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如何产生三角洲 – 译学馆
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如何产生三角洲

Why Do Rivers Have Deltas?

这个世界上有两种人
The world is divided into two kinds of people:
肚脐凹陷的人
those with innie belly buttons,
和肚脐凸起的人
and those with outies.
河流同样也有凹凸之分
Rivers also have innies and outies
不过不是肚脐 而是河口
not belly buttons, but mouths:
在河流入海的地方
where rivers flow into the sea,
陆地会向外延伸 或者向内弯曲
the land either pokes out or bends inward.
但是河流又没有脐带
But rivers don’t have umbilical cords,
那它们为什么会有凹凸的区别呢?
so why do they have innies and outies?
海岸是两种对立力量的前线阵地
Well, coasts are the front lines between two opposing forces
即陆地与海洋
land and water.
当海洋入侵陆地时
In order for the ocean to invade the land,
海平面会升高
sea level either has to come up,
陆地会下沉或者被侵蚀
or the land has to sink down or be eroded away.
当陆地深入海洋时
And in order for the land to advance into the ocean,
要么海平面下降
sea level either has to drop,
要么陆地堆积抬升
or the land has to build or be lifted up.
很显然 如果海平面下降后又上升
Obviously, if sea level drops and then rises back again,
那两边都会回到原点
there’s no net gain on either side.
但河流的参与会让情况变得更加复杂
But things get more complicated when a river joins the battle.
比如 在上个冰河期
For example, during the last ice age,
海平面下降了120多米
sea levels fell by over 120 meters,
而河流也在流向下降的海洋时切割出越来越深的山谷
and rivers cut deeper and deeper valleys to reach the falling seas.
但之后 约18000年前
Then, about 18,000 years ago,
变暖的气温开始融化冰层
warming temperatures began to melt the ice,
而不断上升的海水淹没了世界各地的河谷
and the rising seas flooded river valleys around the world,
并形成巨大的河口
creating giant estuaries,
给我们创造出如今凹陷的海岸线
and giving us the innie-riddled coastlines we have today.
但当海洋向陆地稳步推进的趋势
But when the steady landward march of the seas
终于在大约7000年前开始变缓时
finally began to slow about 7,000 years ago,
某些河口附近的海岸线
the coastlines around the mouths of some rivers
开始夺回一部分的陆地
began to gain back some ground.
其关键因素是河流带来的沉积物
The key factor was the sediment the river dropped
在入海口速度逐渐放慢
as its current slowed at the entrance to the sea.
在沉积物足够多
Where the sediment supply was big enough,
并且海洋足够平静的地方
and the ocean was calm enough,
沉积下来的泥沙就会开始堆积
the dropped dirt piled up,
并最终形成了新的陆地 不仅使河道增长
eventually forming new land that both lengthened the river
还把它一分为二
and divided it in two.
在新的两个河口处 泥沙会继续沉淀堆积
Dirt continued to drop out and build up at the mouths of both channels,
并再次分割河道 这样反复下去
splitting the river again, and again, and again
堆积出一片新的陆地 并缓缓深入海洋
creating a new lobe of land advancing slowly into the sea.
因此 世界上许多大型的外凸型河口
Thus the world’s great outie river-mouths
及其富饶的三角洲 如尼罗河和长江
the fertile deltas like Nile and Yangtze
从诞生起就促进了人类文明的发展
that have helped foster human civilization since its birth
并且几乎都是在同一时间形成
all came into being at just about the same time.
当然 这不适用于世界上所有肚脐凸起的人
The same can’t be said for all the world’s outie belly-buttons.
但我们可以说
What can be said, though, is that innies and outies
不管是河口还是肚脐 凹陷或凸起
for both rivers and people
都只是见证我们诞生的一个小小的纪念
are a small record of how we came to be.
非常感谢以下组织
A huge thank-you to the following organizations,
他们致力于维持三角洲的可持续性
all working toward sustainable deltas,
并赞助了这部视频
for sponsoring this video
包括贝尔蒙论坛 可持续三角洲倡议
the Belmont Forum, the Sustainable Deltas Initiative,
美国国家地球表面动力学中心
the National Center for Earth-Surface Dynamics,
明尼苏达大学的St Anthony Falls实验室
the St Anthony Falls Laboratory ofthe University of Minnesota,
以及三角洲工程
and the DELTAS project.
这些组织研究世界各地的三角洲
These organizations study deltas around the world,
尤其是它们如何受到人类活动的威胁
in particular how they’re threatened by human activities
比如水坝的修建 河流的改道
such as building dams, channelizing rivers,
以及气候变化导致的海平面上升
and climate change induced sea level rise.
如果我们再不去加以关注
If we don’t pay attention,
我们就可能会失去
we might lose the landform that allowed us
最初孕育我们文明的起源地
to become civilized in the first place.

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视频概述

介绍了两种河口的形成原因及三角洲的由来

听录译者

收集自网络

翻译译者

4CObst

审核员

审核MF

视频来源

https://www.youtube.com/watch?v=A47ythEcz74

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