Original subtitles

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.

Narrator: 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.

♪♪

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.

♪♪

Narrator: 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?

Narrator: 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.

Fahrenbach: 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.

♪♪

Narrator: 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.

Monique: 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.

Narrator: 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 Evolution

Among the personal papers Of its creator,

Gutzon borglum.

Reed: 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.

Reed: 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."

Narrator: 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?

Narrator: 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.

Reed: 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."

Narrator: He proposes a gigantic carving,

An unprecedented colossus Of national significance.

Reed: 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 Civilizations.

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.

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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...

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...With potentially Catastrophic results.

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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 Resolution.

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.

Vining: 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.

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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.

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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.

Narrator: 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.

--captions by vitac-- Www.Vitac.Com

Captions paid for by Discovery communications

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