Unearthed (2016–…): Season 6, Episode 4 - Mount Rushmore: The Hidden Secrets - full transcript

Mount Rushmore is one of America's most iconic landmarks, but there are dark mysteries behind its presidential faces; experts use cutting-edge tech and the latest science to reveal what ...

Narrator: Mount rushmore...
Four colossal heads

Of some of america's
greatest presidents

Immortalized in granite.

It's beyond ambitious.
It is monumental.

Narrator: It's one of the most
recognizable images

On the planet,

But today, investigators
uncover new secrets

Hidden inside this modern-day
engineering wonder.

It's kind of working on a puzzle
with half the pieces missing.

Narrator: New evidence shows
how the epic challenge

Of shaping a whole mountain

Nearly defeats it's creators.

You can't just blow everything
up and take all the rock off.

And what could destroy it?

There are 140 fractures,

And they're all over
the sculptures,

Above it, below it, behind it.

Narrator: What are the secrets
of its construction,

And why is america's
most famous landmark

Created on a mountain
in remote south dakota?

To find out, we will blow apart
mount rushmore

And rebuild it to its
astonishing, original design.

We'll explore it's buried
tunnels and hidden chambers...

...And reveal the high-tech
secrets concealed

Within this mysterious
mountaintop mega structure.

EP - 4 - Mount Rushmore: The Hidden Secrets

South dakota...

5,000 feet up a mountainside,

The giant granite faces
of george washington,

Thomas jefferson,

Theodore roosevelt,

And abraham lincoln

Stare out sternly over
the beauty of the black hills.

Mount rushmore.

But behind these familiar
likenesses lie clues

To what this monument
is really for,

Why these four men are here,
and evidence

Of how you carve
a granite mountain

On a scale
no one thought possible.

It's a monumental project

Because it hadn't been
done before.

Narrator: Painstakingly carved
into the black hills,

Four faces,
each towering 60 feet tall.

Hollowed-out irises
plunge 2 feet into the cliff,

Leaving a thin pillar to appear
like a sparkle in their eyes.

Epic, 20-foot noses,
each taller than three people.

Carefully perched spectacles
12 inches thick.

And finely crafted facial hair.

These incredible sculptures
total 14 years in the making.

How do you build
such an epic monument?

It's the brainchild
of danish-american sculptor

Gutzon borglum.

Historian laura pankratz
investigates how borglum carves

His giant masterpiece
from a solid mountain.

She wants to know how he deals

With the epic
engineering challenge

He faces at mount rushmore.

Pankratz: Gutzon was
a very ambitious person.

He would say things like,

"there was great
civilizations in rome,

Incredible monuments in egypt.

I want this monument to be
around for thousands of years."

Narrator: Mount rushmore's
creator attempts a feat

Of precision engineering
not seen on this scale

In the united states before.

It was very different
to be able to remove

A small piece of stone
in the studio

In comparison to removing
450,000 tons of rock

Off of a mountain,

And one mistake,
and there's no putting it back.

Narrator: Gutzon borglum's
first challenge...

To find over 400 workers

Used to working
with rock-hard granite.

The depression was going on,
so there wasn't a lot of work.

There was a lot
of unemployed miners here,

And they were happy
to go to work for borglum.

Narrator: Mines are dotted
right across south dakota.

Miners here
have years of experience

Removing thousands
of tons of hard rock

In search of valuable minerals,

Such as mica,
natural stone, and gold.

Borglum harnesses their
pioneering mining technology

To start transforming
a remote mountain of granite

Into a magnificent monument.

In 1927, they begin carving,

But instead of using chisels,

Workers use dynamite.

They blast away the mountain

To create four giant heads
of smooth rock.

Next, they drill 3-inch holes
all over the rock's surface

To carve the features of
the famous faces into the rock.

And for the finishing touches,

They use air-powered hammers
to smooth the sculpture.

But how can you accurately
carve a mountain with dynamite

While dangling
over 50 stories high?

Wayne van hout runs the milbank
granite quarry in south dakota.

He's an explosives expert
and granite cutter.

Van hout: Granite is
extremely hard to work with.

A shortcut in that
is we can use explosives,

But when you use explosives,
if not done right,

I can cause damage to the stone.

Narrator: Wayne wants
to understand how the workers

At mount rushmore
used dynamite so accurately.

He experiments
with their techniques.

He starts by testing explosives
on a reject granite block.

We'll put one stick of dynashear
here in each hole.

The holes here
are drilled random.

Oh, that's how you
break it up good.

Of course, you don't end up
with much left when you're done.

Narrator: How do you carve
a face using explosives

Without causing this much
damage to the monument?

Here, if we make a mistake
on blasting,

We wrecked a good block,

And it's a financial burden.

On mount rushmore, there,
they wreck the mountain,

And you can't replace that.

Narrator: Wayne needs to blast
off the excess wedges of granite

From around the base
of these large blocks.

He needs to carefully calculate
how to direct the explosion,

Just as the workers do
on mount rushmore.

First, he cuts a series of holes
along the line

Where he wants
the rock to break.

They'll each hold
a small explosive charge.

Van hout: We've already weakened
this surface by drilling the holes.

When we shoot it, the blast
is going to follow that line,

And that will break
right on that line,

And we don't have to worry
about damaging

The stone ahead of it
or behind it.

Narrator: If wayne
has calculated correctly,

Then only the uneven granite
should be blasted off...

[ alarm blaring ]

...Leaving three perfect blocks.

Here it goes.

Looks great.

Narrator: The line of drill
holes precisely directs

The explosive force.

It removes only unwanted granite

And leaves
the remaining rock unspoiled.

Out here, we get to blast
pretty much any time of the day.

At mount rushmore,
they used to do it twice a day.

The reason for that was they had
to clear the mountain

When they did do their blasting.

Everybody has to climb up
the ropes

To get off the mountain.

It must have been quite
an ordeal to get it done.

In the hands of experts,

The dynamite technique
can remove rock

To a remarkable accuracy
of within 3 inches.

At mount rushmore,

This leaves behind
a rough outline of the face.

But how do you sculpt
the final few crucial inches?

On mount rushmore, they would
have come in with jackhammers

And start grinding that away
to make it smooth.

The polished face, they call it.

Narrator: The workers
remove the final 3 inches

With a technique
called honeycombing.

They used jackhammers to drill
a tight pattern of holes.

This weakens the granite
and allows small pieces

To be accurately removed
with hand tools.

They pound the rock
to a smooth finish

By loosening the drill bit
in their air hammers,

A method known as bumping.

I got a small 12x12 area done.

Went really fast for me,

But I'm not hanging from a rope
off the side of a mountain

Trying to go
straight in with this,

Trying to make it
all the perfect shape.

But when you're all done,

This is what they called
their polished surface.

It looks great.

Narrator: Achieving this level
of detail at the giant scale

Of mount rushmore
will take 14 years.

It's an incredibly
complex operation.

When borglum arrives
in the black hills wilderness,

There isn't even a road here.

To realize his epic vision,

He needs giant infrastructure.

A small city springs up
at the bottom of the mountain,

Complete with new roads,
blacksmith shops,

And tool sheds.

A steep, 760-step staircase

And a cable car take the workers

To the top of the mountain
over 5,000 feet high.

Winches lower the carvers
down onto the faces,

Dangling hundreds of feet
above the ground.

Giant compressors pump air
up the mountain

To power the pneumatic drills
and custom-made air hammers.

Mount rushmore is the first
project of its kind

In the united states,

So the mountain carvers
must adapt or invent

All of the tools and techniques
they need from scratch.

Pankratz: It was a learning
experience for them,

An experiment in how do
I hold these tools?

How do I keep them in place

As I'm suspended
over the side of the mountain?

Narrator: Workers move around
the cliff face

In a special harness
called a bosun's seat.

It's used on sailing ships

So sailors can safely
reach the rigging.

Pankratz: Gutzon borglum adapted
and adjusted the bosun's seat

For use on the mountain.

He had to invent tools.

He had to make tools better.

He was ingenious
in all of those areas.

Narrator: Hundreds of specialists
are recruited and trained,

From powder men and blacksmiths

To winch men and call boys.

It was very noisy where
the winches were running,

And they couldn't see the men
over the side of the mountain,

So gutzon had a caller
on the top,

Who would see where
the men had to go

And let the winches know
what they need to do

When they needed to do it.

Amazingly, in the 14 years,
they had zero casualties.

Narrator: But the mega project
creates constant challenges

That force gutzon borglum
to change his plans.

Today, investigators unearth
the unexpected problems

He finds hidden
within the mountain itself.

How does its natural geology

Affect the design of the icon
we know today?

Mount rushmore, south dakota.

Today, it's a famous icon,

But this isn't how
its creator designs it.

Now researchers are examining
why gutzon borglum

Radically transforms
his original vision.

It's kind of working on a puzzle
with half the pieces missing.

Narrator: He starts out
trying to make something

That looks very different.

He plans four busts

With jefferson
on washington's right

And lincoln nestled
behind his left shoulder,

All carved right down
to their waists.

This layout leaves space
for a giant tablet 120 feet high

In the shape of
the louisiana purchase.

It documents key dates
in american history

In 3-foot-tall gilded writing.

So why is mount rushmore today

So different
from the original plan?

Mark fahrenbach is a geologist
for the state of south dakota.

As we can see, most of it

Is the whitish-colored
harney peak granite.

Narrator: Mark investigates and
maps the complex geology of this area

By studying the surface rock.

He wants to know how mount
rushmore's internal structure

Forces its creator
to change his design.

Fahrenbach: As you get in,
there could be little pockets

And seams and veins where
you have different rock types.

Gutzon borglum was looking for
rock that had fairly fine grain,

And the grain size
in the harney peak granite

Ranges quite a bit
from just small, little grains

Maybe a centimeter

To large crystals
5, 10 feet across.

Narrator: Borglum needs rock
made up of smaller mineral crystals

Because they have
a stronger structure.

It lasts far longer and will
give his faces a realistic look.

The crystal size is determined
deep in the earth's history.

1.7 billion years ago,
the black hills area

Is made up of layers
of soft, sedimentary rock,

With molten magma
forming deep within the earth.

The magma pushes up between
the layers of soft rock

And cools quickly, solidifying
into smooth, hard granite.

Over time, cracks in the granite
fill with more magma,

Cooling slowly, leaving behind

Crystalline streaks
in the smooth rock.

The surrounding softer rock
wears away,

Exposing the streaked
slab of granite

That borglum begins to carve.

How does the earth's
geological past

Force borglum to change the
final design of mount rushmore?

Mark investigates these early
templates for the monument.

He compares them with photos
of the construction in progress.

He wants to see if he can
find clues in the rock structure

That explain why rushmore today

Looks completely different
from these original models.

Four years into the work,

They have an almost
complete george washington,

But then they move on
to thomas jefferson.

Fahrenbach: This photo shows
where they were preparing

To put thomas jefferson.
And in the model over here,

Thomas jefferson is to the right
of george washington.

You can see
part of the eye developing

And the nose developing.

Narrator: But after two years
of backbreaking work,

They hit a problem.

It looks like
as he was carving that,

He got into some bad rock there

That was too coarse-grain
or just unstable.

Narrator: The slower-cooled large
crystals he finds in the granite here

Are difficult
to carve accurately.

If they continue, and the rock
doesn't improve

Further into the mountain,

They won't be able
to complete jefferson's face.

It's very frustrating
for gutzon borglum.

He'd prepare an area.

You're digging in there,

But your rock's not
getting any better.

If the rock won't support
the sculpture,

No matter how much
he wants to put it there,

It's not going to happen.

Narrator: Borglum orders
two years' work on jefferson

To be dynamited
off the mountain.

[ explosion ]

He goes back to the studio
to rethink.

He eventually decides
to move jefferson's head

To a new position.

But when he starts work,
borglum discovers

Another potentially
catastrophic surprise

In mount rushmore's
hidden geology.

Fahrenbach: It looks like
there's coarser grain

Running right through his nose.

Narrator: Larger crystals
and the coarse grain

Will weather away more quickly
and leave a scar down his nose,

Wrecking the whole monument.

The differences
with the mountain today

Reveal the ingenious solution.

Fahrenbach: If you compare
to the earlier model,

The expression on the mouth
has changed a little bit.

The eyes have changed
a little bit.

Gutzon borglum changes
the orientation

Of thomas jefferson's face
from looking almost straight out

To looking a little bit
to the left.

And by doing this,
he was able to shift

The position of that
coarser-grained granite dike

To kind of going down behind
the nose and onto the face.

Each tiny change of plan

Takes months of work
to complete.

Finally, the order
of the presidents is settled.

But there's no room
for the giant tablet

Of the louisiana purchase.

Now he needs to tackle the
presidents' elaborate clothing

And upper bodies,
as on the final model.

In a photo of mount rushmore
from before the carving begins,

Mark finds evidence
of more problems.

Fahrenbach: Right in the place
where they put george washington,

You can see a dark band,
and that is mica schist.

Narrator: Mica schist is a much
weaker rock than granite.

It can easily split during
carving and weaken the monument.

Fahrenbach: George washington
does have lapels,

But as you go
halfway down the chest,

That's where he had to stop.

He couldn't carve into
the mica schist,

Because that weathers
very easily,

And it's not strong.

Narrator: Most of this
mica schist is now hidden

By the thousands
of tons of debris

Removed from the mountain above.

The presidents' completed faces
on mount rushmore

Do look almost identical
to this final clay template.

How do stonemasons transfer
the precise contours

Of the ever-changing models

Without modern-day
laser scanners?

Clues lie in another
mysterious mountain carving

Emerging from
the black hills granite today.

Narrator: Mount rushmore,
a giant granite monument

Of four iconic u.S. Presidents.

To build it,
its creator first makes

A finely crafted clay model.

But how do the workers
translate this artwork

Into a colossal piece
of engineering?

9 miles southwest
of mount rushmore,

Another giant monument is slowly
emerging from the mountainside,

Built using
the exact same methods.

The face of the native american
warrior crazy horse

Towers 30 feet taller
than the faces on rushmore.

It's been in the making
for 70 years,

But it's far from complete.

His flowing locks will take
another 10 years,

And his body will be carved from
over 10 million tons of granite,

Revealing the warrior
pointing his 227-foot-long arm

As he rides his horse.

When finished, it will be the
biggest sculpture in the world.

But how do you scale up a model

Into a sculpture
the size of a mountain?

In 1948, one of the original
carvers of mount rushmore,

Korczak ziolkowski,
starts the crazy horse project

Using the techniques
he learns there.

Monique: Dad was assistant
sculptor for a year to gutzon,

And if it weren't for
mount rushmore being carved,

Dad never would have been able
to start this mountain carving.

Narrator: Now his daughter,
monique ziolkowski,

Continues her father's
colossal creation.

Monique: In 1948,

The first blast on the mountain
was set off,

And we've been here
for 70 years.

Narrator: Mountain-carver
monique still works

From her father's scale models.

Just like rushmore's creators,
she uses a pointing machine,

An ingenious
ancient-greek device,

To map the scale model
onto the mountain.

This is our 1/34th scale model,

So 1 inch here equals 34 inches

Up on crazy horse's head.

Narrator: The first step is
to get an accurate measurement

Of each point on the model

From a fixed spot
the machine pivots around.

Monique: So x, y, z coordinates,

And there's been 10,000 of those
taken on crazy horse's face.

It's a labor of love.

Narrator: The carving team high
up on the mountain translates

The measurement of the model
onto the rock's surface.

To do this, they use
scaled-up versions

Of the pointing machine.

Right now, we're going to do
the outline of the fingernail.

Once we establish where
this pivot point is

For carving this area on
the mountain, we won't move it,

So it stays accurate
because it stays put.

Narrator: First, they match the
measured angle from the pivot point.

Monique: Where jesse is now,
when he turns the pointing machine out

To go alongside
crazy horse's finger,

Those are east-and-west degrees.

Narrator: Then they move the plumb
bob horizontally along the crane arm

Before dropping it down
to the rock.

The compare the distance
it falls

With the model measurement.

Those measurements tells us

How much rock we have to move
to get down to finished grade.

Narrator: Any mistakes in the
calculation could ruin 70 years of work,

So they need to be certain
before they begin removing rock.

When you're pointing, you
measure way more than one time

To get to finished grade,

So there's a lot of checks.

Narrator: Crazy horse's image
emerges inch by inch from the mountain.

But why is this native american
hero being carved here?

The black hills belong to the
native american lakota people,

Which the u.S. Government
recognizes in 1868

In an official treaty.

But in 1874, the gold rush
takes over the black hills

And forces the native americans
off their land.

Crazy horse, a lakota chief,

Goes to war to win back
the sacred hills.

But despite his bravery,
the lands are lost.

In 1931, demands to put
crazy horse

Onto mount rushmore
are rebuffed,

So native americans plan
their own monument in his honor.

Monique: The carving
of mount rushmore, I'm sure,

Hurt the native american people.

And if they're going
to carve a mountain

To quite a few white people,

Then perhaps they should carve
a mountain the black hills

To a native person.

Narrator: The crazy horse
carvers use public donations

To complete a monument
that will eventually be

Over 10 times the size of
the carving on mount rushmore.

Dad felt if the interested
public wanted to help carve

This mountain, that they would,
and they have all these years.

Narrator: It's painstaking work.

Monique: The rock was 8 feet
above crazy horse's finger

And came straight across,

And all of this rock has been
moved in the last five years.

Narrator: To improve speed and accuracy,
monique now adds modern methods

To the traditional techniques
pioneered on mount rushmore.

They adapt the latest
diamond-tipped cable saws

From the quarrying industry.

Monique: There's not as much
vibration on the rock

As you drill
and drill and drill.

And it's very accurate.

And you can
make some pretty nice shapes

And put it in places

Where you maybe
couldn't reach with your drills.

They complete the final finish

With an
extremely-high-temperature torch

That flakes the final
few millimeters of rock away.

This is what the rock looks like
after it's been torched.

It's that same finish
as crazy horse's face,

And this is the tip
of crazy horse's finger.

That is this right here.

Narrator: Crazy horse could
eventually take 2 centuries to complete,

Compared to
mount rushmore's 14 years.

Monique: You can't just blow
everything up and take all the rock off.

There's a lot more that goes
to carving a mountain than that.

So as long as we keep making
good, steady, and safe progress,

Then that's what matters.

Narrator: Crazy horse and mount
rushmore are vast monuments

Designed to amaze
for generations to come.

But inside mount rushmore
are secret chambers

And buried caskets.

What can they reveal about
this iconic monument's message

To people far in the future?

Narrator: Mount rushmore...

One of the most recognizable
images on the planet.

But is it simply
a colossal structure,

Or does it have another purpose?

Clues are hidden
inside the mountain.

Behind abraham lincoln's head
lies a secret tunnel

Extending 70 feet deep
into the rock

Until it hits a dead end.

But at the tunnel's mouth,
a 1,200-pound granite capstone

Seals an underground chamber.

Inside, a titanium vault

That contains
a long teak casket.

And carefully stacked inside,

16 super-thin enamel panels.

Why are these mysterious tablets
hidden inside mount rushmore,

And why is there a tunnel
that seems to lead nowhere?

In washington's
library of congress,

Architectural historian paula
reed hunts for an explanation.

There are thousands of documents

Detailing mount rushmore's

Among the personal papers
of its creator,

Gutzon borglum.

There's a lot of correspondence,

Dealing with congress
to get funding.

A lot of the funds were matched
with private funds,

So there was also going out

And beating the bushes
for private donors,

So funding was a problem
from the beginning.

Narrator: The monument is
initially budgeted at $250,000,

But costs rocket
to nearly $1 million.

They kept running out of money.

And there would be
an appropriation,

And it would get spent,
and then work would stop,

And then there would be
another appropriation.

Bair: And here we have records
that were kept in 1939 and 1940.

Narrator: Paula works
with the collection's historian,

Barbara bair, to investigate

Why the project
keeps running out of money.

Gutzon borglum did
change his mind a good bit,

And things evolved.

Narrator: Gutzon borglum's vision
of mount rushmore keeps expanding.

They're searching out evidence

For his most audacious
and expensive plan.

So, these are oversize items.

Original blueprints
reveal detailed designs

For a complex around
the finished monument.

Reed: Part of the proposal
of gutzon borglum

Was to have this grand staircase
that would allow visitors

To climb all the way up
behind the heads.

Narrator: The staircase leads

To the majestically titled
hall of records.

Borglum describes a chamber
hidden within the mountain

That explains
mount rushmore's purpose

And houses a depository of
the country's most sacred texts.

It would have copies
of important documents

Like the declaration
of independence,

The constitution,
and an explanation

Of who the heads were and why
they were on that mountain.

But could the chamber
hold more than just

An explanation
of the mountain carving?

Gutzon borglum reveals
his master plan

For the hall of records in
his unpublished personal memoir.

It's an interesting thing

That is another argument
about the larger plan.

And that's borglum's handwriting
where he was editing himself.

Borglum plans a grand hall
80 by 100 feet

Drilled behind the faces,

With an 800-foot-high granite
stairway climbing up to it.

At the chamber's grand entrance,

A bronze eagle with wings
spanning 38 feet

Sits above huge glass doors.

Inside, bronze and glass
cabinets line the walls,

Showcasing historical documents

Like the declaration
of independence.

Busts of famous americans
decorate the hall,

And the nation's contributions
to the world

Are inscribed on the walls.

Gutzon borglum wants to secure
mount rushmore's place

Among history's
greatest monuments

And idolize
america's achievements

For any future civilization
discovering it.

Borglum was so attracted
to these kind of ideas

Of colossal shrines
like the pyramids.

You see from the outside
this very monumental structure,

But if you go in the inside,
there's this secret chamber

That tell us the story
of that time period.

The records show
that he persuades congress

To grant $50,000

For the construction
of the hall of records.

In 1938, workers start blasting
the cavity for the hall

Out of the mountain.

But the approach of world war ii
forces a halt.

Congress said, "we need
this money for the war efforts,

So we're done here. Don't worry
about the hall of records.

Don't worry about
the grand staircase.

Just get the heads done."

The heads are swiftly completed,

And work on the monument
stops in October 1941.

Reed: The hall of records,
which had been started,

Is still left there
in its unfinished state.

Narrator: The half-completed
hall of records

Still shows the tool marks
of the halted construction.

But in 1998,
gutzon borglum's daughter buries

The 16 enamel tablets
in the entrance to the chamber.

This time capsule contains
a history of the united states

And biographies of the four
presidents and gutzon borglum.

They also detail
the epic struggle

To get the giant monument built.

But why is this national
memorial started

In the first place,

And what can
investigators discover

About why it's here
in remote south dakota?

South dakota's mouth rushmore.

It's an american icon,

But why is it built
in the first place,

And why is it here
in south dakota's black hills?

Architectural historian
paula reed

Pieces together archives
from across the country.

She wants to find out
where the idea

For this unprecedented
monument comes from.

People are surprised,
because, you know,

They just think that rushmore
was always planned as-is.

Narrator: Letters between
the project's early backers

Reveal the first concept
for the mountain carving

Has nothing to do
with presidents or democracy.

His original idea was to do

More regional and local figures

Rather than
these national heroes

And also to do them
on a much, much smaller scale.

Narrator: In the 1920s,
south dakota state historian doane robinson

Looks for a way to boost
the economy in his remote state.

Reed: Doane robinson wanted
to carve figures of the old west

In the black hills area

That would become
a tourist draw.

It was a much, much
smaller-scale operation.

Narrator: The faces of old west
heroes like buffalo bill

And sitting bull could today be
staring out of the black hills.

How does this idea
get transformed

Into a massive mega project

With the president
as its heroes?

Doane robinson's letters
recount the first time

Mount rushmore's creator
arrives in south dakota.

Reed: Doane robinson
selected gutzon borglum,

And it was an experiment,
of course.

He invited him to come and visit
to see what he would do

And also to prepare
a proposal and a price quote.

Narrator: Robinson first
brings gutzon borglum

To this famous rock formation
called the needles,

But borglum
rejects the thin spires

And fractured granite
as unsuitable for portraits.

He spends weeks trekking
across south dakota's stunning,

Rugged landscape
looking for a suitable site.

Letters between
the south dakota promoters

Reveal that gutzon borglum
is inspired

When he finds
the perfect location.

Reed: When borglum saw mount
rushmore in its natural state,

He said, "this is where
I want to do something major."

He proposes a gigantic carving,

An unprecedented colossus
of national significance.

In reading the correspondence,

I'm surprised that they went
along as quickly as they did.

I don't think
they really envisioned

That it would be possible

To do something on the scale
of what mount rushmore became,

And no one had
ever done it before.

Narrator: By 1925, when borglum
is planning mount rushmore,

28 presidents have held office.

Why does he choose these
apparently unconnected four?

Paula finds clues in gutzon
borglum's prolific writing.

I think they were unified
in gutzon borglum's mind.

He referred to them
as empire-makers

Or empire-builders.

Narrator: George washington is
the country's founding president.

Reed: Pretty much an automatic
thing to put him on the mountain

As the most prominent
of the four heads.

And in addition,
during his term,

The united states expanded in
its territory toward the west.

Narrator: Third president thomas
jefferson is also a founding father.

Reed: Well, he drafted
the declaration of independence.

Then, as president, he greatly
expanded the territory

Of the united states
with the louisiana purchase.

Narrator: Abraham lincoln
preserves the union of the united states

By winning the civil war.

Theodore "teddy" roosevelt
is the last

And perhaps
most surprising choice.

First of all, he was a friend
of gutzon borglum's,

But he was also, as borglum
would say, an empire-maker.

Narrator: The united states
completes the panama canal,

And it becomes u.S. Territory
under roosevelt,

Securing america's prosperity.

Reed: All four of the people
who are on mount rushmore

Would become a symbol of america
emerging from its beginnings

Into a major power.

Narrator: Gutzon borglum
creates these four icons

Of the american presidency

Out of the epic landscape
of the nation they build.

By daring to work
at this unprecedented scale,

His vision becomes a temple

To the united states'
founding ideals.

But how long can this symbol
of american achievement last?

What threatens
this iconic memorial?

Narrator: Mount rushmore...
A shrine to four

Of america's
greatest presidents,

Designed to inspire
today's citizens

And impress future

But how long can
this iconic monument last?

There are 140 fractures,

And they're all over
the sculptures,

You know, above it,
below it, behind it.

Narrator: The granite faces
are exceptionally tough,

But tiny fissures in the rock

Can allow rainwater
to trickle in.

[ rock crackling ]

As it freezes, it wedges
open the cracks...

...With potentially
catastrophic results.

To prevent this, the team
at rushmore fills any cracks

With a waterproof sealant.

And to detect even
the tiniest movement,

They install a network of
highly sensitive motion sensors.

Will this be enough
to protect mount rushmore

For centuries to come?

Vining: We can measure down

To thousandths of an inch

Narrator: Engineer cody vining
is an expert in rock mechanics.

He's tasked with monitoring any
deterioration in mount rushmore.

The biggest concern

Is where fractures intersect
inside the rock.

Vining: When they intersect,
they form a discrete block

That have the potential to move
from the current location.

Narrator: Cody and his team
monitor the network

Of high-tech movement
sensors around the faces.

They capture any microscopic
change in the width

Of the fractures
surrounding these blocks.

Here is our real-time feed

From the instruments
up on mount rushmore.

We are measuring
7/1,000 inch displacement.

Narrator: Right now,
an exposed block in the side

Of george washington's cheek
causes the most concern.

Vining: We got
the exposed rock up there.

It snows. Snow accumulates.

The sun comes out.
It melts the snow,

And it can percolate down
into these fractures,

And the water can freeze.

The expansion of the ice
can exert quite a bit of force

On the rock.

Narrator: This process is called
the freeze-thaw cycle.

In cold weather,
water in the cracks can freeze,

Pushing the cracks open.

Then as the weather warms up,
the ice melts.

If this cycle keeps repeating,

The cracks grow larger
and larger,

And whole blocks
can become wedged apart.

Vining: The original carvers,
they knew that these fractures

Had the potential for water
to percolate in them.

To reduce
that freeze-thaw cycle,

You know, they patched the top

With linseed oil
and granite dust.

Narrator: Cody checks that
the sealant is still working.

He uses sensors so accurate
that he can see mount rushmore

Reacting to the weather.

When the rock changes
temperature, it changes shape.

We see variation hour-to-hour.

And then we can really see
the fluctuation

And the displacements
through the seasons.

The instruments also measure
minute temperature fluctuations,

So cody can take into account

These natural rock movements
in his calculations and work out

If the blocks are slipping
further than expected

And damaging the sealant.

He determines that mount
rushmore is stable for now.

But this state-of-the-art system
will sound an early warning

Of any critical deterioration.

Vining: As long as we keep monitoring it,
and they maintain the seal

To prevent water from filtrating
into the fractures,

There's no reason
this sculpture won't be there

For tens, thousands, hundreds
of thousands of years to come.

Narrator: Mount rushmore...

A monument shaped
by the geology of south dakota

And transformed by a feat
of ingenious engineering

With hidden messages
of american greatness

For future civilizations,

An icon to inspire
all americans.