This is our planet's final frontier.|这里是地球上最后的边缘地带

An inner world where only the most adventurous dare to go.|一个只有最勇敢者 才敢涉足的地底世界

行星地球4----洞穴

Beneath our feet are countless miles of cave shafts and passages.|我们脚下有着绵延不绝的洞窟和隧道

The Cave of Swallows in Mexico|墨西哥境内的燕子洞

400 metres to the bottom|深达400多米

deep enough to engulf the Empire State Building.|足以吞没整座帝国大厦

This is the biggest cave shaft in the world,|这是世界上最大的深洞

yet these depths were first explored only two years before men landed on the moon.|然而人类直到登月前两年 才第一次进入这个深渊

Today, caves remain the least explored places on Earth.|今天，洞穴仍是地球上 人类最少涉足的地方

However, human beings are seldom the first to reach these black, damp places.|但是，人类绝非 这个阴暗潮湿地界的第一位到访者

Here live some of the strangest and least known animals on the planet.|这里住着一些地球上最奇异 和最鲜为人知的动物

This galaxy of little lights is created by thousands of living creatures.|这“满天星斗”其实是 几千只小动物发出的荧光

Any animal that lives in a cave has to cope with complete blackness.|住在洞穴里的动物都必须 适应彻底黑暗的环境

But in New zealand, some have turned this darkness to their advantage.|但是在新西兰，有些动物却能利用黑暗的条件

A silken strand is lowered from the ceiling|一根坚韧的丝从天顶上垂下

alongside hundreds of others.|边上还有好几百根

Beautiful though these threads are|虽然这些丝看起来很漂亮

they have a sinister purpose.|它们却是阴险的陷阱

This is a cave glow-worm.|这是一种洞穴萤火虫

To trap its prey, it goes fishing with a line of silk.|它利用一根根的丝来诱捕猎物

The silk comes from glands in the glow-worm's mouth|丝产生自萤火虫口中的腺体

and is loaded with droplets of mucus.|上面缀着一串粘液滴

Each glow-worm produces dozens of these threads.|每条萤火虫都会吐很多根这样的丝

0nce its lines are set|当一排丝架设完毕后

the glow-worm hangs from a mucous hammock|萤火虫便用粘液将自己悬吊起来

and waits like a patient angler.|然后像一位耐心的钓鱼者似的 等待猎物上钩

But the glow-worm doesn't leave everything to chance.|不过，萤火虫并不会听天由命

That ghostly blue light is the result of a chemical reaction|这些诡异的蓝光是一种化学反应的结果

taking place inside a special capsule in its tail.|由尾部的一个特殊腔囊产生

这些从尾部发散出来的荧光|The light literally shines out of its backside. 、

It's a lure for attracting prey.|正是用来吸引猎物的诱饵

Insects seem irresistibly drawn towards the source|昆虫总是禁不住光源的诱惑

and then get trapped by the sticky lines.|结果就被这些粘乎乎的丝拿住了

0nce stuck|一旦被粘住

there is no escape.|根本没有脱逃的机会

Now it's just a matter of reeling in the line|现在，它只需收起丝线

and slowly consuming the catch alive.|然后慢慢吃掉尚且活着的猎物

By ensnaring the insects that hatch in this cave,|通过诱捕洞穴内羽化的昆虫

these glow-worms have solved the biggest challenge|这些萤火虫成功地解决了 终生穴居动物

that permanent cave-dwellers face|面临的最大难题

finding a regular and reliable source of food.|即找到长期而可靠的食物资源

0ne kind of rock makes this whole underground world possible,|这些地底世界之所以会存在，都是因为一种岩石

limestone.|石灰岩

Most of the world's caves are found within it|世界上大部分洞穴内都存在石灰岩

and it covers nearly 1 0% of the Earth's surface.|它覆盖了地球表面将近10%的面积

Limestone is composed of minerals derived from marine shells and corals.|石灰岩由海螺和 珊瑚中的矿物沉积后形成

So although this rocky escarpment in the United States|所以，尽管美国境内的这座石壁

is now hundreds of metres above sea level,|如今矗立在海平面以上几百米高的地方

it was actually formed underwater.|它实际上却是在水下形成的

The limestone towers of Vietnam's Halong Bay|越南下龙湾的石林

are a reminder of this link with the sea.|能说明石灰岩与海洋的关系

0riginally this whole area would have been one solid block of limestone,|起初，这整个地方都是 一整块坚固的石灰岩床

the base of a coral reef.|珊瑚礁的基座

In Borneo, rain has sculpted the limestone into extremely sharp-sided pinnacles.|在婆罗洲，雨水已将石灰岩 雕凿成无比尖削的石塔

But the dissolving power of rainwater has other, much more dramatic, effects underground.|不过在地下，雨水的溶解作用 还能产生其它更壮观的效果

Rivers that flow over limestone often seem to completely disappear.|流经石灰岩的河川 到最后似乎总是无影无踪

When the water reaches a more resistant bed of limestone|当水流遇到更坚硬的石灰岩床时

its course is altered.|就会改变路线

0nce underground|一旦进入地下

the water takes on a new, more erosive power.|水便有了一股新的、更强的侵蚀力

During its journey from the surface,|在地面上流淌时

the water absorbed carbon dioxide from the soil|水从土壤中吸收了二氧化碳

making it mildly acidic.|成为弱酸性

And over millions of years, this acid eats away the limestone,|石灰岩经过几百万年的酸蚀作用

creating a maze of caverns and passages|形成了迷宫般的溶洞和通道

that sometimes go on for miles.|有的甚至深达数英里

This is the biggest underground river passage in the world,|这是世界上最大的地下河通道

so big a jumbo jet could fly through it.|大到可以通过一架大型喷气式客机

It's Deer Cave in Borneo.|它就是婆罗洲的鹿洞

The sheer size of Deer Cave|鹿洞的容量很大

allows some animals to gather there in huge numbers.|使得大批动物到此聚集

A staggering three million wrinkle-lipped bats live here.|这里住着数量惊人的300万只犬吻蝠

The bats roost high on the walls and ceilings|这些蝙蝠倒挂在洞壁和天顶上

where they're well protected from the outside elements|它们在此完全不受外界因素的干扰

and safe from predators.|还能躲开天敌

And while they're up here|它们高悬在洞穴上方时

the bats produce something very important.|会产生一种非常重要的东西

This 100-metre-high mound is made entirely of bat droppings|这堆100多米高的东西 全都是蝙蝠的排泄物

guano.|粪便

Its surface is covered by a thick carpet of cockroaches.|地面上爬满了密密麻麻的蟑螂

Hundreds of thousands of them.|它们的数量无以为计

Caves are one of the few habitats on Earth not directly powered by sunlight.|洞穴是地球上少数几种 不直接依赖阳光的生态环境之一

In the absence of plants, this food chain is based|在缺少植物的情况下，这里的食物链

on a continuous supply of bat droppings.|完全依赖供应不断的蝙蝠粪便

The cockroaches feed on the guano|蟑螂的食物就是粪便

and anything that falls into it.|以及任何掉进里面的东西

The droppings also support other types of cockroaches,|粪便也能养活其它种类的蟑螂

which spend part of their day resting on cave walls.|它们一天大部分时间都呆在洞壁上

These in turn become food for giant cave centipedes,|这些蟑螂也接连成为了 洞穴大蚰蜒的美餐

some more than 20 centimetres long.|有的蚰蜒能长到20厘米长

Bizarrely, there are crabs here, too.|奇怪的是，这里甚至还有螃蟹

Sifting through the droppings for nutrients.|它们从粪便中过滤营养物质

All these animals spend their entire lives within the cave.|所有这些动物都在洞穴内度过一生

They're totally dependent on the digested remains of food|它们完全依赖的食物消化残渣

that's brought in from outside.|都是来自于外界

Each evening, in just two hours|每天傍晚，只是前后2小时内

three million bats leave the safety of the cave|300万只蝙蝠一起离开安全的洞穴

to hunt for insects in the forest outside.|在森林外围捕食昆虫

But not all will return.|但并非所有的蝙蝠都能返回

As they leave the cave|蝙蝠离开山洞后

the stream of bats form a doughnut-shaped ring.|即在空中组成一个面包圈一样的队列

The wheeling bats seem to confuse a rufous-bellied eagle,|旋绕的蝙蝠群似乎已将 棕腹隼雕弄得晕头转向

but they must still survive the attacks of other, more specialised birds of prey.|但它们仍须躲过 其它更专业的猛禽的攻击

Peregrine falcons and bat hawks are the jet fighters of the bird world.|游隼和蝠鹞是鸟类中的喷气式战斗机

[英学网] - 原创中英对照双语影视 视频英语学习网|www.EngXue.com

Good hunting will end as the light fades|天黑后，再高超的捕猎本领 也将无用武之地

so the bat hawks bolt their catches on the wing|于是蝠鹞一边飞一边吞下猎物

and fly straight back for more.|然后径直返回继续捕猎

Any bat separated from the group|任何一只脱离群体的蝙蝠

becomes a clear and obvious target|立刻成为显眼的目标

and is asking for trouble.|很快便遭了殃

Yet the nightly onslaught has little impact on bat numbers.|然而，每天傍晚的攻击只会 对蝙蝠数量产生很小的影响

By the morning, the vast majority will be back in the safety of the cave.|到了早上，大多数蝙蝠 仍会安然无恙地回到洞中

Bats are not the only commuters in these Bornean caves.|蝙蝠并非婆罗洲洞窟中的唯一常客

There's a day shift as well.|这里也有“做日班”的居民

Returning from hunting in the sunlight|完成白天的狩猎工作后

these commuters rely on their loud clicks|这些住客利用它们响亮的叫声

to find their way through the cave passages in total darkness.|在漆黑一片的洞穴通道内辨别方向

(CLICKING)

They're cave swiftlets.|它们就是洞金丝燕

Like bats, they use echolocation to navigate.|和蝙蝠一样，它们也利用回声定位来导航

We need lights to see what's going on,|我们必须有光才能看清前方的路

but in the pitch black, the swiftlets manage unerringly|但是金丝燕却能在黑暗中 准确无误地

to locate their individual nesting sites,|到达自己的筑巢点

which are only a few centimetres across.|而它们的巢窝相隔不过几厘米远

It's a remarkable skill and one we still do not fully understand.|我们至今仍未能完全了解 这种了不起的本领

These birds are unusual for another reason.|这些鸟之所以特别还有另外一个原因

Their little cup-like nests are made entirely from threads of saliva.|它们小巧的杯状燕窝完全由唾液丝筑建

It takes more than 30 days to complete one.|每个燕窝得花上30多天才能完工

Their nests are very precious objects|燕窝是非常珍贵的东西

and not only for the birds.|不仅只是针对这些鸟而言

(MEN SPEAKING F0REIGN LANGUAGE)

For 500 years, people have been harvesting the nests of cave swiftlets.|500年来，人们一直采集洞金丝燕的燕窝

It's a very risky business.|这是一项非常危险的工作

With virtually no safety equipment|事实上没有任何安全措施

and using ladders made from forest vines|采集者利用树藤编成的梯子

the gatherers climb into the highest reaches of the cave,|爬到洞穴的最高处

often more than 60 metres from the floor.|通常高出地面60多米

The work may be hazardous in the extreme|这项工作看起来极度危险

but the rewards are great.|但却能得到丰厚的回报

The pure white nests of cave swiftlets|洞金丝燕的纯白燕窝

are the main ingredient of bird's nest soup|是燕窝羹的主要成分

and, gram for gram, are worth as much as silver.|每克燕窝的价值堪比白银

As soon as its nest is removed, a bird will immediately build another,|燕窝被摘去后，金丝燕很快又会再吐一个

so as long as this valuable harvest is properly controlled,|所以，只要这种利润可观的 采摘行为得到适当控制

the colonies will continue to flourish.|燕群仍旧可以长盛不衰

These Bornean caves are among the biggest in the world|婆罗洲的这些洞窟是世界上最大的洞穴

and they're still getting bigger as, each year|它们仍在不断扩大

rainwater eats away a little more limestone.|因为每年雨水都会侵蚀掉少许石灰岩

But water in caves doesn't only erode|可是洞里的水不光只是侵蚀

it also builds.|它们还能造景

This water is loaded with dissolved limestone,|这些水中含有溶解的碳酸钙

and when it meets the air in the cave|当它与洞内空气接触时

some of that is deposited as a mineral|其中的一些就会沉淀为一种矿物

calcite.|方解石

As it builds up|随着它的积累

so the calcite forms decorations that hang from the ceiling,|方解石形成了悬在洞顶上的装饰物

stalactites.|钟乳石

Each drop leaves behind only a minuscule amount of calcite,|每滴水珠只会留下极少量的方解石微粒

but over time, the process can produce some spectacular results.|但随着时间的推移，它们变成了最引人入胜的景观

If the water seeps through the ceiling quickly,|若是水从洞顶滴落的速度较快

then the calcite is deposited on the floor of the cave,|方解石就会在洞穴地面上沉积

and that creates stalagmites.|最后形成石笋

Variations in water flow and air currents|水流和气流的变化

produce an infinite variety of forms|造就了千姿百态的溶洞地形，

but all are created by the same process|但它们的形成过程都是一样的

the slow deposition of dissolved limestone.|都是由水溶碳酸钙缓慢沉淀而来

And when stalactite meets stalagmite|钟乳石与石笋相遇后

a column is born.|便形成了石柱

Structures like these in North America's Carlsbad Cavern|北美洲卡尔斯巴德溶洞中的这些构造

can take many thousands of years to develop.|经历了数千年的形成过程

But sometimes, the formations in a cave stop growing altogether.|但有时洞穴内的这些活动会完全停止

These flooded caves in Mexico have remained virtually unchanged for thousands of years.|墨西哥的这些水洞 几千年来几乎保持不变

Since the last ice age, they've become cut off from the outside world,|自从上一个冰川期以来，它们便已和外界隔绝

yet their impact on life at the surface has been huge.|然而它们对地面上的生物 却有着极其深远的影响

Five hundred years ago, they supported one of the world's great civilizations,|500年前，它们维系着 一个世界上最伟大的文明

the Maya.|玛雅

Mexico's Yucatan peninsula has no rivers, lakes or streams,|墨西哥的尤卡坦半岛 没有河流、湖泊和小溪

so the Maya relied on the cenotes|因此玛雅文化完全依赖于沼穴

the flooded entrances to the water-filled caves.|——地下水洞的入口

These flooded shafts are the region's only source of open fresh water.|这些水潭是整个地区 唯一的露天淡水资源

The cenotes are, in effect, gigantic freshwater wells.|沼穴于是成了巨大的淡水井

Away from the life-giving rays of sunshine|这里远离给予生命的阳光

one might not expect to find plants.|似乎不太可能会有植物

But in the darkness of the cave tunnels|但是在黑暗的洞穴通道内

roots of giant tropical trees|大型热带树木的根系

have pushed their way through cracks in the limestone|却已穿透石灰岩裂缝

to reach the flooded caverns.|伸入到水洞之中

Without this water|如果没有这些水

the Yucatan's forest could not grow so luxuriantly.|尤卡坦半岛的森林不可能长得如此茂盛

The Maya knew that their lives depended on this water,|玛雅人固然知道 它们的生活离不开这些水

but it's only with the help of today's technology|但只有借助现代科技

that we've come to appreciate the full significance and scale of these flooded passageways.|我们才能完全了解 这些地下水道的重要性及其规模

So far, more than 350 miles|迄今为止，人们已绘制了350英里的

of underwater galleries in the Yucatan have been mapped.|尤卡坦半岛地下水系图

But still, nobody yet knows the true extent of this subterranean water world.|但仍旧无人知晓 这个地下水世界究竟有多大

And with good reason.|以及它形成的原因

Underwater caving is notoriously dangerous.|地下水洞是出了名的危险

When the nearest exit may be hundreds of metres or more away,|最近的出口可能远在 几百米之外或者更远的地方

running out of air down here would be fatal.|在这里，耗尽氧气将是致命的

To avoid getting lost|为了避免迷路

divers carry with them a spool of string.|潜水员必须随身携带一捆轴线

It becomes their lifeline|这成了它们的救生索

literally.|绝对如此

The string also doubles as a measuring tape|这根线同时也是测量尺

a technique that has been used here in Mexico|在墨西哥的这个地方，这种科技被用来

to chart the largest underwater cave in the world|测绘世界上最大的地下水洞

all 100 miles of it.|全长达100多英里

Cave exploration often requires you to push yourself through narrow gaps in the rock.|洞穴探险需要不时挤过 一些狭窄的岩石缝隙

Cavers call such places ''squeezes''.|洞穴专家称之为“瓶颈”

The tighter the squeeze|“瓶颈”越是狭窄

the greater the chance of damaging some vital life-support system.|便越有可能损坏一些重要的生存设备

In these conditions, a diver could easily become disorientated,|在这种情况下，潜水员很容易迷失方向

and that could be fatal.|而这将导致送命

The flooded caverns can play tricks on you in other ways.|地下水洞还会以别的方式戏弄你

What seems like air isn't.|这看上去像是空气，不对

It's just another kind of water.|它只是另一种水

This is a halocline|这里是盐跃层

a meeting of fresh and salt water.|淡水与咸水的交汇处

Fresh water from the jungle flows over the heavier salt water from the sea.|咸水来自海洋，比重较重，来自丛林的淡水在其上方流动

The salt water layer is extremely low in oxygen,|咸水层的含氧量很低

making it a particularly difficult place for animals to live.|对动物而言是极为困难的生境

Yet some have managed it|但有些动物却能在此生存

like the remipede, one of the most ancient of all living crustaceans.|例如桨足虫——一种最古老的甲壳动物

The Maya understood the importance of the cenotes,|玛雅人知道沼穴的重要性

but they could never have known that these flooded passageways|但他们从不知道这些水下通道

were actually the beginning of subterranean rivers|其实是地下河的入口

all of which eventually flow out to the sea.|它们最终都流向大海

Salt water, unlike fresh water, does not erode limestone,|咸水与淡水不同，不会溶解石灰岩

so most sea caves are created by the mechanical pounding of the waves.|所以大部分海洋洞窟 是在海浪的机械冲击下形成的

The rocky outcrops of New zealand's Poor Knights Islands|新西兰坡·骑士岛的

are riddled with sea caves.|岩礁下布满了海蚀洞

And just like those in Borneo,|与婆罗洲的洞窟一样

they have become important shelters for many species.|它们也成了许多动物的重要庇护所

After a day feeding in the open water,|经过一天开放水域的觅食之后

vast shoals of demoiselle fish return to the caves,|大群雀鲷返回到洞窟中

which they use as a refuge from predators.|这里是它们躲避天敌的地方

For these fish, the caves are a night-time retreat|对于这些鱼来说，洞穴是理想的过夜场所

but they're not the only commuters in here.|但它们并非这里的唯一住客

There are other fish working to a different schedule.|这里还有其它 按照不同日程表生活的鱼

The big-eyes are the equivalent of bats|大眼鲷相当于蝙蝠

night feeders that leave the cave each evening.|它们每天晚上出洞觅食

And like all cave commuters,|和所有洞穴动物一样

they are most vulnerable at the scheduled time of departure.|它们在出发阶段最容易遭受攻击

A bottle-neck funnels these exiting bats into dense concentrations,|当大群蝙蝠密集地通过瓶颈出口时

attracting the attention of others.|很容易引起其它动物的注意

The bats can detect the snakes using echolocation,|蝙蝠能利用回声定位觉察到蛇

but the snakes are literally in the dark|而蛇则完全处于黑暗之中

they can see nothing.|它们看不见任何东西

The strikes seem to be largely hit and miss.|这种攻击更像是在碰运气

But the snakes have a secret weapon.|不过蛇也有自己的秘密武器

They can actually sense each bat flying past.|它们实际上能感觉到 每一只飞过的蝙蝠

Receptors in the snake's head pick up the heat given off by the flying bats,|位于头部的“热眼”能觉察到 飞行中的蝙蝠散发出的热量

as this thermal image shows.|正如这幅热影像所示

To the snakes, the bats are apparently glowing|每一只蝙蝠在蛇“眼”前都是活灵活现

and this gives them something to aim at.|这也给了它们瞄准目标的机会

[英学网] - 原创中英对照双语影视 视频英语学习网|www.EngXue.com

This is the price that these cave commuters must pay|这是洞栖动物必须付出的代价

for their daytime sanctuary underground.|以换取它们白天在陆地上的庇护

Small wonder, then, that there are other cave dwellers that stay put.|难怪其它洞穴生物 要终生居住在洞穴中

Many caves are like islands,|很多洞穴都和岛屿一样

cut off from the outside world and from other caves.|与外界及其它洞穴隔绝

This isolation has resulted in the evolution of some very strange creatures.|这种孤立环境导致进化产生 各种各样奇怪的生物

They are the cave specialists, troglobites|它们都是洞穴专家，穴居动物

animals that never emerge from the caves or see daylight.|——从不出洞并且 永远不见天日的动物

These troglobites from Thailand are|泰国的这些穴居动物

possibly the most specialised creatures on Earth|可能是地球上最奇特的动物

for they live only in cave waterfalls.|因为它们只生活在洞穴瀑布中

The entire population of these cave angel fish|世界上所有的洞穴天使鱼

seems to be restricted to just two small caves.|可能只存在于两个较小的洞穴中

It's the same story with other troglobites.|其它穴居动物也是同样的情况

There may well be less than 100 Texas cave salamanders in the wild.|世界上可能只有不到100只 野生洞栖童态河溪螈

And the Belizean white crab is another creature|而伯利兹白蟹是另一个

that is unique to just one cave system.|洞穴生态系统中的特有物种

Living in perpetual darkness,|由于一直生活在黑暗之中

they have all not only lost the pigment in their skin|它们不仅失去了皮肤色素

but also their eyes.|眼睛也退化了

It takes thousands of generations for eyes to be lost|眼睛的退化需要经历数千代的演变

so these species must have been isolated for a very long time.|所以这些物种必定 与世隔绝了相当长的一段时间

But the blind salamander has other highly-developed sensory organs.|不过这些瞎眼的蝾螈 进化出了其它发达的感觉器官

Receptors in the skin detect minute movements in the water made by its prey.|皮肤上的探测器能觉察到 猎物引起的最微小的水流变化

External gills help it to breathe in water that is particularly low in oxygen.|外生的鳃帮助它们 在极度缺氧的水中呼吸

The cave angel fish feed on bacteria in the fast-flowing water,|洞穴天使鱼以急流中的细菌为食

keeping their grip with microscopic hooks on their fins.|它们用鳍上的小钩紧紧抓住岩壁

Food is often in short supply|食物总是很紧缺

and troglobites, like the crab|像螃蟹这样的穴居动物

have to survive on whatever washes into the cave from outside.|必须得吃任何从外边冲进洞内的东西

A salamander might not encounter food for several months,|童态河溪螈可能 已有几个月没有吃东西了

so when something does come along|所以只要眼前有食物出现

it can't afford to miss it.|它绝对不会放过

It's astonishing that these extraordinary cave dwellers|这些奇异的洞栖生物能如此成功地生存

manage to survive at all.|的确令人称奇

But one cave is so inhospitable|可是有一个洞穴的环境过于险恶

that one would not expect it to contain any life whatsoever.|不管什么生物似乎都不可能在那里生存

The water flowing out of the Villa Luz cave in Mexico|从墨西哥露兹别墅山洞流出来的水

is actually coloured white with sulphuric acid.|竟然被硫酸染成了白色

Explorers entering this dangerous cave|探险家们进入这个危险的山洞时

must wear respirators and carry monitors.|必须戴上防毒面具，并携带通话器

Poisonous gases rise to fatal levels so quickly|有毒气体很快就会达到致命的程度

that an early warning system is essential.|所以即时预警设备是最重要的

Bats survive by staying close to the skylights,|蝙蝠之所以能生存是因为 它们始终呆在天窗附近

but venturing deep into the cave is very dangerous indeed.|但是深入洞穴必然极度危险

The source of these toxic fumes lies several miles below.|这些毒气的源头位于地下几英里处

Hydrogen sulphide gas bubbles up from oil deposits in the Earth's crust.|硫化氢气体从地壳内的油气储层中溢出

It mixes with oxygen in the water|与水中的氧发生化合反应

and forms sulphuric acid.|产生了硫酸

These are not the sort of conditions in which you would expect to find fish.|鱼类似乎不太可能生活在这种环境中

Yet these cave mollies seem to thrive|然而这些洞栖帆鳍鳉 看上去却是悠然自得

despite the acid and the low levels of oxygen.|尽管这里是酸性低含氧量环境

There is, in fact, more life here than anyone would think possible,|事实上，这里的生物数量 远比人们预料的更多

but the biggest surprise is something altogether more bizarre.|不过更大的惊奇莫过于 那些更奇怪的东西

These strange stalactite-like formations|这些奇特的钟乳石状的结构

are known, rather appropriately, as snottites.|确切地说，叫做“鼻涕石”

The drops dripping from the ends are sulphuric acid,|其末端滴落的液滴就是硫酸

strong enough to burn skin.|酸性强到足以腐蚀皮肤

The snottites are, in fact, vast colonies of bacteria|“鼻涕石”其实是大型菌落

capable of growing a centimetre a day.|每天能长长1厘米

In this world without sunlight|在这个没有阳光的世界里

these bacteria extract energy|这些细菌只能从硫化氢气体中

from the hydrogen sulphide gas.|吸收能量

Bacteria like these are known as extremophiles|像这样的细菌被称为嗜极生物

because of their ability to survive in such extreme conditions.|因为它们能在这种极端环境中生存

And these extremophiles play another important role in this cave.|这些嗜极生物还在这个洞中 扮演着另一个非常重要的角色

Surprisingly, they are the basis of a food chain|令人吃惊的是，它们竟然是食物链中的第一环

which supports, amongst other creatures, the larvae of these midges.|用以养活其它生物，例如这些蚋的幼虫

Villa Luz's ecosystem was certainly very remarkable,|露兹别墅山洞的生态系统的确非同寻常

but cave explorers were soon to make an even more astonishing discovery.|但是洞穴探险家们 很快又有了更惊人的发现

Beneath this arid landscape lies a subterranean wonderland.|谁能想到在这些贫瘠的土地下 有一处地下仙境

Without water, one might not expect to find any caves,|没有水的地方似乎不可能有洞穴

but beneath these rolling desert slopes in the United States|但是在美国这些荒凉起伏的山崖之下

lies one of the longest, deepest and most surprising caves in the world.|存在着一座世界上最长、最深，也最令人惊奇的洞穴

Its secrets remained unknown until 1 986,|它的秘密直到1986年才被人们发现

when cavers dug through several metres of loose rock|洞穴专家们在松散的岩层中 挖出了一条几十米深的通道

at the bottom of this pit.|直达这个深渊的底部

They named the cave Lechuguilla|他们把这个洞命名为“龙舌兰洞”

and since its discovery|自从那次发现之后

more than 1 20 miles of passageways have been mapped.|迄今已测绘了120多英里的地道

When the first explorers descended|第一批探险家进入这个洞后

no one guessed at the sheer size of this cave|没有一个人能预料到它竟然有这么大

but even that was not going to be the biggest surprise.|即便如此，这也不能算是最大的惊奇

Little did they realise that Lechuguilla would soon be regarded|不久他们便意识到龙舌兰洞很快就会

by cavers the world over as the most beautiful of all caves.|被全世界的洞穴专家公认为地球上最美丽的洞穴

They were about to discover some of the most exquisite formations|因为他们发现了一些 在地底世界中

ever seen underground.|最精美的构造

The walls were covered with the most delicate and fragile crystals.|石壁上布满了光洁美丽的脆弱结晶

Many of these crystals were made of gypsum|许多结晶都是由石膏组成

a mineral that comes from limestone|一种硫酸钙沉积而来的矿物

and there was mile after mile of them.|它们绵延不绝

Water is the creator of most caves|水是大部分洞穴的建造者

but unlike all other limestone caves|但是，和其它石灰岩溶洞不同的是

Lechuguilla's rock had not been eaten away by running rainwater.|龙舌兰洞中的岩石并非被流水侵蚀

Something else was responsible.|而是因为其它的作用力

The only water Lechuguilla has are these wonderfully still, clear pools.|龙舌兰洞中唯一的水 来自这些平静清澈的水塘

As the explorers went deeper into the cave,|随着探险家们深入洞穴

they came across whole galleries filled with the most unusual formations,|他们发现了成片叹为观止的地貌

like these five-metre cones frosted with the most delicate crystals.|例如这些5米高的石锥，上面布满了雪霜一样的松脆结晶

It was Lechuguilla's gypsum crystals|龙舌兰洞的石膏结晶群

that made scientists question|使科学家们产生了

how these caverns were formed.|这个巨洞如何形成的疑问

They discovered that Lechuguilla's limestone had|他们发现龙舌兰洞的石灰岩

actually  been eaten away by sulphuric acid|实际上是被硫酸侵蚀的

cutting through literally miles of limestone.|凿穿了差不多数英里的石灰岩

And when sulphuric acid dissolves limestone|硫酸在溶解石灰岩的同时

it leaves behind gypsum|也留下了石膏

the basis of Lechuguilla's remarkable formations.|它们最终形成了龙舌兰洞的奇景

And there was one set|这里有一组景观

more than a mile from the surface|位于地表之下1英里多的地方

that almost defied belief.|美得简直无法令人相信

The Chandelier Ballroom was the ultimate discovery.|“灯饰大厅”是最后被发现的厅洞

With its six-metre-long crystals|这里尽是6米多长的结晶群

it's surely the most bizarre cave chamber in the world.|它可以说是世界上最奇异的厅洞

And the walls had one further surprise.|而石壁上还有更惊人的发现

Extremophile bacteria were found to be feeding on the rock itself.|嗜极细菌在岩壁上自我生长

The discovery of life that exists without drawing any of its energy from the sun|生命彻底脱离太阳能量 却依然生存的现象

shows us once again how complex and surprising the underground world can be.|再一次向我们展示了地底世界 是多么的复杂和惊人

Each year, explorers chart over a hundred miles of new cave passages.|每年，探险家们都会测绘 上百英里新的洞穴通道

But with half the world's limestone still to be explored,|但世界上仍有一半石灰岩洞尚未被开发

who knows how many Lechuguillas are still waiting to be discovered?|谁知道还会有多少个龙舌兰洞 等着人们去发现呢