Drain Alcatraz (2017) - full transcript

Alcatraz, "the cliff".

The world's most infamous prison.

Alcatraz was the perfect
prison for that time.

The worst ones like Al Capone,
Machine Gun Kelly and Whitey Bulger-

- put everyone imprisoned here.

The island is less than two kilometers

-but it was almost
impossible to escape.

Those who tried encountered icy
water, streams-

-thick fog and
life-threatening predators.

To investigate this, the plug on
the seabed has now been removed-

and drained the San Francisco Bay Area.



The secrets of the seabed are revealed
with incredible computer graphics.

Can the landscape explain Alcatraz's
reputation as escape safe?

In 1962,
three men broke out of Alcatraz.

If the bay is drained,
can you find out what happened to them?

They went in on the north side
of a raft and have not been seen.

Did they reach the mainland and the freedom?

Or did the violent
currents seal their fate?

And can the landscape explain
why Alcatraz is the safest place-

- When will the next
earthquake hit California?

What secrets are revealed
when we drain Alcatraz?

THE TRUTH ABOUT ALCATRAZ

The island of Alcatraz lies alone in
the middle of the San Francisco Bay Area

A large body of water on the
west coast of the United States.

In the dramatic landscape
lies Alcatraz and the remains-



-after the prison just under two
kilometers from the city center.

For 29 years, some of history's
most dangerous prisoners sat here.

Alcatraz was the terminus.
It was designed that way.

That was where they could
isolate the troublemakers.

and the gangster kings,
the most problematic.

The worst prisoners
were sent to Alcatraz.

Officially, no one managed
to escape from the "cliff".

But exactly why did no one
manage to escape from Alcatraz?

To get an answer,
we use high-resolution sonar-

-to explore the hidden
depths of San Francisco Bay.

For the first time,
high-tech computer graphics are used-

-to produce incredible
images of the bottom.

This is how you've never
seen Alcatraz before.

Today, the island is a museum
run by the park administration.

Over a million visitors
come each year.

A man has seen it turn into one of
America's most popular attractions.

Ranger John Cantwell has worked
on the island for over 25 years.

He knows its history.

At Alcatraz, we say history warehouse.

The first layer is when
the army was on Alcatraz.

They arrived in 1853 and built
a fort to protect the harbor.

The Federal Prison Bureau took over
in 1934 and operated it for 29 years.

-as a high-security prison.

American justice reserved
Alcatraz for the very worst.

The prison was fortified so
that they could stay there.

I'm in "Broadway" which is the
main corridor of the cell house.

A high security
prison is very safe.

There was a guard of three prisoners.

They were monitored around the clock.

They counted each prisoner
twelve times a day.

Those who tried to escape
were severely punished.

But fleeing was
always a temptation.

Freedom was just
a short swim away.

The worst thing about sitting here-

-was the view of what was
going on on the other side.

Everything is clearly visible
and the prisoners could see it.

It is probably fair to say
that everyone who sat here

-thought about how they would escape.

Freedom seemed so close that
for some it was irresistible.

The official escape attempts are 14-

and five of them have
still not been found.

To get off the island,
prisoners must first escape-

-out of the prison itself.

One of the most famous escape attempts

is when Roe and Cole tried in 1937.

They went out the windows
and jumped into the bay.

They sent out boats to search
but they were never found.

The official explanation is that
they were washed out to sea.

Strong currents were just
one of the many dangers.

It was popularly said that
dangerous sharks swam in the bay.

In 1959, a college student had been killed
by a great white shark in these waters

-and 2015, the legend of Alcatraz
sharks was confirmed in pictures-

-when tourists witnessed a great white
shark attacking a seal off the island.

But fear of sharks did not
stop the escape attempts.

And it got easier as
Alcatraz began to fall apart.

The complex aged. The concrete
began to crack and fall apart.

Steel rusts. It is almost impossible
to be completely escape safe.

Last year before the
prison was closed-

-took two incredible
escape attempts.

In December 1962,
two men went down to the water.

John Paul Scott and Darl Parker escaped
through the basement of the prison.

They sawed their way
through a reinforced window.

Out the window and
up for some pipes.

Then they ran over the
roof of the cell house and

- came down the west
wall of Alcatraz.

Then down the road and
jumped into the water.

They found Darl Parker
standing on the cliff

-which was called Little
Alcatraz 50 meters out there.

He waved to the guard and
shouted, "Come and get me!"

But they found John Paul Scott
away at the Golden Gate Bridge.

John Paul Scott is the
only one officially-

-has managed to swim across the bay-

-but he was so exhausted that he
was quickly returned to Alcatraz.

It was an escape attempt until 1962-

-which is the most
famous of all.

Three prisoners,
Frank Morris and the Clarence brothers-

-and John Anglin planned
his escape for months.

They managed to get off the
island on a homemade raft.

But they have never been found.

The case is still open.
They were believed to have drowned.

It's one of Alcatraz's
great mysteries.

Can Morris and the Anglin brothers
be the only ones who made it?

Alcatraz was closed in the spring of 1963.

Officially,
no one managed to escape from there.

But the strength of the
prison can not be explained-

-just with how thick the walls were.

Or how vigilant the guards were.

The waters around the cliff were also
a deadly barrier during an escape.

Now science can explain how and
why the bay was so dangerous.

Imagine being able to pull the
plug on the bottom of the bay-

and drain the water around Alcatraz.

For the first time,
we combine sonar with HD-

-and high-tech computer
images to reveal-

seabed and stunning scenery.

Finally, we have a clear
picture of Alcatraz.

A cliff rising from
San Francisco Bay.

It is isolated but clearly visible
from land. You can touch it

-but it's two kilometers out.

When the bay is drained,
Alcatraz is revealed as a cliff-

-which rises from the seabed.

It is surrounded by mountain peaks.

All these ancient mountains
were created by earthquakes.

Tom Parsons is a geophysicist
at the U.S. Survey.

He has been studying
the field for decades.

We're at the Golden Gate and
we're standing on the mountain

which was formed a
hundred million years ago.

The San Andreas
and Hayward faults

-makes sure there is movement between-

-the two plates here.

San Francisco is right on the
edge of the North American plate.

When the Pacific plate
is scraped against it-

-it's getting anxious along
all the fault lines here.

Partly at Hayward and
especially at San Andreas.

The region is unstable
with major earthquakes.

In 1906 and 1868 there were devastating
earthquakes in San Francisco.

The nightmare-like effects
of the 1906- earthquake

-who measured 7.9 on the Richter
scale is a reminder of how geology-

- threatens the existence of the beautiful city.

100 million years ago,
the landscape was very different.

There was a third record between
the two big ones called Farallon.

It was located between the
Pacific Ocean and North America.

It was printed under North
America throughout that time.

When Farallon moved,
the Gulf of San Francisco was created-

and Alcatraz when ground under
the North American plate.

The process is called subduction.

When Farallon disappeared, fragments
from the earth's crust were forced-

-upward,
creating a valley and mountains.

Alcatraz was part of the coastline
that was lifted by the subduction.

Back then, the bay was a long wooded
valley with many high mountains.

One of these mountains was Alcatraz.

10,000 years ago,
the last ice age ended.

The whole area was submerged
in billions of liters of water.

It created what we call
the San Francisco Bay Area.

Alcatraz became an island.

This photo from 1853 shows the
top of the submerged mountain-

-like a contourless rock
in the middle of the bay.

Alcatraz may look
peaceful and isolated.

But it is surrounded by
mighty forces of nature.

By draining the bay, we can explain
the island's deadly reputation-

-and what may have happened
during the escape in 1962.

We're pulling the plug in San
Francisco Bay and emptying it-

-to discover why it was so
dangerous to escape from Alcatraz.

In three decades,
there have been 14 daring escape attempts.

The story behind one
of them is legendary

The most famous escape attempt is
probably the one that took place in 1962.

Frank Lee Morris,
and brothers Charles and John Anglin

- made a bold attempt
to achieve freedom.

The escape attempt was very ingenious.

They stole lots of different things-

-like dozens of raincoats, glue,
and engines to make drills from.

They even made a periscope,
and a flashlight.

Homemade tools were used
to get through the walls.

Here sat one of the brothers
and they were skilled enough-

-to create a portal at the back.

They built a drill of
a vacuum cleaner motor

-and put a diamond on top and
made small holes in the concrete-

-to dissolve it around
the ventilation.

Doll heads were made
of hard material

-with glued human hair
and painted faces.

So at night they seemed to
be sleeping in their cells.

In the cell house,
the light goes out at 21:30.

That was when they broke out.

When the heads are in place,
they rise to the roof.

-and has between 21:30 and
6:30 to get to the mainland.

With over 50 glued
together raincoats-

- they make a makeshift
raft and life jackets.

It is their lifeline to freedom.

They carry everything over the
roof and drag it down to the water.

Right here they went into the water.

Morris and the Anglin
brothers came down here.

They dragged down their raft
and filled it with air here.

Then they jumped in and
disappeared into the night.

They searched the
water for the three men

-but neither the raft
nor they were found.

The official FBI documents
state that the men and the navy-

-believably pulled out to sea.

The bodies were never found.

But was that really what happened?
Did they disappear at sea?

Or could they have
gone to the mainland?

To understand the fate
of refugees on the navy-

-students study the
geology of the bay itself.

Can the seabed provide an answer?

First,
Patrick Barnard from Surveying-

-examine the underwater
landscape in the bay opening.

An analysis of the seabed can
explain the strong currents-

-which surrounds Alcatraz and
makes escape attempts so dangerous.

Today we map from
Golden Gate and west.

Interesting to see what
is on the seabed there.

For the first time,
multi-beam plumbing is used to see-

-how the seabed itself may have
affected the fate of the prisoners.

The fantastic with multi-beam plumbing

-is that they capture the bottom
in HD so we get sound every meter-

-and can see in incredible detail
what the seabed looks like.

Advanced technology sends thousands
of sound waves to the seabed.

The waves are reflected against the
contours and give an unmatched overview.

The investigation begins under San
Francisco's most famous landmark.

We are right below the Golden gate
at the narrowest part of the strait.

The purple shows the
deepest parts of the canal.

It's about 92 meters deep here.

After several passages through the
canal, a strange landscape can be seen.

We see a bottom without
direct features.

The entire middle part of the
sweep is ground down bedrock.

When the water is emptied under the
Golden Gate, a huge gorge is revealed.

Much deeper than the rest of the bay.

Deep enough to house
a thirty-story house.

But what happens to the seabed
when you move west towards the sea?

We are now a little more than
a mile west of the Golden Gate

-but the bottom is still
empty and mostly bedrock.

As the boat moves further away from the
Golden Gate, the water becomes shallower.

The sonar shows a dramatic
change in the seabed.

That is changing, we see much
more sediment at the bottom here.

When the water is drained,
an incredible sight is revealed.

We're starting to see some
very large sand waves here-

-which arose in the depths
of the Golden Gate Strait.

These formations on the
seabed are enormous.

The largest sand waves
are 200 meters long

- and 6 meters high.
The highest is 10 meters.

They're just a few feet
from the harbor entrance.

It looks almost like
walking through the Sahara.

The sand waves are formed when the
tide rushes through the strait.

Water that rushes forward carries
with it sand which it then releases.

The sand waves are there
because it is a large estuary-

-and all tides,
about two trillion liters of water-

- rushes through every time.

Strong tidal forces force the
water through the narrow channel.

The solid bedrock at the
gorge does not erode.

The strait acts as a fire hose
when the water rushes through.

The flow is 160 times greater
than the volume of water-

-which flows over Niagara Falls.

All sand and gravel is dragged along
and forced through the opening-

-and when the opening
gets bigger and bigger-

-it falls to the bottom.

The drained landscape shows
how the geology of the seabed-

-shapes powerful tidal currents
in the San Francisco Bay Area.

The deep ravine
acts as a funnel.

To the west beyond the
bridge, the seabed rises-

-from about 90 meters
deep to only 40 meters.

We see how the rushing current
dumps thousands of tons of sand

-and creates huge sand waves
that are up to ten meters high.

But what has the underwater
landscape at Golden Gate-

-to do with fleeing Alcatraz?

These tides were tamed by
the prisoners as they fled.

Could Frank Morris and the Anglin
brothers have been caught in the currents?

The report from the
FBI investigation 1962-

-shows that the tide in June 1962-

-between 21 in the evening and 3 in the
morning, strong tides were on their way out.

The highlight came at exactly 23:46.

So when were the prisoners in
the water on their homemade raft?

From the time the light went
out, which was 9:30 p.m.

- they left the cells
as soon as they could.

Say one to one and a half hours

-to get everything through
the valve on the roof-

-about the roof, down the
side, down into the water.

I think they started paddling

-as soon as they were in the water.
I'm guessing at 11pm.

The three prisoners should have
been in the water when it was tidal.

It was low tide then,
the water was on its way out.

What chance did they have if their
raft of raincoats fell apart-

-so they got to swim
in the strong currents?

If you tried to escape via the north
side of the island when it is ebb-

-as in 1962,
the currents were extremely strong-

-and went straight into the sea.

It is difficult to swim out,
within an hour and a half

- could you be out on the coast.

So Morris and the Anglin
brothers had to fight against-

-the deadliest currents in the bay.

And the currents show no mercy.

They have destroyed ships
far larger than rafts.

San Francisco Bay is a shipyard.

When the bay is drained,
a deep ominous gorge is revealed-

-under the Golden Gate
and huge sand waves-

-which rises from the seabed.

Huge amounts of water rush
through the bay opening.

Four miles east of
the Golden Gate-

-locates Alcatraz.

This is a good example
of the tide here.

The tide holds about five knots.

You can swim from
Alcatraz to the mainland.

But only during the short
periods when the tide turns-

and the currents slow down.

I swam here when it was calm-

and would never try to
take me to San Francisco.

Wild currents were just one
of the prisoners' challenges-

-when they tried to escape.

There were other deadly dangers.

Bill Baker is one of the few
Alcatraz prisoners still alive.

He was sent to Alcatraz for a
three-year sentence in 1957-

-after trying to escape
from other prisons.

But fleeing Alcatraz was
something completely different.

I thought about it
but I did not think-

-how to win over the water.
The water is icy cold.

The water is the wall that
kept us here and it killed many

-who tried to escape so it becomes-

-very ugly after
watching it for a while.

The icy water that
scared Bill Baker-

-created by cold currents
from the deep sea.

They replace the hot surface
water that is constantly whipped-

-of the strong winds
of San Francisco Bay.

The average temperature is
between icy 10 to 15 degrees.

Under these conditions,
anyone gets chilled quickly.

When the cold water
meets the hot air-

-creates a new killer who
silently invades the bay - fog.

Thick fog can be a prisoner's
friend and hide an escape.

In 1937, two men escaped from
the workshop when it was foggy.

They calculated the time so they had

-45 minutes lead on the guards-

-before anyone noticed
that they were gone.

For Ralph Roe and Ted Cole, the fog
offered protection as they left the island.

But it was also a threat.

If someone tries to
escape into the misty bay-

-then it will be almost
an impossible situation.

Very dangerous, confusing.

That's probably the worst case
scenario to try to escape.

Jan Null knows all about fog.

He's been a meteorologist in
San Francisco for many years.

But why is fog so
common right here?

The mechanism that
creates our classic fog is

-circulating sea breeze.

When the air flows over the
very cold water along the coast-

-becomes the condensation that
turns into fog that goes inland.

There's only one way for fog
to get into San Francisco.

The only place with water it can
get through is the Golden Gate.

So there it will be mostly fog.

It goes from the Golden
Gate towards the Alcatraz

-and then on to Berkeley.

When Roe and Cole escaped,
they quickly disappeared into the thicket.

It was December and cold.
An eyewitness saw them.

He saw them in the
water swept out.

99.9 percent chance that
they did not make it.

The thick fog made a rescue
operation impossible.

Roe and Cole were never seen again.

The FBI thought they had
died in the icy water.

San Francisco fog combined
with fast currents

-is a recipe for disaster.

By draining the water,
we can see the result of this.

There are large spooky figures
scattered on the seabed.

Dozens of shipwrecks.

San Francisco Bay is a
cemetery for missing ships.

There's one just east
of the Golden Gate-

-long down the gorge
with a tragic story.

The shipwreck is called City of Chester.

But how did this end up?

August 1888

City of Chester is moving
towards the Golden Gate Strait.

In August it is thick fog here.

It was foggy, and she was going
out through the Golden Gate

-while a large ocean
steamer enters.

It was much bigger.

And much faster.

Now, 130 years later,
the historian Steve Haller-

and archaeologist Peter Gavette
in search of the missing ship.

The City of Chester sank
rapidly and it was about

-60 meters deep.
We're just above her now.

The multi-beam plumbing gives a
tickling glimpse of the sunken ship.

-You can see the structure.
-This is the bow.

That the City of Chester has not
been covered by sediment is great.

With this data,
we can see the wreck as it looked.

With the data from the scan-

- we can drain the wreck
of the City of Chester.

Can you determine how
the disaster happened?

One can see exactly where
the decisive blow was

-and you can see how
this section is skewed-

-compared to the rest of the
ship, so the keel was broken off.

The drained ship is the crime scene.
The evidence is clear.

We can see where it hit
exactly aft on the port side-

files about the shoulder and was
divided almost into two parts.

In the thick fog is the City
of Chester and an ocean liner

-in collision course.

They did not see each other
until it was too late.

Strong currents drive
them towards each other.

City of Chester turns and
Oceanic hits her in the side.

The much heavier vessel
punches holes in the hull.

The smaller ship is
mortally wounded.

City of Chester drops
in just six minutes-

and 16 people die.

She's just one of many wrecks on
the bottom of San Francisco Bay.

The result of the extreme forces
that make the bay so dangerous.

The same forces that those who tried
to escape from Alcatraz encountered.

The most famous are Frank
Morris and the Anglin brothers

-which fled on June 11, 1962.

What chances did they have
under these conditions?

If you keep in mind
that two large ocean

-can be tossed around and one
of them almost halves the other-

-what chances do three guys
have in a homemade rubber raft?

But can the strong
currents in the bay-

-Instead of having helped the escapees?

Could they have been taken
to land and to freedom?

In 1962, three prisoners
embarked on a legendary escape

-from Alcatraz in
a homemade raft.

Since then, there have been
many rumors about their fate.

Some claim to have
seen them on land.

But that contradicts
the official FBI report-

-that means they were on
their way to Angel Island.

It is located three
kilometers north of Alcatraz.

They did something no one else could
do, they left the island

-with a lead and was
never seen again.

The official report
on the three men

-says the raft took in water
in the San Francisco Bay-

and that they were cooled and
taken out to the Pacific Ocean.

But it has never been proven.

When the news spread around the
world, many became very imprisoned.

It seemed to be the first
successful escape from prison.

For several weeks, the FBI searched the bay.

-with the goal of finding
them, dead or alive.

It's the largest hunt in
San Francisco's history.

Even though they never found
any traces of the bodies-

- FBI found traces of the escape.

They found two of the life jackets.

They found two paddles in plywood

-which floated in different places in the bay.

Another life jacket was
found outside the Golden Gate

-on a beach just north.

There was clear evidence of the escape.

Evidence was available throughout the bay

-but there were no
traces of the men.

How did it happen?
Could the three escapees have done it?

Is there a possibility that
the currents helped them-

-and brought them to the beach?

Patrick Barnard and his
colleague Josh Logan-

-examines this
fascinating theory.

They use high-tech buoys with
gps to follow the currents.

The circumstances are very similar

-as they were on the run in 1962.
It's ebb now.

The water moves at one and
a half meters per second.

The GPS measures the
position every five seconds.

We get it on our laptop and
can follow it in real time.

Then we get to know the
direction and speed of the water.

Okay, now we're tracking.
I put in the buoy.

The buoy is laid north of Alcatraz

-on the refugees'
road to Angel Island.

At first, the buoy's trajectory
seems to confirm the theory

-that the men were pulled out to sea.

It operates at about 6
kilometers per hour now.

In a quarter of an hour we have driven
halfway between Alcatraz and Golden gate.

It seems to lie in the middle
of the Golden Gate Strait.

Despite a strong headwind,
the currents pull the buoy out to sea.

But then the unexpected happens...

It did six kilometers per hour
until the current took it.

Then it slowed down to
one kilometer per hour.

The buoy stops just before
the Golden Gate Bridge.

It's unexpected.

It seems to have slowed down

-because it ended up in a vortex.

It's quite interesting.

It went southwest in a straight line.

-until it slowed down in the
vortex and changed direction.

A vortex is created by
water moving in circles-

-almost like a slow whirlpool.

Can a drainage of the
San Francisco Bay-

-discover what creates
such a huge vortex?

Just east of the bridge is
something strange on the seabed.

Away at the Golden Gate,
it is shallow in some places due to

-a large rock slab there.

It forces the water upwards
and creates this vortex.

The deep undercurrents go
straight into the bedrock-

-forcing the rushing
water to the surface.

It creates the huge vortex
that makes the buoy stop.

A drainage of the bay reveals
how powerful currents-

-on the surface, which has killed
humans, is created in the depths.

Other strange phenomena at the
bottom explain the deadly outcome-

-from a previous escape attempt.

Burglar Aaron Burgett fled-

- against freedom in September 1958.

His friend Bill Baker was a
prisoner at the same time.

He was a young man
and he was strong.

He was as strong as a donkey.

Burgett overpowered a guard
and jumped into the water-

-on the west side of Alcatraz.

They did not know where he
had gone and locked us all up.

There were boats circulating around
the island both night and day.

-with headlights and for every day-

-which passed we
became more optimistic.

Despite the prisoners' hopes

-founded Burgett
two weeks later.

One day his body was flushed
up and then it was over.

I was sad because I really
wanted him to do it.

Strangely enough,
Burgett's body was found

-just meters from Alcatraz.

So why was he not taken out
to sea by the strong currents?

This may be due to the
shallow water around Alcatraz.

They have never been examined before.

Now Professor Rikk Kvitek
from Monterys University uses-

-a unique surveillance
vehicle to survey the terrain.

It is designed to get where
other vehicles cannot.

It moves in shallow
water and is equipped

-with the same kind of sonar as others,
but can be handled by one person.

After one day of scanning

-along the western cliffs-

- Kvitek can explain what
happened to Aaron Burgett's body.

The drained lake bottom around
Alcatraz shows dozens of

-large rocks and caves.

When Burgett drowned,
his body probably sank to the bottom-

-and got stuck among the rocks.

When it broke down, gases were
created that caused it to float.

The 1962 refugees did not
try to swim towards freedom.

They made a raft.

But if they disappeared into
the sea or went to safety-

is a big mystery.

Patrick Barnard and Josh
Logan hope to confirm-

-how the seabed in the bay
affects the currents above.

They want to determine what
course the refugees took in 1962.

The first buoy stopped
in a large vortex.

They lay two other buoys
in different places-

- along the road to Angel Island.

We put it a little further
north than we put the other.

The two buoys begin to move
toward the Golden Gate.

The second ends up in the
same vortex as the first-

-but the third continues
straight towards the bridge.

This one is on its way
out and will not end up

-in the same vortex as the others.

Just a moment later,
it has crossed the bridge.

The third buoy has gone
straight into the main canal-

-and increased in speed.

The drained seabed shows why
the buoy is moving southwest.

When it flows slightly north-

-it takes over the rock
and misses the vortex.

Then the currents carry it through
the gorge and under the Golden Gate.

Soon the buoy is out at sea.

It was out for about an hour
and covered 6.8 kilometers.

-with a maximum speed of
ten kilometers per hour.

It is about as expected.

I was surprised by the others.

They got stuck but this one just went

-as the model predicted at
ten kilometers per hour-

-which is far faster
than anyone can swim.

Getting caught in the vortex would
probably not have saved the escapees.

They had to fight against
strong currents to survive.

Anyone trying to paddle in land

-had probably ended up sideways.

The test with the buoys sheds
new light on the 1962 FBI report

The two buoys in the vortex
moved in different directions

-and unbelievably,
one moved back against Alcatraz.

It may explain why
remnants of the fleet-

-found near the island
after the escape.

The third buoy shows that
if the prisoners drowned-

-as the FBI thought, the bodies
would have been taken out to sea.

One thing that the test really shows-

- is that San Francisco
Bay is unpredictable.

The currents are so
complex that you can

a few meters in one
direction and end up-

-in completely different places.

Ten kilometers out to
sea or back on Alcatraz.

But if the three prisoners
reached the open sea-

-there was another deadly threat in the
form of large numbers of great white sharks.

The area is called the Red Triangle.

In June 1962,
it was the same kind of season as now.

With a lot of nutrition in the water.

Lots of fish, so there should have
been many more great white sharks

-in the area than the rest of the year.

If they made it all the way
here, dead or alive-

-so they may have fallen
victim to great white sharks.

The three prisoners were never found.

But research shows that they
are unlikely to succeed.

The infamous prison was closed
in 1963 without any remarks.

Officially, no one managed to escape
from Alcatraz, despite many attempts.

It was the surroundings
that made it safe to escape.

The bay was the
perfect prison wall.

It can be said that the bay has
created the reputation of Alcatraz.

The "perfect prison" was the
result of unusual geology.

Deep ravines, huge
dunes, hard cliffs-

in the Golden Gate Strait,
strong currents and large predators-

-waiting in the water
outside the bay.

Natural phenomena that made the
rock "impossible" to escape from.

But there is another powerful
force of nature in the bay-

-which surpasses ocean currents.

A drained Pacific Ocean
reveals the first clue.

Deep underwater
off San Francisco-

- lies the infamous
San Andreas Fault.

The moving tectonic plates
have created major earthquakes.

The deadliest occurred in 1906.

More than 3,000 people died.

But can an even worse
earthquake occur here?

The so-called "big one"?

We have predicted an earthquake-

-which can start in the
far south of San Andreas-

-and walk all the way
north along the bay-

-and involves the whole area.

It would be 8.2 to 8.4
on the Richter scale.

The devastation would
be much greater-

-until the earthquake of 1989.

If such an earthquake
affected the San Francisco

-would there be many casualties,
many buildings collapse-

and motorways and
infrastructure are shut down.

The destruction would affect the city

-the whole bay and the
whole of California.

The earthquake would cause parts of
the city to collapse into the sea.

Large parts of the city
center would be destroyed.

Golden Gate might not work.

But when the smoke dissipates,
a place would remain.

Alcatraz would be safe to

-it's a solid rock.

It would not collapse
like soft earth.

It has existed for 100 million years
and would withstand an earthquake.

If the geologists are right
and when the San Andreas

cracks, Alcatraz is the safest
place, ironically.

The island that so many
men wanted to escape from

- offers a sanctuary.

By draining Alcatraz and
revealing the seabed's secrets-

-shows a different picture of the island.

The explanation behind the secrets-

-involves more than just prison.

The Geography of the San Francisco Bay Area

-water, cliffs,
wind and fog form a net-

-which makes Alcatraz
impossible to escape-

-if "the big one" does not occur.

By draining the waters
around Alcatraz-

-the secrets of the
cliff have been revealed.