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那场下了两百万年的雨

That Time It Rained for Two Million Years

PBS数码工作室
Imagine a world so warm that the ocean feels like a hot tub.
想象一个如此温暖的世界 海洋就像一个热水浴缸
Huge volcanic eruptions have pumped the air full of globe-warming carbon dioxide.
大规模的火山爆发使空气中充满了温室气体二氧化碳
And with the continents locked together from pole-to-pole
在泛大陆的超级大陆上
in the supercontinent of Pangea,
大陆从北极到南极连在了一起
the world is hot, flat, and very, very dry.
世界炎热 平坦 而且奇旱无比
Early reptiles and mammal ancestors
早期爬行动物和哺乳动物的祖先
thrive in this sweltering land,
在这片闷热的土地上繁衍生息
dominating a landscape that’s still struggling to recover from the Permian extinction.
统治着这片仍在努力从二叠纪大灭绝中复苏的土地
This is Earth, 250 million years ago, at the beginning of the Triassic Period.
这就是两亿五千万年前 三叠纪初期的地球
But then, starting around 234 million years ago,
但是 从大约2.34亿年前开始
the climate suddenly changed, for the wetter.
气候突然变得更潮湿了
The rains finally came to this hot, dry world.
雨水终于降临这个炎热干燥的世界
And then they stayed … for two million years.
然后雨一直下……下了两百万年
This period of intense rain killed off many of the early reptiles and …
这场暴雨杀死了许多早期的爬行动物
confused the heck out of the geologists
地质学家们也被搞糊涂了
who found the flood deposits millions of years later.
因为他们发现了数百万年后的洪水沉积
This time is known as the Carnian Pluvial Episode,
这一时期被称为卡尼安雨积期
and it set the stage for a new group of animals to take over the world:
它为一群新生物统治世界奠定了基础
the dinosaurs.
这群新生物就是恐龙
万古
Evidence of just how hot and dry the world was at the start of the Triassic is trapped
证明三叠纪开始时地球多么炎热干燥的证据
in the land beneath our feet.
就隐藏在我们脚下的土地中
Rocks from that period are mostly swaths of red sandstones and soil deposits from dry
那个时期的岩石大多是红色的砂岩和干旱森林的土壤沉淀
woodlands, with no sign of the coal swamps
没有煤沼泽的迹象
that had covered the world during much of the Permian.
而世界在二叠纪大部分时间里都被煤沼泽覆盖
And one major reason that the world was so dry was the shape of Pangea.
泛大陆的形状是造成地球极度干燥的一个主要原因
With all the continents locked together, rain clouds couldn’t move much past the coastlines,
由于所有大陆都紧紧相连 雨云在海岸线外的活动受限
and there were no big mountain ranges to break up the low, arid land.
而且这片干旱的土地地势低洼 没有高大的山脉将它分割开来
Now, dinosaurs did exist in this dry, post-Permian world.
恐龙确实存在于这个干燥的后二叠纪世界
But they were still vying for their place
但在当时 它们仅仅是
among early reptiles and reptile-like mammal ancestors.
在早期爬行动物和爬行类哺乳动物祖先的夹缝中生存
The dominant carnivores back then were the early crurotarsans, a broad group of croc-like
当时占统治地位的食肉动物是早期的鳄踝初龙
animals that included reptiles like pseudosuchians and phytosaurs.
这是一大类类似于鳄鱼的动物 包括爬行动物 如假苏氏动物和植龙
For example, there was Ornithosuchus, which had long hind legs and could actually stand up
例如鸟喙龙 它们有长长的后腿
when it wanted to run,
在跑的时候可以站立起来
which I imagine would’ve been both awesome and terrifying to actually see.
我想 要是真碰上一头鸟喙龙 还是敬而远之吧
But even stranger than these were the rhynchosaurs, herbivores with parrot-like beaks and, sometimes,
但比它们更奇怪的是喙龙 这是一种食草动物 长着像鹦鹉一样的喙
cheekbones to die for, all on a chubby lizard body.
有时 可爱至极的颧骨 都长在一个胖乎乎的蜥蜴身上
And although there were no true mammals, there were dicynodonts —
虽然没有出现真正的哺乳动物
the closest things to them at the time.
但二齿兽是当时最接近哺乳动物的物种
They’re actually more closely related to us than, say, Dimetrodon, despite being scaly,
尽管它们是有鳞、喙和长牙的四足动物
four-legged creatures with bills and tusks.
但实际上它们与我们的亲缘关系比异齿龙更近
All of these fascinating creatures were widespread for most of the Triassic, with one species
所有这些迷人的生物在三叠纪大都分布广泛
of dicynodont – called Lystrosaurus – being so common all over the world that its fossils
其中一种叫做水龙的二齿兽在世界各地都很常见
were actually used to help construct the idea of Plate Tectonics
它的化石被用来帮助构建板块构造学说
But these animals, adapted as they were to life in a dry climate, were in for a big shakeup.
但是这些已经适应了干旱气候的动物 将面临一场大变革
Most of what we know about the history of the climate comes from plant fossils and rock types.
我们对气候历史的了解大多来自植物化石和岩石
And in the early 1990’s, two British geologists found rocks didn’t match the dry climate
在20世纪90年代初 两位英国地质学家发现了
of the Triassic that they knew.
与已知的三叠纪干旱气候不符的岩石
Instead of finding red, slowly-deposited sand,
他们没有发现红色的缓慢沉积的沙子
they found thick layers of river rocks, sediments
而是发现了河岩厚层 巨大湖泊里的沉积物
from giant lakes, and evidence of coal swamps.
以及煤沼泽的证据
All of these were signs of massive rainfall, over the course of some two million years.
所有这些都表明 在约200万年的时间里发生过大规模降雨
But stranger still, these traces of a suddenly wet climate turned out to be everywhere, from
但奇怪的是 事实证明 到处都是气候突然变湿的痕迹
England to the Americas to IsraelIsrael, in regions that were far apart at the time.
英格兰 美洲 以色列 在这些当时相距遥远的地区都有发现
That meant the rise in rainfall must have been world-wide.
这意味着降雨量的增加肯定是全球性的
Initially, other geologists were skeptical.
起初 其他地质学家对此持怀疑态度
Couldn’t these rocks just be explained by a lot of big local floods?
难道这些岩石不能用当地常发洪水来解释吗?
Well, over the next two decades, reports of more and more weird rocks kept trickling in,
在接下来的二十年里 关于越来越多奇怪岩石的报道不断涌现
and they kept pointing to a world that was getting wetter and wetter.
它们一直指向一个越来越潮湿的世界
The rocks revealed coal deposits in Austria, traces of ancient lakes in Italy, wet soils
岩石揭示了奥地利的煤矿 意大利古代湖泊的痕迹
in Utah, and giant rivers in China.
以及犹他州的湿润土壤 中国大河的地理位置情况
And they all dated to the same window of time — between 232 and 234 million years ago.
它们都可以追溯到相同的时间段——2.32亿到2.34亿年前
In time, this phenomenon came to be known as the Carnian Pluvial Episode, or CPE.
随着时间的推移 这种现象逐渐被称为卡尼安雨积期或CPE
The Carnian is the name of the geologic age within the Triassic when this all happened.
卡尼安时期是三叠纪的地质时代 这一切都发生在这个时期
And for what it’s worth I seriously thought about naming this episode the Chronicles of Carnia
不论是否有用 我认真的想过把这一集命名为《卡尼亚编年史 》
but I didn’t because that would have been dumb.
但是我没有 因为那样太蠢了
And “pluvial” means rain, and it rained a whole awful lot.
“pluvial”的意思是下雨 下了很多雨
For example, one estimate suggests that the average annual rainfall in what’s now Utah
例如 一项估计表明 现在犹他州的年平均降雨量几乎翻了两翻
almost quadrupled, reaching a peak of 1400 millimeters, or about 55 inches of rain a year.
达到1400毫米的峰值 即大约每年55英寸的降雨量
For context, that’s how much that a temperate rainforest gets today,
作为背景补充 一个温带雨林才会有这样的降雨量
like say, in the Pacific Northwest.
就比如 太平洋西北的降雨量
And this would have happened over, and over, and over again, all around the world.
大雨一次又一次地侵袭着世界各地
It was not one big flood; it was more like floods every year, all over the place,
不止一次发大洪 更像是年年都有且各地无一幸免
for two million years.
一直持续了200万年
And with all this rain, things were bound to change – and one of the biggest changes
大雨不断 各种变化随之而来 一个最大的变化
was the sudden abundance of dinosaurs.
就是恐龙突然大量出现
In rock dated to the start of the Carnian Pluvial Episode, dinosaurs account for about
在卡尼安雨积期初期的岩石中
5% of the fossils of terrestrial vertebrates.
恐龙化石约占陆地脊椎动物化石的5%
But by the end, they make up more than 90% of those fossils.
但到后期 恐龙化石已经达到90%以上
So what made the dinosaurs so suddenly successful?
那么 什么原因导致了恐龙数量的剧增?
Were they better off than their competitors in this newly wet world?
在这个突然变潮湿世界里 恐龙较其竞争对手更有优势吗?
Or did other animals simply die, leaving them to rule the world by default?
或者其他动物就这么死了 默认它们统治世界?
The key might not have been the rain itself, but what the rain brought with it:
关键可能不是雨水本身 而是随之而来的东西
a proliferation of giant plants!
那就是巨型植物迅速生长!
During this time, we begin to see lots of large conifers, and big coal-forming plants,
在此期间 开始出现许多大型针叶树和大型产煤植物
like the primordial-looking Bennettitales.
就像贝内特蒂故事集里描绘的原始一样
For herbivores, this change in food supply could have been a game changer.
对食草动物来说 这种食物供应的变化改变了游戏规则
For example, rhynchosaurs were abundant, but they were also … short.
例如 喙龙数量很多 但它们很…矮小
And they couldn’t stand on their hind legs to reach higher leaves.
即使他们后腿能站起来也够不到更高的树叶
This would’ve been fine in a dry environment, where plants tend to stay close to the ground.
在干燥的环境中还好 因为植物往往靠近地面
But in a wet forest, rhynchosaurs would’ve only been able to eat smaller plants, or whatever
但在潮湿的森林里 喙龙只能吃较小的植物
leaves and fruit fell to the ground.
或者其他什么落在地上的树叶和水果
Meanwhile, dicynodonts were herbivores, too, but they didn’t have teeth.
与此同时 二齿兽也是食草动物 但它们没有牙齿
And, they also didn’t use gastroliths, the rocks that some animals – like birds – swallow
而且 它们也不用胃石 鸟类等一些动物
to help digest plant material.
会吞下胃石来帮助消化植物组织
Without teeth or gastroliths, dicynodonts would have had a hard time eating anything
没有牙齿和胃石 二齿兽难吃到像木头
fibrous, like wood.
这样的纤维食物
And sure enough, fossils of dicynodont poop from this time have been found to contain
果然 在这个时期发现的二齿兽粪便中含有的
mostly soft ferns, with only very small amounts of wood.
大部分是软蕨类植物消化残留物 只有很少的木材
By comparison, some plant-eating dinosaurs – which had both teeth and gastroliths – left
相比之下 一些既有牙齿又有胃石的植食恐龙
us poop fossils that are up to 85% wood!
留下的粪便化石有85%是木头!
Which is a lot of fiber.
这些化石富含纤维
So as the climate became wetter, soft small ferns were quickly replaced by tall woody
随着气候变得潮湿 细小的蕨类植物很快被高大的针叶树所取代
conifers, which the dicynodonts and rhynchosaurs didn’t eat.
然而二齿兽和喙龙不吃针叶树
And without the rhynchosaurs and dicynodonts, then the carnivores — those crurotarsans
没有了喙龙和二齿兽 肉食动物鳄踝初龙的食物供应
— would’ve lost a lot of their food supply.
就会大量减少
So maybe, instead of being better-adapted to this new environment, dinosaurs were just
所以 恐龙或许并没有更好地适应这种新环境
the only major group of reptiles left standing.
它们只是唯一幸存的爬行动物罢了
Or, y’know, squatting.
或者 蹲着行走的动物
Even though we don’t know exactly why the rain helped the dinosaurs, we do know that
尽管我们不能明确雨为什么帮助了恐龙
dinosaurs became a lot more abundant during the Carnian Pluvial Episode.
但我们知道恐龙的数量在卡尼安雨积期日渐庞大
And the dicynodonts, the rhynchosaurs and many of the early crurotarsans soon went extinct.
而二齿兽 喙龙和许多早期的鳄踝初龙很快就灭绝了
Now, there’s still the question of:
现在 仍然有一个问题
What made it rain for two million years in the first place?
究竟是什么让雨持续下了两百万年?
Well, right before the rains came, some 235 million years ago,
大约2.35亿年前 就在雨来临之前
there was a huge burst of volcanic activity in Alaska and British Columbia.
阿拉斯加和不列颠哥伦比亚省发生了大规模的火山爆发
Today it’s known as the Wrangellian eruptions.
如今它被称为弗兰格里火山爆发
These eruptions lasted for more than 5 million years, churning out a layer of lava that got
这次火山爆发持续了五百多万年 喷出的熔岩足有六千米厚
to be 6 kilometers thick, and releasing enough CO2 to raise temperatures by about 3 to 10
而且放释放出大量的二氧化碳
degrees Celsius worldwide.
足以全球温度升高了3到10摄氏度
And, over a very long time, warmer temperatures can create a wetter climate, because they
而且 在很长一段时间内 较高的温度使得气候更加湿润
can speed up the water cycle, driving more evaporation of surface water into the atmosphere,
因为 除其他因素外 它可以加速水循环
among other things.
促使更多地表水蒸发到大气中
And in fact, because of this increase in atmospheric moisture,
事实上 由于大气湿度增加
the CPE is also sometimes called the Carnian Humid Episode.
CPE有时也被称为卡尼安湿润期
But for what it’s worth, my favorite name for this episode is called The Wet Intermezzo.
但不论真伪 这一集我最中意的名字叫《潮湿间奏曲》
Which I think is delightful so let’s try to bring that term back, OK?
我认为这很有诗意 后面也会继续提到它 行吗?
Anyway, after about a million years of these eruptions, the atmosphere became so warm and
无论如何 在火山爆发后约100万年的时间里
wet that rain could finally reach even Pangea’s vast interior.
大气变得如此暖和潮湿 使得雨水最终能够达到盘古大陆广阔的内部
OK but then, how did it stop?
但它是怎么停止的呢?
Well, when carbon levels are really high for a really long time, our planet can be pretty
当环境中碳含量长时间居高不下时
good about getting some of the extra carbon back into the ground where it belongs.
地球就会很熟练地把一些多余的碳回收到地下
Plants take it in and store it in their tissues; weathering and eroding rocks absorb it; and
被植物吸收并储存在自身的组织中 被风化和侵蚀岩吸收
the oceans soak it up to form carbonate rocks like limestone.
被海洋吸收形成碳酸盐岩 如石灰石
So as the Wrangellian eruptions slowed down, the carbon cycle was eventually able to stabilize,
随着兰格里火山喷发势头减弱 碳循环最终稳定下来
excess CO2 was reabsorbed from the atmosphere, and the CPE gradually came to an end.
大气中过量的二氧化碳被重新吸收 卡尼安雨积期逐渐结束
By the time the eruptions had completely ended 230 million years ago,
当两亿三千万年前的火山爆发完全结束
the world had returned to a classically hot, dry Triassic climate
地球重新回到典型的炎热干燥的三叠纪气候
that only ended when Pangea began to break up.
直到盘古大陆开始分裂才结束
But even though the Carnian Pluvial Episode was short – only 2 million years – its impacts
但是 尽管卡尼安雨积期很短——只有200万年
on life were permanent.
但它对生命的影响是永久的
All that rainfall helped conifers spread and diversify,
这些降雨帮助针叶树传播以及种类的多样化
leading to the pine trees we know today.
从而形成我们今天所知道的松树
And while the start of the Triassic may have been the land of weird
三叠纪初期可能是奇怪生物的国度
croc-like-things running on their hind legs.
它们长的像鳄鱼又能用后腿奔跑
By the time the rains had ended, the world had fully entered the age of dinosaurs.
等到雨停了 世界完全进入了恐龙时代
万古
Thanks for joining me for this wet intermezzo!
感谢与我一同欣赏潮湿的间奏曲!
Now, wouldn’t you like to have all of natural history right there on your wall?
现在 你愿意把所有的自然史都挂在墙上吗?
I would and now you can!
我愿意 现在你也可以!
With the first-ever Eons poster, created by Franz Anthony
这是第一张由Franze Anthony创作的万世海报
Just go to DFTBA.com and links are in the description
链接就在DFTBA.com的介绍中
Now, let me know what you want to learn about,
让我知道你想了解什么
because you know by now that we read your comments!
因为你现在知道我们读了你的评论!
And if you haven’t already and I don’t know why you wouldn’t have
如果你还没有订阅 虽然我也不知道因为什么
— but if you havent, you should go to youtube.com/eons and subscribe. Thank you.
但如果没有 你应该前往youtube.com/eons订阅 非常感谢

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视频概述

一场下了两百万的大雨是如何改变远古生物进化史呢?一起来看看吧!

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视频来源

https://www.youtube.com/watch?v=_1LdMWlNYS4

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