Original subtitles

>> Earth. A 4.5-billion-year-

old planet, still evolving.

As continents shift and clash,

volcanoes erupt, and glaciers

grow and recede, the Earth's

crust is carved in countless

and fascinating ways, leaving

a trail of geological

mysteries behind.

Water. One of the most powerful

forces on the planet. It plays a

crucial role in creating life

and destroying it, in forging

landscapes and in breaking apart

the Earth. In its most dramatic

form, it becomes a killer wave

known as a tsunami. Until

recently, predicting when these

monsters may next strike has

been impossible.

But today, scientists are

starting to understand these

giant waves. By connecting clues

as varied as ancient Japanese

writings and landslides, ancient

corals and buried Native

American settlements, the

secrets of tsunamis are finally

being unlocked.

How The Earth Was Made 01x09 Tsunami Original Air Date on April 7, 2009

== sync, corrected by elderman ==

Tsunamis. One of the most deadly

forces of nature. Giant waves

that travel faster than a jet

plane, they can cross entire

oceans in just hours.

They have the power to smash

buildings, vehicles, anything

in their way.

By itself, you wouldn't

think that water just streaming

fact, they are very fast moving

and they pick up everything in

its path, so it's not the water

by itself, it's what comes with

the water that is also a part of

the big hazard.

>> A tsunami isn't over in just

a few seconds, it is a torrent

of raging water that keeps

coming.

>> The main thing about a

tsunami is the persistence. It

comes on and on and on, and just

when you think it has to quit,

it keeps coming, and it's the

power plus the--the duration

that is unstoppable, really.

>> Tsunamis have ravaged the

Earth for billions of years.

When the Earth was first

created, the moon was much

closer. It filled the sky.

Its gravitational pull was much

stronger, and it generated

towering waves over half a mile

high that raced across the

primeval oceans.

Oh, my God!

>> Today, tsunamis are still a

threat to coastlines all over

the world.

Tsunamis will always

occur, and have always occurred,

throughout Earth's history. But

it's only been more recently, as

population densities have

increased and people have moved

and migrated to the coastal

regions, that we've become much

more aware of the tsunami

hazards.

>> The investigation into what

caused these monster waves

began over a thousand years ago

on the islands of Japan.

This country is the world's

tsunami hotspot. Its coasts have

been pounded with these enormous

waves more than anywhere else on

the planet. Evidence for this is

the word tsunami itself. It is

Japanese and literally means

"harbor wave".

Japan has the longest written

tsunami record of anywhere in

the world. The records go back

as far as 684 A.D.

By studying these records, it is

possible to work out that, on

average, this country has been

struck nearly every seven years.

Samurai writings speak of people

living on the coasts running

for higher ground as soon as

they felt an earthquake. The

Japanese knew this was a clue, a

warning sign that a deadly

tsunami would soon follow. But,

despite their attempts to

escape, tsunamis have

continually bought death and

destruction to these islands.

In 1896, a wave that hit Honshu

in the northeast claimed the

lives of 27,000 people.

In 1933, the same area was

smashed again. This time, 3,000

people were swept away.

And in 1993, the island of

Okushiri was rocked by an

enormous earthquake measuring

7.8 on the Richter scale.

Buildings were leveled and fires

raged. But worse was to come.

Minutes after the shaking had

subsided, an ominous white

crest appeared on the horizon -

a tsunami. A gigantic wave swept

in, flattening any buildings

still standing.

In Japan, the locals had already

worked out the connections

between earthquakes and

tsunamis. But there's another

hotspot on Earth where tsunamis

regularly strike - the Hawaiian

islands. But very few of them

were preceded by an earthquake.

The city of Hilo on the Big

Island has been dubbed the

Tsunami Capital of the World.

Dozens of these enormous waves

have hit these beautiful

islands, and the mystery is why.

With no natural warning to go

on, the people of Hawaii must

rely on the world's biggest

tsunami monitoring station.

Set up in 1949, it is connected

to a network of buoys spread

across the Pacific Ocean. These

buoys provide important clues.

They monitor changes in sea

level that indicate the

approach of any potential

tsunamis.

In 1960, scientists got the

breakthrough they were looking

for. They were finally able to

work out the type of event at

the root of Hawaii's mystery

tsunamis. An enormous quake on

the coast of Chile, the biggest

recorded of all time, with a

factor 9.5 on the Richter scale,

triggered a tsunami that swept

across the entire Pacific Ocean

in just a few hours. The islands

of Hawaii where thousands of

miles away, directly in its

path. The Tsunami Warning Center

was monitoring its progress,

revealing for the first time

that a single massive wave

crossed thousands of miles of

ocean. The warning center was a

success. They were able to

evacuate the communities closest

to the shore before the wave

struck. But the homes they left

behind were decimated. In Hilo,

the tsunami was so strong it

even bent parking meters in

half. The wave continued past

Hawaii to Japan. It had lost

none of its power. Pacific-wide,

this tsunami cost more than

2,000 lives and caused millions

of dollars' worth of damage.

Devastating as it was, the 1960

event was a turning point in

the study of tsunamis. It was

the first time that scientists

could accurately measure how the

size of an underwater earthquake

directly affected the size of a

tsunami. And conclusive proof

that a tsunami can travel

thousands of miles across the

Earth.

>> And It was with this Chilean

earthquake that we really could

prove that the, uh, undersea

motions associated with the

earthquake are generating these

huge effects.

>> Now scientists had the

evidence to confirm that

undersea earthquakes were

directly responsible for

tsunamis. The ancient Japanese

suspicion was now scientific

fact. In terms of modern tsunami

study, the 1960 wave was year

zero.

The Chilean

earthquake was, you might say,

the perfect storm, it's when

scientific understanding had

advanced to the point where

scientists had begun to see the

link connecting everything, so

it's a new science, we're

talking about something which is

really only less than 50 years

old.

>> There are more tsunamis in

the Pacific Ocean than any

other. So in 2004, the world was

taken by surprise when one of

the largest recorded tsunamis of

all time took place in the

Indian Ocean.

On December 26th, 2004,

Indonesia was rocked by the

second largest recorded

earthquake ever, 9.2 on the

Richter scale.

Minutes later, a 90-foot tsunami

slammed into the Southeast

Asian coastline.

225,000 men, women and children

lost their lives.

The Indonesian earthquake had

as much energy in it as the

total energy consumption in the

United States in one year.

>> This enormous burst of energy

had been released in just

seconds. Once again, the world

had been reminded of the Earth's

awesome power. In the last 50

years, scientists were finally

able to confirm a solid link

between earthquakes and

tsunamis.

By monitoring the size of the

Chilean earthquake in 1960,

scientists were able to prove

conclusively that earthquakes

triggered these gigantic waves.

By following the path of this

tsunami, they were able to

prove that a tsunami could

travel thousands of miles from

its origin.

Monitoring the earthquakes that

cause this incredible

devastation involves looking

many miles underground.

By investigating the power at

the root of these giant waves,

scientists can begin to figure

out when and where these waves

may strike next.

These dramatic pictures of the

aftermath of the 2004 Indian

Ocean tsunami show the havoc a

tsunami can unleash.

It's almost impossible to

imagine something like that

happening here in the Pacific

Northwest. But Professor Brian

Atwater believes that events

like the 2004 tsunami could one

day happen right here too.

He was intrigued by early

settlers' accounts of Native

American folklore tales that

spoke of great waves sweeping

inland. They convinced him that

huge, locally generated tsunamis

have struck here before, and

could strike again, posing a

threat to tens of thousands of

people living on the Pacific

Northwest coast. To find out if

he was right, he needed to

uncover evidence of past giant

waves hidden in this landscape.

To be really sure it's a

tsunami, though, he would also

have to find evidence of the

earthquake that caused it.

Atwater's starting point is the

Copalis River in Washington

State, just a couple of miles

from the long sandy beaches

that make this area a thriving

tourist resort. In the banks of

this estuary lie buried

thousands of years of

history.

This is one of the dirtiest jobs

in science. Hunting for evidence

of earthquakes is a muddy

business, but it's worth it.

Atwater has found signs of a

potential tsunami.

>> There's a clue in this bank

that nature has provided, it's

this notch. And notches like

this are common where tsunamis

have laid out sheets of sand and

then later currents and--and

waves come along and they pluck

the sand grains out of the bank,

but they leave the mud.

>> Atwater has to dig deeper to

find what he is looking for, a

layer of sand that could have

been swept miles inland by a

tsunami.

>> OK, so now you can see the

sand. What deposited this sand?

Maybe it was a tsunami.

>> To prove that this was sand

from a tsunami, Atwater's muddy

quest must continue. He also

needs to find proof that the

land here around the river has

moved up or down - a sure sign

of an earthquake. After some

hard work, Atwater finds what he

has been looking for - clear

evidence of both an earthquake

and a tsunami. This time, there

was a human cost as well.

>> Here we have evidence for

abrupt lowering of land, and we

also have evidence for the

associated tsunami. In this

case, humans are involved - this

was a fishing camp. Here you

have the remains of that fishing

camp in the form of fire-cracked

rocks which were--the rocks were

used to heat water, mainly.

OK, so fishing camp, overrun by

tsunami. Because the land

dropped after the tsunami, the

tides came in and covered the

fishing camp site and made sure

that people wouldn't use it

again.

>> The land the fishing camp was

built on was dragged down

during the earthquake. The

tsunami deposited sand over the

remains, and finally, the tide

covered the settlement with mud,

where it remained undisturbed -

until now. Atwater finally had

the proof he needed. His Native

American myths of giant waves

were no mere legend.

But what was it that caused the

earthquake? The prime suspect

lay 50 miles offshore - the

Cascadia fault. Cascadia is a

major weakness in the Earth's

crust. Although the Earth may

seem to be a solid sphere,

beneath the oceans and

continents it is divided into

eight major and many minor

segments known as tectonic

plates. Where they meet, they

can grind and jostle against

each other at fault lines,

causing earthquakes. Geologists

had long thought that the

Cascadia fault line was

incapable of generating a major

quake. But Atwater's

investigation has proved that it

was highly active. The big worry

for Atwater and the thousands of

people who live in this region

is that the Cascadia fault line

bears an uncanny resemblance to

another highly active fault

line, the Sunda Megathrust.

It was an earthquake along this

fault that was responsible for

the Indian Ocean tsunami that

killed nearly a quarter of a

million people.

>> Where we get two tectonic

plates coming together, such as

the case of the Indonesian

tsunami in 2004, one plate

pushes beneath the other plate

and creates lots and lots of

friction and tension and drags

the upper plate down with it,

and that process can take

hundreds of years, even

thousands of years. It's a very

slow process. But eventually the

pressure of this one trying to

push back up again wins, and it

flips like that.

And that creates a megathrust, a

sudden movement of the seabed,

and that's what creates a

phenomenal tsunami.

>> Two factors made this Sunda

Megathrust earthquake so deadly.

The first was its size. At

factor 9.2 on the Richter scale,

this was the largest in nearly

50 years. The second was that it

took place not far below the

surface.

When we talk about a

megathrust, that's really where

the seabed is disturbed

dramatically. Sometimes, if the

earthquake is deep in the

Earth's crust, then you see very

little surface manifestation of

that earthquake. If it's quite

close to the surface or very

intense, then quite often you'll

see the seabed itself moving,

and that's what creates a

powerful tsunami.

>> Investigating the ocean floor

after the quake revealed that

more than 1,000 miles of

fault line had fractured and

sprung up by 60 feet. This

massive jolt pushed up billions

of tons of water, enough to

cover Manhattan to a depth of

nearly five miles.

>> The rift zone itself was

about a thousand miles long. We

had this entire stretch of

subsea moving, which creates a

huge wave. So the whole thing

was a phenomenal size and

certainly one of the biggest

tsunamis in living memory.

>> Atwater's determined research

showed that the Pacific

Northwest was at risk from this

level of devastation too. But he

didn't want to unnecessarily

alarm the coastal inhabitants

until he had collected all the

evidence he could. Atwater

needed to find out precisely

when this tsunami struck this

coastline to see if there could

be more. He first tried

radiocarbon dating the soil

along the Copalis River. But the

result could only take him so

far. They showed that the

earthquake and tsunami occurred

somewhere between 1680 and 1720.

More importantly, Atwater still

needed precise evidence of how

big it had been.

But so far, his investigation

has uncovered two extraordinary

facts. By unearthing the

abandoned fishing camp, Atwater

could see th a Cascadia

earthquake here had caused the

land to drop. The notch in the

bank was proof that this same

earthquake had generated a

tsunami. But what these clues

didn't tell Atwater was just how

big the tsunami was. He had no

way of pinning down the size of

the threat to the Pacific

Northwest. His investigation was

about to take an unexpected

turn, with clues coming from not

only thousands of miles away,

but also from hundreds of years

ago.

Japan has the oldest record of

tsunamis of anywhere in the

world. Samurai writings told of

a huge tsunami in 1700 that had

swept over the east coast of

Japan. It hit without warning,

and destroyed entire

settlements. Japanese scientists

were baffled as to where this

wave had come from. There had

been no earthquake to warn the

villagers to make for higher

ground. The mystery wave was

dubbed an orphan tsunami.

Back in the U.S., Brian

Atwater's investigation into the

mysterious Cascadia earthquake

and tsunami needed more

evidence. He had no accurate way

to pin down either the size or

the date of the event.

All he knew was that it had

taken place sometime between

1680 and 1720. But Atwater's

dates were a revelation to the

Japanese scientists. Could this

event be the birthplace of their

300-year-old orphan tsunami?

>> And they said, "By the way,

we have this tsunami we've been

trying to, uh, find a home for

in 1700, so we think your--your

earthquake happened in 1700,

specifically in the evening of

the 26th of January 1700, and it

was of magnitude nine."

>> A Cascadia earthquake that

produced a wave with enough

power to cross the entire

Pacific Ocean to Japan would

have had to be a factor nine at

the very least. This is roughly

equivalent to the enormous

Indian Ocean earthquake.

Earthquakes like this have so

much power that they can send a

tsunami across an entire ocean

with ease.

The amount of energy

involved is very hard to

estimate, and it's hard to put

it into sort of terms that

people can understand.

We are looking at the phenomenal

forces of several Hiroshimas,

hundreds of Hiroshimas, in fact.

>> But tsunamis are not just a

very big wave, they're fast.

>> The big difference is the

scale of the wave - it's

typically three or 400 miles

long. It's also not very high -

when it starts off life, it's

usually about two or three foot

high. But it's moving very fast.

It moves at a speed determined

by the water depth. The deeper

the water, the faster it moves,

so in the deep ocean, this wave

is moving at over 500 miles an

hour.

>> Deceptively, as a tsunami

speeds through deep water, it

may appear completely harmless

and scarcely detectable.

Close to shore, the wave becomes

a deadly killer. It is only then

that a tsunami's true power

becomes clear.

>> As the wave gets to shallower

and shallower water, as it

approaches a coastline, the wave

slows down. The shallower the

water, the slower the wave, so

it goes from 500, to 400, to

300, to 200, much, much slower.

The back of the wave is still

going full speed, and so the

whole thing piles up, and that's

why tsunamis are so destructive.

>> It is this immense speed and

power that reveals how events

here in Cascadia could devastate

a coastal village in Japan, how

an earthquake in Chile could

decimate Hawaii, and how the

Indian Ocean earthquake could

kill almost a quarter of a

million people. If a quake like

this happened in Cascadia, the

damage it would do to the

Pacific Northwest coastline

would be catastrophic.

But to be sure about the scale

of this threat, Brian Atwater

has to be 100 percent certain

that the dates of the two

tsunamis were the same.

After fully exploring the

estuary of the Copalis river, he

found one site that might hold

the information he was looking

for - a ghost forest.

>> This spruce root marks the

remains of a forest that

includes the ghost forest behind

us, dropped down into tidewater

during the Cascadia earthquake.

This ghost forest is made up of

the standing dead trunks of

western red cedar, and they were

killed on account of the land

here dropping, and then tides

coming in and surrounding these

trees and bringing in saltwater.

> This area would once have been

covered with a dense forest.

But today, only the bleached

trunks of the rot-resistant

western red cedar remain in

place. When Atwater and expert

tree ring specialists cut them

open and studied the lines of

growth inside, they finally

cracked the 300-year-old tsunami

puzzle.

The dates of the Japanese and

Cascadia events were exactly

the same - January 1700. The

Japanese orphan tsunami finally

had a parent.

>> Maybe there's a certain

amount of justice to it

that--that a place that doesn't

have written records has these

outstanding geological records.

>> The link between the two

events made it certain that the

Cascadia earthquake had been at

least an awesome magnitude nine.

And ominously, it is almost

certainly not the only time that

Cascadia has rocked this area.

Atwater believes he has found

proof of a whole series of

tsunamis stretching back 5,000

years.

Each layer of sand in this

sample represents a separate

tsunami.

>> There are places at Cascadia

where I've seen nine stacked up

in a column about 20 feet long.

Uh, nine buried soils, some of

them coated with little sand

sheets. And--and they, you know,

you--you say, "OK, it's--it's

not a question of if, but it's

just a matter of when."

>> Atwater's tireless detective

work alerted officials to the

increased tsunami threat.

As a result, the towns along the

Washington State coast have

been able to prepare for this

potential catastrophe. If a

Cascadia quake occurred, the

first waves could arrive here in

just 25 minutes. Tsunami warning

signs line the roads, and sirens

stand ready to warn of an

approaching wave. The lives of

thousands of people are safer

thanks to the work of Atwater,

and to some 300-year-old

Japanese writings.

>> This is a hazard that shows

its face often enough for us to

take precautions, to fasten the

seatbelt against it.

>> By dating the ghost forest

along the Copalis River to

precisely 1700, Atwater had the

final proof that Cascadia was

capable of creating a

Pacific-wide tsunami.

Uncovering the multiple layers

of tsunami debris in the

riverbank dating back 5,000

years show that monster waves

have struck here many times.

This is an ongoing threat.

Atwater knows that another

earthquake is due here, but he

has no way of knowing exactly

when. Back in the Indian Ocean,

the site of the world's most

lethal tsunami in 2004, one man

has taken the investigation of

tsunamis to a new level. He

believes that he has found a way

to make the Earth's fault lines

give up their secrets and

accurately predict when the next

deadly tsunami could be on its

way.

The idyllic looking Mentawai

island chain in Indonesia hides

a violent secret, one that makes

it today one of the most

dangerous places on Earth.

These islands lie directly on

top of the Sunda Megathrust,

south of where the enormous

Indian Ocean earthquake

triggered the 2004 tsunami.

The Sunda Megathrust is one of

the largest fault lines on the

planet. Since it caused the

2004 earthquake, it has also

become one of the most

notorious.

Predicting earthquakes here is

tricky, but Professor Kerry

Sieh has a good track record.

He has successfully forecast two

along the Sunda Megathrust

already.

The key to successful tsunami

prediction is to forecast when

and where earthquakes will

strike. And to do this,

scientists must look into the

past.

If you want to answer

questions about earthquakes

that only happen every few

hundred years or few thousand

years, well you've got to find

some--some geological

instrument that allows you to

see those earthquakes.

>> Professor Sieh has found an

unusual way to unlock the

secrets of the Sunda

Megathrust's turbulent history.

Corals. These coral atolls are

built from the limestone

skeletons of millions of tiny

creatures. Each generation

builds on the remains of the

last. Over time, the atoll gets

bigger and bigger. As long as

the corals remain underwater,

they flourish, but once they're

above water, they die.

Earthquakes are responsible for

killing all the coral stranded

above water on this beach.

This beach contains corals of

many different ages. Altogether,

Professor Sieh has nearly a

thousand years of history at his

fingertips. But to unlock the

secret history the corals

contain, he and his team have to

take a less than delicate

approach.

>> We're looking at a sawcut

that we just made through a

coral micro atoll. And the great

thing about this head is it

records a sudden drop of about a

foot and a half down to here. It

died down to here, because the

island rose. The new low tide is

way down here. Everything that

was so bold as to grow up this

high, dies.

>> The shape of the coral

records the fall of the

Mentawai islands as they are

literally pulled down by the

Sunda Megathrust.

But, crucially, the corals also

record the moments when the

islands are thrust up out of the

water during an earthquake.

Between quakes, the islands are

once again pulled down by the

fault in a never-ending cycle.

>> You have to imagine that

rocks actually are elastic. Take

a diviving board, the diver--the

diver walks out on the platform

and it--it bends like this, and

then he jumps and he springs up

and he jumps off. And when he

jumps off, the diving board

doesn't stay here, it doesn't go

like--it doesn't go like this,

you know, the diving board

springs back up, it's elastic.

Well, rocks are the same, rocks

are elastic too, so when the

Indian Plate goes down it pulls

the Sumatran section down too,

and then later, it fails. So it

just springs up like a diving

board.

>> By analyzing corals all over

this beach, Professor Sieh has

discovered a regular pattern to

this cycle. A major earthquake

rocks these islands roughly

every 200 years.

>> What we have here in Sumatra

with the corals is what I call

the Holy Grail of, uh--of

earthquake science, of--of

palaeoseismology, and that is a

long record that has many

cycles in it, a

thousand-year-long history of

earthquakes.

>> But when the geologist looked

even closer, he saw that the

cycle was more complex.

>> When we cut a slab, we can

see it in much more exquisite

detail because we can see what

we call the stratigraphy, or

the--the--the layering and how

the layering relates to the

changes of the tide, so what we

can see over here, then, is the

annual bands of growth, right

here, so there's about ten years

between this earthquake and

this earthquake.

>> Professor Sieh had discovered

a major clue. The corals record

that, not only does a major

earthquake and tsunami hit here

every 200 years, but that they

are always accompanied by a

number of smaller quakes.

This is a cycle within a cycle,

a supercycle.

And by counting back the layers

of growth within the coral, the

geologists can put an exact date

on all of these earthquakes.

>> We know there's a sequence in

the 1350s, 1370s, we know

there's a sequence in the

1560s, 1600s--1600, we know

there's a sequence 1797, 1833.

Those sequences are about 200,

to 200--yeah, 230 years apart.

>> This is crucial information

for the people of the Mentawai

islands, who have no written

history. But Professor Sieh's

work doesn't stop here. By

uncovering their history in the

corals, he believes that he can

now predict the future for these

islands. And he's already had

some success. Professor Sieh

began his work here in 1993, and

soon realized an earthquake was

imminent. The Mentawai islands

were about to start their next

deadly supercycle.

OK! Experienced an

earthquake!

>> In September 2007, he was

proved right, when an earthquake

shook the islands just enough to

generate a small tsunami that

wrecked homes and schools.

History is repeating itself,

exactly as he predicted it

would. A much bigger earthquake

and more dangerous tsunami could

be due any day.

One section hasn't

failed since 1797, so, since

George Washington was President

of the United States. We know

we're now in a sequence of at

least three giant earthquakes,

we're expecting another one. The

question is whether the

earthquake and tsunami will be

in the next 30 minutes or the

next 30 years.

>> Thanks to Sieh's research,

the people of these islands

have had time to prepare. When

the wave comes, they will be

ready.

>> Earthquakes are forecastable.

If you--if you have enough

information about how they've

behaved over the last thousand

years, or two or three or four

cycles, you can really make a

significant forecast that people

living in the area actually can

do something about.

>> Education is key. Children

here are now taught that as soon

as they feel the shaking of an

earthquake, they should run for

higher ground.

Newly built roads snake up steep

hills from waterside villages

to allow rapid escape from the

deadly waves.

>> I'll bet that young children

alive today, if they--certainly

if they live to be 60, they're

gonna see that earthquake. In

fact, I think there's a better

than 50 percent chance that

it'll happen in--within the next

30 years.

>> By analyzing the shape of the

corals on the Mentawai islands,

Sieh has proved that a major

tsunami cycle starts here every

200 years. By dating the lines

within the coral, he can be even

more exact. They show that these

cycles contain not just one, but

several deadly tsunamis. The

Sunda Megathrust is the clear

culprit for tsunamis here. But

not every tsunami is generated

by an earthquake. A rarer,

different type of wave is out

there - a megatsunami.

>> Although earthquakes are by

far the most common cause of

tsunamis, there is another

source for these deadly waves -

landslides. And these tsunamis

have the potential to be so big

that they have been called

megatsunamis. Scientists had

long suspected that waves could

be generated in this way, but

conclusive photographic proof

wasn't available until 1958.

A landslide into Lituya Bay in

Alaska triggered a wave that

reached heights of several

thousand feet.

This footage, shot just after

the tsunami struck, shows the

wave's enormous power. The trees

here once stretched all the way

down to the shores of the bay,

but were ripped off the slopes

by a wall of water, leaving

nothing but bare exposed rock.

The tsunami was generated when a

relatively small earthquake

triggered a single enormous

landslide of rocks and debris

into the bay.

The resulting wave was higher

than the Empire State Building

and stunned scientists around

the world. Tsunamis on this

scale are incredibly rare.

But another megatsunami,

triggered by a rockfall 10,000

times bigger than Lituya Bay,

could be on its way from a

small island across the Atlantic

Ocean.

The Canary Islands, off the

coast of Africa,re formed

from a series of volcanoes.

The youngest is the island of La

Palma. It is formed from two

volcanic ridges. The first is

the extinct Cumbre Nueva to the

north of the island. The

younger, active Cumbre Vieja

lies to the south.

It erupted as recently as 1971.

Geologist Dr. Simon Day's

research was crucial in

developing the La Palma

megatsunami theory. It began

with an unusual rift that had

opened up during a major

volcanic eruption in 1949.

>> We're standing here in the

fault and it runs way down

to the south along the crest of

the volcano for two and a half

miles, so it's one continuous

long structure.

>> Day believes this fault is

evidence of a geological

time bomb, the beginning of a

giant landslide.

>> What we see here to my right

are layers of--of volcanic

rocks, volcanic blocks here and

layers of volcanic ash.

And on the west of the fault, we

see the same layers of blocks

and ash and those, before the

fault moved, were joined up and

then when the fault moved, they

were separated and the rocks to

my left moved down and to the

west. What we think will happen

in some future eruption is that

this fault will have gotten

bigger and the whole of this

western side will slide away in

a giant landslide into the

ocean to create the tsunami.

>> This landslide would send the

entire southwest section of La

Palma, one sixth of the island's

total mass, crashing into the

Atlantic Ocean in a single giant

landslide.

>> What we envisage is the

whole of this coastline and the

slope extending up all the way

to the crest of the volcano that

is now in the clouds, all of

that mass of rock would slide

away in a single massive

landslide into the ocean and

pushing the water up in front of

it to create the tsunami wave.

>> Initially, this wave would be

over 30 times bigger than the

2004 Indian Ocean tsunami, more

than 3,000 feet high.

The 1980 eruption of Mount St.

Helens was proof that a volcano

could collapse in this

terrifying fashion.

This was impressive, but the

collapse of the Cumbre Vieja

would be 200 times the volume of

this.

1,200 billion tons of rock would

hurtle towards the ocean at top

speed.

The resulting wave would head

straight out into the Atlantic.

That wave, of course,

would then spread out and

separate out into smaller waves,

but even so, after crossing the

Atlantic and piling up again on,

for example, the eastern

seaboard of the United States or

in the Caribbean or in northern

Brazil, the waves there, we

predict, would still be between

30 and 100 feet high. So that's

as large as, if not larger, than

the tsunami that struck Sumatra

in 2004.

>> Boston...

New York...

and even Miami could all be

under threat from the giant

waves.

This was a bold prediction. Day

needed more evidence to back up

his theory. As he was about to

see, the rift in La Palma's

landscape was far worse than he

expected. The 1949 eruption had

left a different type of

geological scar on the island.

Evidence of a more serious

weakness within La Palma came

from a series of eerie looking

lava flows dotted across the

island.

>> One of the characteristics of

the 1949 eruption that's unusual

is that, instead of starting at

one vent and just continuing

there, a series of volcanic

vents opened up in different

parts of the island.

>> When Day plotted these

weaknesses on a map, he came to

a frightening conclusion. The

rift was far bigger than he had

first suspected.

>> The area that's potentially

affected is very much greater

than the length of the fault at

the crest of the volcano would

indicate, extending out, um, ten

or 15 miles from the crest out

to sea.

>> This growing body of evidence

proved that the rift wasn't

just a mere crack in the surface

of La Palma, but a deep fissure

that reached hundreds of feet

down into the island's

foundations. It is La Palma's

volcanic heritage that is the

key to this tsunami threat.

>> The big hazard here isn't the

eruptions themselves, it's the

fact that the volcano is

building up and building up

over time and becoming more and

more unstable, so that will

eventually lead to a collapse.

>> And it seems that this is not

the first time a La Palma

eruption may have triggered a

giant landslide. Proof lies in

the north of the island in these

sheer cliff faces, formed

65,000 years ago.

>> What we see in the north of

La Palma is the landslide scar

left when the old volcano in the

north of La Palma experienced a

giant collapse and produced a

giant landslide off to the west.

So that was a huge collapse - it

removed as much as 100 cubic

miles of rock and deposited it

out into the ocean, so it's the

sort of event that we think is

going to happen again in the

future at the--at the Cumbre

Vieja.

>> This ancient collapse of the

old Cumbre Nueva volcano is

almost certain to have generated

a gigantic wave.

And the next collapse might not

be that far away. This tsunami

could strike in our lifetime.

Even though it seems so

extraordinary when we consider

it in human terms, and we talk

about a tsunami striking the

east coast of North America and

causing huge devastation on the

scale of the Sumatra tsunami--

but this is what happens in the

geological record, this is what

Earth does.

>> Although tsunamis have been

documented for thousands of

years, it is only in the last

century that geologists have

been able to prove how they are

connected to the movements of

the Earth.

By analyzing data from the great

Chilean earthquake of 1960,

scientists were finally able to

firmly link earthquakes with

tsunamis. Unearthing buried

Native American settlements

proved that the Cascadia

fault line in the Pacific

Northwest was an active tsunami

threat. Corals in the Indian

Ocean proved that some

earthquake-generated tsunamis

follow a pattern, and strike the

same area with regular

intervals. And the giant rift in

La Palma's landscape shows that

tsunamis generated by landslides

are also a very real threat,

megatsunamis, which could prove

to be the biggest waves that

threaten our coastline.

Tsunamis are an inevitable part

of Earth's dynamic structure.

Their capacity to destroy is

awesome, but, as scientists

begin to understand more about

the origins of tsunamis, they

are coming closer to predicting

where and when these monsters

may strike.

== sync, corrected by elderman ==