Placeholder Image

字幕列表 影片播放

  • And now for a really deep topic.

  • The Earth's lowest known place is the Challenger Deep, almost 36,000 ft below the ocean's surface!

  • But however incredible it may sound, dry land also has some extreme points which lie way,

  • way lower than sea level.

  • And the lowest of them, previously hiding under a massive glacier, has been discovered

  • only recently!

  • But how about we work up to this awesome aha moment?

  • First, let me tell you about other, probably not so deep but no less amazing places!

  • - Death Valley One of the world's hottest and driest national

  • parks, Death Valley knows a thing or two about extremes.

  • Snow-covered mountain peaks in the middle of a scorching desert, burning sun - and meadows

  • of blooming wildflowers.

  • But the most amazing thing about Death Valley is that it's home to the lowest point in North

  • America - Badwater Basin.

  • This place lies 282 ft below sea level, which is just a bit smaller than the Statue of Liberty!

  • When you see this surreal place for the first time, you won't believe your eyes: how come

  • snow doesn't melt under such blazing sun?

  • Several moments later, you'll realize your mistake - it's not snow!

  • A huge chunk of the desert is covered with a thick layer of salt that's been gathering

  • there for centuries!

  • - The Dead Sea Even though it has the word "sea" in its name,

  • the Dead Sea is actually one of the most intriguing and unusual lakes on Earth.

  • You don't need any flotation device to swim in this lake - the water is so salty and dense

  • that its surface will keep you afloat without any effort from your side!

  • The Dead Sea has the highest salt concentration among all water bodies in the world and is

  • 8 times saltier than any ocean.

  • The lake's made it to this list because until recently, its surface and shores were considered

  • the lowest point on dry land.

  • The Dead Sea is on average more than 1,400 ft below sea level - that's just a bit less

  • than the height of the Empire State Building!

  • And yes, I did say "until recently," and I do hope that you're thoroughly intrigued!

  • - Lake Baikal The next mega-deep place on land is also covered

  • with water because it's a freshwater lake.

  • The Baikal is a unique water body that contains more than 20% of all unfrozen surface freshwater

  • in the world.

  • Situated in south-eastern Siberia in Russia, Lake Baikal is also considered to be the world's

  • most ancient lake.

  • And no wonder - the thing is about 25 million years old!

  • The amount of water in the lake would be enough to fill the Grand Canyon five and a half times.

  • The Baikal's area is as large as Belgium and almost as large as Massachusetts!

  • The lake's total depth is more than five Eiffel Towers piled on top of each other.

  • And if we talk about the lake's lowest point below sea level, at 4,000 ft, it's more than

  • 11 football fields placed side by side!

  • How’s that for comparison?

  • - The Krubera Cave No one knows for sure how deep this cave really

  • is.

  • Believe it or not but this abyss may drop down to 7,200 ft underground.

  • Imagine 17 Great Pyramids of Giza stacked up on top of each other, and you'll understand

  • why there aren't too many volunteers eager to explore the Krubera Cave!

  • This ancient formation is likely to be more than 5 million years old.

  • It's an almost vertical system of tunnels plenty of which are flooded.

  • That's why if you want to explore this wondrous place, remember to take your diving gear!

  • Even though the world's lowest natural underground point is in the Krubera Cave, it's only the

  • second-deepest cave on the planet.

  • The record-holder is the Veryovkina cave which is just one Hollywood sign deeper than the

  • Krubera Cave!

  • - Denman Glacier Antarctica's massive ice sheet effectively

  • hides the continent's mysteries.

  • But scientists don't give up: they've been using radar equipment to crack Antarctica's

  • riddles.

  • And recently, their efforts have paid off!

  • Previous radar instruments sent off small microwave pulses that helped researchers to

  • sneak a peek through the ice mass.

  • But this method didn't allow them to measure the full depth of some regions.

  • A new technology called BedMachine solved this problem.

  • That's when researchers made an astonishing discovery: stretching more than 11,500 feet

  • below sea level, a canyon under Denman Glacier turned out to be 8 times deeper than the Dead

  • Sea shores!

  • BedMachine's technology allowed scientists to combine radar readings with the information

  • about seismic activity and ice flows in the region and make this conclusion.

  • - Mponeng & TauTona Gold Mines But even though the newly-discovered canyon

  • under Denman Glacier is the deepest natural point on land, it doesn't mean that there

  • are no places deeper than that.

  • They DO exist, but these places were created by people, just like the two world's deepest

  • gold mines in South Africa.

  • Being almost the same in size, Mponeng and TauTona mines are as deep as 700 giraffes

  • and filled with complicated mazes of underground tunnels.

  • (uh, ‘xcuse me.

  • Do you really want me to say 700 giraffes?

  • [blah blah] Okay.)

  • Combined, each mine's tunnels are longer than the New York subway systemfilled with

  • giraffes.

  • Thousands of workers use elevators, called cages, to get down to the mines.

  • These triple-decked constructions (which DO look unnervingly similar to cages) transport

  • more than 100 people at a time.

  • - By the way, few people know the mines are so deep that the rock at their bottom can

  • heat up to 140˚ F. To keep these underground temperatures from becoming too dangerous,

  • surface workers have to pump down ice mixed with salt.

  • When this salted ice gets into the shafts, giant fans blow air over the mixture - and

  • this huge DIY AC cools the tunnels down to an almost tolerable 85˚ F. To keep this complicated

  • system running, above-ground plants produce more than 6,000 tons of ice every day!

  • - KTB Borehole But even gold mining hasn't taken people as

  • deep as their curiosity - or should I say thirst for knowledge?

  • One of the lowest underground points in the world appeared thanks to a scientific drilling

  • project in Germany.

  • The main KTB borehole (that's a hole branching from the main hole) reached a mind-blowing

  • depth of almost 30,000 ft, which is the cruising altitude of passenger airlinersfilled

  • with giraffes!

  • Down there, scorching temperatures reached 500˚F!

  • Luckily, drill heads used in the project could withstand up to 570˚F - otherwise, the drilling

  • wouldn't have been possible.

  • Lots of modern boreholes, though, are much longer than the KTB Borehole.

  • But however long they are, the world's deepest artificial point record belongs to ---drum

  • roll please ( bad drum roll) uh, never mind.

  • - SG-3 Kola Superdeep Borehole.

  • (boy that’s a mouthful.)

  • This borehole is almost 400 ft shorter than the longest man-made well.

  • But we're talking about the lowest points below sea level - the Kola Borehole is number

  • one.

  • The thing is 40,230 ft deep, which is twice as tall as Kilimanjaro - the world's tallest

  • freestanding mountain!

  • With a herd of giraffes on it.

  • The incredible borehole took about 20 years to drill.

  • The idea was to reach the Earth's mantle or at least drill as deep into the planet's crust

  • as possible.

  • Unfortunately, by the moment the project was closed, the hole had only reached one-third

  • of the way through the crust.

  • The site is often visited by curious sightseers but they mostly leave the place disappointed:

  • all there is to see is a welded borehole.

  • No fence around - it's unlikely that someone manages to squeeze into a 9-inch-wide hole!

  • In any case, come to think of it, most of the Earth's surface actually lies below sea

  • level because oceans cover more than 70% of our planet.

  • During the Ice Age, some 18,000 years ago, (I wasn’t around then), sea level was more

  • than 400 feet lower.

  • Many areas that are underwater today used to be dry land.

  • No one knows how much of the Earth's surface will get flooded in the future - below-sea-level

  • trenches and depressions may become much more impressive!

  • Or humans will just dig way, way deeper holes!

  • Hey, if you learned something new today, or just like giraffes -- then give the video

  • a like and share it with a friend!

  • And here are some other videos I think you'll enjoy.

  • Just click to the left or right, and stay on the Bright Side of life!

And now for a really deep topic.

字幕與單字

單字即點即查 點擊單字可以查詢單字解釋

B1 中級

科學家發現了地球上最低的土地 (Scientists Have Found the Lowest Land on Earth)

  • 1 0
    林宜悉 發佈於 2021 年 01 月 14 日
影片單字