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NARRATOR:
Deep below the Pacific Ocean
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lies a tectonic monster.
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MAN: You know how we told you
not to panic?
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Well, that's all off.
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Panic. Run for your life.
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(screaming)
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NARRATOR: The world's biggest
tsunami machine,
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its dangers hidden from view,
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until now.
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Imagine if we could
empty the oceans,
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letting the water drain away
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to reveal the secrets
of the seafloor.
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Now, we can,
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using the latest underwater
scanning technology,
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piercing the deep oceans,
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and turning accurate data
into 3D images.
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This time, is the world's
next mega-earthquake
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brewing
off the coast of Seattle?
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MAN: We can have the big one
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right now, as we speak.
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NARRATOR:
Why has the discovery
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of an underwater volcano,
just 44 miles from Tokyo,
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got seismic experts so worried?
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And what do scientists caught
up in a undersea earthquake
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learn about the dangers
facing New Zealand?
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MAN: The front of it would have
a huge amount of energy.
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The scale is just immense.
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NARRATOR: Drain the Oceans
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reveals the secrets
of the deadly Pacific.
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(music)
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(music)
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The Pacific Ocean--
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the planet's largest
and deepest.
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500 million people
live around its coast.
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But deep beneath the waves
lurks a terrifying monster
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that threatens all of them,
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the planet's largest and
most dangerous seismic zone--
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the Ring of Fire.
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90 percent of all earthquakes
strike here
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and when they do,
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the consequences
are devastating.
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(siren)
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(siren)
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March 11, 2011.
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(speaking Japanese)
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NARRATOR:
Tohoku, northeastern Japan.
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(shouting)
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A magnitude 9 earthquake
violently shakes the region.
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MAN: Oh!
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NARRATOR: The quake causes
buildings to collapse
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and people to flee
for their lives.
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(shouting)
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But that's not the end
of the destruction.
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A defining characteristic
of the Ring of Fire
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is that
the biggest earthquakes here
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shake not just the land,
but the seabed as well...
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...generating
huge surges of water...
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(speaking Japanese)
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NARRATOR: ...deadly tsunamis.
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(shouting)
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(music)
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(music)
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(shouting)
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(shouting)
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(music)
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(music)
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In Japan, almost 16,000 people
are killed.
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And geologists are certain
it will happen again
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somewhere around
the Pacific Ring of Fire,
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but when and where?
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Pulling the plug
on the Pacific Ocean
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reveals a glimpse of one
of its most terrifying secrets,
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just off the west coast
of America--
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not the infamous
San Andreas Fault
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in California,
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but something close
to the teeming cities
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of Portland,
Seattle, and Vancouver,
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something far more menacing.
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(music)
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LELAND O'DRISCOLL: It's known
that it's an active structure.
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It could happen now, and that's
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truly the source of fear.
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(music)
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NARRATOR:
This region of North America
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is known as Cascadia,
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one of the most beautiful
and peaceful in North America.
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It's also home
to 10 million people.
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They feel safe here,
and why wouldn't they?
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In all recorded history,
there's been no trace
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of any natural disasters
in the region,
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but on the 18th of May 1980,
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everything changes.
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(rumbling)
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MAN: There is no question at all
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that the volcanic activity
has begun.
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NARRATOR: Mount St. Helens,
50 miles from Portland.
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Huge eruptions blast
a 1,300-foot crater
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in the summit of a volcano
long thought to be dormant.
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REPORTER: It is the biggest
eruption ever recorded
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of Mount St. Helens so far.
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REPORTER:
I think it does not look good
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for people in that area now.
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NARRATOR: It's the worst
volcano disaster
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in U.S. history,
claiming 57 lives.
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(music)
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(music)
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Scientists are now forced
to ask a tough question.
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MAN: Is it, is it scaled
to look at tsunamis?
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NARRATOR: Does the eruption
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of the supposedly inactive
Mount St. Helens
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mean the 10 million inhabitants
of Cascadia
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are now sitting
on a seismic time bomb
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that just started ticking?
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To find out, scientists
launch an urgent investigation
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on land
and deep under the sea.
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Off the coast of Cascadia,
the latest scanning technology
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reveals something extraordinary
and terrifying.
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Based upon their exact data,
for the first time,
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we can pull the plug
on the Pacific Ocean
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to reveal
their shocking discovery.
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As the water drains away,
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a vast world no human has
ever seen before is laid bare.
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For mile after mile
across its heart,
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the Pacific Ocean floor
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is a vast, flat,
featureless plain...
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...until suddenly,
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the landscape changes.
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Here, just 150 miles
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from the great cities
of the Pacific Northwest,
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a dramatic transformation
takes place,
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revealing a fractured,
broken seafloor...
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...brooding,
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menacing.
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O'DRISCOLL: One of the best
analogies I can think of
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is looking
at the, the front end of a car
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that's been
in a head-on collision,
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dented and corroded
and corrugated
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into this complex mess.
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NARRATOR: The scale of
this geological fender bender
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is truly epic.
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Colossal cliffs,
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almost twice the height
of the Grand Canyon...
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...some deep enough to hide
six Empire State Buildings
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stacked on top of each other,
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all of it stretching 700 miles
along the Cascadian coastline.
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This titanic rupture
in the earth's crust
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is what geologists call
a subduction zone.
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At the core of our planet
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is a boiling cauldron
of molten iron,
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surrounded
by a thick mantle of rock.
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That outer crust is divided
into huge tectonic plates
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that are constantly
in motion.
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When they collide,
they thrust mountains upwards
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and carve deep trenches
into the ocean floor
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as one plate drives the other
back inside the earth.
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If the plates lock together,
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tremendous pressure
begins to build.
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O'DRISCOLL:
Only in subduction zones
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where the plates
are compressing together
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and there's this lock
between the plates,
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that, those are
the only fault zones
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that have the potential
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to create magnitude
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9.0 and higher events.
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NARRATOR: But that's not all.
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Subduction zones,
because they are underwater,
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can generate not just
earthquakes, but huge tsunamis.
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Written history suggests
that Cascadia's subduction zone
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has been inactive
for centuries,
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but does written history
go back far enough?
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Is this monster really
as sleepy as it seems?
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(music)
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Scientists scour
the landscape around Cascadia
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in search of answers,
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and, in the banks
of coastal rivers like this,
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they find an alarming pattern.
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DAVID YAMAGUCHI: It's very much
like a chocolate cake.
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You slice a chocolate cake,
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and there's a layer
of brown frosting,
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and then, down below, there's
another layer of brown frosting,
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and the Washington coast
looks very much like that.
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NARRATOR:
But there's nothing sweet
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about these layers
of peat and sand.
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YAMAGUCHI:
Each of these buried soil layers
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on the Washington coast
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reflected times when the coast
had been jerked downwards
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by the occurrence
of an earthquake.
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NARRATOR:
In the layers of peat,
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David Yamaguchi
and geologist Brian Atwater
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unearth evidence
of seismic devastation
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stretching back
over thousands of years,
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quakes that scarred the entire
coastline of Cascadia.
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The question now is,
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when was the last one,
and how big was it?
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NARRATOR: The Copalis River,
Washington State.
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Scientist David Yamaguchi
is on a quest.
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He and his fellow scientists
already suspect
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that the 10 million inhabitants
of Cascadia
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are living
on a seismic time bomb,
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but when did it last go off,
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and how big was it
when it did?
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Three miles inland, he comes
across a haunting sight.
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(music)
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(music)
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This is what's left
of a once mighty forest
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of red cedar
and spruce trees,
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thousands of petrified corpses
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scattered
over hundreds of miles
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along Cascadia's coast.
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YAMAGUCHI: And the mystery here
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is what killed the trees,
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and when did they die?
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(chainsaw)
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NARRATOR:
Sampling dozens of the trees,
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Yamaguchi analyzes
their age rings,
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and what he finds
is a new mystery.
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YAMAGUCHI: The trees were fine
and healthy in 1699.
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Then, the following summer,
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the trees that, that would
normally have produced
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another annual ring
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were nearly all dead.
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NARRATOR: What happened
to kill an entire forest
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in one instant?
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Another scientist
thinks the answer could lie
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deep in the geological
car crash
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of the Cascadia
subduction zone,
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just 100 miles away.
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(music)
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Chris Goldfinger is an
underwater earthquake detective
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seeking evidence
in core samples
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taken from deep
under the seafloor.
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Studying the layers of sediment
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reveals when and where
earthquakes struck in the past
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and how powerful they were.
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CHRIS GOLDFINGER: Sediment
settles to the seafloor,
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but it got there somehow,
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from some storm, an earthquake,
and even a volcanic eruption
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will leave a deposit
on the seafloor,
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and so it's just
a very precise,
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three-dimensional
tape recorder,
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just recording
every single thing that happens.
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Well, this is a core sample
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from, from the seafloor
off of Cascadia,
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and it's about
2,000 years' worth of sediment.
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NARRATOR:
In the middle of the sample,
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dating to roughly
300 years ago,
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Goldfinger finds the classic
signs of a large earthquake.
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GOLDFINGER: Well, in fact,
the shells like this
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turn out to be
shallow-water fossils,
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but this is a deep-water core,
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so these things
were carried down
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from shallow water
to deep water.
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What this points to is
a fairly dramatic kind of event.
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(rumbling)
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NARRATOR: That dramatic event
was an earthquake
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that triggered
a vast underwater landslide.
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And it all happened
around the same time
258
00:14:50,072 --> 00:14:54,208
that Yamaguchi's trees died.
259
00:14:54,210 --> 00:14:57,946
Next, he compares core samples
of the same date,
260
00:14:57,948 --> 00:14:59,948
taken along the 700 miles
261
00:14:59,950 --> 00:15:03,150
of the Cascadia
subduction zone.
262
00:15:03,152 --> 00:15:07,321
Core after core reveals
the same disturbed layer,
263
00:15:07,323 --> 00:15:10,825
all occurring
at the exact same time.
264
00:15:14,164 --> 00:15:18,766
This is evidence
of no ordinary earthquake,
265
00:15:18,768 --> 00:15:21,436
but a monster.
266
00:15:21,438 --> 00:15:24,772
GOLDFINGER: Cascadia, through
the study of past earthquakes,
267
00:15:24,774 --> 00:15:26,907
has shown that it's capable
of generating earthquakes
268
00:15:26,909 --> 00:15:31,646
that run the full length,
roughly 1,000 kilometers.
269
00:15:31,648 --> 00:15:35,315
NARRATOR: In 1700,
the Cascadia subduction zone
270
00:15:35,317 --> 00:15:39,520
generated a cataclysmic quake
along its entire length,
271
00:15:39,522 --> 00:15:42,656
with a magnitude that
Goldfinger and other scientists
272
00:15:42,658 --> 00:15:45,893
calculate as level 8.
273
00:15:48,264 --> 00:15:50,531
But that's not all.
274
00:15:50,533 --> 00:15:55,302
This was more
than just an earthquake.
275
00:15:55,304 --> 00:16:00,074
Japan has a long history
of earthquakes and tsunamis,
276
00:16:00,076 --> 00:16:04,879
with written evidence
going back 1,400 years.
277
00:16:04,881 --> 00:16:07,081
Among these historical records,
278
00:16:07,083 --> 00:16:10,418
in accounts written
by samurai and merchants,
279
00:16:10,420 --> 00:16:14,555
researchers uncover reports
of a 16-foot tsunami
280
00:16:14,557 --> 00:16:18,426
that arrives
from far out in the Pacific,
281
00:16:18,428 --> 00:16:20,762
swamping the eastern coast.
282
00:16:20,764 --> 00:16:22,430
It destroys houses
283
00:16:22,432 --> 00:16:25,566
and causes villagers
to flee to higher ground.
284
00:16:27,237 --> 00:16:31,339
The date of these reports?
285
00:16:31,341 --> 00:16:34,241
1700.
286
00:16:34,243 --> 00:16:38,312
YAMAGUCHI: They propose that
our earthquake was magnitude 9.
287
00:16:38,314 --> 00:16:40,381
A magnitude 8
was not big enough
288
00:16:40,383 --> 00:16:43,117
to produce a wave
that's that wide.
289
00:16:43,119 --> 00:16:44,384
In addition,
290
00:16:44,386 --> 00:16:47,188
based on the arrival times
of the waves in Japan,
291
00:16:47,190 --> 00:16:48,522
the earthquake
must have happened here
292
00:16:48,524 --> 00:16:51,826
on January 26, 1700
293
00:16:51,828 --> 00:16:53,894
at 9:00 at night,
294
00:16:53,896 --> 00:16:55,029
yes, local time.
295
00:16:56,999 --> 00:17:00,267
NARRATOR: The Cascadia
mega-quake was so powerful
296
00:17:00,269 --> 00:17:01,936
that it generated a tsunami
297
00:17:01,938 --> 00:17:06,774
that hit Japan,
4,500 miles away.
298
00:17:09,479 --> 00:17:10,878
Using the combined insights
299
00:17:10,880 --> 00:17:14,215
of experts from both sides
of the Pacific
300
00:17:14,217 --> 00:17:16,617
and the extraordinary
drained landscape
301
00:17:16,619 --> 00:17:19,387
of the subduction zone,
302
00:17:19,389 --> 00:17:21,556
it's now possible to visualize
303
00:17:21,558 --> 00:17:26,427
the titanic events
of January 1700
304
00:17:26,429 --> 00:17:30,030
and its deadly trail
of destruction.
305
00:17:30,032 --> 00:17:34,168
(music)
306
00:17:34,170 --> 00:17:35,402
GOLDFINGER:
The entire subduction zone
307
00:17:35,404 --> 00:17:37,805
shakes very hard.
308
00:17:40,509 --> 00:17:43,778
The ground motion is big,
and it's over a big area,
309
00:17:43,780 --> 00:17:45,980
so it's gonna shake
a lot of sediment loose.
310
00:17:45,982 --> 00:17:50,918
(music)
311
00:17:50,920 --> 00:17:52,786
There are gonna be
hundreds of landslides.
312
00:17:52,788 --> 00:17:54,822
They're gonna all
come tumbling down the slope
313
00:17:54,824 --> 00:17:56,524
and leave a deposit.
314
00:17:56,526 --> 00:18:02,463
(music)
315
00:18:02,465 --> 00:18:04,298
(music)
316
00:18:06,603 --> 00:18:09,737
NARRATOR: The quake
also triggers a huge tsunami
317
00:18:09,739 --> 00:18:14,475
which smashes
into the coast of Cascadia,
318
00:18:14,477 --> 00:18:17,779
flooding the land
with seawater,
319
00:18:17,781 --> 00:18:20,347
including the red cedar forest
320
00:18:20,349 --> 00:18:23,217
and everything else
in its path.
321
00:18:27,557 --> 00:18:29,623
Although
there is no written history
322
00:18:29,625 --> 00:18:33,527
of the 1700 earthquake
and tsunami in Cascadia,
323
00:18:33,529 --> 00:18:35,296
native peoples of this region
324
00:18:35,298 --> 00:18:40,000
do hold haunting memories
of these terrible events.
325
00:18:40,002 --> 00:18:42,302
GOLDFINGER: The First Nation
peoples had oral histories
326
00:18:42,304 --> 00:18:45,873
about the great battle
of Thunderbird and Whale
327
00:18:45,875 --> 00:18:47,775
that had a lot of shaking
of the ground,
328
00:18:47,777 --> 00:18:50,244
washing away of villages.
329
00:18:50,246 --> 00:18:51,779
MAN: The Great Thunderbird
330
00:18:51,781 --> 00:18:55,082
finally carried the Whale
to its nest.
331
00:18:55,084 --> 00:18:58,085
There were a shaking,
jumping up,
332
00:18:58,087 --> 00:19:00,788
and trembling
of the earth beneath
333
00:19:00,790 --> 00:19:03,724
and the rolling up
of the great waters.
334
00:19:03,726 --> 00:19:05,326
GOLDFINGER: So, once
these stories came to light,
335
00:19:05,328 --> 00:19:07,461
the Native Americans
essentially said,
336
00:19:07,463 --> 00:19:11,332
'Why didn't you just ask us?
We knew all about that.'
337
00:19:11,334 --> 00:19:12,800
The story had a moral,
and the moral was,
338
00:19:12,802 --> 00:19:15,369
don't build your village
too close to the beach.
339
00:19:18,741 --> 00:19:24,211
NARRATOR: But evidently,
no one was listening.
340
00:19:24,213 --> 00:19:28,950
Today, 10 million people live
along the coast of Cascadia
341
00:19:28,952 --> 00:19:33,921
and in the cities of Seattle,
Portland, and Vancouver,
342
00:19:33,923 --> 00:19:36,890
and the question is
how likely is it
343
00:19:36,892 --> 00:19:40,227
that the monster
will roar again?
344
00:19:40,229 --> 00:19:42,096
THOMAS HEATON: It's not at all
like a clock,
345
00:19:42,098 --> 00:19:43,497
but the average time
346
00:19:43,499 --> 00:19:44,765
between the earthquakes
347
00:19:44,767 --> 00:19:47,869
is on the order of 400 years.
348
00:19:47,871 --> 00:19:50,103
NARRATOR:
If the Cascadia subduction zone
349
00:19:50,105 --> 00:19:52,973
repeats its 400-year cycle,
350
00:19:52,975 --> 00:19:56,911
then its next mega-quake
could be imminent.
351
00:19:56,913 --> 00:19:58,645
O'DRISCOLL:
We know the strain is building,
352
00:19:58,647 --> 00:20:00,581
and we know, one day,
it's gonna be released,
353
00:20:00,583 --> 00:20:02,516
and that could happen any day.
354
00:20:02,518 --> 00:20:06,520
NARRATOR: So, what will happen
when the monster wakes?
355
00:20:06,522 --> 00:20:08,089
GOLDFINGER:
In a subduction zone earthquake,
356
00:20:08,091 --> 00:20:11,692
energy is stretched out,
not 10 seconds or 20 seconds,
357
00:20:11,694 --> 00:20:13,194
more like three minutes.
358
00:20:13,196 --> 00:20:14,194
HEATON: The shaking's not
359
00:20:14,196 --> 00:20:16,130
incredibly violent,
360
00:20:16,132 --> 00:20:17,465
but it lasts for a long time,
361
00:20:17,467 --> 00:20:19,266
and it's a very long,
362
00:20:19,268 --> 00:20:21,168
rolling motion.
363
00:20:21,170 --> 00:20:24,672
For tall buildings,
that's not good news.
364
00:20:28,277 --> 00:20:30,144
NARRATOR:
With buildings collapsing
365
00:20:30,146 --> 00:20:32,680
and infrastructures shattered,
366
00:20:32,682 --> 00:20:35,182
it will be hard
for the population to escape
367
00:20:35,184 --> 00:20:38,085
from the coastal area,
368
00:20:38,087 --> 00:20:42,823
the worst place to be trapped.
369
00:20:42,825 --> 00:20:44,959
HEATON: You know that
if you get a giant earthquake,
370
00:20:44,961 --> 00:20:46,160
you'd better assume you're
371
00:20:46,162 --> 00:20:47,762
about to get a giant tsunami.
372
00:20:50,599 --> 00:20:53,734
NARRATOR: The tectonic plates'
sudden release of pressure
373
00:20:53,736 --> 00:20:58,439
forces a massive swell
in the ocean above.
374
00:20:58,441 --> 00:21:00,708
GOLDFINGER:
So, the wave height, initially,
375
00:21:00,710 --> 00:21:02,509
might only be
a couple of meters,
376
00:21:02,511 --> 00:21:05,012
but it might be
200 kilometers long,
377
00:21:05,014 --> 00:21:07,247
and it heads out
at the deep-water wave speed,
378
00:21:07,249 --> 00:21:09,316
which is very fast,
so it's jetliner speed,
379
00:21:09,318 --> 00:21:11,252
500 or 600 miles an hour.
380
00:21:13,122 --> 00:21:16,090
Everything we've seen in Japan,
we can expect, basically,
381
00:21:16,092 --> 00:21:17,925
the exact same thing
in Cascadia.
382
00:21:17,927 --> 00:21:21,929
(man on loudspeaker)
383
00:21:21,931 --> 00:21:25,065
HEATON:
30 meters of water rushing in
384
00:21:25,067 --> 00:21:28,869
at 10 meters a second
kind of velocities...
385
00:21:31,273 --> 00:21:32,206
...it just scours
386
00:21:32,208 --> 00:21:33,541
everything off the,
387
00:21:33,543 --> 00:21:35,343
off the surface of the earth.
388
00:21:36,446 --> 00:21:38,045
NARRATOR: Within 20 minutes,
389
00:21:38,047 --> 00:21:41,349
the tsunami will approach
the coast of Cascadia.
390
00:21:41,351 --> 00:21:42,817
GOLDFINGER: When that wave
starts feeling bottom,
391
00:21:42,819 --> 00:21:43,950
like all other waves do,
392
00:21:43,952 --> 00:21:45,920
it gets compressed
from 200 kilometers
393
00:21:45,922 --> 00:21:48,188
down to a kilometer or two.
394
00:21:48,190 --> 00:21:49,523
HEATON: It's like an enormous
395
00:21:49,525 --> 00:21:52,259
tide happening very quickly.
396
00:21:52,261 --> 00:21:57,298
(music)
397
00:22:01,504 --> 00:22:04,238
NARRATOR: A Cascadia mega-quake
is predicted to be
398
00:22:04,240 --> 00:22:08,976
North America's
worst ever natural disaster.
399
00:22:08,978 --> 00:22:11,912
O'DRISCOLL: The fatalities
could be fairly large.
400
00:22:11,914 --> 00:22:14,781
We're looking at, at a few tens
of thousands of people,
401
00:22:14,783 --> 00:22:16,083
at least, on our coastline.
402
00:22:16,085 --> 00:22:18,118
We know the strain is building,
403
00:22:18,120 --> 00:22:19,453
and that's quite harrowing
to know
404
00:22:19,455 --> 00:22:23,591
that we could have the big one
right now, as we speak.
405
00:22:23,593 --> 00:22:26,793
NARRATOR: But Cascadia is not
the only populated region
406
00:22:26,795 --> 00:22:30,598
in the Ring of Fire
danger zone.
407
00:22:30,600 --> 00:22:34,402
As the waters of the Pacific
continue to drain away,
408
00:22:34,404 --> 00:22:37,471
they reveal
another sleeping giant
409
00:22:37,473 --> 00:22:40,207
near the east coast
of New Zealand,
410
00:22:40,209 --> 00:22:44,478
where scientists discover
traces of an epic seismic event
411
00:22:44,480 --> 00:22:47,547
that reshaped
the Southern Hemisphere
412
00:22:47,549 --> 00:22:52,486
and ask,
when will it happen again?
413
00:22:59,595 --> 00:23:01,462
NARRATOR:
The islands of New Zealand
414
00:23:01,464 --> 00:23:05,198
lie directly
on the Ring of Fire.
415
00:23:05,200 --> 00:23:10,270
Small earthquakes shake
the ground here every week.
416
00:23:10,272 --> 00:23:14,007
(sirens)
417
00:23:14,009 --> 00:23:15,676
(screaming)
418
00:23:15,678 --> 00:23:19,814
In 2011, the country's second
largest city, Christchurch,
419
00:23:19,816 --> 00:23:24,385
is devastated
by a magnitude 6.3 quake...
420
00:23:24,387 --> 00:23:26,753
WOMAN: I can confirm
that there have been deaths.
421
00:23:26,755 --> 00:23:29,490
NARRATOR:
...killing 185 people.
422
00:23:29,492 --> 00:23:31,192
(siren)
423
00:23:37,800 --> 00:23:40,100
100 miles from Christchurch
424
00:23:40,102 --> 00:23:42,203
is the town of Kaikoura.
425
00:23:44,040 --> 00:23:45,172
MAN: Kaikoura, welcome aboard.
426
00:23:45,174 --> 00:23:46,439
WOMAN: Thank you.
427
00:23:46,441 --> 00:23:48,142
NARRATOR:
A peaceful holiday resort
428
00:23:48,144 --> 00:23:50,177
that's popular
with nature lovers.
429
00:23:50,179 --> 00:23:51,511
MAN: Keep looking out there.
430
00:23:51,513 --> 00:23:54,048
You'll see them just
out of the front of us there.
431
00:23:54,050 --> 00:23:56,717
NARRATOR:
Its deep, nutrient-rich waters
432
00:23:56,719 --> 00:23:59,252
entice whales
close to the shore.
433
00:23:59,254 --> 00:24:02,590
MAN: This is
the beautiful humpback,
434
00:24:02,592 --> 00:24:06,594
and it is awesome to see humps.
435
00:24:06,596 --> 00:24:07,794
NARRATOR:
While these leviathans
436
00:24:07,796 --> 00:24:12,333
are Kaikoura's
star attraction,
437
00:24:12,335 --> 00:24:16,537
geologists now come here
for a very different reason.
438
00:24:18,474 --> 00:24:21,474
New Zealand's geologists
constantly monitor
439
00:24:21,476 --> 00:24:24,278
the threat posed
by the faults and fissures
440
00:24:24,280 --> 00:24:26,280
that run under the islands,
441
00:24:26,282 --> 00:24:30,150
trying to discover where the
next big quake might strike.
442
00:24:32,288 --> 00:24:34,154
Ground surveys can help,
443
00:24:34,156 --> 00:24:36,357
but investigating
under the waves
444
00:24:36,359 --> 00:24:39,093
has always been a challenge,
445
00:24:39,095 --> 00:24:40,760
until now,
446
00:24:40,762 --> 00:24:44,097
because the latest
multiple-beam sonar technology
447
00:24:44,099 --> 00:24:47,668
is opening up a hidden world.
448
00:24:47,670 --> 00:24:50,838
JOSHU MOUNTJOY: It's multiple
beams of sound energy
449
00:24:50,840 --> 00:24:53,173
being released from
the instrument on the vessel,
450
00:24:53,175 --> 00:24:56,443
and we time how long it takes
for that beam to come back.
451
00:24:56,445 --> 00:24:57,845
(beeping)
452
00:24:57,847 --> 00:24:59,780
We do what we call
mowing the grass,
453
00:24:59,782 --> 00:25:02,449
and we're just collecting
this continuous image
454
00:25:02,451 --> 00:25:05,686
of what the shape
of the seabed is.
455
00:25:05,688 --> 00:25:08,455
NARRATOR: And the shape
of the seabed near Kaikoura
456
00:25:08,457 --> 00:25:12,660
is not what they expected.
457
00:25:12,662 --> 00:25:15,929
As the data comes in,
it slowly reveals
458
00:25:15,931 --> 00:25:19,967
something astonishing
and potentially lethal.
459
00:25:23,139 --> 00:25:26,406
Pulling the plug
on the Pacific Ocean
460
00:25:26,408 --> 00:25:28,776
exposes the remarkable sight.
461
00:25:33,883 --> 00:25:37,684
Just a half mile
from the town of Kaikoura,
462
00:25:37,686 --> 00:25:40,521
as the water drains away,
463
00:25:40,523 --> 00:25:45,526
it reveals the plunging walls
of a vast, undersea chasm...
464
00:25:48,431 --> 00:25:52,532
...the Kaikoura Canyon.
465
00:25:52,534 --> 00:25:53,500
MOUNTJOY: The Kaikoura Canyon,
466
00:25:53,502 --> 00:25:55,369
it comes within
a really short distance
467
00:25:55,371 --> 00:25:59,172
of the coastline out here,
less than a kilometer,
468
00:25:59,174 --> 00:26:01,975
and, from there,
it drops down at 30, 40 degrees
469
00:26:01,977 --> 00:26:05,178
down to about 600 meters
water depth.
470
00:26:05,180 --> 00:26:10,017
Then it carries on down to
about 2,000 meters water depth.
471
00:26:10,019 --> 00:26:12,853
NARRATOR:
Stretching for over 37 miles,
472
00:26:12,855 --> 00:26:14,454
the canyon forms part
473
00:26:14,456 --> 00:26:17,658
of one of the deepest
sea channels in the world.
474
00:26:19,862 --> 00:26:25,666
The walls nose-dive
over 6,000 feet--
475
00:26:25,668 --> 00:26:27,701
the depth of the Grand Canyon.
476
00:26:32,541 --> 00:26:35,542
Geologists wonder at
the immense geological forces
477
00:26:35,544 --> 00:26:38,545
involved to create
such a huge canyon...
478
00:26:41,617 --> 00:26:43,917
...but also ask themselves,
479
00:26:43,919 --> 00:26:48,255
does it pose a threat to those
living on the nearby coast?
480
00:26:52,828 --> 00:26:54,894
Geologists know that landslides
481
00:26:54,896 --> 00:26:57,798
triggered by earthquakes
in underwater canyons
482
00:26:57,800 --> 00:27:01,235
can generate lethal tsunamis.
483
00:27:01,237 --> 00:27:05,038
Could the Kaikoura Canyon
do the same?
484
00:27:05,040 --> 00:27:09,509
On board the research ship
Tangaroa, they investigate.
485
00:27:09,511 --> 00:27:10,744
MAN: Let's try it again, Mitch.
486
00:27:10,746 --> 00:27:13,647
(radio chatter)
487
00:27:13,649 --> 00:27:16,650
NARRATOR: Using Perspex tubes,
they gather evidence
488
00:27:16,652 --> 00:27:21,255
from the sedimentary layers
on the canyon's floor,
489
00:27:21,257 --> 00:27:25,125
looking for signs of seismic
activity in the past.
490
00:27:27,229 --> 00:27:28,195
MAN: Yep.
491
00:27:30,298 --> 00:27:32,466
MAN: This is core two.
492
00:27:32,468 --> 00:27:36,203
NARRATOR: But then, just
as they're studying history,
493
00:27:36,205 --> 00:27:38,906
they get the chance
to make some.
494
00:27:41,944 --> 00:27:47,214
Midnight, November 14, 2016.
495
00:27:47,216 --> 00:27:48,682
(static)
496
00:27:48,684 --> 00:27:52,085
WOMAN: And we are undergoing
a fairly dense earthquake
497
00:27:52,087 --> 00:27:53,687
at the moment,
498
00:27:53,689 --> 00:27:55,021
so, please,
just get to somewhere
499
00:27:55,023 --> 00:27:59,426
where you are safely
under some protection.
500
00:27:59,428 --> 00:28:01,328
I can honestly say,
I doubt that I'll be able
501
00:28:01,330 --> 00:28:04,631
to stay in the chair
for much longer.
502
00:28:04,633 --> 00:28:07,234
(alarm)
503
00:28:11,506 --> 00:28:16,110
NARRATOR: The 7.8 magnitude
quake rips apart the earth,
504
00:28:16,112 --> 00:28:21,682
creating giant crevices and
billions of dollars of damage.
505
00:28:21,684 --> 00:28:27,988
Geologist Joshu Mountjoy has
never seen anything like it.
506
00:28:27,990 --> 00:28:29,723
MOUNTJOY: The key thing was
that it just covered
507
00:28:29,725 --> 00:28:31,592
such a large geographic area,
508
00:28:31,594 --> 00:28:33,660
and it was right
on our coastline.
509
00:28:33,662 --> 00:28:36,530
NARRATOR: The quake rattles
the ground for two minutes,
510
00:28:36,532 --> 00:28:38,665
causing thousands
of landslides
511
00:28:38,667 --> 00:28:42,135
across 3,800 square miles.
512
00:28:42,137 --> 00:28:45,606
Just north of Kaikoura
is the biggest.
513
00:28:45,608 --> 00:28:50,377
800 million cubic feet
has shaken to the ground,
514
00:28:50,379 --> 00:28:55,348
exposing a virgin cliff face
almost a mile wide.
515
00:28:55,350 --> 00:28:57,217
MOUNTJOY: Grass and tussock
we're standing on
516
00:28:57,219 --> 00:28:59,620
was connected to
that grass and tussock up there,
517
00:28:59,622 --> 00:29:01,955
and then the whole block
slid right down
518
00:29:01,957 --> 00:29:04,357
to bring it down
to where it is now,
519
00:29:04,359 --> 00:29:06,360
so this has happened
during the earthquake.
520
00:29:06,362 --> 00:29:08,662
We call that co-seismic,
and there's actually
521
00:29:08,664 --> 00:29:10,096
a fault line
running through here
522
00:29:10,098 --> 00:29:12,733
that runs
right down to the coastline.
523
00:29:12,735 --> 00:29:14,201
NARRATOR:
The shaking is so severe
524
00:29:14,203 --> 00:29:16,970
that it thrusts the foreshore
of Kaikoura
525
00:29:16,972 --> 00:29:21,441
upwards by three feet
in just one second.
526
00:29:21,443 --> 00:29:22,376
MOUNTJOY: We're looking at here,
527
00:29:22,378 --> 00:29:23,577
we can see
a whole a lot of seaweed
528
00:29:23,579 --> 00:29:25,845
that's stranded
above the tide line.
529
00:29:25,847 --> 00:29:26,913
Before the earthquake,
530
00:29:26,915 --> 00:29:30,650
that would have been
down below the sea level.
531
00:29:30,652 --> 00:29:33,319
NARRATOR: But Joshu Mountjoy
isn't only interested
532
00:29:33,321 --> 00:29:37,057
in how the earthquake
tears apart the land.
533
00:29:37,059 --> 00:29:39,526
As soon
as the earthquake begins,
534
00:29:39,528 --> 00:29:41,461
he wants to know
the effect it's having
535
00:29:41,463 --> 00:29:43,997
deep under the ocean,
536
00:29:43,999 --> 00:29:48,067
in the newly scanned
Kaikoura Canyon.
537
00:29:48,069 --> 00:29:52,205
Mountjoy makes contact with
the research ship Tangaroa,
538
00:29:52,207 --> 00:29:55,675
which is mapping
the very far end of the canyon.
539
00:29:55,677 --> 00:29:57,344
MOUNTJOY: We requested
that they divert their energy
540
00:29:57,346 --> 00:30:00,547
to focus on doing
some earthquake response.
541
00:30:00,549 --> 00:30:03,883
NARRATOR: That response is to
immediately gather core samples
542
00:30:03,885 --> 00:30:07,754
from the floor of the canyon
before the dust has settled.
543
00:30:07,756 --> 00:30:08,922
ALAN ORPIN:
So, we really had
544
00:30:08,924 --> 00:30:11,758
an unprecedented opportunity
to assist.
545
00:30:11,760 --> 00:30:14,561
Well, what, what is the
aftermath of a major earthquake?
546
00:30:14,563 --> 00:30:16,597
NARRATOR:
If the crew responds in time,
547
00:30:16,599 --> 00:30:19,533
they can achieve a world first,
548
00:30:19,535 --> 00:30:22,502
recording the impact
of an earthquake
549
00:30:22,504 --> 00:30:26,240
in a deep-sea canyon
as it happens.
550
00:30:29,979 --> 00:30:32,179
NARRATOR: Within minutes
of the earthquake,
551
00:30:32,181 --> 00:30:37,484
the crew retrieves precious
core samples from the seafloor.
552
00:30:37,486 --> 00:30:39,653
MOUNTJOY: They collected
the sedimentary deposit
553
00:30:39,655 --> 00:30:42,055
that had only just happened,
so they were boring it
554
00:30:42,057 --> 00:30:45,058
while it was probably still
settling out of the ocean.
555
00:30:45,060 --> 00:30:48,461
NARRATOR: And what marine
geologist Alan Orpin discovers
556
00:30:48,463 --> 00:30:51,464
is intriguing.
557
00:30:51,466 --> 00:30:53,800
ORPIN: What we found was
a very soupy, fluidized mud
558
00:30:53,802 --> 00:30:56,803
that was lying
on the seabed.
559
00:30:56,805 --> 00:30:57,738
As we moved south,
560
00:30:57,740 --> 00:31:00,006
what we found
was compelling evidence
561
00:31:00,008 --> 00:31:03,777
of core after core
for a thickness of material
562
00:31:03,779 --> 00:31:05,679
that had spilled down
through the channel.
563
00:31:05,681 --> 00:31:07,613
NARRATOR:
The more samples they take,
564
00:31:07,615 --> 00:31:10,017
the clearer
the picture becomes.
565
00:31:10,019 --> 00:31:13,286
The shaking of the quake
has created a secondary
566
00:31:13,288 --> 00:31:17,291
and truly spectacular
undersea upheaval.
567
00:31:17,293 --> 00:31:19,592
MOUNTJOY: No one's ever
been able to observe one
568
00:31:19,594 --> 00:31:23,496
of these huge landscape
scale canyon-flushing events
569
00:31:23,498 --> 00:31:25,365
to show exactly
what effect it had
570
00:31:25,367 --> 00:31:27,167
on the canyon itself.
571
00:31:27,169 --> 00:31:31,505
(music)
572
00:31:31,507 --> 00:31:32,773
NARRATOR: Using the data
573
00:31:32,775 --> 00:31:34,975
gathered by the crew
of Tangaroa
574
00:31:34,977 --> 00:31:37,910
and the remarkable
drained seascape,
575
00:31:37,912 --> 00:31:39,980
the impact
of a large earthquake
576
00:31:39,982 --> 00:31:42,782
on a gigantic underwater canyon
577
00:31:42,784 --> 00:31:48,522
can now be visualized
for the very first time.
578
00:31:48,524 --> 00:31:53,393
The seabed shudders ominously
as huge tectonic forces
579
00:31:53,395 --> 00:31:55,395
power through
the earth's crust.
580
00:31:55,397 --> 00:31:57,464
(rumbling)
581
00:31:57,466 --> 00:32:01,802
This dislodges
a top layer of sediment,
582
00:32:01,804 --> 00:32:06,406
becoming a gigantic
canyon-flushing landslide.
583
00:32:06,408 --> 00:32:10,877
(rumbling)
584
00:32:10,879 --> 00:32:14,814
(music)
585
00:32:14,816 --> 00:32:17,918
Rock and sediment
tumble down the steep walls.
586
00:32:22,091 --> 00:32:27,227
850 million tons of debris
roars through the canyon,
587
00:32:27,229 --> 00:32:32,165
gouging 160 feet
out of the floor.
588
00:32:32,167 --> 00:32:34,668
MOUNTJOY: There's really like
a powder snow avalanche.
589
00:32:36,838 --> 00:32:39,573
The front of it would have
a huge amount of energy
590
00:32:39,575 --> 00:32:41,707
moving at about
70 kilometers an hour
591
00:32:41,709 --> 00:32:43,777
and maybe 400 meters high.
592
00:32:47,649 --> 00:32:49,749
It's spreading
tens of kilometers
593
00:32:49,751 --> 00:32:52,652
across the ocean floor.
594
00:32:52,654 --> 00:32:56,456
It's just gonna take over
everything that's down there.
595
00:32:56,458 --> 00:32:59,326
NARRATOR: The landslide travels
with such velocity,
596
00:32:59,328 --> 00:33:02,395
it carves a path
across the seafloor
597
00:33:02,397 --> 00:33:07,034
for an astonishing 435 miles.
598
00:33:12,941 --> 00:33:16,609
A landslide of this ferocity
has the potential
599
00:33:16,611 --> 00:33:21,882
to generate a tsunami
that could devastate Kaikoura.
600
00:33:21,884 --> 00:33:23,917
MOUNTJOY: When a landslide
creates a tsunami,
601
00:33:23,919 --> 00:33:27,420
you need a large chunk
of material to slide downslope,
602
00:33:27,422 --> 00:33:29,755
and what happens is it's
coupled to the water above it
603
00:33:29,757 --> 00:33:31,558
and actually
pulls it down with it,
604
00:33:31,560 --> 00:33:32,892
and then,
as that water rebounds,
605
00:33:32,894 --> 00:33:35,728
then you create your wave.
606
00:33:35,730 --> 00:33:38,432
NARRATOR:
This time, Kaikoura is lucky.
607
00:33:38,434 --> 00:33:42,301
No large objects
fall off the canyon rim.
608
00:33:42,303 --> 00:33:45,572
Next time, the town may not
be so fortunate.
609
00:33:48,377 --> 00:33:53,580
And the dramatic events of 2016
draw the geologists' attention
610
00:33:53,582 --> 00:33:57,050
to an even bigger
tsunami threat nearby.
611
00:33:59,121 --> 00:34:01,387
By continuing
to drain the ocean
612
00:34:01,389 --> 00:34:03,990
off the northeast coast
of New Zealand,
613
00:34:03,992 --> 00:34:07,327
we can see the reason
for their fear.
614
00:34:07,329 --> 00:34:09,963
Lurking just north
of the canyon
615
00:34:09,965 --> 00:34:11,197
and frighteningly close
616
00:34:11,199 --> 00:34:15,201
to the New Zealand capital
of Wellington--
617
00:34:15,203 --> 00:34:18,805
the Hikurangi subduction zone,
618
00:34:18,807 --> 00:34:23,910
2,174 miles
of seismic trouble.
619
00:34:27,416 --> 00:34:30,950
Geologists recently learned
that stress has been building
620
00:34:30,952 --> 00:34:36,423
at its southern end
for hundreds of years,
621
00:34:36,425 --> 00:34:39,492
and they believe
that the 2016 earthquake
622
00:34:39,494 --> 00:34:42,829
has ratcheted the pressure
up even further.
623
00:34:46,234 --> 00:34:48,368
Understanding
what's happening here
624
00:34:48,370 --> 00:34:52,872
has become
an international priority.
625
00:34:52,874 --> 00:34:55,976
100 ocean floor
seismic measuring devices
626
00:34:55,978 --> 00:35:01,314
and support scientists
recently arrived from Japan.
627
00:35:01,316 --> 00:35:04,918
They're here to monitor and
record the mounting stresses
628
00:35:04,920 --> 00:35:10,123
in the hope of discovering
the true danger of Hikurangi.
629
00:35:10,125 --> 00:35:15,061
(music)
630
00:35:15,063 --> 00:35:16,663
Geologists delve deep
631
00:35:16,665 --> 00:35:19,733
into the subduction zone's
tectonic past.
632
00:35:22,604 --> 00:35:26,406
And their results
are astounding.
633
00:35:26,408 --> 00:35:30,477
It hasn't fractured recently,
but deep in its past,
634
00:35:30,479 --> 00:35:35,315
it produced something bigger
than anyone had imagined.
635
00:35:35,317 --> 00:35:38,284
Now, using
the geologists' data,
636
00:35:38,286 --> 00:35:42,222
it's possible to reconstruct,
for the first time,
637
00:35:42,224 --> 00:35:47,760
a tectonic event
that reshaped a hemisphere--
638
00:35:47,762 --> 00:35:51,297
the Ruatoria avalanche.
639
00:35:51,299 --> 00:35:54,634
Just 200 miles from
what today is New Zealand's
640
00:35:54,636 --> 00:35:57,837
bustling capital, Wellington,
641
00:35:57,839 --> 00:36:00,974
the epicenter of one
of the biggest seismic events
642
00:36:00,976 --> 00:36:03,509
in the history of the earth.
643
00:36:03,511 --> 00:36:05,378
(rumbling)
644
00:36:05,380 --> 00:36:09,649
170,000 years ago,
the Australian plate
645
00:36:09,651 --> 00:36:12,652
is bearing down
on its Pacific neighbor,
646
00:36:12,654 --> 00:36:15,421
grinding down
everything in its path.
647
00:36:15,423 --> 00:36:18,257
Even a towering
volcanic cone
648
00:36:18,259 --> 00:36:20,594
six times the volume
of Mount Fuji
649
00:36:20,596 --> 00:36:23,163
becomes collateral damage.
650
00:36:26,201 --> 00:36:28,535
The resulting seismic shock
651
00:36:28,537 --> 00:36:31,004
triggers
an underwater landslide
652
00:36:31,006 --> 00:36:33,506
on a scale rarely seen.
653
00:36:33,508 --> 00:36:36,109
Moving a swath of broken rock,
654
00:36:36,111 --> 00:36:38,878
the equivalent
of three-quarters the size
655
00:36:38,880 --> 00:36:40,947
of the Grand Canyon.
656
00:36:40,949 --> 00:36:41,915
(rumbling)
657
00:36:41,917 --> 00:36:48,221
(rumbling)
658
00:36:48,223 --> 00:36:49,622
MOUNTJOY:
So, the Ruatoria avalanche
659
00:36:49,624 --> 00:36:51,891
is the second biggest submarine
landslide in the world.
660
00:36:51,893 --> 00:36:54,827
It's absolutely enormous,
3,000 cubic kilometers.
661
00:36:54,829 --> 00:36:56,896
And if you can try and visualize
a cubic kilometer,
662
00:36:56,898 --> 00:36:58,497
that's a kilometer high
663
00:36:58,499 --> 00:37:00,567
by a kilometer long
by a kilometer wide,
664
00:37:00,569 --> 00:37:02,502
3,000 of them.
665
00:37:02,504 --> 00:37:08,375
(music)
666
00:37:08,377 --> 00:37:11,377
NARRATOR: Nobody knows when
the Hikurangi subduction zone
667
00:37:11,379 --> 00:37:14,246
will facture again,
668
00:37:14,248 --> 00:37:15,682
but when it does,
669
00:37:15,684 --> 00:37:19,318
geologists estimate the tsunami
wave from the mega-quake
670
00:37:19,320 --> 00:37:21,388
will take only seven minutes
671
00:37:21,390 --> 00:37:24,991
to reach New Zealand's
capital city, Wellington,
672
00:37:24,993 --> 00:37:27,027
and its
half a million residents.
673
00:37:32,334 --> 00:37:33,933
And such a huge tsunami
674
00:37:33,935 --> 00:37:37,604
wouldn't only impact
New Zealand.
675
00:37:37,606 --> 00:37:39,939
There would be
an ocean-wide alert
676
00:37:39,941 --> 00:37:42,575
as the waves fan out
into the Pacific.
677
00:37:46,147 --> 00:37:49,315
(screaming)
678
00:37:49,317 --> 00:37:51,518
The last time a tsunami
on this scale
679
00:37:51,520 --> 00:37:53,986
hit the southern arc
of the Ring of Fire
680
00:37:53,988 --> 00:37:58,858
was December 26, 2004,
681
00:37:58,860 --> 00:38:02,662
devastating 14 countries
682
00:38:02,664 --> 00:38:08,234
and killing 230,000 people--
683
00:38:08,236 --> 00:38:12,405
a terrible reminder of the
power of the deadly Pacific.
684
00:38:16,211 --> 00:38:19,111
Continuing to drain away
the Pacific Ocean
685
00:38:19,113 --> 00:38:23,115
reveals a very different kind
of seismic threat
686
00:38:23,117 --> 00:38:27,153
5,000 miles away,
687
00:38:27,155 --> 00:38:31,123
right next to one of the most
densely populated cities
688
00:38:31,125 --> 00:38:32,992
on the planet.
689
00:38:32,994 --> 00:38:36,429
Just 44 miles
from bustling Tokyo,
690
00:38:36,431 --> 00:38:38,832
a mysterious underwater feature
691
00:38:38,834 --> 00:38:42,235
has scientists
on the edge of their seats.
692
00:38:46,475 --> 00:38:48,474
The island nation of Japan
693
00:38:48,476 --> 00:38:53,413
suffers from its position
on the Ring of Fire.
694
00:38:53,415 --> 00:38:55,748
The country accounts
for about 20 percent
695
00:38:55,750 --> 00:39:00,487
of the world's earthquakes
of magnitude 6 or greater.
696
00:39:00,489 --> 00:39:02,689
Its biggest city, Tokyo,
697
00:39:02,691 --> 00:39:05,291
has been hit
by nine mega-earthquakes
698
00:39:05,293 --> 00:39:09,162
in the past 95 years.
699
00:39:09,164 --> 00:39:12,898
But just 44 miles
off the city's shoreline,
700
00:39:12,900 --> 00:39:15,034
geologists
have recently discovered
701
00:39:15,036 --> 00:39:18,872
a new and very different
tectonic troublemaker.
702
00:39:25,847 --> 00:39:31,083
The first discovery is made
by scientist Ken Tani.
703
00:39:31,085 --> 00:39:32,585
He's heading out to test
704
00:39:32,587 --> 00:39:37,457
his new underwater remotely
operated vehicle, or ROV,
705
00:39:37,459 --> 00:39:40,460
in the waters
just off the island of Oshima,
706
00:39:40,462 --> 00:39:42,729
south of Tokyo Bay.
707
00:39:42,731 --> 00:39:47,266
Until now, the waters here have
been considered safe passage
708
00:39:47,268 --> 00:39:49,135
for one of the busiest
shipping lanes
709
00:39:49,137 --> 00:39:51,070
into the port of Tokyo,
710
00:39:51,072 --> 00:39:55,274
with 400 vessels
passing through here every day,
711
00:39:55,276 --> 00:39:58,144
but that is about to change.
712
00:40:05,353 --> 00:40:08,054
NARRATOR:
44 miles from Tokyo Bay,
713
00:40:08,056 --> 00:40:12,926
Ken Tani prepares an underwater
survey, using an ROV.
714
00:40:12,928 --> 00:40:16,595
(speaking Japanese)
715
00:40:16,597 --> 00:40:19,999
Passing over a rocky mound
on the seafloor,
716
00:40:20,001 --> 00:40:23,536
he discovers
something extraordinary,
717
00:40:23,538 --> 00:40:26,806
a seismic beast
that has lain hidden
718
00:40:26,808 --> 00:40:31,277
for hundreds of thousands
of years.
719
00:40:31,279 --> 00:40:36,215
Using Ken Tani's own data,
draining away the Pacific Ocean
720
00:40:36,217 --> 00:40:39,219
reveals what is lurking
below the waves.
721
00:40:47,495 --> 00:40:49,629
As the water recedes,
722
00:40:49,631 --> 00:40:54,767
it exposes
a large flat plateau.
723
00:40:54,769 --> 00:40:56,202
Near its center,
724
00:40:56,204 --> 00:40:59,272
what looks like an ordinary
hole in the seafloor.
725
00:41:02,010 --> 00:41:06,846
But on closer inspection,
the frightening truth emerges.
726
00:41:06,848 --> 00:41:10,550
It's the vent
of an undersea volcano.
727
00:41:12,854 --> 00:41:14,654
Thousands of years ago,
728
00:41:14,656 --> 00:41:17,123
it very likely
had a towering cone,
729
00:41:17,125 --> 00:41:20,727
but erosion and wave action
has worn it down,
730
00:41:20,729 --> 00:41:23,363
which is why
no one discovered it before.
731
00:41:25,667 --> 00:41:30,603
But is it as dormant
as it appears?
732
00:41:30,605 --> 00:41:34,040
Ken wastes no time
in exploring the crater.
733
00:41:34,042 --> 00:41:36,142
KEN TANI:
So, that's the sea surface.
734
00:41:36,144 --> 00:41:38,278
NARRATOR: Testing the water
temperature around the outlet
735
00:41:38,280 --> 00:41:40,680
with a submarine thermometer,
736
00:41:40,682 --> 00:41:44,117
and what he finds
surprises everyone.
737
00:42:02,871 --> 00:42:09,108
(music)
738
00:42:09,110 --> 00:42:11,644
NARRATOR:
The smoldering undersea volcano
739
00:42:11,646 --> 00:42:13,912
is named Oomurodashi,
740
00:42:13,914 --> 00:42:18,484
44 miles south of Tokyo,
741
00:42:18,486 --> 00:42:21,787
placing at risk the lives
of thousands of mariners
742
00:42:21,789 --> 00:42:23,556
in the shipping lanes above.
743
00:42:26,527 --> 00:42:31,330
In 1952, an underwater volcano
like Oomurodashi
744
00:42:31,332 --> 00:42:35,335
erupts 260 miles
south of Tokyo.
745
00:42:35,337 --> 00:42:38,537
Super-heated magma
reacts with water
746
00:42:38,539 --> 00:42:42,342
to produce what's called
a phreatomagmatic explosion,
747
00:42:42,344 --> 00:42:46,412
an underwater steam bomb.
748
00:42:46,414 --> 00:42:49,949
A nearby ship is engulfed
in the explosion,
749
00:42:49,951 --> 00:42:52,485
killing all 31 on board.
750
00:43:07,635 --> 00:43:09,635
NARRATOR:
A stirring volcanic giant
751
00:43:09,637 --> 00:43:12,972
is not just
a danger to shipping.
752
00:43:12,974 --> 00:43:16,208
A major eruption
could send tsunami waves
753
00:43:16,210 --> 00:43:21,347
racing towards Tokyo,
population 38 million.
754
00:43:29,524 --> 00:43:30,923
NARRATOR: Ken decides he needs
755
00:43:30,925 --> 00:43:33,660
to keep Oomurodashi
under surveillance.
756
00:43:35,797 --> 00:43:38,931
Nothing happens for five years.
757
00:43:38,933 --> 00:43:42,535
Then, when he returns
to gather fresh samples,
758
00:43:42,537 --> 00:43:46,372
Oomurodashi has another
unpleasant surprise for him.
759
00:43:48,643 --> 00:43:50,943
Returning
to the drained ocean floor
760
00:43:50,945 --> 00:43:54,680
reveals his next
shocking discovery.
761
00:43:54,682 --> 00:43:56,949
In addition to the crater,
762
00:43:56,951 --> 00:44:00,686
five more volcanic cones.
763
00:44:00,688 --> 00:44:05,491
That's five more possible
outlets for the volcano.
764
00:44:05,493 --> 00:44:10,563
Only one is currently active,
but all could become so.
765
00:44:10,565 --> 00:44:13,966
And if the volcano
keeps growing,
766
00:44:13,968 --> 00:44:17,369
Oomurodashi could become
an even greater threat
767
00:44:17,371 --> 00:44:19,305
by breaking the surface
768
00:44:19,307 --> 00:44:21,941
and spewing toxic ash
into the sky.
769
00:44:24,245 --> 00:44:29,182
Active volcanos can do this
astonishingly quickly.
770
00:44:29,184 --> 00:44:33,386
It took Nishinoshima,
Japan's latest volcanic island,
771
00:44:33,388 --> 00:44:34,987
just two years to grow
772
00:44:34,989 --> 00:44:39,992
from a flat-topped,
underwater summit
773
00:44:39,994 --> 00:44:45,064
to this tectonic monster,
774
00:44:45,066 --> 00:44:49,869
measuring one square mile
and 443 feet high.
775
00:44:51,672 --> 00:44:52,738
But Nishinoshima
776
00:44:52,740 --> 00:44:55,608
is nearly 600 miles from Tokyo.
777
00:44:55,610 --> 00:44:59,278
Oomurodashi is only 44.
778
00:45:00,381 --> 00:45:02,081
Once out of the water,
779
00:45:02,083 --> 00:45:04,350
any major eruption
of Oomurodashi
780
00:45:04,352 --> 00:45:09,555
could shower Tokyo
in choking volcanic ash.
781
00:45:09,557 --> 00:45:13,125
Despite the dangers,
Ken Tani and his team
782
00:45:13,127 --> 00:45:16,562
continue
to monitor Oomurodashi.
783
00:45:16,564 --> 00:45:19,865
Any increase
in the volcano's activity
784
00:45:19,867 --> 00:45:22,101
could signal
impending disaster
785
00:45:22,103 --> 00:45:26,572
for the thousands living
on nearby islands
786
00:45:26,574 --> 00:45:30,643
and threaten the safety
of millions in nearby Tokyo.
787
00:45:33,181 --> 00:45:34,980
Draining the Ring of Fire
788
00:45:34,982 --> 00:45:39,518
has revealed
hidden geological wonders
789
00:45:39,520 --> 00:45:41,787
and terrors,
790
00:45:41,789 --> 00:45:44,790
exposing new evidence
of this immense power
791
00:45:44,792 --> 00:45:47,660
of plate tectonics
792
00:45:47,662 --> 00:45:52,331
and its ability to create
793
00:45:52,333 --> 00:45:53,933
and destroy.