地球 这个独特的星球 Earth, a unique planet,
不安且又好动 restless and dynamic.
大陆飘移 碰撞 Continents shift and clash,
火山喷发 volcanoes erupt,
冰河生长 消融 glaciers grow and recede--
巨大的力量不断发挥作用 titanic forces that are constantly at work,
留下的是一系列地质奇迹 leaving a trail of geological mysteries behind.
奇迹之一便是位于亚利桑那州的大峡谷 One of these mysteries is centered here in the Grand Canyon in Arizona.
近十亿吨的岩石 Close to a billion tons of rock
在蚀刻作用下消磨殆尽 have been carved out of the ground.
即便把地球上全部河水灌入大峡谷中 The canyon left behind could hold all the river water
也不及其容积的一半 on Earth and still be less than half full.
一百多年来 For more than a century,
科学家就峡谷生成的原因和年代争论不休 scientists have debated how and when this vast chasm was created.
现在 地质学家即将揭开大峡谷之秘 And now geologists are uncovering fresh evidence of how the Grand Canyon
看它是如何在这颗星球上演化而成 fits into the ever-evolving story of "How the Earth Was Made."
YYeTs人人影视纪录片组诚意奉献
历史频道
地球
起源
科罗拉多大峡谷
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翻译：zhanginfo Aries crossfirezf 柠檬meg 阿橙 NaryKing 校对：水烟 时间轴：海边鸟 后期&特效：WiLL 总监：阿橙
美洲大陆最令人叹为观止的自然奇迹之一 one of America's most spectacular natural wonders...
一条最宽处横跨18英里的峡谷 A canyon 18 miles across at its widest point...
纵贯277英里 277 miles long...
深度逾1英里 and more than a mile deep.
它如此之宏大 甚至在太空都可以看到 It is so vast that it can even be seen from space.
[赫尔峡谷: 亦称地狱谷 全美最深峡谷]
尽管爱达荷州的赫尔峡谷较其深近半英里 Although Hell's Canyon in Idaho is almost half a mile deeper,
澳洲的嘉伯蒂峡谷较其宽近一英里 and Australia's Capertee Valley is nearly a mile wider,
但其中最著名的仍当属科罗拉多大峡谷 the Grand Canyon remains the most famous of them all.
同时它还蕴含着另一大地质之谜 And it also holds one of geology's greatest mysteries--
这便是 长度仅为密西西比河1/10的 just how did the Colorado River,
科罗拉多河究竟何以冲刷出这条深谷 only a tenth the size of the Mississippi, form such a large canyon?
这让科学界困惑了一个多世纪 The answer has eluded scientists for more than a century,
因为科学家赖以分析的众多线索 because many of the clues they normally rely on
都已被数百万年的河水冲逝 have been swept away by the river's water over millions of years
山崩掩埋 或火山破坏 or buried by landslides or destroyed by volcanoes.
我们似乎应当对大峡谷的成因了若指掌 It seems like we should understand perfectly how the Grand Canyon formed.
可问题是 我们丧失了大量的证据 The problem is, we've lost a tremendous amount of evidence.
这就如同遗失了大部分证据的凶杀谜案 It's like a murder mystery where most of the evidence is lost.
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天堂谷社区学院地质学家
约翰·道格拉斯博士
因此最佳方式便是将我们现有的证据汇总 And so the best we can do is piece together the evidence that we have.
即便如此 这一地质奇迹 Even so, slowly but surely,
最为远古的奥秘终究还是逐浮出水面 this geological icon is giving up its most ancient secrets.
峡谷色彩缤纷的岩层为科学家提供了 The canyon's richly colored layers offer scientists
地球上最为完整的地质记录之一 one of the most complete geological records on Earth.
当您想到大峡谷时 The first concept you have to
脑海中浮现的第一个概念应该就是 get your mind around as you're thinking about the Grand Canyon
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卡尔·卡尔斯托姆博士
新墨西哥大学地质学家
这些岩石讲述了一个极其悠远的故事 is that the stories told by
其历史可追溯至数百万甚至数十亿年前 the rocks are exceedingly old, millions and billions of years.
卡尔斯托姆及其团队准备沿科罗拉多河 Karlstrom and his team are setting out on a grueling
进行一次极限式野外地质考察 geology field trip along the Colorado River.
这趟旅程绝非易事 It won't be an easy ride,
因为这条1450英里长的河流遍布艰险 because this 1,450-mile-long river packs a punch.
科罗拉多河每小时的泄水量 More than 800 million gallons
超过8亿加仑[约300万吨] of water can flow down the Colorado every hour...
其每秒钟的水量超过了 more water every second
一个美国家庭的年平均用水量 than the average U.S. household uses in a year.
卡尔斯托姆正着手调查在大峡谷出现之前 Karlstrom is investigating the ancient history of the land
这片陆地的地质经历 that was here before the Grand Canyon even existed.
为此他需要鉴别出历史最久远的岩石 And for that, he needs to identify its oldest rocks.
他沿着探险先驱 约翰·韦斯利·鲍威尔的 He is following in the footsteps of pioneer explorer
足迹展开行程 John Wesley Powell.
[约翰·韦斯利·鲍威尔 19世纪美著名地质学家]
他曾于1869年成为顺科罗拉多河漂流 In 1869, he was the first man to successfully ride the Colorado
成功穿越整个大峡谷的第一人 through the entire length of the canyon.
所有我们这些在大峡谷考察的科学家 All of us who work in the canyon as scientists
都为约翰·韦斯利·鲍威尔对大峡谷的 admire John Wesley Powell immensely for his pioneer
开创性科考所倾倒 对其无比地景仰 and scientific exploration of the Grand Canyon,
他所提出的疑问至今我们仍在苦苦思索 and the questions that he framed are still questions that we work on today.
鲍威尔先生的发现之一便是 One of Powell's discoveries
峡谷最深处这些摄人魂魄的黑色岩石 was these intimidating black rocks at the very base of the canyon.
我们这是在大峡谷的深处 Well, we're deep in the Grand Canyon,
紧挨着科罗拉多河 right by the Colorado River.
大家可以看到这壮观的黑色岩石 You can see these spectacular black rocks.
约翰·韦斯利·鲍威尔称之为"邪恶黑岩" Actually John Wesley Powell called them ugly black rocks
因为对他来说 because for him,
这些坚实的岩块形成了可怕的湍滩 these hard rocks made bad rapids,
使其漂流更加艰难 and that was harder on his trip.
但在我们这些对峡谷早期历史着迷的人看 But for those of us who are interested in the early history of Grand Canyon,
这些岩石就如同宝藏 these rocks are the bonanza.
鲍威尔无从测定这些岩石的地质年代 Powell had no way of dating these rocks,
它们现在被勘定为毗湿奴片岩 now identified as vishnu schist.
他只能从岩石的形貌得出结论 All he could conclude from their appearance was that
它们曾在地下深处 处于熔融状态 they had once been molten deep underground,
但卡尔斯托姆借现代先进仪器之便 but Karlstrom has an advantage-- modern instruments that can
通过测量放射性衰变 accurately date the rocks
可以准确测定岩石的地质年代 by measuring radioactive decay.
探究远古时期这里地质活动的第一步 And the first step in figuring out what happened here in the ancient past
便是记录下这些岩石的生成年代 is to record when these rocks were created.
这些岩石已有约17亿年之久 These rocks are about 1.7 billion years old.
但尚不足地球年龄的一半 It's less than half of the age of the Earth.
因此科罗拉多大峡谷 So we have a great story here
为我们描绘了一段近20亿年的精彩地球史 in the Grand Canyon of the last almost 2 billion years of Earth's history.
不过卡尔斯托姆尚需要更多的信息 But Karlstrom needs more information,
对于峡谷生成前这里的地质地貌特征 and these ugly black rocks hold another crucial clue
这些"邪恶黑岩"提供了另一重要线索 to what this land looked like before the canyon was cut.
它们不仅说明了岩石的生成年代 They can tell him not only when they were formed,
还提供了岩石在地壳中生成的确切深度 but also precisely how deep in the Earth's crust they were made.
这些遍布于远古巨石之中的小东西 These tiny stones embedded
其实是货真价实的珠宝 throughout the ancient boulders are literally jewels,
石榴石只有在极大的压力下才可以生成 garnets that only form under immense pressure,
上方数以百万吨计的岩石强烈的挤压 the sort of pressure that's found when layers are crushed
方能产生上述压力 by the weight of millions of tons of rock on top of them.
石榴石就是一条绝佳的线索 The silver-bullet clue is the garnet.
这些石榴石就是 These garnets are the key
知晓我们头上这些岩石量的关键 to understanding the amount of rock above us.
通过分析石榴石的化学结构 By analyzing the chemical structure of the garnet,
特别是钙的含量 in particular its calcium content, investigators can
科学家们就可以获知 determine how much weight of
石榴石在形成时上方所挤压岩石的重量 rock was crushing down upon it at the moment it was made.
简单来说 In simple terms,
通过分析石榴石 if you analyze the garnet
如果其含钙量越高 and you see higher calcium content of the garnet,
你在山区所处的位置就越低 it means you're deeper into a mountain belt,
你头上的岩层就越厚 more rocks above you.
所以我们将这些石榴石带回实验室 So we take these garnets back to the laboratory.
切下非常薄的一片 We cut a very thin section.
将其置于电子微探针下 We put them under an electron microprobe,
科学分析的结果显示 and the scientific result after this analysis is that
我们处于山巅之下6英里处 we were 6 miles deep beneath the surface of the peaks
这还真是挺长的一段距离 which were above us, and that's a long ways.
因此 在将近20亿年之前 So, nearly 2 billion years ago,
大峡谷尚未形成时 before the canyon evolved,
这里屹立着海拔六英里的古老山峰 ancient mountains 6 miles above sea level stood here,
其高度可媲美现在的喜马拉雅山脉 towering peaks as high as the modern Himalayas.
在接下来的五亿年里 Over the next 500 million years,
这些山峰被自然的侵蚀力无情地磨蚀 these mountains were worn away by the relentless forces of erosion.
千年之后 冰川反反复复的消长 Over millennia, the freezing and thawing of ice
凿去了高耸的山坡 cracked open the rock of the mountain slopes.
风力和水力将岩石碎屑运入大海 Wind and water carried the rock debris down towards the oceans,
塑造出平坦无奇的平原 leaving behind a flat and featureless plain
毫无日后形成的大峡谷的影子 with no sign at all of a canyon.
地质学家会设想这个地方以前的地质情景 Geologists learn to visualize the way that this place looked in the past.
掌握了如何鉴别岩石的成分结构 Knowing how to read the texture of the rock,
即岩石的种类 the kind of rock it is,
和其中蕴藏的化石 the fossils that are in it,
地质学家就能 geologists can--
像侦探小说里的情节 It's like a detective story.
就能了解到这个地方几百万年前的情况 You can uncover what this place looked like billions of years ago.
如今这里已经成了一片荒漠 This is now desert country,
位于300英里远的大陆腹地 more than 300 miles inland.
然而这些嵌在坚硬岩石里的贝壳 And yet these shells encased in solid rocks...
属于海洋化石 are ocean fossils.
在这面悬崖上 In this one cliff,
你能找到如今只有在海边 you can find fossil shells that look like
才会看见的贝壳类化石 you'd pick up on the seashore today.
这些贝壳死亡后落入海床底部 They die, they fall to the bottom of the sea floor,
陷入它们所处年代的海底淤泥当中 and they get trapped and die in the mud at the bottom of the ocean
就此逐渐累积起来 at the time that they're being deposited.
这些壳类原本来自热带的浅海 Shells like these come from shallow, tropical waters,
这个内陆海形成于5亿年前 an inland sea that first arrived here half a billion years ago
它的到来淹没了这块低平的土地 and covered the flat, low-lying plain.
而类似情况发生了不止一次 But that did not happen just once.
通过大峡谷崖面上的众多不同分层 Many different layers in the walls of the Grand Canyon
卡尔斯托姆得知在过去数百万年时间里 tell Karlstrom that over hundreds of millions of years,
这片土地曾不止一次地浸没入海水中 this land has been submerged by the sea not just once,
而是至少被浸没了八次 but at least 8 times.
亚利桑那的这片土地最后一次没入海底 The last time this part of Arizona was under the sea
大约是在8千万年前 was around 80 million years ago.
沿着大峡谷的分层向上数 As we go higher in the layers in the Grand Canyon,
就能区分出不同地质年代的海层 we have different-aged seas, which are
每一层都包含着不同岩石种类和地质环境 depositing different kinds of rocks, different environments,
以及不同时期的生物化石 different fossils that live at the different times.
海洋在此处形成后又消退的循环往复 This chapter of seas coming in and seas going out
这过程本身就经历了数百万年的时间 is itself hundreds of millions of years.
每次形成的海洋带来各种物质 Each sea deposited different types of material
这些物质最后沉降并固化成岩石 that hardened to become solid rock.
有的是沙子沉淀下来形成的淡黄色砂岩 Some sediment was sand that became buff-colored sandstone,
有的是泥浆硬化成的深色页岩 some was mud that hardened into darker shale,
而海洋生物钙化的残骸 while the calcified remains of marine organisms
则在挤压下形成浅色的石灰岩 were crushed into light-colored limestone.
但大峡谷的主色却是红色 And yet the dominant color is red.
这是由普遍存在于岩石中的铁造成的 That comes from iron locked within all the rocks.
在数百万年的时间里 Over millions of years,
铁不断氧化形成这种独特的红色 the iron rusts into a distinctive red hue.
对地质观察者而言 For the geology detectives,
在大峡谷沿河而下就像进行时间旅行 descending into the Grand Canyon is like traveling back in time.
从石榴石中的钙成分推知 The calcium content inside garnet gemstones reveals that
大约20亿年前 nearly 2 billion years ago,
大峡谷的前身本是可与珠峰媲美的山脉 mountains the size of Mt. Everest stood where the Grand Canyon is now.
悬崖上的海洋化石证明了5亿万年前 Sea fossils exposed in the cliffs show that as late as 500 million years ago,
这里是古老内陆海的泥泞海底 the land was the muddy bottom of an ancient inland sea.
地质学家面临的下一个难题是 The next puzzle for geologists
弄清是什么力量把这片平坦无奇的土地 is uncovering which awesome forces transformed that unremarkable flat land
塑造成如此令人屏息凝神的自然奇迹 into this breathtaking natural wonder of the world.
从17亿年前到7千万年前 From 1.7 billion years ago to 70 million years ago,
亚利桑那州西部的地貌经历了一系列巨变 the landscape of western Arizona has undergone a series of extraordinary changes.
古老的山脉被史前海洋所取代 Ancient mountains have given way to prehistoric seas
当海洋退去之后显现出了 which have withdrawn to reveal
一望无垠的宽广平原 a low-lying flat plain stretching as far as the eye can see.
而景象壮观的大峡谷尚未形成 The magnificent gorge of the Grand Canyon does not yet exist
直到此后的2千万年 but over the next 20 million years,
这里的地貌将经过天翻地覆的改头换面 this landscape was to undergo immense changes
形成独特的高原地区 that would create a unique high plateau and
为大峡谷的形成提供基础场所 set the scene for the formation of the canyon.
由远古海洋生物化石 地质学家们可推知 Ancient fossils of sea animals tell geologists that
这里曾经被浸没在内陆海的波涛中 this land was once under the waves of an inland ocean,
但另一个谜题由此产生 but that leads to yet another mystery.
现在的调查就是来查明 The investigation needs to figure out
为什么这些海底岩石层现在却高高在上 why these undersea rocks are now high in the air,
位于海拔数千英尺的高空 thousands of feet above sea level.
在海拔1英里的高处的这些发现令人称奇 It's surprising to go up a mile above sea level,
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卡尔·卡尔斯托姆博士
新墨西哥大学地质学家
如果你捡到一块蛤壳之类的碎片 and you find a clam shell or what looks like a clam shell,
你会想 这不是海边才有的东西吗 and you say, "that's what I see when I go down to the ocean."
为什么在海拔1英里的地方也能看到它 "so why is it here, a mile above sea level?"
这显示这里曾经发生了某种地质扰动 It's clear that this region underwent a type of geological disturbance
以至于海床被整个抬升 that pushed up the entire seabed.
20世纪60年代 地质学家们发现 Geologists discovered that in the 1960's that
地球上各个板块之间的挤压碰撞的力量 collisions between separate plates of the Earth's crust
能将陆地抬升 could force land up into the air.
这种情况发生在全球各处 It happens all over the globe
通常的后果是将陆地变成倾斜的山脉 and usually deforms the land into tilted mountain ranges.
但在亚利桑那州的这种抬升现象非常独特 But this Arizona uplift was unique.
所有平坦的岩层沉降到海拔平面后 After all the flat layers are deposited at sea level,
便开始了名为拉拉米造山运动的抬升过程 there was a major uplift event called the Laramide Orogeny,
即把这块岩石平行抬升而不使之倾斜 which lifted these rocks without tilting them,
保持平面 并上升到高海拔 still flat, lifted them up to high elevation.
由于整个地面搭乘在升降机上一样被垂直枱高 Because the land rose straight up, like being in an elevator,
最终便形成了表面平坦的高原 it formed a high, smooth plateau.
曾经存在着的海洋 The sea that had been there
向东北方向消退 drained back toward the northeast,
但大峡谷的出现仍需时日 but as of yet, there was no Grand Canyon.
科罗拉多河这股将岩石塑造成峡谷的自然力 The Colorado River, the force that cut the canyon from the rock,
也尚未形成 had yet to arrive.
很早以前 早在19世纪晚期 Geologists, from the very early days, from the late 1800's
地质学家们已经达成共识 are quite comfortable with the knowledge
即科罗拉多河塑造了大峡谷 that the Colorado River has carved the Grand Canyon.
这块高原曾被更高的山脉包围着 The high plateau was surrounded by even higher mountain ranges.
新形成的河流开始从山间流下穿过高原 New rivers began flowing from the mountains out across the plateau.
确定这些河流 尤其是科罗拉多河 It's essential for the investigation to establish
形成的时期是非常有必要的 when the Colorado River, in particular, arrived,
因为那正是峡谷开始形成的时期 because only then could it begin to carve the canyon.
直到几十年前 Until a few decades ago,
有调查者认为 some investigators thought
印度峡谷这条古老的河床才是答案之所在 this ancient riverbed called Hindu Canyon provided the answer.
他们坚信五千万年前印度峡谷的出现 They believed that Hindu Canyon's creation 50 million years ago
[大峡谷西南部]
印度峡谷
标志着科罗拉多河的形成 marked the arrival of the Colorado River
以及大峡谷的诞生 and the beginnings of the Grand Canyon.
但是在1969年 这些卵石的发现 But in 1969, the discovery of these pebbles turned
彻底推翻了地质学家们长久以来对大峡谷的认识 everything that geologists thought they knew about the canyon on its head.
事实证明 要解释 It turns out that to explain
大峡谷的形成 how the Grand Canyon got there
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理查德·杨博士
纽约州立大学地质学家
远比人们想象的要复杂得多 is very much more complex than people thought.
早期的地理学家认为其易如反掌 So the early geologists thought it was simple,
但是现在我们发现事实并非如此 but now we realize there's a lot more to the story,
这感觉就像侦探小说 and it's kind of a detective story.
你得先从一些线索开始 You start out with a few clues,
然后把它们组合到一起 and you put the clues together,
到最后你可以满意地说 and then finally you get the satisfaction of saying,
"我比其他人要先发现这个" "Well, you know, I figured this out before anybody else did."
早在1969年 杨就率先探明了真相 Figuring it out before anyone else was just what Young did in 1969,
那时他24岁 when he was a 24-year-old
是华盛顿大学的一名地质学研究生 geology graduate student at Washington University.
他的教授派他去调查印度峡谷 His professor sent him to investigate Hindu Canyon.
但是当杨到达满是沙子的河床时 But when Young arrived at the dusty riverbed,
他发现这和科罗拉多河 he discovered that it had nothing to do with the Colorado
以及大峡谷本身毫无关系 or the Grand Canyon itself.
他的发现无疑沉重的打击了 His discovery flew in the face
当时已达成共识的地质理论 of all the established geological theories
并将大峡谷的历史重新改写 and revolutionized thinking about the canyon's history.
杨发现的证据 The evidence Young had uncovered
就是河床上卵石的排列方式 was the alignment of pebbles in the bed of the river.
看看这些卵石 Look at these pebbles.
你能发现这些卵石 You can see that the pebbles
正流向 或者说 are flowing, or the pebbles
是向这个方向排列 are arrayed in this direction,
这清楚表明了了水是稳定向我右边流动的 which is a stable direction for water flowing to my right.
如果鹅卵石朝向这个方向 If the pebbles had been oriented this way,
水就会把他们翻转过来 the water would have flipped them over.
所以说当我们发现鹅卵石朝这个方向时 So when we find pebbles that are oriented this way,
我们就能断定水是向我右边流动的 that tells us that the water was flowing to my right.
这就是决定性的证据 It is a crucial clue.
科罗拉多河绝对 The Colorado River could never
从来没有向杨的右边流动 have flowed to Young's right.
而是向相反的方向 It has always run in the opposite direction,
流向太平洋 towards the Pacific Ocean.
这条五千万年前的河 绝对不是科罗拉多河 The river here, 50 million years ago, was not the Colorado,
也没有凿出大峡谷 and it did not cut the Grand Canyon.
杨的发现意味着 Young's findings meant
科学家必须重新审视 scientists had to rethink
曾经关于科罗拉多河何时到达高原 all their ideas about when the Colorado had arrived on the plateau
以及大峡谷年代的看法 and about the age of the canyon.
他们又开始从另外一个年代较近的地方开始调查 They started examining evidence from another less-ancient site.
[泥溪 科罗拉多河支流]
这就是泥溪 This is Muddy Creek,
位于亚利桑那州米德湖附近 near Lake Mead, Arizona,
就在如今科罗拉多河 just a few miles downstream
流出大峡谷下游数英里的地方 from where the Colorado River exits the Grand Canyon today.
泥溪
下面的石头证明了 The underlying rocks prove
这里曾经有一个大型淡水湖 that this was once the site of a vast freshwater lake.
泥溪之下的地层的上层 The upper part of the Muddy Creek formation
是这种漂亮的石灰石 is this nice limestone,
这种石头就是在淡水湖中形成的 which formed in a freshwater lake.
湖水应该是非常清澈的 The water would have been very clean.
水中可能栖息有大量的植物和动物 There would have been lots of plants and animals living in the water.
当它们死后沉积在湖底 And as they sank to the bottom,
它们壳里所含的碳酸钙 the calcium carbonate in their shells
能形成这种石灰石 would form this limestone,
石灰石通常都是这样形成的 which is typically what forms the limestone rock.
石灰石 The limestone
是由曾经栖息在湖里的生物尸体钙化而成 is the calcified remains of the creatures that once lived in this lake.
550万年前 Then 5.5 million years ago,
这些动物全部消失了 the animals all disappeared.
于是再也没有壳可供生成新的石灰石 There were no shells to make fresh limestone.
唯一的解释就是 The only explanation
这些动物早在550万年前就死去了 is that the animals died 5.5 million years ago
因为就在那个时候 because that was the date
科罗拉多河来到了此地 when the Colorado River arrived here.
科罗拉多河夹杂着大量泥土和岩石沉积物 The river would have been carrying masses of dirt and rock sediment
这些都是从年轻的大峡谷中带来的 from the fledgling Grand Canyon.
河水泥泞浑浊 The water would have been too muddy and dirty,
石灰石在泥泞浑浊的水中是不会形成的 and limestone does not form in dirty, silty, muddy water.
因为条件不合适 It's just incompatible.
生活在湖里的动植物 The animals and plants that live in such a lake
在含有大量泥沙的水里是不会存在的 can't exist if there's a lot of silt and mud in the water.
浑浊的湖水带来的死 给了地质学家们 So the muddy death of the lake gave geologists
一个科罗拉多河到达亚利桑那 a confirmed date for when the Colorado arrived in Arizona
以及其开始凿出大峡谷的确切年代 and commenced its excavations.
大峡谷诞生于仅550万年前 The Grand Canyon was born a mere 5.5 million years ago.
调查至此到达了一个重要的里程碑 The investigation has reached a significant milestone.
通过调查确认了大峡谷的年代 It has discovered the age of the canyon.
鹅卵石与古老河床所形成的角度揭示出了 The angle at which pebbles lie in ancient riverbeds reveal
大峡谷远比以前地理学家 that the Grand Canyon is far younger than geologists
推测的要年轻得多 had previously ever suspected.
在泥溪发现的石灰石揭示了 The limestone discovered at Muddy Creek reveals the date
科罗拉多河到达高原的时间 that the Colorado River arrived on the plateau
以及大峡谷的真实年龄 and the true age of the canyon--
550万年 5.5 million years old.
现在地质学家 Now geologists had
面临一个新的亟待解决的谜题 a new mystery to solve--
找出为何科罗拉多河 discovering why the Colorado River
在550万年前选择这样的路线 took the path it did some 5.5 million years ago
以及其如何凿出了如此宏伟的大峡谷 and why it carved a canyon of such remarkable dimensions.
对于大峡谷历史的调查 The investigation into the history of the Grand Canyon
向世人揭示了一个有17亿年历史的景观 has uncovered a 1.7 billion year old landscape
它从古老的山脉演变成了 that has evolved from ancient mountains
现在的科罗拉多高原 through to the Colorado plateau.
550万年前 5.5 million years ago,
科罗拉多河开始 the Colorado River began
在这个高原上凿出了大峡谷 carving out the Grand Canyon from this plateau.
现代科学家要回答的问题就是 The question scientists now had to answer was
那时候发生了什么 what happened at that time
使得科罗拉多河深挖并且开凿出大峡谷 to cause the river to dig deep and carve out the canyon.
这场辩论持续了超过100年 It is a debate that has been going on for more than a century
至今仍然争执不休 and which continues today.
我对大峡谷产生兴趣 I got interested in the Grand Canyon
是在我进入学校开始学习的时候 when I went to school and started studying,
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天堂谷大学地质学家
约翰·道格拉斯博士
当我听到不同的关于大峡谷的想法 and I heard about the different ideas associated with the Grand Canyon
而同时又发现我们并不能理解 and was just blown away when I found out we did not understand
大峡谷是如何形成时 我感到很震惊 how the Grand Canyon formed.
作为如此标志性的景观居然不被人了解 That something as iconic as the Grand Canyon wasn't
这对我来说很疯狂 understood just seemed crazy to me,
因此我基本决定了投入我大半生的精力 and so I basically decided to dedicate a large portion of my life
来找出答案 to trying to figure it out.
其中一个理论就是许多古代的河流汇聚在一起 One theory is that several ancient rivers merged,
这汇集起来的切割的力量凿出了大峡谷 and their combined cutting power started digging out the canyon.
另外一个理论是随着周边地表的抬升 Another assumes that the river cut down into the plateau
河流切割出了峡谷 as the land uplifted around it.
但是约翰·道格拉斯有他自己的理论 But John Douglass has his own theory, one that has
这一理论在2000年发表的时候 gained respect among many
就受到著名地质学家们的广泛赞誉 leading geologists since he first published his ideas in 2000.
道格拉斯把他的理论称作"溢出理论" What Douglass calls his "Spillover theory"
这在理论上是可行的 seems to work well on paper.
溢出理论很容易理解 Spillover is incredibly easy.
这个理论就是说科罗拉多河的水倾入了一个盆地 All it means is the Colorado river poured into a basin.
当水倾入盆地时 When it poured into that basin,
形成了一个湖泊 it had to form a lake,
一个很大的湖泊 and this lake was huge.
这样湖就不可避免地会上升 All that lake had to do was rise
然后漫出 流过高原 and spill across the plateau.
倾泻而下 快速地侵蚀高原 It poured down, cutting rapidly,
久而久之 and over time,
就轻易的将大峡谷凿至它的开端 you would have ended up the beginnings of Grand Canyon very quickly.
在他菲尼克斯市的校园里 At his college campus in Phoenix,
道格拉斯正在准备进行一个比例模型实验 Douglass is building a scale model experiment
证明他的溢出理论在现实中是否的确可行 to see if his spillover theory actually works in real life.
他用数吨泥土塑造出科罗拉多高原的模型 He sculpts tons of dirt into a model of the Colorado plateau.
从水龙头中流出的自来水则代表 Running faucets represent
科罗拉多河流入古老湖泊里的涌流 the flow of the Colorado River into the ancient lake.
现在我们的大湖完成了 Now we have our large lake.
水位开始上升 The water's getting higher.
它即将要溢出了 It's getting ready to spill across.
开始有一股细小的水流从湖泊中奔泻而出 We have a tiny little trickle of water pouring down off the lake.
这淌涓涓细流 That little tiny trickle
看上去似乎并没有什么 of water doesn't seem like much,
但久而久之 这股小水流 but over time, that little bit
流经那个陡峭的斜坡 获取充分的能量 of water flowing down that steep slope is going to gain energy,
它开始凿谷了 it's going to start cutting,
进而产生了瀑布 沿河道一路去向上游 making waterfalls that work their way back.
现在一个瀑布已经到达湖边 One waterfall has now reached the lake.
你可以看到我们刚释放出大量的水 You can see that we have just released a significant amount of water,
比之前更大流量 much more water than was previously pouring down.
现在我们就有了开山凿谷的力量 Now we have huge canyon-cutting.
山泥从峡谷侧壁脱离 落入湖中 Landslides are sloughing off the side of the canyon walls into the water,
被冲至下游 flushing it downstream.
而此时 可以看到 湖泊开始缩小 The lake, you can see that it's starting to shrink in size.
水位随之降低 That lake is getting lower.
然后 你就可以看到 And right there, you can see
我们已经凿出我们自己的缩微版大峡谷了 that we have cut our own small-scale version of the Grand Canyon.
道格拉斯的实验证明 Douglass' experiment proves
溢出理论在微小的模型上成立 that the spillover theory works in miniature,
但他还需要继续寻找证据 but he needs evidence
以证实其理论在广袤的范围里也成立 to show that it could have happened on an infinitely bigger scale.
道格拉斯开始着手寻找 Douglass sets out in search
一个面积足够大 of a lake large enough
且年代足够久远的湖泊 and old enough to be the source
以作为他溢出理论里的水源 of his spillover flood.
他心中已有一个中意的对象 He has a prime suspect in mind.
位于大峡谷东部100英里处 This is the site of the ancient lake Bidahochi,
古老的毕达霍奇湖 100 miles to the east of the Grand Canyon.
毕达霍奇湖
昔日的河床向我们传达了一个线索 And a clue here on the old lakebed
告诉我们该湖的深度 reveals how deep this lake once was.
这些绿色的粘土 These green clays,
它们可以证实这里曾有很深的湖水 which indicate deep lake water,
这是证明溢出理论中有大湖泊存在的 this is the classic evidence for the giant lake necessary
最为有力的证据 for the overflow explanation of Grand Canyon.
这些绿色的沉积物只会出现在特定的环境 These green deposits are only created in one specific environment.
绿粘土的形成 需要极深的湖水 To have green lake clays, you need deeper water,
因为深水中很少发生氧化反应 where there is little oxidation.
我认为那表明科罗拉多河曾到过此盆地 I think that's an indication that the Colorado River has arrived in this basin,
它从洛矶山脉而来 流经这里 that it's made its way from the Rocky Mountains to this location,
而这里只是它的一处歇脚的地方 and this is its basically stopover point before it eventually spills across
最终它将奔流而下凿出大峡谷 to form the Grand Canyon.
建立了这点使得道格拉斯得以计算出 Establishing the depth of this point lets Douglass work out
湖水曾经覆盖的面积究竟有多大 how large this area was once covered by water.
他将湖水的深度和 He compares the depth of the water
周围原野的轮廓高度进行对比 with the contour hightlight of the surrounding countryside.
毕达霍奇湖
结果显示 And that shows that
毕达霍奇湖曾一度扩延至2万平方英里 Lake Bidahochi once spread over 20,000 square miles
拥有3000立方英里的蓄水量 and contained more than 3,000 cubic miles of water.
如此一来 它比密歇根湖要大得多 That makes it bigger than Lake Michigan.
道格拉斯还需要确证该湖泊的年代 Douglas needs to date the age of this lake.
如果他的溢出理论成立 For his spillover theory to work,
那么这个湖就得比大峡谷的历史更为悠久 it has to be older than the Grand Canyon,
存在于超过550万年前 more than 5.5 million years.
在此处的深水化石堆里 He unearths the proof he needs
他挖掘出了他所需要的证据 in these deep-water fossils.
好了 这些是淡水域软体动物的化石 Ok. These fossil shells are freshwater mollusks
也许距今有六百万年 maybe as young as 6 million years old.
时间吻合了 The dates match up.
湖泊在正确的时间溢出 The lake was here at the right time
然后开始凿大峡谷 to have spilled over and begun cutting the Grand Canyon.
化石年代的考证应验了道格拉斯观点 Dating the fossils helped confirm Douglass' belief.
但他还需要找寻更多的证据 But his search for more evidence continues.
现实中 In reality,
我们从不会百分百确信它即是如此形成 we're never going to know how it formed to 100% certainty,
除非某人能制造出一台时间机器 unless someone builds a time machine.
从事我们这个学科的工作 By doing this kind of work,
你要提升你观点的可信度 all you're trying to do is increase your level of confidence on your ideas,
建立你自己的例证 丰富对应的证据 build up your case, build up your evidence.
积累他的证据 Building up his evidence is exactly
正是乔尔·佩德森目前在做的事情 what Joel Pederson is doing.
他正运用最先进的技术 He is using the very latest technology
来证明大峡谷被雕蚀出的速度 to prove exactly how fast the Grand Canyon was carved.
他在大峡谷的起点 He has found the evidence he needs right here
找到了证据 at the very start of the Grand Canyon.
李氏渡口
在李氏渡口 Here at Lee's Ferry,
到处都有这样的沙砾 there are all of these gravels
它们的存在显示河流曾流经至此 that are evidence of where the river has been in the past
■
乔尔·佩德森博士
犹他州立大学地质学家
而且还能显现侵蚀的过程中河流的路径 and the path it has taken during incision,
在这些沙砾中 有时你会看到晶体沙石 and amongst the gravels, sometimes you see these great lenses of sand,
我们可以利用它们追溯沉积物的确切年代 and we can use the sand to get an absolute date on these deposits.
当科罗拉多河凿开峡谷时 As the Colorado River carved out the canyon,
越来越多的碎石和沙砾残片沉积于此 it deposited more and more of the gravel and sand debris at this spot.
数百万年来 新岩层覆盖了旧岩层 Newer layers buried older layers over millions of years.
如今 地质学家已拥有先进的仪器 And geologists now have instruments
能检测到光线如何影响沙石中的原子 that can measure how light has affected individual atoms within the sand.
从而精确显示 每一岩层何时被覆盖 That reveals precisely when each sand layer was originally buried,
何时远离日光照射 away from the light of the sun.
鉴于技术要求精密 For the technique to be accurate,
必须保证样本一直与光隔绝 it is essential that the sample is not exposed to daylight.
所以我们带来了一个金属试管 So here we can take a metal tube,
我们把它从沙石露出地面的部分插入 and we can hammer it into the sand outcrop,
随后 试管中就盛有我们的样本 and in the metal tube then, we'll get a sample of the sand,
并且还是遮光保存的 and it'll stay out of sunlight,
然后我们把它带到一间暗室实验室 and then we take it back to a darkroom laboratory
取出沙砾 依旧与光隔绝 and remove the sand, still sheltered from light,
我们就可以分析其光学特性 and then we can analyze the optical properties of it
以测算它的绝对年龄了 to get an absolute age.
这个例子中 绝对年龄将会告诉我们 In this case, the absolute age would tell us
河流何时到达这里的 when the river was at this point in the landscape.
回到实验室 Back at the lab,
佩德森对比了峡谷各个层面的沙石样本 Pederson compares multiple sand samples, each from a different depth in the canyon deposits.
确定每一层沙石的年龄 Discovering the age of each individual layer of sand
从而估算出河流冲刷石头的速度 lets him estimate how rapidly the river has been cutting down through the rocks.
在李氏渡口 Here at Lee's Ferry,
我们可以利用后50万年历史以及绝对年龄 we can use this last half-a-million-year history along with our absolute dates
再结合我们手中的信息 and all the information we get,
得到峡谷当时的冲刷速度 and the rate of canyon-cutting here is
约等于每百万年1000英尺 about 1,000 feet per million years.
也就是 每1000年1英尺 That's one foot in every thousand years,
每世纪一英寸多一点 a little more than one inch every century.
那说明凿开整个5300英尺深的大峡谷 It proves that the entire 5,300-foot-deep grand Canyon
约莫花费的时间 could have been cut in a little more
刚刚超过5百万年 could have been cut in a little more than 5 million years.
按地质时间来讲 In geological terms,
不过是在一夕之间 the mere blink of an eye.
调查正在一步步搜集 The investigation is assembling
大峡谷如何形成的证据 evidence on how the Grand Canyon was created.
青黏土沉积物证实了 Green clay deposits support the theory
曾经有一片大到足以溢出河流的古老湖泊 that an ancient lake was big enough to spill over and
引发了大峡谷形成 trigger the canyon's creation.
深水区化石证明了 Deep-water fossils prove
这一湖泊存在于6百万年前 that the lake existed 6 million years ago,
与湖泊溢出 凿出大峡谷的时间刚好吻合 the right time to have overflowed and cut the Grand Canyon.
但证明对大峡谷的切凿是如何开始的 But proving how the canyon-cutting began is
不过是调查的一个部分 only part of the investigation.
这可是世界上最宽阔深邃的大峡谷之一 This is one of the widest and deepest canyons in the entire world,
为了揭示它是如何变得如此壮观 and to discover how it grew so large,
地质学家必须调查 geologists will have to examine
大峡谷的一些最惊人 最危险的地质特征 some of the most dramatic and dangerous features the canyon has to offer.
亚利桑那西部的地形 The landscape of western Arizona has transformed
由古老的山脉 from ancient mountains
变成史前海洋 to prehistoric seas
再到平坦的高原 to a flat uplifted plain.
仅仅550万年前 Just 5.5 million years ago,
大峡谷被开凿出来 纵贯整个高原 the Grand Canyon was cut through this plateau.
它发生的如此迅速 It happened so fast that
以至于地质学家不得不重新考量 geologists had to think again
科罗拉多河的惊人威力 about the awesome power of the Colorado River.
它不仅仅是靠河水的冲蚀凿开的石块 It cuts through rock not by the water wearing it away.
就算将河水倾泻在石块上很久 You could pour water over rock for a long time,
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卡尔·卡尔斯托姆博士
新墨西哥大学地质学家
也不会有任何事情发生 and nothing would happen.
凿开石块的是河流所携带的工具 It's the tools that the river carries.
河流中的浮石泥沙 The river carries boulders and sand,
互相冲撞 and those bump against each other,
侵蚀了此处的石块 and they eat away at the rock.
每天 科罗拉多河 Every day, the Colorado
可以携带50万吨岩石和碎片 can carry almost 500,000 tons of rock and debris,
足够填满100个奥运标准泳池 enough material to fill more than 100 olympic swimming pools.
每秒5吨 That is 5 tons every second.
因此调查河流侵蚀从来就是项艰巨的任务 So investigating river erosion is never an easy task,
因为强大的科罗拉多水流 because the powerful flow of the Colorado River
已经将调查石块岩石侦探们需要的许多证据 has scoured and washed away many of the clues that
冲刷殆尽 the rock detectives need.
他们在扰乱河水前行的无数湍滩处 They looked for evidence in the hundreds of rapids that
寻找证据 disrupt the river's progress.
这些纷乱的湍滩形成于 The swirling rapids are created
随狭窄的峡谷坡面冲泄而下的暴洪中 when flash floods sweep boulders into the river
卷入河流的巨砾 from the many smaller side canyons.
河流不得不将许多能量汇集在这些地方 The river has to focus a lot of energy at these points
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乔尔·佩德森博士
犹他州立大学地质学家
来对抗迎面而来的卵石 to deal with all of the boulders that are coming in it.
粗糙的卵石越多 The more coarse boulders
河流切割河道所遭遇的 and more resistant material that the river has to fight against
障碍物越多 to accomplish its incision,
切割得就越深 the steeper it gets.
当河流流过湍滩时 As the water flows over the rapids,
其下游的河床被切割得更深 it cuts deep into the bedrock below.
单这片湍滩 At this set of rapids alone,
河道就下降了10英尺 the river drops 10 feet,
而科罗拉多河在这一河段有很多湍滩 and there are a lot of rapids on this section of the Colorado.
整个大峡谷接连不断的出现湍滩 So put all these rapids together in a string through Grand Canyon,
使得河流穿过的整个大峡谷剖面 and that gives you the overall sort of unusually steep
整体不同寻常的深邃 Grand Canyon profile of the river going through it.
重力和简单的物理原理就足以解释 Gravity and simple physics are at the heart of how
克罗拉多河如何如此迅速的凿开这样多的岩石 the Colorado has carved so much rock so quickly.
550万年前 5.5 million years ago,
科罗拉多河流到这片时被抬高 the Colorado River was flowing over the steep edge of the plateau
高出海平面几千英尺的高原峭壁边缘 that had been pushed up thousands of feet above sea level.
河流沿着这片陡峭的坡面飞流直下 The river ran rapidly over the steep downward slope
倾泻而出 岩石碎片紧随其后 and swept rough, rocky debris along in its wake.
凿开了一个切口 An incision formed,
一直凿至高原的底部 digging back into the edge of the plateau.
河流下切 The power of the river
使河道下落形成如此巨大的峭壁 to incise as it dropped off that huge escarpment
其力量一定非同凡响 must have been really great.
河流就这样迅速地将那里切开 And so the river quickly incised there,
那一陡峭的切口 and that very steep drop-off of incision
一路向上游后退 would have worked its way back upstream
跨越了整个大峡谷区域 through the Grand Canyon region.
在某种程度上算是一个瀑布 It's sort of a waterfall that,
用了几百万年时间 a few million years later,
便流经了整条河道 has spread itself out through the length of the river.
正是科罗拉多高原 It is this steep drop-off
和其下游的地面如此陡峭的落差 between the Colorado plateau and the land beneath it
赋予了科罗拉多河惊人的侵蚀力量 that fuels the Colorado's incredible erosive power.
这条河流源于 The river begins its life
科罗拉多高耸的落基山脉 high in the Rocky Mountains in Colorado.
每流经一英里 For every mile that it travels,
河道下降10英尺 the river falls 10 feet.
与其相反 密西西比河 By contrast, the Mississippi River,
拥有多于科罗拉多河10倍的水量 a river moving 10 times as much water as the Colorado,
缓缓流过开阔的平原 meanders across a flat landscape.
没有陡峭的下坡提供助力 With no steep slope to drive it,
密西西比河无力切割出任何峡谷 the Mississippi can't carve any canyons.
不过大峡谷不只深邃 But the Grand Canyon is not just steep.
而且开阔 It's also wide.
在大峡谷南缘 And here on the south rim,
国家公园腹地 at the heart of the National Park,
大峡谷的雄伟壮阔跃然纸上 the true majesty of the Grand Canyon is revealed.
大峡谷南缘
这是峡谷最宽广的区域 This is where the canyon is at its widest,
峡谷两缘相距18英里 as much as 18 miles from rim to rim.
如今此地显得安详静谧 This landscape appears serene now,
然而却是强横的外力锻造了如此独特的壮美 but its unique beauty was forged by violent forces.
大峡谷 Grand Canyon,
我们时常将它和科罗拉多河联系在一起 oftentimes we just associate it with the Colorado River.
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天堂谷社区学院地质学家
约翰·道格拉斯博士
科罗拉多河确实切开了大峡谷 The Colorado River is what cut the Grand Canyon.
形成了最初的切口 It formed the initial gash
使河流得以穿过 to allow the river to flow across.
而真正使得大峡谷波澜壮阔的是它的宽阔 But what makes Grand Canyon grand is really its width.
所有的岩层淋漓尽致地展现出来 And all the layers of rock that are exposed,
而这不只归功于科罗拉多河 and that isn't only solely tied to the Colorado River.
而是归功于裸露的岩石 What's happening is this rock that's exposed,
它们被雨水拍打着 it's being beaten on by rain,
雨水渗入其中 and the rain gets in there,
将其风化 变得不再坚硬 and it weathers the rock, and it weakens it.
因为这里如此陡峭 And then because this is so incredibly steep,
受到重力的影响 gravity will act on that material,
坡体下滑 被河水冲走 transporting it deeper down into the river, flushing it back out.
这一过程不断重复 And that process just repeats over and over again
随着时间的推逝 越变越宽 to allow the canyon to get wider over time.
远处那里有典型的岩崩 We have classic rockfalls that are cascading down
像瀑布一样泻在黑岩坡面上 onto the black rock in the far distance.
这些岩崩显示了 Those events are indications
峡谷仍在继续变宽 that this is actively ongoing canyon-widening
不断在这一过程中被侵蚀 and retreating from these processes.
这些岩石的滑落不是缓慢发生的 The fall of these rocks is not a gradual process.
这种风化发生得极其剧烈 This is erosion at its most violent.
很少有人 Very few people are ever
会真的看到大峡谷发生变化 going to see Grand canyon actually change.
我无数的夜晚都待在大峡谷 I've spent numerous nights in Grand Canyon.
也只听到一两块石头滑落 I've only heard one or two rocks ever fall,
但变化一定会发生 而且一旦发生 but change will happen, and when it does happen,
会在瞬间完成 it happens very rapidly.
岩石的滑落是由于 The rocks fall because both
坚硬和松软的岩石以层状分布 harder and softer rocks are layered,
在大峡谷的山壁上层层交叠 one on top of the other, in the canyon walls.
坚硬的岩石由石灰石和砂岩构成 The harder layers are made of limestone and sandstone.
这些岩石不易被侵蚀 These rocks don't weather easily,
而其下层的页岩则由泥土构成 but the softer shale beneath is made of mud that
下雨时会发胀 expands when it rains,
使得页岩坍塌 causing the shale to crumble away.
这些相对脆弱的岩石 Those weaker rocks,
易风化易退缩 they weather and retreat back,
渐渐破坏到上面坚固的峭壁岩石 and they undermine the resistant cliff rocks above
导致其以惊人的岩崩 that will then fail as dramatic
或山崩的方式后撤 rockfall, landslide events,
该峡谷由此逐渐变宽 allowing the canyon to increase its width.
岩崩只是增加大峡谷 The rockfalls are merely the first step towards
不可思议的宽度的第一步 increasing the Grand Canyon's enormous width.
倘若没有它物的一臂之力 Without the help of an accomplice,
这整个峡谷就会积满泥石碎屑 the entire canyon would fill up with debris.
倘若没有科罗拉多河 Without the Colorado River,
就不会存在宽度如此惊人的大峡谷 you could not have the Grand canyon as wide as it is.
通过水流将泥石碎屑冲往下游 就像... By flushing that material downstream, it like...
将它们都冲刷干净 it wipes it all clean
以便全新的物质可以取而代之 to allow a whole new material to build up again.
倘若这个过程不断地重复 And once you repeat that over and over again,
峡谷的岩壁会向后退缩 it allows the canyon walls to retreat back,
随着水流继续前行 and the entire canyon just grows,
继续将泥石碎屑全部冲往下游 as these guys continue to march and push
整个峡谷仍旧会随之不断成长 and move all that material downstream.
大峡谷之所以那么深 The mystery of how the Grand Canyon
那么宽的谜底已经解开了 grew so deep and so wide is being solved.
科罗拉多湍滩展示了 The Colorado rapids demonstrate
陡峭的河床在快速雕刻出大峡谷的 how the steepness of the riverbed helps carve
过程中起到的辅助作用 the canyon so quickly.
峡谷岩壁上的石崩 Rockfalls on the canyon walls
揭示了那些脆弱的岩石是如何快速地 reveal how weaker rocks rapidly widen the canyon
使大峡谷在亚利桑那州的平原上变宽 across the plains of Arizona.
但是关乎大峡谷的故事还远未结束 But this is far from the end of the Grand Canyon's story.
仅仅百万年前 In just the last million years,
大峡谷的形状就由于其它一些 the canyon has been transformed
不可抵抗的强大的自然力量而改变了 by other overwhelmingly powerful natural forces.
地质学家已经证实了 Geologists have established
经过17亿年的时间 that over 1.7 billion years,
大峡谷 继古老山脉 the Grand Canyon emerged from ancient mountains
和史前海洋之后出现 and prehistoric seas to become
并成为北美洲的地质图标之一 one of North America's geological icons.
这可是个弥足珍贵的机会可以一睹 This is a rare look at one of the most remote
大峡谷最偏僻最神秘地区之一的风采 and secret parts of the Grand Canyon.
在大峡谷的边缘处 A series of small cone-shaped
一系列圆锥状的山脉成排矗立 mountains line the canyon's edge.
每座山的侧面都有 And there are flows of black rock
大量的黑色岩石 running down from each rim.
它们来自于意义非凡的时代 They come from a remarkable era
仅仅725,000年前 just 725,000 years ago,
正是那时候大峡谷的平静 when the peace of the canyon was shattered...
被火山打破了 by volcanoes.
这里是土威普点 This is Toroweap Point,
土威普点
在一个名为亚利桑那狭地的偏远地区 in a remote area known as the Arizona strip...
这是美国本土最为人迹罕至的地方之一 One of the most isolated places in the continental U.S.
除了地质学家以外 Few people, other than geologists,
很少有人来过这个地区 ever see this area,
虽然它拥有大峡谷一些最令人惊叹的美景 although it boasts some of the canyon's most stunning views.
岩石侦探们逐步发现了 The rock detectives come to see
在相对近期的地质历史中 how explosive volcanic eruptions have changed
爆炸性火山喷发是如何改变大峡谷的 the canyon in the comparatively recent geological past.
这些看起来像是溢出于 This black rock that seems
峡谷边缘的黑色岩石 to have spilled over the rim of the canyon
是古老的熔岩流 is an ancient lava flow,
曾一度是滚烫的岩石 what was once boiling-hot rock,
现在可谓永远冻结了 forever frozen in time.
鲍威尔谈到一条满是熔融岩浆的河流 Powell talked about a river of molten magma pouring down
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新墨西哥大学地质学家
瑞恩·克罗
注入一条溶化的雪水的河流里 into a river of melted snow.
他还谈到那场景是多么激动人心 And he talked about how dramatic it must have been,
沸腾火热的岩浆 the boiling and seething
还有水蒸气 and the steam, and...
那场景肯定相当震撼 it must have been amazing.
你可以想象一下 You would picture red-hot lava
如你在夏威夷所见的炽热的岩浆 like you would see in Hawaii
沿着峡谷岩壁奔泻而下 pouring down the canyon walls
覆盖在岩壁上 and coating them, and then
之后当岩浆流至河流时 once it reached the river,
就会... it would...
你知道的 就会立刻形成 You know, it would immediately create just giant
巨型团状的水蒸气 clouds of steam.
从多达一百座锥形火山上 The extensive lava flows
喷发出来的大量的岩浆流 erupting from as many as 100 cinder-cone volcanoes
对其下面的科罗拉多河产生了巨大的影响 had a dramatic effect on the Colorado River running below.
克罗认为火山喷发至少形成了 Crow believes that on at least 8 occasions,
八个巨型岩浆坝 the volcanic eruptions created huge lava dams
从而完全阻塞了这条河流 that blocked the river completely.
我身后是 Well, behind me here
众多玄武岩遗迹之一 is one of many basalt remnants.
它们是从峡谷倾泻而下的 They're the remains of lava flows
岩浆流的残骸 that poured down the canyon,
是组成峡谷的一部分 partially filling it.
随后 科罗拉多河将岩浆残骸 And then subsequently, the Colorado River has removed
几乎都冲刷走了 只留下一小部分 all but a few little chunks.
强大的科罗拉多河 The lava dams brought
也因为岩浆坝而暂停下它的脚步 even the powerful Colorado River to a halt...
只是暂时的而已 For a while.
最终岩浆坝再也阻挡不了科罗拉多河 In time, the dams were no match for the Colorado.
岩浆流后面堰塞河的 The rising pressure
水压日益增大 of the dammed river behind them
最终压力超负荷 从而导致大坝崩塌 eventually became too much, and they shattered.
这段爆炸性的插曲 This explosive episode
在峡谷岩壁上留下了痕迹 has left its mark on the canyon's walls.
今天这些锥形山脉看起来似乎已经熄灭了 Today, the cones appear to be extinct and lifeless,
虽然一些地质学家认为 although some geologists believe
这些火山或许仍是活火山 that the volcanoes might not be finished quite yet.
上一次的火山喷发 The last eruption that sent
岩浆注入大峡谷的事件 lava pouring into Grand Canyon
大约发生在10万年前 probably occurred about 100,000 years ago.
有证据表明 There is evidence for an eruption
锥形山脉上的火山喷发 on the rim that didn't actually
并没有真正雕刻出 make it into Grand Canyon
这个只有1千年历史的大峡谷 that's 1,000 years old.
因此有可能... So there's... there's, you know,
我认为 这里将来很有可能 I think, a good chance that in the future,
也会发生火山喷发 there may be eruptions here as well.
虽然大峡谷的未来之路 The Grand Canyon's future
目前并未明确 has yet to be written,
但是现在研究人员对它的过去 but investigators now understand
有了一定的认识 the story of its past.
在峡谷底部发现的 The calcium in the garnet
石榴石中的钙元素揭示了 discovered at the base of the canyon reveals
该地形的古老源头是 the ancient beginnings of this landscape--
一片广阔的山脉 an immense mountain range.
石灰石说明了 Limestone rocks show
该峡谷在550万年前才形成的 that the canyon was only formed 5.5 million years ago.
只有在深水中方能形成的青黏土证明了 Green clays that can only form in deep water prove that
一个大于密歇根湖的巨大湖泊 a huge lake, bigger than Lake Michigan,
可能引发了 could have been
开凿峡谷的鬼斧神工 the trigger for this canyon-carving.
来自破碎峡谷峭壁表面的 And rockfalls from the crumbling cliff faces
岩崩是峡谷如何演变为 of the canyon rim are evidence
今日所见的这种形状的证据 of how the canyon grew to the shape it is today.
自十九世纪中叶以来 Geologists have been studying
地质学家就一直在研究大峡谷 the canyon since the mid-1800's.
尽管已研究调查了一百余年 Yet even after more than a century of investigation,
故事仍远未结束 the story is still far from finished.
大峡谷的景观仍在不断地变化中 The landscape is evolving,
在未来它仍会在地质学上 and it's going to be changing
发生变化 through the geological future.
因此这个述说它的地质以及 And so the story about the geology and
这些引人入胜的问题的故事 the fascinating questions here is not one
并未结束 that's over,
它将继续进化 and it's going to continue to evolve
科学家们则继续在这里做调查研究工作 as scientists continue to do work here.
大峡谷动态的地质现象 The dynamic geological phenomenon of the Grand Canyon
是由于地壳内部那些巨大的炽热力量 is a place where the vast fiery forces within the Earth's crust
在与不可抗拒的水能不断进行着斗争 do battle with the inexorable power of water.
其结果 就是形成如此自然奇观 The result--a natural wonder
它的岩壁记载了 whose walls record
地球近20亿年躁动不安的地质史 nearly 2 billion years of our planet's turbulent geological history.