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

隨著它們把物質從山上推到海中，

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

有些沙、泥、石頭會卡在地上，

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

卡在地上的這些東西就會被埋掉，

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

隨著時間，會讓沉積物更多更厚，

that eventually turn into rocks.

最終變成岩石。

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

這意味著，我們可以到 圖上的這種地方，

where we see big, thick stacks of sedimentary rocks,

在這裡會看到厚實的 層層大型沉積岩，

and go back in time

再回到過去，

and see what the landscapes looked like in the past.

看看過去的地景是什麼樣子的。

We can do this to help reconstruct

我們可以這樣做，來重新建造

and understand how earth landscapes evolve.

並了解地球地景是如何演化的。

This is pretty convenient, too,

這也挺方便的，

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

因為地球的歷史還蠻壯觀的，對吧？

So this video here is a reconstruction of paleogeography

這段影片是古地理學的重建，

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

它僅呈現了地球歷史的前六億年。

So just a little bit of time here.

只是一點點時間而已。

So as the plates move around,

隨著板塊移動，

we know climate has changed, sea level has changed,

我們知道氣候改變了、 海平面改變了，

we have a lot of different types of landscapes

我們有許多不同的地景，

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

及不同型的環境， 如果我們有時光機，

if we have a time machine --

就可以回到過去，

we can go back and look at,

我們可以回去看看，

and we do indeed have a time machine

且我們的確有時光機，

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

因為我們可以去看 這些時代所沉積的岩石。

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

讓我來舉個例子，

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

帶大家回到地球 過去的一個特殊時點，

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

大約五千五百萬年前，

and what happened was a whole bunch of carbon dioxide

當時的狀況是有大量的二氧化碳

被排放到地球的大氣層，

was released into earth's atmosphere,

造成了快速且極端的全球暖化事件。

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

And when I say warm, I mean pretty warm,

我說的暖化，是非常暖的暖化，

that there were things like crocodiles and palm trees

當時甚至會有鱷魚和棕櫚樹，

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

出現在很北方如加拿大、 以及很南方如巴塔哥尼亞的地方。

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

這是相當溫暖的時期， 且發生的非常突然。

So what we can do

我們能做的是，

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

回到過去，找出 在這個時期沉積的岩石，

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

然後重建出因應這暖化事件 而改變的地景。

So here, yay, rocks.

所以，這裡是──太棒了，岩石。

(Laughter)

（笑聲）

Here's a pile of rocks.

這裡有一堆岩石。

This yellow blob here,

這裡黃色的部份，

this is actually a fossil river,

其實是古河流，

so just like this cartoon I showed,

就像我剛剛展示的連環圖，

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

這些沉積是五千五百萬年前發生的。

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

身為地質學家， 我們可以更近距離去看，

and reconstruct the landscape.

並重建出地景來。

So here's another example.

這裡還有另一個例子。

The yellow blob here is a fossil river.

這裡的黃色部份是古河流。

Here's another one above it.

上面還有一條。

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

我們可以更細部去看， 並做些測量與觀察，

and we can measure features.

我們可以去測量特徵。

For example, the features I just highlighted there

比如，我剛剛強調出來的特徵，

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

告訴我們這條河流可能有三英呎深。

You could wade across this cute little stream

如果五千五百萬年前你在這裡行走，

if you were walking around 55 million years ago.

你可以徒步跋涉通過這條小溪。

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

這些河床上面和下面的紅色部份，

those are ancient soil deposits.

是古時的土壤沉積。

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

看著這些，我們就可以知道 在這地景上住著或生長著什麼，

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

並了解這些河流如何 與它們的泛濫平原互動。

So we can look in detail and reconstruct with some specificity

我們可以去看細節， 並更明確地重建出

how these rivers flowed and what the landscapes looked like.

這些河流如何流動、 以及當時地景是什麼樣子。

So when we do this for this particular place

當我們針對這個時期的特定地點

at this time,

這麼做時，

if we look what happened before this abrupt warming event,

如果我們去探究在突發暖化事件 之前發生了什麼事，

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

河流有點像是從 山上切下一條路通往海洋，

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

看起來會有點像是我先前展示的 亞瑪遜盆地的狀況。

But right at the onset of this climate change event,

但就在這氣候變遷甚至開始時，

the rivers change dramatically.

河流有了戲劇性的改變，

All of a sudden they got much broader,

突然間它們變寬許多，

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

且它們開始更快速地 在地景上前後滑動。

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

最終，河流回復到類似

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

氣候事件發生之前的狀態，

but it took a long, long time.

但這花了非常長的時間。

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

我們可以回到地球的過去 並做這種重建，

and understand how earth's landscape has changed

以了解地球的地景如何改變，

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

來因應像這樣的氣候事件 或土地使用事件。

So some of the ways that rivers change

河流改變的方式、

or the reasons that rivers change their pattern and their movements

或河流改變的原因以及移動，

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

要歸因於像是當氣候變熱時 有額外的水落在

when climate is hotter,

地球表面的這類狀況。

we can move more sediment and erode more sediment,

更多沉積物被搬移、 更多沉積物被侵蝕，

and that changes how rivers behave.

就會改變河流的行為。

So ultimately,

所以，最終，

as long as earth's surface is our home,

只要地球表面還是我們的家園，

we need to carefully manage the resources and risks

我們就需要小心管理與居住在

associated with living in dynamic environments.

動態環境相關的資源與風險。

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

我認為，要做到這一點的 永續方法只有一個，

is if we include information

就是我們要能納入

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

關於地景如何演化 以及過去行為的資訊。

Thank you.

謝謝大家。

(Applause)

（鼓掌）