Secrets of the Earth

We have uncovered

a remarkable planet,

a world of extreme weather,

alien landscapes,

and bizarre phenomena.

It's the most complex system

we know of in the universe.

That planet

is Earth,

and we are only beginning

to unlock its secrets.

At sea, the wave

is virtually invisible,

but it has a secret.

It can travel

at 600 miles per hour.

And it's headed

straight for shore.

What would happen if it hit

one of the United States'

most popular cities?

Generated by cataclysm,

and with the power to kill

hundreds of thousands,

tsunamis decoded

on Secrets of the Earth.

For mankind,

the oceans of planet Earth

are treasured resources,

but they have a dark side.

Periodically, they erupt

in violent tsunamis.

90% of them are triggered by

strong undersea earthquakes.

When you think

of a tsunami,

you have to think

of a wall of water

with the strength

of a wall of bricks.

They are

fundamentally different

from all other waves

in the sea.

A magnitude-9.0 earthquake

strikes Japan.

It hurled a tsunami

toward Tohoku Province,

pushing water in some places

120 feet high.

Eighteen thousand people killed

or missing,

6,000 injured,

$235 billion in damage.

Earth's most expensive

natural disaster.

Kesennuma is a small city

300 miles north of Tokyo.

It's home

to a tuna fishing fleet

hard-hit by the tsunami.

This ship is more than

a mile inland.

This is a tuna ship that used

to be in Kesennuma Harbor,

and the tsunami came

and it floated all the way here.

Japan sits on the edge

of Earth's Ring of Fire,

a belt of earthquake faults

and volcanoes

encircling the Pacific.

Fourteen fatal tsunamis

in the past century

make Japan this world's most

tsunami-prone country,

but it is far from alone.

An offshore earthquake

could trigger a tsunami

in the northwest United States.

Take a look at

the Cascadia fault,

going from Canada

down to Washington State

down to Oregon.

We know that it's ruptured

in the past.

Mud cores

taken from the seafloor

hold evidence for tsunamis

throughout the past.

Tsunamis

have been occurring

for millions

and millions of years,

as long as the Earth

has had oceans.

A Cascadia fault

tsunami left behind sediment

scientists can date

to the year 1700.

Stories of a great earthquake

followed by flood waters

exist in the oral traditions of

Native Americans in the area.

And tree ring studies reveal

stands of dead trees

with outermost rings

dating to 1699,

the last growing season

before the tsunami.

A precise date comes from

a secret source.

By going to Japan,

they found records

of an ancient tsunami

of the year 1700.

Therefore, we now realize that

that very same tsunami

that hit the United States

back then also hit Japan.

We know the exact date

and the exact hour

that the tsunami hit.

The Japanese records tell us

the tsunami struck

the American Northwest

on Tuesday,

January 26th, 1700,

at 9 p.m.

In Japan today,

scientist Costas Synolakis

revisits the scene

of the Tohoku tsunami.

He is one of 300 scientists

who surveyed

the initial damage.

The stranded tuna ship

stands as a monument

and still reveals surprises.

Shh.

What is this?

My God, heh.

Do you see that?

That's a car.

The ship is sitting

on top of the car.

When I was here,

the debris was about higher

than where I'm standing,

so you couldn't see this.

The 330-ton

Kyotoku Maru Number 18

is propped up across Route 210.

It's surrounded by

the foundations of buildings

that the water washed away.

The tsunami here began

as most of them do,

with a violent shift

of the ocean's bed.

If I have an earthquake,

and I have a fault subduction

that goes like this,

then the sudden vaulting

of the ocean floor

can cause a uplifting

of the water,

which creates a tsunami.

When a large

earthquake strikes

under the seafloor,

it can jolt

35 billion gallons of water

into motion.

Yet, in the open ocean,

a tsunami wave

has so much room to spread out,

it may only be a few feet high.

If you're an ocean liner,

and a tsunami goes by you

in the middle of the Pacific,

you hardly notice it.

But as the wave

gets toward shore,

the shoreline starts to get

thinner and thinner,

meaning that water is pushed

upwards as a consequence.

And that's why tsunamis can have

such a devastating effect

as they go toward the shoreline.

Originating

just 60 miles offshore,

the Tohoku earthquake

shoved Japan's coast

200 feet to the east.

The movement

of the Earth's crust

redistributed the entire