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>> Earth, a 4.5-billion-year-
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old planet, still evolving. As
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continents shift and clash,
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volcanoes erupt, and glaciers
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grow and recede, the Earth's
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crust is carved in numerous
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and fascinating ways, leaving
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a trail of geological
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mysteries behind. In this
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episode, the Marianas Trench,
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the deepest point on Earth, is
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explored. Its sheer walls cut
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seven miles into the Pacific
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Ocean. The mystery of what
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created this deep, dark chasm
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takes science detectives on
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some of the most dangerous
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dives ever attempted, deep
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into the abyss. Scouring the
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ocean floor, scientists
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uncover a strange,
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undersea world of fiery
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mountains, bizarre mud
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volcanoes and the largest
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geological structure on Earth.
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Discoveries from this unique
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underwater world will
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revolutionize our
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understanding of the powerful
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forces that shape not just the
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trench, but the Earth itself.
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S01x02 The Deepest Place on Earth
Original Air Date on February 17, 2009
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Hidden deep beneath the waves
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of the western Pacific lies
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the Marianas Trench, the
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deepest point of all the
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oceans.
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The first step on the journey
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of what created this
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mysterious scar in the Earth's
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crust, and how it continues to
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mold the planet, takes us
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back to 1872, when a British
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research vessel, HMS
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Challenger, set out on the
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first ever mission to map the
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ocean floor.
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>> Throughout most of recorded
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history, men had just assumed
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that, beyond a certain level,
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the sea was pretty flat,
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pretty dead, pretty lifeless.
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They weren't expecting to find
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anything very interesting.
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>> For four years, the
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Challenger crisscrossed the
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oceans, covering 70,000 miles,
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a third of the distance to the
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moon.
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The crew plumbed the depths
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every 140 miles, using a total
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of 249 miles of rope, and
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hundreds of pounds of
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lead weight. It was tedious,
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backbreaking work, but at the
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time, it was the only way to
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measure the depth of the ocean
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floor.
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When they got to the western
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Pacific, 200 miles off the
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island of Guam, the crew
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routinely lowered the rope for
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a measurement.
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But the weight kept on
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dropping and dropping.
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>> It's a big surprise! Nobody
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thought the ocean was this
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deep. So all of sudden we've
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got scientists saying, "Why
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is that?"
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>> Eventually, the weight
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struck the bottom at 4,475
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fathoms, nearly five miles
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beneath the ocean's surface.
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>> The scientists would be
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going, "Wow, we've found
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something and what does it
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mean? Is it a little hole? Is
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it a big hole? What kind of
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feature is it down there?"
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There--there's a whole lot
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of questions you get when you
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find this one spectacular
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reading.
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>> The Challenger expedition
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marked the birth of modern
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oceanography, and provided the
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first crude map of the ocean
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floor.
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It showed how the ocean floor
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gently slopes away from the
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land, and then plummets
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thousands of feet into vast
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flat plains. But the western
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Pacific is different. It drops
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off again, into the five mile
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deep hole, a hole that blew
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right out of t water the
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long-held belief that the sea
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floor was flat and
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featureless.
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And it spawned a mystery,
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because nobody could
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understand how this strange
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underwater feature came about.
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It would be 75 years before
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any answers emerged. It took a
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revolutionary new technology,
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sonar, to push the
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investigation forward to the
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next crucial stage.
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Sonar was first developed in
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the early 1900s and then
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perfected during the 1940s to
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detect submarines lurking in
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the deep.
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The system works by pumping
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sound waves through the water.
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The waves bounce off solid
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objects and are reflected back
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to a detector. By measuring
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the time it takes for the
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sound waves to bounce
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back, scientists realized they
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could build a remarkably
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accurate picture of the world
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beneath the waves.
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>> The world's major navies
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spend a lot of time and effort
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developing submarine hunting
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technology, then the
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hydrographers discover that
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you can use this to chart the
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bottom of the sea and it's an
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awful lot cheaper and easier
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than using large numbers of
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sailors pulling on ropes.
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>> In 1951, a British Navy
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research ship returned to the
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deep hole found by the
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Challenger expedition.
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But, this time, they were
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armed with sophisticated new
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sonar equipment.
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And the results were amazing.
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Detailed sonar maps revealed
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that the deep hole in the
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Pacific Ocean floor isn't a
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hole at all, but part of a
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massive trench, 30 times
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deeper than the Empire State
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Building is high.
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It runs twice the length of
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California, 1,500 miles from
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the southeast of Guam to the
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northwest of the Mariana
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Islands.
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>> People were probably
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astounded by what they were
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seeing, because, clearly, the
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ocean floor had enormous
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changes in relief. It was very
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mountainous in some places,
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had great deeps in other
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places. To a geologist, this
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would be extremely exciting.
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Even within the trench itself,
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there are remarkable
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variations. At its southern
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end lies the greatest surprise
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of all.
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The sea floor drops down
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another two miles to its
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lowest point, a staggering
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seven miles beneath the waves.
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Scientists had discovered the
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deepest part of the oceans.
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Even today, it is the lowest
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known point on the planet.
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They named this part of the
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trench the Challenger Deep, in
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honor of the ship that
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discovered it.
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>> To get a sense of just how
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deep trenches are, if we take
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the heig
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we would still have about a
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mile of water above us before
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we get to the ocean surface.
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>> But how the Marianas Trench
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was formed remained a mystery.
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Investigators decided the best
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way to find the answer was to
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dive to the bottom of the
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trench, to see for themselves
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the lowest point on the
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planet, the Challenger Deep.
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But they faced a major
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problem. At the bottom of the
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trench, they would have to
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contend with pressure a
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thousand times stronger than
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at the surface, that's the
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equivalent of being squeezed
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on all sides by the weight of
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50 jumbo jets.
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To demonstrate the effects of
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such pressure, scientists
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use a dummy head.
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>> Today, what we are going
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to do is actually put one of
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these Styrofoam wig heads in
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the, uh, pressure chamber and
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expose it to the, uh, pressure
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we would see in the Marianas
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Trench. That's about 16,000
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psi.
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>> A human skull would be
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crushed to a pulp, but the
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rubbery head will only have
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all the air squeezed out.
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>> Wow, the head's smaller.
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Here's what the original size
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was, just for comparison.
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[LAUGHS]
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Quite dramatic! Pretty stark
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difference between, uh,
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something that hasn't been
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seven miles deep in the ocean
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and something that has.
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Glad I'm not going there.
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[BOTH LAUGH]
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At the Mariana Trench, human
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life is impossible, we're not
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equipped to resist those kinds
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of pressures, and so it's
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necessary to protect humans
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from that type of an
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environment.
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>> The challenge to engineers
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was how to accomplish this.
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In 1953, Swiss scientist
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Auguste Piccard designed the
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Trieste, a pioneering vehicle
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that could withstand the
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crushing pressures.
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The submersible was dominated
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by a 50 foot long hull, filled
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with light aviation gasoline
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and lead weights to control
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buoyancy. Slung underneath it
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was a tiny six foot spherical
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cabin with five inch thick
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steel walls.
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Finally, after seven years of
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modifications and manned test
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dives no deeper than three and
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a half miles, the Trieste was
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ready to attempt the seven
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miles to the bottom of the
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trench. The commander of this
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perilous undertaking was US
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Navy Lieutenant and deep sea
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explorer Don Walsh.
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>> I know the astronauts that
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go through this all the time.
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"Why do you have to be there?
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Why can't we just put up a
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robot to do things?" You've
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got to be there because that's
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what we do.
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>> Only a few officers and
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scientists knew about the
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risky mission, which was
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launched in January 1960 from
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the western Pacific island of
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Guam.
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>> Guam in those days was kind
289
00:10:50,501 --> 00:10:51,932
of a backwater, it was just
290
00:10:52,033 --> 00:10:53,198
right for us because we were
291
00:10:53,232 --> 00:10:55,197
trying to do this project sort
292
00:10:55,264 --> 00:10:57,396
of out of sight, because we
293
00:10:57,497 --> 00:10:58,462
weren't too sure it was gonna
294
00:10:58,496 --> 00:11:01,027
work. The navy just didn't
295
00:11:01,095 --> 00:11:02,259
want to be embarrassed by a
296
00:11:02,360 --> 00:11:05,058
failed science spectacular.
297
00:11:07,591 --> 00:11:08,889
>> Accompanying Walsh was the
298
00:11:08,957 --> 00:11:10,688
son of the Trieste's designer,
299
00:11:10,756 --> 00:11:12,221
engineer and oceanographer
300
00:11:12,255 --> 00:11:15,585
Jacques Piccard. The two men
301
00:11:15,686 --> 00:11:16,784
would spend the next nine
302
00:11:16,852 --> 00:11:18,484
hours squeezed inside the
303
00:11:18,585 --> 00:11:21,282
cramped sphere.
304
00:11:21,316 --> 00:11:23,281
>> And we had, erm, 20 cubic
305
00:11:23,315 --> 00:11:25,213
feet of space inside, that's
306
00:11:25,314 --> 00:11:26,046
about the same as a
307
00:11:26,114 --> 00:11:28,812
household refrigerator, and
308
00:11:28,846 --> 00:11:30,310
the temperature was almost
309
00:11:30,378 --> 00:11:32,942
that cold inside. It was a
310
00:11:33,010 --> 00:11:34,108
drama.
311
00:11:36,908 --> 00:11:37,939
>> The story of how the
312
00:11:38,007 --> 00:11:39,905
Marianas Trench came to be is
313
00:11:40,006 --> 00:11:43,536
beginning to take shape.
314
00:11:43,603 --> 00:11:46,101
In 1874, British surveyors
315
00:11:46,169 --> 00:11:47,434
were the first to discover
316
00:11:47,468 --> 00:11:49,266
a five mile deep hole in the
317
00:11:49,367 --> 00:11:52,731
ocean. 75 years later, sonar
318
00:11:52,799 --> 00:11:54,064
mapping revealed the hole to
319
00:11:54,131 --> 00:11:56,328
be a vast, 1,500-mile long
320
00:11:56,430 --> 00:11:58,894
trench, with the deepest part
321
00:11:58,961 --> 00:12:00,627
seven miles beneath the
322
00:12:00,694 --> 00:12:03,892
surface waves of the Pacific.
323
00:12:03,958 --> 00:12:05,490
To gather further evidence,
324
00:12:05,525 --> 00:12:07,289
two courageous men were about
325
00:12:07,323 --> 00:12:08,389
to undertake the most
326
00:12:08,423 --> 00:12:11,387
dangerous dive in history.
327
00:12:11,422 --> 00:12:13,019
They would venture into the
328
00:12:13,054 --> 00:12:15,818
abyss and go to the bottom of
329
00:12:15,852 --> 00:12:18,849
the Marianas Trench.
330
00:12:21,316 --> 00:12:23,147
The Marianas Trench is one of
331
00:12:23,215 --> 00:12:24,847
the most remote, inhospitable
332
00:12:24,948 --> 00:12:26,879
places on Earth.
333
00:12:30,045 --> 00:12:32,775
In January 1960, two deep sea
334
00:12:32,843 --> 00:12:34,640
explorers, Don Walsh and
335
00:12:34,675 --> 00:12:37,139
Jacques Piccard, plunged into
336
00:12:37,207 --> 00:12:38,672
its depths on board the
337
00:12:38,740 --> 00:12:41,037
submersible, the Trieste.
338
00:12:47,534 --> 00:12:49,299
At a speed of just three miles
339
00:12:49,367 --> 00:12:51,032
per hour, they began their
340
00:12:51,100 --> 00:12:52,997
slow descent into the twilight
341
00:12:53,064 --> 00:12:54,463
zone.
342
00:12:57,096 --> 00:12:59,194
By 3,000 feet, the darkness
343
00:12:59,261 --> 00:13:02,325
was total. The only
344
00:13:02,360 --> 00:13:03,691
illumination was from the
345
00:13:03,726 --> 00:13:05,790
Trieste's powerful lights.
346
00:13:08,456 --> 00:13:09,154
>> At the depths we were
347
00:13:09,222 --> 00:13:10,354
operating at, it was always
348
00:13:10,421 --> 00:13:12,686
black. The only thing that lit
349
00:13:12,721 --> 00:13:13,985
up the abyss was the
350
00:13:14,053 --> 00:13:16,683
bioluminescence from animals
351
00:13:16,751 --> 00:13:20,581
and plankton. Like fireflies,
352
00:13:20,682 --> 00:13:21,947
they carry their own light
353
00:13:22,048 --> 00:13:24,779
sources with them.
354
00:13:24,880 --> 00:13:26,411
>> Encased in their five-inch
355
00:13:26,479 --> 00:13:28,377
thick steel sphere, Walsh and
356
00:13:28,411 --> 00:13:29,943
Piccard quickly passed their
357
00:13:30,043 --> 00:13:31,942
test dive record of 18,000
358
00:13:32,009 --> 00:13:35,107
feet. Everything appeared to
359
00:13:35,207 --> 00:13:38,838
be going to plan. At the rear
360
00:13:38,906 --> 00:13:40,303
of the cabin, the crew were
361
00:13:40,371 --> 00:13:41,936
protected by a double layer of
362
00:13:42,004 --> 00:13:44,201
glass. But, two hours into the
363
00:13:44,269 --> 00:13:47,100
dive, the outer pane cracked.
364
00:13:50,465 --> 00:13:52,097
>> We, um, had a great big
365
00:13:52,165 --> 00:13:53,996
bang. We didn't know what it
366
00:13:54,064 --> 00:13:55,362
was. We were at about 20,000
367
00:13:55,430 --> 00:13:57,161
feet, and we looked around and
368
00:13:57,262 --> 00:13:59,959
checked everything,
369
00:13:59,994 --> 00:14:01,525
>> Every square inch of their
370
00:14:01,592 --> 00:14:02,957
tiny life-supporting capsule
371
00:14:02,992 --> 00:14:04,790
was fighting back eight tons
372
00:14:04,891 --> 00:14:08,221
of pressure. With the outer
373
00:14:08,256 --> 00:14:10,253
pane broken, the only thing
374
00:14:10,321 --> 00:14:11,619
between the men and instant
375
00:14:11,687 --> 00:14:13,218
death was a single pane of
376
00:14:13,320 --> 00:14:14,217
glass.
377
00:14:14,319 --> 00:14:15,318
>> If the inner window had
378
00:14:15,418 --> 00:14:17,150
cracked, erm, we would have
379
00:14:17,217 --> 00:14:20,148
been instantly dead, maybe
380
00:14:20,215 --> 00:14:22,946
even before we knew it.
381
00:14:23,047 --> 00:14:24,478
>> But, incredibly, the inner
382
00:14:24,579 --> 00:14:27,044
pane remained watertight.
383
00:14:27,111 --> 00:14:28,543
Walsh and Piccard decided to
384
00:14:28,577 --> 00:14:32,474
continue the descent.
385
00:14:32,574 --> 00:14:34,373
After a tense, claustrophobic
386
00:14:34,473 --> 00:14:36,372
four hours and 48 minutes,
387
00:14:36,472 --> 00:14:37,638
they approached the bottom of
388
00:14:37,705 --> 00:14:39,337
the trench, only to be
389
00:14:39,371 --> 00:14:40,836
startled by movement on the
390
00:14:40,903 --> 00:14:43,101
sea floor.
391
00:14:43,169 --> 00:14:45,100
>> Just before we landed, we
392
00:14:45,168 --> 00:14:47,898
saw a flatfish about a foot
393
00:14:47,999 --> 00:14:50,264
long, and that's a
394
00:14:50,332 --> 00:14:51,996
bottom-dwelling fish, so if
395
00:14:52,064 --> 00:14:54,062
you see one there are others,
396
00:14:55,595 --> 00:14:57,426
>> Nobody expected to see life
397
00:14:57,494 --> 00:14:59,525
at these crushing depths, but
398
00:14:59,593 --> 00:15:00,891
it meant the explorers had
399
00:15:00,959 --> 00:15:06,521
reached their goal, the very
400
00:15:06,589 --> 00:15:08,953
bottom of the Marianas Trench.
401
00:15:10,320 --> 00:15:11,419
The depth gauge, with a
402
00:15:11,486 --> 00:15:14,317
reading of 35,800 feet, nearly
403
00:15:14,385 --> 00:15:16,849
seven miles below the surface,
404
00:15:16,916 --> 00:15:19,681
confirmed the sonar findings.
405
00:15:24,579 --> 00:15:26,111
Squeezed inside their bubble
406
00:15:26,177 --> 00:15:27,643
of breathable air, the two
407
00:15:27,744 --> 00:15:29,009
explorers were closer to the
408
00:15:29,110 --> 00:15:30,475
Earth's centre than man had
409
00:15:30,542 --> 00:15:32,474
ever been.
410
00:15:32,540 --> 00:15:35,904
We took a self-portrait,
411
00:15:35,972 --> 00:15:37,170
that's the picture that you
412
00:15:37,238 --> 00:15:38,737
see. We said we were going
413
00:15:38,804 --> 00:15:40,602
to do it, and we did it.
414
00:15:43,168 --> 00:15:44,166
>> But there was work to be
415
00:15:44,268 --> 00:15:47,132
done. Walsh and Piccard wanted
416
00:15:47,166 --> 00:15:48,764
to make detailed observations
417
00:15:48,798 --> 00:15:50,596
of the enormous trench.
418
00:15:52,429 --> 00:15:53,961
Unfortunately, the Trieste
419
00:15:54,062 --> 00:15:55,593
stirred up a cloud of fine,
420
00:15:55,661 --> 00:15:57,059
powdery sediment from the sea
421
00:15:57,160 --> 00:15:58,492
floor that obscured their
422
00:15:58,560 --> 00:15:59,524
view.
423
00:16:01,591 --> 00:16:02,689
>> WALSH: It was like being in
424
00:16:02,757 --> 00:16:04,289
a bowl of milk at that point.
425
00:16:04,323 --> 00:16:05,754
So, realizing that we weren't
426
00:16:05,822 --> 00:16:07,686
gonna see anything, we decided
427
00:16:07,754 --> 00:16:08,686
to go on back up to the
428
00:16:08,754 --> 00:16:10,385
surface.
429
00:16:10,453 --> 00:16:11,185
>> ANNOUNCER: Off the island
430
00:16:11,219 --> 00:16:13,217
of Guam, the Trieste surfaces
431
00:16:13,285 --> 00:16:14,116
after a descent into the
432
00:16:14,184 --> 00:16:16,082
Marianas Trench.
433
00:16:16,116 --> 00:16:17,748
>> After nine grueling hours
434
00:16:17,848 --> 00:16:19,614
underwater, Walsh and Piccard
435
00:16:19,648 --> 00:16:20,846
returned to the surface on
436
00:16:20,914 --> 00:16:24,344
January 23rd 1960 and
437
00:16:24,378 --> 00:16:25,610
officially entered the record
438
00:16:25,644 --> 00:16:27,542
books for the deepest dive of
439
00:16:27,610 --> 00:16:31,007
all time. To this day, their
440
00:16:31,075 --> 00:16:32,806
extraordinary feat has never
441
00:16:32,907 --> 00:16:33,805
been repeated.
442
00:16:37,338 --> 00:16:40,602
The mission was a success, but
443
00:16:40,669 --> 00:16:43,234
the mystery remained.
444
00:16:43,301 --> 00:16:44,966
Geologists still didn't
445
00:16:45,033 --> 00:16:46,332
understand what could have
446
00:16:46,399 --> 00:16:49,030
formed the immense trench.
447
00:16:50,130 --> 00:16:51,229
And if they couldn't find the
448
00:16:51,296 --> 00:16:53,261
answer inside the trench,
449
00:16:53,295 --> 00:16:54,260
they would have to look
450
00:16:54,294 --> 00:16:55,993
elsewhere.
451
00:16:58,559 --> 00:16:59,724
Perhaps there was something,
452
00:16:59,792 --> 00:17:01,656
somewhere, on the ocean floor
453
00:17:01,657 --> 00:17:02,689
that might explain the
454
00:17:02,756 --> 00:17:04,688
trench's origins.
455
00:17:08,486 --> 00:17:09,851
Throughout the '50s and '60s,
456
00:17:09,919 --> 00:17:11,417
a team of geologists led by
457
00:17:11,484 --> 00:17:12,849
Princeton's Harry Hess
458
00:17:12,917 --> 00:17:14,815
compiled sonar data from all
459
00:17:14,849 --> 00:17:16,847
of the world's oceans.
460
00:17:20,646 --> 00:17:21,711
It was as though they had
461
00:17:21,745 --> 00:17:23,643
pulled out a giant plug, to
462
00:17:23,744 --> 00:17:25,542
drain away all the water, and
463
00:17:25,577 --> 00:17:29,107
expose the ocean floor.
464
00:17:29,175 --> 00:17:30,207
Their maps revealed that the
465
00:17:30,274 --> 00:17:32,272
Marianas Trench is just a tiny
466
00:17:32,373 --> 00:17:33,804
fraction of a network of
467
00:17:33,905 --> 00:17:35,903
enormous underwater canyons
468
00:17:36,004 --> 00:17:37,269
stretching right around the
469
00:17:37,337 --> 00:17:41,134
planet. But that wasn't all.
470
00:17:41,168 --> 00:17:42,166
Running parallel to the
471
00:17:42,234 --> 00:17:43,532
trench, on the other side of
472
00:17:43,600 --> 00:17:45,165
the Pacific, the maps showed a
473
00:17:45,265 --> 00:17:46,630
giant underwater mountain
474
00:17:46,698 --> 00:17:50,262
range, the East Pacific Ridge.
475
00:17:50,329 --> 00:17:52,227
And this too is part of a
476
00:17:52,328 --> 00:17:54,859
global network, a 40,000 mile
477
00:17:54,960 --> 00:17:56,691
long chain of mountain ranges
478
00:17:56,759 --> 00:17:58,057
that ring the globe like the
479
00:17:58,125 --> 00:18:00,423
seams of a baseball, to make
480
00:18:00,490 --> 00:18:02,389
the largest geological feature
481
00:18:02,422 --> 00:18:03,687
on Earth.
482
00:18:06,121 --> 00:18:07,486
It was a major development in
483
00:18:07,553 --> 00:18:09,218
the investigation, one that
484
00:18:09,319 --> 00:18:10,917
scientists hoped might explain
485
00:18:10,951 --> 00:18:12,715
the trench's formation.
486
00:18:15,382 --> 00:18:17,213
The next step was clear.
487
00:18:17,281 --> 00:18:18,612
Investigators needed to
488
00:18:18,647 --> 00:18:19,912
understand whether there was a
489
00:18:20,013 --> 00:18:21,544
connection between the trench
490
00:18:21,611 --> 00:18:23,876
and the East Pacific Ridge.
491
00:18:32,438 --> 00:18:34,137
The breakthrough came from the
492
00:18:34,172 --> 00:18:38,168
unlikeliest of sources. During
493
00:18:38,235 --> 00:18:40,033
the Cold War, the US built a
494
00:18:40,067 --> 00:18:41,799
vast network of underground
495
00:18:41,867 --> 00:18:43,698
seismometers to pick up atomic
496
00:18:43,766 --> 00:18:45,863
bomb testing around the world.
497
00:18:48,596 --> 00:18:49,595
Inadvertently, the
498
00:18:49,695 --> 00:18:51,394
seismometers also detected
499
00:18:51,428 --> 00:18:52,426
naturally occurring
500
00:18:52,494 --> 00:18:56,757
earthquakes. When geologists
501
00:18:56,858 --> 00:18:58,323
plotted these on a map, a
502
00:18:58,391 --> 00:19:00,389
pattern emerged.
503
00:19:03,288 --> 00:19:05,286
The earthquakes were clustered
504
00:19:05,387 --> 00:19:07,218
along the ocean's ridges and
505
00:19:07,286 --> 00:19:09,750
trenches. It was a discovery
506
00:19:09,818 --> 00:19:10,749
that transformed our
507
00:19:10,850 --> 00:19:13,648
understanding of the Earth.
508
00:19:13,749 --> 00:19:15,280
Geologists realized the
509
00:19:15,381 --> 00:19:16,313
friction that cause
510
00:19:16,348 --> 00:19:17,812
earthquakes comes from
511
00:19:17,880 --> 00:19:18,978
movements that must be
512
00:19:19,045 --> 00:19:20,344
occurring deep beneath the
513
00:19:20,411 --> 00:19:22,676
ridges and trenches.
514
00:19:22,744 --> 00:19:23,876
>> With this great investment
515
00:19:23,943 --> 00:19:25,774
in seismology, it became
516
00:19:25,842 --> 00:19:27,673
possible to locate very
517
00:19:27,741 --> 00:19:29,305
precisely where earthquakes
518
00:19:29,406 --> 00:19:32,037
had occurred. And it was these
519
00:19:32,105 --> 00:19:33,570
things, the precise location,
520
00:19:33,670 --> 00:19:35,735
the depth and the motion that
521
00:19:35,769 --> 00:19:37,001
really gave the outlines of
522
00:19:37,035 --> 00:19:40,199
plate tectonics.
523
00:19:40,267 --> 00:19:41,532
>> It was the birth of an
524
00:19:41,566 --> 00:19:45,463
extraordinary new theory. The
525
00:19:45,564 --> 00:19:47,095
solid layer of rock, the
526
00:19:47,196 --> 00:19:48,795
crust, on which the land and
527
00:19:48,829 --> 00:19:50,926
ocean sits, is broken up into
528
00:19:50,994 --> 00:19:53,259
a series of vast slabs, that
529
00:19:53,360 --> 00:19:55,091
geologists call tectonic
530
00:19:55,192 --> 00:19:57,690
plates. It's these plates that
531
00:19:57,724 --> 00:20:00,088
are moving, grinding past each
532
00:20:00,156 --> 00:20:01,887
other, and triggering
533
00:20:01,988 --> 00:20:03,520
earthquakes.
534
00:20:06,785 --> 00:20:08,051
The underwater ridges and
535
00:20:08,151 --> 00:20:10,116
trenches sit on the boundaries
536
00:20:10,150 --> 00:20:12,581
between tectonic plates.
537
00:20:12,615 --> 00:20:14,513
The East Pacific Ridge and the
538
00:20:14,614 --> 00:20:16,313
Marianas Trench lie on
539
00:20:16,413 --> 00:20:18,011
opposite edges of the Pacific
540
00:20:18,046 --> 00:20:19,411
Plate.
541
00:20:21,044 --> 00:20:22,209
The journey to discover what
542
00:20:22,310 --> 00:20:23,842
formed the Marianas Trench is
543
00:20:23,943 --> 00:20:25,141
accumulating additional
544
00:20:25,209 --> 00:20:28,406
evidence. The Trieste dived to
545
00:20:28,473 --> 00:20:30,771
the bottom of the trench,
546
00:20:30,839 --> 00:20:33,002
and confirmed that it is the
547
00:20:33,037 --> 00:20:35,801
deepest point on the planet.
548
00:20:35,836 --> 00:20:37,433
Sonar maps then revealed the
549
00:20:37,468 --> 00:20:39,100
East Pacific Ocean Ridge,
550
00:20:39,201 --> 00:20:40,532
running parallel to the
551
00:20:40,567 --> 00:20:44,696
trench. To solve the mystery
552
00:20:44,730 --> 00:20:46,162
of the Marianas Trench,
553
00:20:46,197 --> 00:20:47,761
investigators needed to find
554
00:20:47,795 --> 00:20:49,494
out exactly what was happening
555
00:20:49,594 --> 00:20:51,759
at the East Pacific Ridge, and
556
00:20:51,827 --> 00:20:53,491
that meant exploring these
557
00:20:53,559 --> 00:20:56,689
vast mountains, 8,000 feet
558
00:20:56,757 --> 00:20:58,137
underwater.
559
00:21:04,572 --> 00:21:05,870
The pieces of the Marianas
560
00:21:05,938 --> 00:21:07,303
Trench puzzle are falling into
561
00:21:07,403 --> 00:21:08,668
place with the knowledge that
562
00:21:08,769 --> 00:21:10,567
it lies on the western edge of
563
00:21:10,668 --> 00:21:12,933
the Pacific tectonic plate.
564
00:21:15,299 --> 00:21:16,464
On the opposite side of the
565
00:21:16,565 --> 00:21:18,097
plate lies the East Pacific
566
00:21:18,164 --> 00:21:20,195
Ocean Ridge, part of an!
567
00:21:20,296 --> 00:21:22,260
enormous chain of underwater
568
00:21:22,295 --> 00:21:23,893
mountain ranges that ring the
569
00:21:23,928 --> 00:21:25,726
globe to create the largest
570
00:21:25,760 --> 00:21:29,190
geological feature on Earth.
571
00:21:29,257 --> 00:21:30,823
Scientists had a hunch that
572
00:21:30,890 --> 00:21:32,421
this colossal ridge might help
573
00:21:32,456 --> 00:21:34,220
explain how the trench was
574
00:21:34,254 --> 00:21:38,185
formed. And they found a major
575
00:21:38,219 --> 00:21:40,683
clue halfway round the globe,
576
00:21:40,751 --> 00:21:42,216
where the ridge passed beneath
577
00:21:42,317 --> 00:21:43,482
the middle of the Atlantic
578
00:21:43,583 --> 00:21:44,815
Ocean.
579
00:21:48,213 --> 00:21:50,012
During the Cold War, the US
580
00:21:50,046 --> 00:21:51,811
Navy developed a new technique
581
00:21:51,845 --> 00:21:55,109
to spot Soviet submarines.
582
00:21:55,177 --> 00:21:56,607
They scanned the seas with a
583
00:21:56,642 --> 00:21:59,106
tool called MAD, a magnetic
584
00:21:59,174 --> 00:22:01,072
anomaly detector, which could
585
00:22:01,173 --> 00:22:02,904
pinpoint steel hulls lurking
586
00:22:03,005 --> 00:22:07,002
in the deep. But they stumbled
587
00:22:07,070 --> 00:22:11,232
across something else. Running
588
00:22:11,267 --> 00:22:12,699
parallel on either side of the
589
00:22:12,766 --> 00:22:14,397
ridge, they found strange
590
00:22:14,432 --> 00:22:16,330
stripes of magnetic rocks,
591
00:22:16,397 --> 00:22:17,696
alternating positive and
592
00:22:17,763 --> 00:22:19,494
negative away from the ridge's
593
00:22:19,595 --> 00:22:21,393
peak.
594
00:22:21,428 --> 00:22:23,959
Here's the Mid-Atlantic Ridge
595
00:22:24,026 --> 00:22:25,224
coming down through here.
596
00:22:25,326 --> 00:22:27,223
Almost perfectly symmetric on
597
00:22:27,325 --> 00:22:28,957
either side of that are these
598
00:22:29,023 --> 00:22:31,288
white and black stripes, these
599
00:22:31,323 --> 00:22:32,954
have often been called zebra
600
00:22:33,021 --> 00:22:34,486
stripes.
601
00:22:36,086 --> 00:22:37,584
>> Geologists know that the
602
00:22:37,652 --> 00:22:39,383
Earth is like a giant magnet
603
00:22:39,484 --> 00:22:42,015
with a north and a south pole.
604
00:22:42,116 --> 00:22:43,747
But the magnetic poles aren't
605
00:22:43,848 --> 00:22:46,912
fixed. Every 300,000 years or
606
00:22:46,980 --> 00:22:48,278
so, the magnetic field
607
00:22:48,346 --> 00:22:49,911
suddenly flips 180 degrees.
608
00:22:54,276 --> 00:22:55,808
When the field flips, a
609
00:22:55,908 --> 00:22:57,273
compass that was previously
610
00:22:57,341 --> 00:22:59,072
pointing north will swing to
611
00:22:59,173 --> 00:23:00,805
the south.
612
00:23:00,873 --> 00:23:02,437
>> This reversing of the
613
00:23:02,505 --> 00:23:05,069
Earth's magnetic field is a
614
00:23:05,137 --> 00:23:06,535
very interesting and exciting
615
00:23:06,603 --> 00:23:08,167
but very puzzling phenomenon
616
00:23:08,235 --> 00:23:10,066
for a geophysicist to explain.
617
00:23:11,966 --> 00:23:13,331
>> Scientists think this
618
00:23:13,399 --> 00:23:15,030
reversal explains the stripes
619
00:23:15,064 --> 00:23:16,496
either side of the ocean
620
00:23:16,597 --> 00:23:21,294
ridge. In the 1960s,
621
00:23:21,327 --> 00:23:22,759
geologists discovered that
622
00:23:22,860 --> 00:23:24,925
molten volcanic rock, known as
623
00:23:24,959 --> 00:23:26,556
magma, swelled up from deep
624
00:23:26,591 --> 00:23:28,123
underground to create the
625
00:23:28,190 --> 00:23:29,455
ridges in the Atlantic and
626
00:23:29,490 --> 00:23:30,921
Pacific.
627
00:23:32,854 --> 00:23:34,719
As magma wells up between the
628
00:23:34,753 --> 00:23:36,918
tectonic plates, it pushes the
629
00:23:36,985 --> 00:23:39,017
sea floor up, and forms the
630
00:23:39,084 --> 00:23:40,715
colossal mid-ocean ridge,
631
00:23:40,783 --> 00:23:42,981
thousands of feet high.
632
00:23:46,480 --> 00:23:47,845
When the rock is hot and
633
00:23:47,879 --> 00:23:49,677
molten, its magnetic minerals
634
00:23:49,778 --> 00:23:51,309
line up with the north-south
635
00:23:51,377 --> 00:23:52,509
direction of the Earth's
636
00:23:52,543 --> 00:23:55,407
magnetic field. As the magma
637
00:23:55,508 --> 00:23:57,373
cools, the minerals are locked
638
00:23:57,407 --> 00:23:59,038
in position.
639
00:24:02,304 --> 00:24:04,302
These rocks act as a permanent
640
00:24:04,370 --> 00:24:05,801
record of the magnetic poles'
641
00:24:05,836 --> 00:24:07,433
location when the rocks were
642
00:24:07,468 --> 00:24:12,564
formed. As more and more magma
643
00:24:12,632 --> 00:24:14,696
is forced up, the old crust is
644
00:24:14,731 --> 00:24:16,162
pushed away from the ridge and
645
00:24:16,229 --> 00:24:17,594
records the reversals in the
646
00:24:17,662 --> 00:24:19,693
Earth's magnetic polarity.
647
00:24:19,794 --> 00:24:20,759
>> If you have reversals of
648
00:24:20,793 --> 00:24:22,392
magnetic polarity, then the
649
00:24:22,426 --> 00:24:23,791
sea floor acts sort of like a
650
00:24:23,858 --> 00:24:25,923
tape recorder and records
651
00:24:26,024 --> 00:24:26,923
these changes in
652
00:24:27,023 --> 00:24:28,256
magnetization, then the
653
00:24:28,290 --> 00:24:30,354
pattern of magnetic stripes
654
00:24:30,421 --> 00:24:33,086
allows people to calculate the
655
00:24:33,153 --> 00:24:34,418
speed at which the plates are
656
00:24:34,453 --> 00:24:35,684
moving apart.
657
00:24:39,250 --> 00:24:40,815
The zebra stripes are proof
658
00:24:40,883 --> 00:24:42,881
that, over time, the sea floor
659
00:24:42,948 --> 00:24:44,246
in both the Atlantic and the
660
00:24:44,313 --> 00:24:45,979
Pacific, is spreading away
661
00:24:46,046 --> 00:24:47,611
from the ridges at a rate of
662
00:24:47,712 --> 00:24:49,877
more than two inches a year.
663
00:24:51,343 --> 00:24:53,041
But geologists needed proof
664
00:24:53,142 --> 00:24:56,772
that magma created the ridge.
665
00:24:56,840 --> 00:24:58,671
If red-hot molten rock is
666
00:24:58,739 --> 00:25:00,004
forming the enormous mountain
667
00:25:00,038 --> 00:25:01,569
range in the Pacific, the
668
00:25:01,637 --> 00:25:02,935
surrounding water should be
669
00:25:03,003 --> 00:25:05,201
warm.
670
00:25:08,133 --> 00:25:10,764
In 1977, a team of scientists
671
00:25:10,832 --> 00:25:12,197
set out to discover whether
672
00:25:12,298 --> 00:25:13,563
this warm water really
673
00:25:13,663 --> 00:25:15,195
existed.
674
00:25:17,428 --> 00:25:19,026
Dudley Foster was the pilot
675
00:25:19,094 --> 00:25:21,258
for these historic dives.
676
00:25:21,292 --> 00:25:22,924
>> It's been an exciting
677
00:25:22,992 --> 00:25:24,790
occupation because you're on
678
00:25:24,891 --> 00:25:26,589
the cutting edge of science,
679
00:25:26,690 --> 00:25:28,021
uh, new discoveries all the
680
00:25:28,056 --> 00:25:31,420
time. Every cruise, there's a
681
00:25:31,486 --> 00:25:32,552
new group of scientists with
682
00:25:32,587 --> 00:25:34,184
new scientific objectives and
683
00:25:34,219 --> 00:25:35,283
there's the exploration and
684
00:25:35,318 --> 00:25:37,849
the discovery and that's
685
00:25:37,950 --> 00:25:39,814
really what puts the thrill in
686
00:25:39,915 --> 00:25:40,848
the job.
687
00:25:46,178 --> 00:25:47,844
>> For weeks, the crew scanned
688
00:25:47,911 --> 00:25:49,475
the undersea mountains without
689
00:25:49,543 --> 00:25:53,107
success. And then, they hit
690
00:25:53,174 --> 00:25:59,437
the jackpot, a bizarre pillar
691
00:25:59,537 --> 00:26:02,701
of rock, spewing hot toxic
692
00:26:02,802 --> 00:26:04,367
gas.
693
00:26:06,967 --> 00:26:08,165
>> And we saw the water was
694
00:26:08,266 --> 00:26:09,698
sort of shimmering, sort of
695
00:26:09,798 --> 00:26:12,130
like, uh, bubbling in a glass
696
00:26:12,231 --> 00:26:14,595
teapot or something.
697
00:26:15,695 --> 00:26:16,860
We stuck the temperature probe
698
00:26:16,961 --> 00:26:19,159
in there and it measured 38,
699
00:26:19,227 --> 00:26:21,025
39 degrees Fahrenheit, which
700
00:26:21,059 --> 00:26:22,590
was really amazing, 'cause
701
00:26:22,691 --> 00:26:24,056
the--the ocean's a huge heat
702
00:26:24,124 --> 00:26:26,388
sink, and so to see something
703
00:26:26,489 --> 00:26:27,854
warm like that was kind of
704
00:26:27,955 --> 00:26:30,120
startling.
705
00:26:30,187 --> 00:26:31,685
>> In these pillars of rock,
706
00:26:31,753 --> 00:26:33,218
the expedition had found the
707
00:26:33,286 --> 00:26:35,283
heat from the magma surging up
708
00:26:35,350 --> 00:26:37,715
from deep inside the Earth.
709
00:26:39,382 --> 00:26:40,814
It wasn't warming the water
710
00:26:40,848 --> 00:26:43,379
evenly along the ridge, it was
711
00:26:43,446 --> 00:26:45,011
channeled up through strange
712
00:26:45,078 --> 00:26:48,442
hydrothermal vents.
713
00:26:48,544 --> 00:26:49,275
>> FOSTER: When you make these
714
00:26:49,342 --> 00:26:50,375
discoveries, you don't know
715
00:26:50,442 --> 00:26:53,706
how significant they are. The
716
00:26:53,773 --> 00:26:56,138
true significance of 'em maybe
717
00:26:56,173 --> 00:26:57,337
takes several years to
718
00:26:57,438 --> 00:26:59,336
appreciate, and this was one
719
00:26:59,437 --> 00:27:01,169
of those times.
720
00:27:03,035 --> 00:27:04,233
>> For the investigation into
721
00:27:04,334 --> 00:27:05,965
the Marianas Trench, these
722
00:27:06,066 --> 00:27:07,532
vents are a decisive piece of
723
00:27:07,599 --> 00:27:09,330
evidence.
724
00:27:11,330 --> 00:27:13,061
They confirm that magma is
725
00:27:13,129 --> 00:27:15,127
continually creating new crust
726
00:27:15,228 --> 00:27:17,126
at the Pacific Ocean Ridge.
727
00:27:18,326 --> 00:27:19,725
And magnetic zebra stripes
728
00:27:19,826 --> 00:27:21,457
prove that old crust is pushed
729
00:27:21,558 --> 00:27:22,990
away from the ridge towards
730
00:27:23,090 --> 00:27:24,555
the other side of the Pacific
731
00:27:24,623 --> 00:27:26,788
Plate, towards the Marianas
732
00:27:26,822 --> 00:27:31,152
Trench. But this presents
733
00:27:31,253 --> 00:27:33,050
scientists with a puzzle.
734
00:27:33,085 --> 00:27:34,783
If new crust is being created
735
00:27:34,884 --> 00:27:36,515
at the ocean ridge, and the
736
00:27:36,582 --> 00:27:38,348
Earth isn't expanding, then
737
00:27:38,414 --> 00:27:39,614
the old crust must be
738
00:27:39,714 --> 00:27:42,311
disappearing somewhere else.
739
00:27:42,346 --> 00:27:43,778
>> The reason that the Earth's
740
00:27:43,845 --> 00:27:45,377
not getting bigger with sea
741
00:27:45,410 --> 00:27:46,510
floor spreading is because the
742
00:27:46,611 --> 00:27:47,876
same amount of sea floor is
743
00:27:47,943 --> 00:27:49,241
being destroyed in the
744
00:27:49,308 --> 00:27:51,306
Pacific.
745
00:27:51,374 --> 00:27:52,572
>> Something in the Pacific
746
00:27:52,640 --> 00:27:54,404
Ocean is devouring the sea
747
00:27:54,506 --> 00:27:57,770
floor. And all the evidence
748
00:27:57,837 --> 00:28:02,900
points to the Marianas Trench.
749
00:28:06,157 --> 00:28:07,489
In the hunt to discover what
750
00:28:07,523 --> 00:28:09,121
formed the Marianas Trench,
751
00:28:09,155 --> 00:28:11,120
scientists now know crust
752
00:28:11,188 --> 00:28:13,052
created at the ocean ridge is
753
00:28:13,120 --> 00:28:15,051
being devoured somewhere and
754
00:28:15,119 --> 00:28:16,683
by something in the Pacific
755
00:28:16,751 --> 00:28:18,049
Ocean.
756
00:28:21,948 --> 00:28:23,480
They suspect the Marianas
757
00:28:23,581 --> 00:28:28,177
Trench is involved. But the
758
00:28:28,211 --> 00:28:29,643
proof would come, not from the
759
00:28:29,744 --> 00:28:34,274
trench, but from these, the
760
00:28:34,342 --> 00:28:36,872
Mariana Islands, a chain of
761
00:28:36,907 --> 00:28:38,638
volcanoes that break through
762
00:28:38,706 --> 00:28:41,403
the ocean's surface 200 miles
763
00:28:41,471 --> 00:28:44,734
west of the trench. Scientists
764
00:28:44,768 --> 00:28:46,233
noticed the island chain
765
00:28:46,301 --> 00:28:47,833
mirrors the trench's exact
766
00:28:47,867 --> 00:28:50,365
shape. This led them to think
767
00:28:50,433 --> 00:28:51,963
the trench was responsible for
768
00:28:51,998 --> 00:28:53,630
the islands' creation.
769
00:28:56,096 --> 00:28:57,328
>> If, uh, you see pictures of
770
00:28:57,362 --> 00:28:58,527
the Marianas Trench, it's
771
00:28:58,594 --> 00:29:00,326
curved, and the line of
772
00:29:00,360 --> 00:29:01,692
volcanoes that it generates is
773
00:29:01,726 --> 00:29:03,424
curved exactly parallel to it,
774
00:29:05,590 --> 00:29:06,989
>> Geologists believe that the
775
00:29:07,056 --> 00:29:08,587
trench formed the volcanoes
776
00:29:08,689 --> 00:29:10,120
via a process called
777
00:29:10,155 --> 00:29:13,951
subduction. Subduction occurs
778
00:29:14,053 --> 00:29:15,583
where two tectonic plates
779
00:29:15,651 --> 00:29:17,915
collide. As they grind past
780
00:29:17,949 --> 00:29:19,415
each other, the heavier plate
781
00:29:19,482 --> 00:29:20,947
is pushed beneath the lighter
782
00:29:21,015 --> 00:29:23,745
plate. The descending plate is
783
00:29:23,846 --> 00:29:25,278
forced down into the Earth's
784
00:29:25,313 --> 00:29:27,210
intensely hot interior, called
785
00:29:27,278 --> 00:29:29,442
the mantle. It takes with it
786
00:29:29,476 --> 00:29:31,008
water and sediment built up
787
00:29:31,076 --> 00:29:32,940
over millions of years.
788
00:29:33,008 --> 00:29:34,639
>> Volcanoes form above
789
00:29:34,740 --> 00:29:36,471
subduction zones not because
790
00:29:36,539 --> 00:29:37,904
the Earth is hotter there but
791
00:29:38,005 --> 00:29:39,103
because this is where we're
792
00:29:39,204 --> 00:29:41,102
taking the water that once was
793
00:29:41,170 --> 00:29:42,901
in the ocean. It gets taken
794
00:29:42,969 --> 00:29:44,634
into the mantle and gets
795
00:29:44,701 --> 00:29:46,433
sweated out, causes the mantle
796
00:29:46,534 --> 00:29:47,898
to melt and this magma is what
797
00:29:47,966 --> 00:29:49,065
then rises and erupts
798
00:29:49,099 --> 00:29:50,497
explosively out these
799
00:29:50,531 --> 00:29:51,696
volcanoes.
800
00:29:58,061 --> 00:29:59,159
>> The water in the sediment
801
00:29:59,260 --> 00:30:01,324
forces magma to swirl up and
802
00:30:01,425 --> 00:30:04,223
push through the plate above.
803
00:30:04,291 --> 00:30:05,222
And when it breaks the
804
00:30:05,323 --> 00:30:07,554
surface, it creates volcanoes,
805
00:30:07,589 --> 00:30:09,153
like the volcanoes that form
806
00:30:09,221 --> 00:30:11,319
the Mariana Islands.
807
00:30:13,385 --> 00:30:14,916
It was subduction that formed
808
00:30:14,951 --> 00:30:18,581
the islands west of the trench
809
00:30:18,649 --> 00:30:20,114
and gave investigators the
810
00:30:20,215 --> 00:30:21,113
breakthrough they'd been
811
00:30:21,180 --> 00:30:24,845
looking for. Because here, at
812
00:30:24,911 --> 00:30:26,744
last, was a process powerful
813
00:30:26,810 --> 00:30:28,643
enough to create the Marianas
814
00:30:28,709 --> 00:30:32,474
Trench. As the descending
815
00:30:32,540 --> 00:30:34,805
plate dives down, it digs into
816
00:30:34,873 --> 00:30:37,004
the mantle. Here, the
817
00:30:37,071 --> 00:30:38,370
colliding plates form a
818
00:30:38,437 --> 00:30:40,602
trench, a giant crease in
819
00:30:40,637 --> 00:30:42,534
the ocean floor.
820
00:30:44,167 --> 00:30:45,699
It seemed that scientists had
821
00:30:45,800 --> 00:30:47,165
finally explained how the
822
00:30:47,232 --> 00:30:49,430
trench was formed.
823
00:30:50,697 --> 00:30:54,128
There was just one problem. A
824
00:30:54,162 --> 00:30:57,559
very large problem. Around the
825
00:30:57,593 --> 00:30:59,424
world, subduction zones cause
826
00:30:59,492 --> 00:31:00,757
violent earthquakes and
827
00:31:00,858 --> 00:31:03,123
catastrophic tsunamis.
828
00:31:05,322 --> 00:31:06,021
>> We know subduction is
829
00:31:06,122 --> 00:31:07,320
happening because of the
830
00:31:07,388 --> 00:31:08,386
active earthquakes and these
831
00:31:08,454 --> 00:31:10,019
are the most devastating
832
00:31:10,087 --> 00:31:13,750
earthquakes. This is the
833
00:31:13,818 --> 00:31:14,882
earthquake that generated e
834
00:31:14,984 --> 00:31:19,347
tsunami in Sumatra, also the
835
00:31:19,448 --> 00:31:20,512
other very large earthquakes
836
00:31:20,580 --> 00:31:21,613
in Alaska and Chile.
837
00:31:25,477 --> 00:31:27,142
>> But the Marianas Trench,
838
00:31:27,244 --> 00:31:28,841
the deepest subduction zone in
839
00:31:28,875 --> 00:31:30,507
the world, hasn't caused a
840
00:31:30,574 --> 00:31:32,039
devastating earthquake since
841
00:31:32,107 --> 00:31:33,672
records began in the 17th
842
00:31:33,772 --> 00:31:37,036
century. Investigators needed
843
00:31:37,137 --> 00:31:38,302
to know why.
844
00:31:38,403 --> 00:31:40,201
>> Ah, that's--that's, uh, the
845
00:31:40,302 --> 00:31:41,834
$60,000 question.
846
00:31:45,499 --> 00:31:46,564
>> They hoped the trench's
847
00:31:46,632 --> 00:31:48,197
shallower western edge might
848
00:31:48,265 --> 00:31:49,929
provide the answer.
849
00:31:57,060 --> 00:31:58,525
Here, they found an intriguing
850
00:31:58,593 --> 00:32:00,490
chain of underwater hills two
851
00:32:00,525 --> 00:32:01,956
miles below the surface of the
852
00:32:02,023 --> 00:32:04,021
sea.
853
00:32:07,820 --> 00:32:09,551
Engineers drilled down into
854
00:32:09,652 --> 00:32:10,917
the hills and collected core
855
00:32:11,018 --> 00:32:12,250
samples.
856
00:32:17,615 --> 00:32:18,713
An$ when the scientists
857
00:32:18,781 --> 00:32:20,445
analyzed the samples, they
858
00:32:20,546 --> 00:32:21,445
discovered the hills were
859
00:32:21,513 --> 00:32:24,510
actually volcanoes, and they
860
00:32:24,544 --> 00:32:29,141
spewed out not lava, but mud.
861
00:32:30,607 --> 00:32:32,505
The fine, powdery mud is made
862
00:32:32,606 --> 00:32:34,504
up of a soft type of rock that
863
00:32:34,605 --> 00:32:35,736
has been ground up in the
864
00:32:35,837 --> 00:32:39,368
subduction zone. It seemed
865
00:32:39,436 --> 00:32:41,067
this soft rock might explain
866
00:32:41,101 --> 00:32:42,300
why there have been no
867
00:32:42,367 --> 00:32:43,632
major earthquakes at the
868
00:32:43,733 --> 00:32:45,731
Marianas Trench.
869
00:32:46,798 --> 00:32:47,829
>> Everybody has a sense of
870
00:32:47,897 --> 00:32:49,995
what a volcano is but not all
871
00:32:50,096 --> 00:32:51,727
volcanoes erupt igneous rocks,
872
00:32:51,795 --> 00:32:54,226
there's some volcanoes that
873
00:32:54,260 --> 00:32:56,592
erupt mud. And a certain kind
874
00:32:56,626 --> 00:32:58,157
of unusual kind of mud in the
875
00:32:58,258 --> 00:32:59,956
Marianas is made out of
876
00:32:59,990 --> 00:33:01,689
serpentine, and serpentine is
877
00:33:01,789 --> 00:33:04,254
a very weak rock and it can be
878
00:33:04,321 --> 00:33:05,786
scratched with a knife or
879
00:33:05,854 --> 00:33:07,885
something like that.
880
00:33:09,052 --> 00:33:10,651
>> Investigators realized the
881
00:33:10,685 --> 00:33:12,483
grinding plates crush the soft
882
00:33:12,551 --> 00:33:14,714
rock to form a lubricating mud
883
00:33:14,749 --> 00:33:15,980
that prevents large
884
00:33:16,015 --> 00:33:19,745
earthquakes. Then the mud
885
00:33:19,812 --> 00:33:21,511
bubbles up to the ocean floor,
886
00:33:21,545 --> 00:33:23,177
where it forms the strange mud
887
00:33:23,278 --> 00:33:24,875
volcanoes found along the
888
00:33:24,910 --> 00:33:27,440
trench's western edge.
889
00:33:27,542 --> 00:33:28,806
>> Other parts of the world,
890
00:33:28,874 --> 00:33:29,972
like the Andes or maybe
891
00:33:30,040 --> 00:33:31,605
Indonesia, you've got two
892
00:33:31,706 --> 00:33:32,604
plates that are grinding
893
00:33:32,672 --> 00:33:34,037
together and the--one
894
00:33:34,071 --> 00:33:35,702
of the plates is quite strong,
895
00:33:35,770 --> 00:33:37,235
and it takes a big earthquake
896
00:33:37,336 --> 00:33:38,501
to rupture that plate
897
00:33:38,569 --> 00:33:40,433
interface. But if these rocks
898
00:33:40,501 --> 00:33:41,799
are weak like they are in the
899
00:33:41,867 --> 00:33:42,932
Marianas, where you've got
900
00:33:42,966 --> 00:33:44,498
these serpentinites, those
901
00:33:44,565 --> 00:33:45,697
are very weak and it doesn't
902
00:33:45,765 --> 00:33:47,530
take much energy at all to get
903
00:33:47,597 --> 00:33:48,862
the two plates to glide one
904
00:33:48,930 --> 00:33:50,327
past the other.
905
00:33:53,194 --> 00:33:55,025
>> At last, geologists had
906
00:33:55,093 --> 00:33:56,558
discovered what created the
907
00:33:56,592 --> 00:33:58,723
Marianas Trench.
908
00:34:00,123 --> 00:34:01,754
50 million years ago, the
909
00:34:01,822 --> 00:34:03,020
Pacific Plate slipped under
910
00:34:03,088 --> 00:34:04,187
the edge of the Philippine
911
00:34:04,287 --> 00:34:07,085
Plate. As it bent and dived
912
00:34:07,119 --> 00:34:08,618
into the Earth's mantle, it
913
00:34:08,652 --> 00:34:10,450
formed the colossal Marianas
914
00:34:10,518 --> 00:34:14,348
Trench. And the plate is still
915
00:34:14,415 --> 00:34:16,980
moving. Like a giant conveyor
916
00:34:17,080 --> 00:34:18,445
belt, the Earth's crust
917
00:34:18,513 --> 00:34:20,178
travels slowly across the
918
00:34:20,245 --> 00:34:21,776
Pacific Plate, from its
919
00:34:21,811 --> 00:34:22,976
birthplace in the East
920
00:34:23,043 --> 00:34:24,342
Pacific Ridge to its
921
00:34:24,409 --> 00:34:26,607
graveyard, 10,000 miles away
922
00:34:26,708 --> 00:34:28,772
in the Marianas Trench.
923
00:34:30,606 --> 00:34:32,071
Today, the Pacific Plate's
924
00:34:32,139 --> 00:34:33,504
movement can be tracked in
925
00:34:33,605 --> 00:34:35,035
real time.
926
00:34:36,569 --> 00:34:38,034
>> Confirmation has come from
927
00:34:38,135 --> 00:34:39,766
GPS technology, where we can
928
00:34:39,834 --> 00:34:42,499
actually put a transmitter on
929
00:34:42,565 --> 00:34:43,930
an island and come back year
930
00:34:44,031 --> 00:34:45,663
after year and actually follow
931
00:34:45,731 --> 00:34:47,562
it moving a few centimeters a
932
00:34:47,630 --> 00:34:49,294
year towards the trench.
933
00:34:51,560 --> 00:34:53,025
>> It's devouring the crust at
934
00:34:53,127 --> 00:34:55,457
a rate of three inches a year,
935
00:34:55,558 --> 00:34:56,990
about as fast as a human
936
00:34:57,024 --> 00:34:59,089
fingernail grows.
937
00:35:01,088 --> 00:35:03,086
Every four million years, it
938
00:35:03,154 --> 00:35:04,652
swallows an area the size of
939
00:35:04,720 --> 00:35:07,284
the United States. By
940
00:35:07,352 --> 00:35:08,816
consuming the crust created at
941
00:35:08,884 --> 00:35:10,349
the Pacific Ocean Ridge,
942
00:35:10,450 --> 00:35:12,148
the ravenous Marianas Trench
943
00:35:12,182 --> 00:35:13,547
is the world's largest
944
00:35:13,615 --> 00:35:15,246
recycling plant.
945
00:35:21,144 --> 00:35:22,875
But there was one remaining
946
00:35:22,976 --> 00:35:24,707
and major piece of the puzzle
947
00:35:24,775 --> 00:35:27,206
to find. Scientists still
948
00:35:27,240 --> 00:35:28,772
didn't know why it is the
949
00:35:28,873 --> 00:35:30,771
deepest trench on Earth.
950
00:35:32,804 --> 00:35:34,203
They suspected the age of the
951
00:35:34,236 --> 00:35:35,501
sea floor at the bottom of the
952
00:35:35,569 --> 00:35:38,300
trench may provide the answer.
953
00:35:38,367 --> 00:35:39,133
>> It turns out there's a
954
00:35:39,201 --> 00:35:40,566
really strong relationship
955
00:35:40,632 --> 00:35:42,198
between the age of the sea
956
00:35:42,265 --> 00:35:43,764
floor and its depth in the
957
00:35:43,831 --> 00:35:45,030
water.
958
00:35:47,929 --> 00:35:50,259
>> In 1999, a team of deep sea
959
00:35:50,294 --> 00:35:51,725
drillers returned to the
960
00:35:51,827 --> 00:35:52,791
trench to collect core
961
00:35:52,826 --> 00:35:54,624
samples.
962
00:35:55,924 --> 00:35:56,889
>> PLANK: One great thing
963
00:35:56,924 --> 00:35:57,888
about drilling this ocean
964
00:35:57,923 --> 00:35:58,922
crust is we actually got
965
00:35:58,989 --> 00:36:01,454
pieces of it. So, we're
966
00:36:01,555 --> 00:36:03,186
holding in our hands here the
967
00:36:03,253 --> 00:36:04,218
material that's actually getting
968
00:36:04,252 --> 00:36:05,351
subducted at the Marianas
969
00:36:05,453 --> 00:36:06,817
Trench, and it turned out to
970
00:36:06,884 --> 00:36:09,682
be 170 million years old. So
971
00:36:09,716 --> 00:36:10,714
we can say with confidence
972
00:36:10,782 --> 00:36:12,347
that's the oldest ocean floor
973
00:36:12,415 --> 00:36:13,580
before it's getting swallowed
974
00:36:13,614 --> 00:36:14,979
up in the mantle at the
975
00:36:15,046 --> 00:36:16,611
trench.
976
00:36:16,679 --> 00:36:18,577
>> But why is this piece of
977
00:36:18,611 --> 00:36:20,576
rock the oldest on the ocean
978
00:36:20,610 --> 00:36:22,408
floor?
979
00:36:22,509 --> 00:36:23,474
>> PLANK: The sea floor at the
980
00:36:23,508 --> 00:36:25,140
Marianas Trench is so old
981
00:36:25,208 --> 00:36:26,939
because it's been so long
982
00:36:27,040 --> 00:36:28,571
since it was born, so it was
983
00:36:28,639 --> 00:36:30,004
born in the equivalent of the
984
00:36:30,038 --> 00:36:31,503
eastern Pacific today and it's
985
00:36:31,571 --> 00:36:33,668
just been going on longer
986
00:36:33,769 --> 00:36:35,101
than--than any other place in
987
00:36:35,202 --> 00:36:36,300
the oceans before it's been
988
00:36:36,368 --> 00:36:37,766
subducted.
989
00:36:40,099 --> 00:36:41,264
>> The Pacific Plate is the
990
00:36:41,298 --> 00:36:42,663
planet's largest tectonic
991
00:36:42,731 --> 00:36:44,729
plate, covering an area 11
992
00:36:44,797 --> 00:36:46,428
times the size of the United
993
00:36:46,462 --> 00:36:48,094
States.
994
00:36:51,893 --> 00:36:53,323
When crust bubbled up at the
995
00:36:53,358 --> 00:36:55,889
ridge 170 million years ago,
996
00:36:55,956 --> 00:36:58,721
it was light and buoyant.
997
00:36:58,789 --> 00:37:00,353
But as it traveled 10,000
998
00:37:00,421 --> 00:37:02,419
miles across the plate, it
999
00:37:02,520 --> 00:37:04,251
cooled and became compact and
1000
00:37:04,352 --> 00:37:07,616
dense. Over millions of years,
1001
00:37:07,683 --> 00:37:09,314
the dense crust got heavier
1002
00:37:09,349 --> 00:37:10,680
and began to sink into the
1003
00:37:10,748 --> 00:37:12,313
mantle below.
1004
00:37:17,145 --> 00:37:18,576
Scientists realized that,
1005
00:37:18,644 --> 00:37:19,675
because the crust at the
1006
00:37:19,743 --> 00:37:21,374
Marianas Trench is the oldest
1007
00:37:21,409 --> 00:37:23,407
ocean crust, it's also the
1008
00:37:23,474 --> 00:37:25,106
heaviest and so has sunk
1009
00:37:25,206 --> 00:37:26,638
deeper into the mantle than
1010
00:37:26,672 --> 00:37:29,669
any other area of ocean crust.
1011
00:37:32,569 --> 00:37:34,101
Here, at last, was the
1012
00:37:34,201 --> 00:37:35,633
explanation for the trench's
1013
00:37:35,734 --> 00:37:39,098
extraordinary depth. The
1014
00:37:39,166 --> 00:37:40,530
picture of the Marianas Trench
1015
00:37:40,564 --> 00:37:42,729
is almost complete.
1016
00:37:44,462 --> 00:37:46,993
Volcanic islands mirroring the
1017
00:37:47,094 --> 00:37:47,993
trench's exact shape lead
1018
00:37:48,094 --> 00:37:49,625
scientists to believe it runs
1019
00:37:49,726 --> 00:37:52,257
along a subduction zone.
1020
00:37:52,358 --> 00:37:54,156
And slippery mud volcanoes
1021
00:37:54,224 --> 00:37:55,988
explain why it doesn't create
1022
00:37:56,056 --> 00:37:58,854
large earthquakes. But one
1023
00:37:58,888 --> 00:38:01,585
question remains unanswered.
1024
00:38:01,619 --> 00:38:02,785
Towards the trench's southern
1025
00:38:02,852 --> 00:38:06,116
end, the vast chasm drops a
1026
00:38:06,150 --> 00:38:07,849
further two miles to its
1027
00:38:07,883 --> 00:38:09,681
lowest point, the Challenger
1028
00:38:09,749 --> 00:38:11,846
Deep, seven miles beneath the
1029
00:38:11,947 --> 00:38:15,877
waves. The question is, what
1030
00:38:15,945 --> 00:38:19,575
makes it plunge so deep?
1031
00:38:24,284 --> 00:38:25,482
The investigation into the
1032
00:38:25,516 --> 00:38:27,481
Marianas Trench has one final
1033
00:38:27,548 --> 00:38:29,179
puzzle to solve.
1034
00:38:31,179 --> 00:38:32,711
At the trench's southern end,
1035
00:38:32,746 --> 00:38:34,077
the sea floor plummets a
1036
00:38:34,177 --> 00:38:37,142
further 10,000 feet into a
1037
00:38:37,176 --> 00:38:39,074
seven mile deep chasm called
1038
00:38:39,142 --> 00:38:42,339
the Challenger Deep. It's the
1039
00:38:42,439 --> 00:38:45,271
lowest point on the planet,
1040
00:38:45,338 --> 00:38:47,270
but so far, scientists have
1041
00:38:47,337 --> 00:38:49,601
been unable to explain why
1042
00:38:49,702 --> 00:38:51,800
this one section of the trench
1043
00:38:51,868 --> 00:38:55,864
is so deep. Now, they believe
1044
00:38:55,932 --> 00:38:57,197
the shape of the descending
1045
00:38:57,265 --> 00:38:59,296
tectonic plate may hold the
1046
00:38:59,364 --> 00:39:00,729
answer.
1047
00:39:00,830 --> 00:39:01,628
>> The Challenger Deep, in
1048
00:39:01,662 --> 00:39:03,094
addition, is a little bit
1049
00:39:03,161 --> 00:39:05,093
deeper, because of some
1050
00:39:05,160 --> 00:39:07,791
peculiarities relating to how
1051
00:39:07,826 --> 00:39:09,457
the slab that's going down is
1052
00:39:09,558 --> 00:39:11,056
behaving.
1053
00:39:12,357 --> 00:39:14,320
>> A narrow slab of crust has
1054
00:39:14,355 --> 00:39:15,820
torn away from the Pacific
1055
00:39:15,887 --> 00:39:18,151
Plate's descending edge.
1056
00:39:18,253 --> 00:39:19,185
>> STERN: Well, it's basically
1057
00:39:19,253 --> 00:39:20,683
got to do with how the slab
1058
00:39:20,718 --> 00:39:21,783
pushes the mantle out of the
1059
00:39:21,884 --> 00:39:24,082
way. Where you have a narrow
1060
00:39:24,149 --> 00:39:25,615
slab, like you have at the
1061
00:39:25,716 --> 00:39:27,614
Challenger Deep, it can sink
1062
00:39:27,680 --> 00:39:29,412
almost vertically, because the
1063
00:39:29,513 --> 00:39:30,678
mantle that it's trying to
1064
00:39:30,746 --> 00:39:32,244
displace can move around out
1065
00:39:32,311 --> 00:39:33,776
of the way.
1066
00:39:36,042 --> 00:39:37,641
Investigators have finally
1067
00:39:37,675 --> 00:39:39,206
unraveled the mysteries of the
1068
00:39:39,274 --> 00:39:41,205
Marianas Trench.
1069
00:39:43,505 --> 00:39:45,203
And in the process, they've
1070
00:39:45,304 --> 00:39:46,402
made a discovery with
1071
00:39:46,470 --> 00:39:48,368
implications that stretch far
1072
00:39:48,436 --> 00:39:50,967
beyond the trench itself.
1073
00:39:56,564 --> 00:39:58,495
Studying the ocean ridges led
1074
00:39:58,530 --> 00:40:00,162
geologists to believe that
1075
00:40:00,229 --> 00:40:01,627
magma, welling up at the
1076
00:40:01,728 --> 00:40:03,392
ridges, was pushing the plates
1077
00:40:03,460 --> 00:40:06,024
apart.
1078
00:40:06,092 --> 00:40:08,556
>> How much weight is that--
1079
00:40:08,624 --> 00:40:09,989
>> But the exploration of the
1080
00:40:10,023 --> 00:40:11,888
Marianas Trench has changed
1081
00:40:11,922 --> 00:40:14,286
this idea forever.
1082
00:40:14,354 --> 00:40:16,053
>> People used to think that
1083
00:40:16,087 --> 00:40:17,818
maybe the magma would kind of
1084
00:40:17,886 --> 00:40:20,183
push the plates apart, and
1085
00:40:20,251 --> 00:40:22,548
that idea is largely
1086
00:40:22,616 --> 00:40:24,547
discounted now.
1087
00:40:25,981 --> 00:40:27,446
>> As the ocean crust travels
1088
00:40:27,514 --> 00:40:28,879
from the Pacific Ocean Ridge
1089
00:40:28,946 --> 00:40:31,244
to the trench, it changes from
1090
00:40:31,345 --> 00:40:33,409
a buoyant, red-hot magma into
1091
00:40:33,476 --> 00:40:35,575
a colder, denser and heavier
1092
00:40:35,609 --> 00:40:39,506
crust. The plate's leading
1093
00:40:39,574 --> 00:40:41,671
edge becomes so heavy that it
1094
00:40:41,772 --> 00:40:43,170
drags the rest of the plate
1095
00:40:43,238 --> 00:40:45,136
along behind it.
1096
00:40:46,369 --> 00:40:48,767
>> The heavy cold plates at
1097
00:40:48,834 --> 00:40:51,200
the trenches are sinking down
1098
00:40:51,300 --> 00:40:53,931
into the mantle and pulling
1099
00:40:54,032 --> 00:40:56,297
the plates apart, uh, at the
1100
00:40:56,363 --> 00:40:58,528
ridges, and the magma just
1101
00:40:58,563 --> 00:41:00,460
passively, uh, fills in the
1102
00:41:00,528 --> 00:41:01,927
gaps.
1103
00:41:04,926 --> 00:41:06,291
>> The investigation into the
1104
00:41:06,358 --> 00:41:07,523
Marianas Trench has
1105
00:41:07,558 --> 00:41:08,722
revolutionized our
1106
00:41:08,823 --> 00:41:09,988
understanding of how the
1107
00:41:10,056 --> 00:41:11,987
Earth's plates move.
1108
00:41:15,153 --> 00:41:17,084
We now know a worldwide
1109
00:41:17,152 --> 00:41:19,217
network of subduction zones
1110
00:41:19,251 --> 00:41:21,149
drag tectonic plates around
1111
00:41:21,249 --> 00:41:23,780
the globe, powering the
1112
00:41:23,881 --> 00:41:25,246
movement of continents over
1113
00:41:25,314 --> 00:41:28,511
millions of years and moving
1114
00:41:28,579 --> 00:41:31,509
the very Earth we stand on.
1115
00:41:32,943 --> 00:41:34,241
>> The plates that are moving
1116
00:41:34,309 --> 00:41:36,040
fastest on the Earth are
1117
00:41:36,108 --> 00:41:37,740
the ones that have all the
1118
00:41:37,774 --> 00:41:39,105
trenches.
1119
00:41:40,306 --> 00:41:41,404
>> The Pacific Plate is the
1120
00:41:41,472 --> 00:41:42,936
fastest moving of the nine
1121
00:41:43,037 --> 00:41:44,902
major plates on the planet,
1122
00:41:44,936 --> 00:41:46,401
because it is surrounded by
1123
00:41:46,469 --> 00:41:48,367
dozens of destructive trenches
1124
00:41:48,401 --> 00:41:51,365
like the Marianas. They are
1125
00:41:51,432 --> 00:41:53,197
consuming the ocean crust
1126
00:41:53,298 --> 00:41:54,830
faster than the Ocean Ridge
1127
00:41:54,931 --> 00:41:57,995
can produce it. Over millions
1128
00:41:58,062 --> 00:41:59,727
of years, the Pacific Plate
1129
00:41:59,828 --> 00:42:02,359
will shrink until, some time
1130
00:42:02,426 --> 00:42:04,324
in the distant future, the
1131
00:42:04,359 --> 00:42:06,623
largest ocean on Earth will
1132
00:42:06,690 --> 00:42:08,955
disappear. Australia will
1133
00:42:08,990 --> 00:42:10,787
crash into the United States,
1134
00:42:10,855 --> 00:42:13,052
reshaping our planet.
1135
00:42:14,520 --> 00:42:16,417
Perhaps one day, downtown
1136
00:42:16,519 --> 00:42:17,983
Seattle will compete for real
1137
00:42:18,050 --> 00:42:19,150
estate with a suburb of
1138
00:42:19,250 --> 00:42:22,114
Sydney, Australia. And
1139
00:42:22,149 --> 00:42:23,580
all because of subduction
1140
00:42:23,615 --> 00:42:25,045
zones like the Marianas
1141
00:42:25,113 --> 00:42:26,045
Trench.
1142
00:42:31,210 --> 00:42:33,208
But for all its significance,
1143
00:42:33,276 --> 00:42:35,107
man has only ever dived to the
1144
00:42:35,207 --> 00:42:37,572
bottom of the trench once, and
1145
00:42:37,673 --> 00:42:39,005
there are no immediate plans
1146
00:42:39,038 --> 00:42:40,936
to return.
1147
00:42:41,004 --> 00:42:45,901
>> Imagine asking someone,
1148
00:42:45,935 --> 00:42:49,898
"What is the flora and fauna
1149
00:42:49,999 --> 00:42:52,630
of California?" and saying
1150
00:42:52,731 --> 00:42:54,462
that someone's spent ten
1151
00:42:54,530 --> 00:42:56,961
minutes there, picked up two
1152
00:42:56,995 --> 00:42:59,093
ants, come back and said
1153
00:42:59,161 --> 00:43:01,092
they've sampled California.
1154
00:43:01,160 --> 00:43:02,525
That's probably how well we
1155
00:43:02,593 --> 00:43:03,891
know the Marianas Trench.
1156
00:43:08,256 --> 00:43:09,987
>> To date, less than five per
1157
00:43:10,055 --> 00:43:11,420
cent of the world's oceans
1158
00:43:11,521 --> 00:43:14,151
have been explored. But only
1159
00:43:14,219 --> 00:43:15,584
by returning to the oceans'
1160
00:43:15,685 --> 00:43:17,683
very deepest reaches will we
1161
00:43:17,750 --> 00:43:19,215
fully comprehend the
1162
00:43:19,282 --> 00:43:21,380
incredible forces that recycle
1163
00:43:21,415 --> 00:43:24,113
and rebuild our world.
1164
00:43:25,779 --> 00:43:27,577
>> The way I like to think of
1165
00:43:27,644 --> 00:43:31,441
it is that ocean exploration
1166
00:43:31,476 --> 00:43:32,941
leads to new research
1167
00:43:33,008 --> 00:43:36,839
questions. And if we don't
1168
00:43:36,940 --> 00:43:39,204
have exploration, we don't
1169
00:43:39,271 --> 00:43:40,837
even know the right questions
1170
00:43:40,903 --> 00:43:42,368
to ask.
1171
00:43:44,268 --> 00:43:45,733
It is now known what a
1172
00:43:45,801 --> 00:43:47,799
geological wonder the Marianas
1173
00:43:47,900 --> 00:43:52,163
Trench is. Since this deep
1174
00:43:52,264 --> 00:43:53,962
chasm in the Earth's crust was
1175
00:43:53,996 --> 00:43:55,428
first discovered with a length
1176
00:43:55,496 --> 00:43:57,160
of rope and a lump of lead
1177
00:43:57,261 --> 00:43:58,759
more than a century ago,
1178
00:43:58,793 --> 00:44:01,591
evidence has piled up. A
1179
00:44:01,692 --> 00:44:03,423
record-breaking dive to the
1180
00:44:03,491 --> 00:44:06,322
lowest point on Earth. Giant
1181
00:44:06,422 --> 00:44:08,154
undersea mountain ranges with
1182
00:44:08,222 --> 00:44:09,753
bizarre magnetic zebra
1183
00:44:09,787 --> 00:44:11,952
stripes, proof that the ocean
1184
00:44:12,020 --> 00:44:13,784
crust is spreading towards
1185
00:44:13,852 --> 00:44:16,116
the hungry Marianas Trench,
1186
00:44:16,184 --> 00:44:17,649
lined with slippery mud
1187
00:44:17,683 --> 00:44:19,115
volcanoes which prevent
1188
00:44:19,182 --> 00:44:21,647
devastating earthquakes.
1189
00:44:21,681 --> 00:44:23,812
And the planet's oldest ocean
1190
00:44:23,846 --> 00:44:25,577
crust, the reason that the
1191
00:44:25,645 --> 00:44:27,576
Marianas Trench is the deepest
1192
00:44:27,644 --> 00:44:29,842
point in the oceans.
1193
00:44:30,909 --> 00:44:33,007
In the darkest and most remote
1194
00:44:33,041 --> 00:44:35,372
place in the world, scientists
1195
00:44:35,473 --> 00:44:36,905
have added to their knowledge
1196
00:44:36,972 --> 00:44:39,270
about the powerful forces that
1197
00:44:39,371 --> 00:44:41,069
contribute to the dynamic
1198
00:44:41,170 --> 00:44:42,701
story of our planet.
78632
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