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>> Earth, a unique planet,

restless and dynamic.

Continents shift and clash,

volcanoes erupt,

glaciers grow and recede--

titanic forces that are

constantly at work,

leaving a trail

of geological mysteries behind.

This episode explores

the incredible journey of

one of the most indestructible

and valuable metals

on the planet--gold.

Created in outer space,

an immense explosion

blasted minute particles of gold

at 70 million miles per hour

into the rocks that form

our planet.

How tiny pieces of scattered

gold accumulate to form

massive deposits is one

of Earth's great mysteries.

To find the answer,

Geological detectives sift

Through ancient riverbeds,

Hunting for hidden treasures

Above and below ground

And investigating

Alien natural wonders,

Finding clues that will

Ultimately reveal

"How the Earth Was Made." S02x13 America's Gold Original Air Date on March 2, 2010

-- Sync, corrected by elderman -- -- for www.MY-SUBS.com --

>> Gold has mesmerized man

for thousands of years.

The oldest known precious metal,

it plays a powerful role in

almost every culture on Earth.

>> Since humans have been

on this planet,

gold has been prized.

It is such a unique mineral.

It is beautiful.

You can take an ounce of gold

and stretch it in a thin string,

and it'll go for 35 miles.

>> But the key to gold's

enduring value is its

inactivity. It won't bind with

anything else except itself.

>> Gold doesn't get used up.

It gets recycled.

The ring you're wearing

may be the exact same gold

that was in some of the gold

the pharaohs wore centuries ago.

With all these properties,

it's no wonder gold

has been treasured by man

down through history.

>> Man has mined gold

for thousands of years but found

only 160,000 tons worldwide,

enough to fit comfortably

inside a 4-bed house.

Physicists discovered

that this ultimate metal

was created in outer space long

before planet Earth existed.

Over 5 billion years ago,

gold and other heavy-metal atoms

formed in the maelstrom

of a supernova,

a giant dying star.

As it exploded, shock waves

blasted minute gold particles

across the universe

at 70 million miles per hour,

scattering them far and wide

throughout the early

Solar System. As this cloud

of rubble compacted together,

the gold became trapped

inside the rocks of the newly

forming planet Earth.

Widely dispersed and inactive,

to this day, most of the Earth's

gold remains as tiny, isolated

particles in the rocks.

>> It's ironic, but gold

is around us everywhere.

It's in the soil

in our backyards.

It's in these rocks here

in the riverbeds.

But the problem is

it's in very small amounts.

In these rocks, the gold may be

at one part per billion.

That's like finding just a grain

of sand in an olympic-sized

swimming pool.

>> Unusually large stashes

of gold are concentrated

in a handful of very special

places around the world.

The largest, in southern

Australia, China,

South Africa, Peru,

and the western United States.

It is the geologists' job to

find out where and why the Earth

accumulates gold in large enough

quantities to mine.

The first pioneers of gold

geology were not scientists,

but gold-hungry prospectors

who scrutinized the rocks.

Their story began

over 150 years ago by accident.

In 1848, in the small

Californian town of Coloma,

along the American River,

James Marshall was digging

a trench for a water wheel

to power his lumber mill when he

made an extraordinary discovery.

>> He was digging it down

during the day and then using

water at night to flush out

the sand and gravel,

and he looked, and there

on the bedrock were

a couple of gold nuggets.

>> Rumors of California's

River gold spread like wildfire.

By 1849, over 90,000 people

from around the world

descended on the state.

Nicknamed the Forty-Niners,

these early investigators

searched the streams

in a bid to find their fortune.

Their first challenge

was to figure out where gold

accumulates in the river.

And they quickly discovered

that gold wasn't just strewn

anywhere along its course.

>> A clue to where the gold

would be concentrated is

black sand in areas like this.

You take a sample

and pan it out.

>> The Forty-Niners soon learned

if they found heavy black sand

in their pan, they were

onto a winner.

>> The process of panning

is a simple one.

You're really trying

to separate light materials

from heavy material.

>> In this sluggish water,

the heavy particles sink

to the bottom of the pan.

>> And you repeat the process

of washing away light materials

and then concentrating

the heavies on the bottom

until you get down

to just the black sand

and hopefully some nice gold,

even a small nugget like that.

>> IIn the same way,

rivers and streams

separate the heavy particles

from the light.

The gold and black sand

are flushed downstream,

but as they hit the sluggish

water on the inner bend,

they drop out of the flow.

And it's here in the sandbanks

on the inside bends of the river

that the Forty-Niners discovered

an absolute fortune.

In total, over 20 million ounces

of river gold were discovered

in the waterways of California.

But when they investigated

the valley sides above

the river, the Forty-Niners

discovered an even bigger

stash of gold.

>> And they wondered,

what was the deal with these

gold deposits that were up

and away from the water?

They took a close look at them,

and they could see that

these boulders were round

and smooth.

>> These rounded boulders

are identical to those found

in the rivers nearby.

>> And the reason is because

it's an ancient riverbed.

It's been left high and dry

by the flow of the river.

The river cuts downward and

leaves these deposits behind.

The miners continued to explore,

and they found some just above

the river like this,

but they found others tens

and even hundreds,

even a thousand feet

above the modern stream.

>> Using powerful water jets,

the Forty-Niners blasted

and flushed out a further

50 million ounces

of ancient river gold

from California's hills,

which still bear the scars

over 150 years later.

Similar river gold deposits

have formed all over the world,

including the greatest

treasure-trove ever found--

Witwatersrand in South Africa.

Its discovery in 1886 caused

another massive gold rush.

But this river gold is not found

on the surface.

Miners must descend over 2 miles

down the deepest mine shaft

on Earth.

>> Half the gold on this planet

has been produced from that one

group of deposits.

Most geologists believe

that these unique deposits

formed from ancient river

systems, concentrating these

in old river gravels.

>> Over millions of years,

thousands of ancient rivers

carrying gold spilled

into a huge lake, dumping

a massive gold deposit.

This ancient lake bed is now

buried miles underground.

To date, Witwatersrand

has produced over 1.4 billion

ounces of gold,

worth over $1.5 trillion.

And geologists believe

the same value of gold

still remains untouched.

In the search for California's

River gold, Forty-Niners found

heavy black sand, a sign

that gold is deposited

on the inside bend of a river,

and gold buried beneath rounded

boulders in the valley walls,

proof that rivers have been

depositing gold for millions

of years. The Forty-Niners

suspected that rivers were

carrying gold down from a source

somewhere in the mountain,

the mother lode.

but the quest to understand

where this mother lode gold

originated would take geologists

deep inside the Earth

and face to face with some

of the most destructive powers

on the planet.

>> In the 19th century,

the Forty-Niners plucked

70 million ounces of river gold

from California's streams

and ancient riverbeds,

valued at more than $80 billion.

But this easy gold didn't last.

The race was on to find

the source of the river gold,

the mother lode, and they

set off into the mountains

to investigate.

>> And this is what

the old-timers were

really looking for--

A big wide vein of quartz

filled with gold.

It runs literally for miles

through the countryside.

They were able to mine

millions of ounces of gold

from sources just like this.

>> With the discovery

of mother lode gold,

prospecting changed from

a solo quest to big business.

Hundreds of mines sprung up

all over California,

employing thousands of men.

Discovering what geological

force had concentrated gold

in California's mountains was

a puzzle that would bamboozle

scientists for decades.

In 1853, the Alleghany mine

opened in Sierra County,

California. Today, it's over

3,300 feet deep with over

40 miles of tunnels,

all leading to one special

slice of rock in the mountain.

>> Here I am, in the middle

of the mother lode vein.

It must be about 40 feet thick,

and it goes down half a mile

into the Earth.

This is the gold-bearing

quartz vein that the miners

were seeking.

>> Quartz forms from a liquid,

and as it solidifies,

it somehow traps lumps of gold

inside it.

>> It is loaded with gold.

If we break these quartz veins

open, though, we can see...

perhaps small amounts of gold

within the quartz.

This is just an amazing

piece of quartz. You can see

all the free gold in it.

It's just bright and glistens.

There are actually clues

to how the gold got here

within the quartz that was

deposited with the gold.

>> Trapped inside the quartz

are tiny bubbles of fluid.

They are minute remnants of

a stream of water and minerals

that once gushed up this vein.

Analysis of these fluid bubbles

has revealed the extreme

conditions that created

the gold seam.

>> That gold was deposited

at 600 degrees fahrenheit.

It was a very, very hot fluid

that brought the gold

and the quartz to this location

and deposited the vein.

>> But it was a mystery.

What was the driving force

creating all this hot fluid

which carried the gold?

In an old quarry nearby

lies a clue.

The gold-bearing quartz vein,

here stained brown,

is flanked by strange beds

of altered rock.

When the old-timers saw rocks

like this they would get excited.

They knew they were getting close

to the source of the gold.

They would see these rocks

had changed their color.

And then they would get

to the big mother lode quartz vein.

The source of most of the gold ore.

This quartz vein is sandwiched

between these altered rocks.

And looking at these altered

rocks, you see they're

all deformed. They're up on end.

They're sheared up.

They're broken. They're folded.

>> These veins run for hundreds

of miles in a north-south

direction. Similar sandwiches

of gold quartz and broken rock

are found along the entire

length of California,

and strangely, they all run

parallel to the coast.

Whatever immense force

shattered these rocks

must also have created

the hot fluid which carried

and concentrated the gold.

But what was it?

Geologists finally solved

the mystery in the 1950's,

when the revolutionary theory

of plate tectonics shed light

upon how California

and its mountains were made.

They discovered that beneath

the Pacific Ocean, a giant plate

of the Earth's crust moved

eastwards. It plowed into

the American continent,

crumbling huge slabs

of the sea floor as it went.

>> If this big rock

is ancient North America,

over the last 300 million years,

we had a spreading ocean floor

push the ocean and sediments

on top of the ocean

against North America

and stack these pieces

of ocean floor and sediments

on ocean floor up on end

against western North America.

>> California was pushed

above the waves, a mountainous

mass of crushed, crumpled,

and upended rocks separated

by huge cracks running deep

into the crust, creating

a landscape compiled of giant

slabs stacked parallel

to the coast.

This immense mountain-building

process also had the power

to create a piping-hot fluid.

Buried rocks were squashed

under unbearable pressure.

They superheated,

and a 600-degree fluid

was squeezed from them.

Like water running in a river,

this piping-hot fluid

had the ability to concentrate

the scattered gold.

As it washed through the rock,

it leached out minute particles

of gold, creating

a mineral-rich soup.

It poured into the giant cracks,

which pipelined it

to the surface.

As the fluid cooled,

the gold coagulated,

and the quartz crystallized,

forming a solid

gold-bearing quartz vein.

In total, 35 million ounces

of this mountain gold

were blasted out of California,

one of the most profitable

gold-mining areas of its time.

>> Wherever you have oceanic

plates colliding with the edge

of a continent, you're always

going to create fluid,

you're always going to move

those trace amounts of gold,

and that will get focused

into major faults to form

large lode gold deposits.

They're part of

the mountain-building process.

>> Similar gold-bearing quartz

veins lie beneath the coastal

mountains all around

the Pacific rim, where the ocean

floor has crumpled under

gigantic Earth forces.

Scientists investigating

how California's mountain gold

formed have found...

Ancient fluid bubbles,

proof that a hot liquid

deposited the quartz and gold;

Parallel beds of broken,

altered rock, evidence

that the gold-rich fluid

was squeezed from rocks

as mountains formed.

By the 1880's, only 30 years

after the first gold strike,

California's mountain gold

became increasingly difficult

to find. By then, gold hunters

in neighboring Nevada

had stumbled upon an entirely

different type of gold deposit,

but it was the sort of deposit

that could drive men to murder.

>> In the 19th century,

Forty-Niners found

70 million ounces of river gold.

Then they began to ransack

the mother lode, blasting out

over 35 million ounces

of mountain gold,

squeezed from the rocks

as California formed.

[explosion]

For many years, scientists

believed that only the colossal

forces that created mountains

had the power to concentrate

gold scattered throughout

the rocks. But gold strikes

made in neighboring Nevada

were to shatter this theory.

Massive gold veins were found

in the Sagebrush Hills

of the desert. A tidal wave

of gold hunters left California

heading east. The almost

uncharted desolate state

of Nevada began to light up

with life, as gold strikes were

made across the high desert.

This was the gunslinging

Wild West, and the rough

mining town of Bodie had one

of the toughest reputations.

>> It's hard to imagine

more than 8,500 people

up along this stretch here,

lawlessness, lots of fights

breaking out.

[gunshots]

Lots of saloons, opium dens,

and brothels.

>> It was said that a man a day

was killed in Bodie.

[gunshot]

And some historians believe

the fickle geology

of these gold deposits

may have played a part

in this murder rate.

>> Here, the veins were much

more segmented and broken up.

So while one miner

might be mining along

on the vein, another miner

might not be, which would lead

to animosity and tension

and the occasional fight.

>> Geologists realize that,

unlike California's gold seams,

which ran parallel to the coast,

Nevada's were scattered

randomly across the desert.

The hunt was on to understand

why Nevada's gold veins

were so chaotic.

300 miles northeast

of the cramped old mine in Bodie

is the Midas mine.

Large enough to drive

a truck down, it's one

of a handful of remaining

gold quartz mines in Nevada,

and it's a geologist's paradise.

>> It's wonderful to have

an underground mine, because

when you go underground,

you have a 3-dimensional picture

of the geology.

It really helps you get

a feel for what clues

to be looking at that we

might see on the surface

that we might see

better expressed underground.

>> Working mines like Midas have

become geological laboratories

and are helping to unlock

the mystery of Nevada's

scattered gold veins.

Every day, the miners drill

the face and pack it

with explosives, exposing

new networks of quartz veins.

This is just like the old days

but we're high-tech.

They're gonna drill a space out.

Will load it with explosives

and blow it up.

>> 450 pounds of explosives

are about to blow to reveal

the gold-bearing quartz vein.

[explosion]

>> That was great, and to think,

it's so much safer than what the

old-timers had to go through.

>> Once the dust settles,

it's possible to take

a closer look.

>> This is quite a nice big

quartz vein. If I compare

these quartz veins to the veins

that I've seen in California,

they're substantially different.

For one, if I look at these

bands, these dark gray bands

in here.

>> These gray bands are

the first sign that something

very strange has happened here.

>> In a hand sample,

I'll see that there's

lots of gray material.

All that gray material

is silver.

If I look even closer,

I can see little fine flecks

of yellow. That's gold.

The source rock that formed

all of these veins

was much different

than the source rock that caused

the California veins to form.

The California veins

only have gold, and these

are loaded with silver.

>> And the clue to the identity

of the source of Nevada's gold

lies either side

of the quartz vein.

Unlike California, these

wall rocks are not crushed

and have never been

on the ocean floor.

>> This wall rock is

of a volcanic origin,

very similar to, like,

Mount St. Helen's.

>> So it wasn't

mountain-building

that concentrated the gold

and silver in this vein.

It was a volcanic process.

Perhaps the Midas mine

was once a giant volcano.

Geologists went looking

for clues not inside the mine,

but directly above it.

>> Everywhere above

the Midas mine, we see

these strange outcrops.

They're flat on the top

like a table, and if I look

closer, I can see fine

little bands and layers.

>> The outcrop is made of thin

layers less than 1/8" thick.

And there are thousands

stacked on top of each other

like a deck of cards.

>> You've got browns and

yellows, whites, and purples.

Understanding outcrops like this

will help us understand why gold

is deposited at such shallow

depths within the Midas mine.

>> These distinctive

layered rocks are not formed

by a volcano, but another type

of volcanic process that can

still be seen today in Gerlach,

northwest Nevada.

In the middle of the dry

blackrock desert, they found

a mysterious oasis,

and rising out of the landscape

a spectacular multicolored

hot spring, one of over 300

in Nevada.

This bizarre geological wonder

began to form just 45 years ago.

>> Volcanic processes beneath

the Earth heat the groundwater.

It spills out at the surface,

and like a boiling teakettle,

dumps a layer of mineral scale.

>> The water is slowly running

over the tops of these terraces.

It's depositing minerals

in fine little sheets,

kind of like a deck of cards

or a book on end.

This rock, from over there,

has fine laminations or layers.

Rocks like these and terraces

like those are found right above

the Midas mine, which tells me

that Midas was once

an enormous hot spring.

>> Geologists realized it was

hot springs that brought

the gold and silver quartz veins

to the surface in Nevada.

Gold and silver particles

are scattered in molten rocks

deep inside the Earth.

This hot rock released

a gold and silver rich fluid.

As rainwater soaked into

the ground, it reached

the scorching rocks deep

in the crust and superheated

to 900 degrees fahrenheit.

Hot and buoyant, the water began

to rise, sucking up the gold

and silver soup as it went.

As it neared the surface,

the water boiled and dumped

bands of silver and flecks

of gold in the chaotic fractured

pipework of the hot spring.

>> Imagine this landscape

15 million years ago--volcanoes

as far as the eye could see,

hot springs dotting

the landscape here and there.

>> Gold is forming at this

moment in hot springs

all over the world.

Even Yellowstone has traces

of gold in its water.

One of the world's biggest

and most profitable gold mines,

Yanacocha, northern Peru,

is a gold and silver deposit

which man has plundered

since the rule of the Inca

800 years ago.

High in the volcanic Andes,

it's a massive 535 square miles

and has produced over $5 billion

worth of gold, all of it

originating beneath

a bubbling hot spring.

Scientists investigating

how gold-silver veins

formed in Nevada

have found volcanic wall rock,

proof that the gold-rich fluid

came from molten rock,

and a multicolored layered

outcrop, evidence that ancient

hot springs deposited gold

in Nevada.

Nevada's hot-spring gold

deposits yielded over 40 million

ounces of gold and 500 million

ounces of silver, but by 1920,

Nevada's gold seams were

increasingly uneconomical

to mine. The desert became

littered with ghost towns.

It looked like America

had run out of gold.

But in 1961, a new type

of deposit was found.

But it couldn't be seen

or touched. It was invisible.

It would become the biggest

strike in the history

of America's gold.

>> America's gold was

concentrated by incredible

mountain-building forces

that formed California...

and volcanic processes deep

beneath Nevada's hot springs.

But as the deposits

became exhausted,

geologists frantically searched

for new stashes of gold.

Then in 1961, geologist and

gold prospector John Livermore

noticed a suspicious

50-mile-long crack

in the middle of Nevada

called the Carlin Trend

and set out to investigate.

>> John Livermore came to these

hills following up a theory

that gold deposits would be

aligned directly above a deep

crack in the Earth's crust.

He'd come up to outcrops

like this, and he would go ahead

and want to look at them.

>> The rocks are a strange

mixture of mud and quartz,

a mineral created in hot fluid

and a good clue that gold

might be deposited nearby.

>> Based on his experience,

he knew a lot of hot fluid

had come up this crack.

However, he couldn't see

any evidence of gold,

no quartz veins,

no visible gold.

But on a hunch,

he sampled this rock,

took it back to the assay lab

to see if there was

any gold in it.

>> In assay labs,

rocks are crushed

and blasted in a furnace

to over 1,800 degrees.

And as the liquid rock cools,

the minerals begin to separate.

>> At the end of this process,

something extraordinary

has happened.

An ordinary-looking rock

actually contained a grain

of gold at a concentration

of about 5,000 times you would

normally see in the Earth.

It doesn't look like much,

but this is what they mine

every day.

>> Livermore's hunch paid off.

50 miles long and 5 miles wide,

the Carlin Trend is now one

of the largest mining districts

in the world.

This vast man-made pit is big

enough to be seen from space.

>> This is the BetzePpost pit,

one of the world's

largest gold mines.

It contains 45 million ounces

of gold. They have to mine

10 tons of rock in order

to get one ounce out.

As you can see, it's huge--

2 miles long, a mile wide,

2,000 feet deep.

>> Because gold is so valuable,

the extraction of just a few

thousand ounces a day pays

for this extraordinary

mining operation.

And removing the gold ore

requires drastic action.

[explosion]

>> Wow. That's what 400,000

pounds of explosives looks like.

>> Giant diggers work 24 hours

a day excavating over

90 million tons of rock a year,

Enough to cover Central Park

in 55 feet of rubble.

But within this raw gold ore,

not a speck of gold has ever

been seen with the naked eye.

>> The mystery is,

where's the gold?

You can't see it.

The rocks look really ordinary.

The clue to where this gold

is hidden is in the internal

structure of this rock.

>> Magnified 500 times,

the gold is still invisible.

But this rock is

an extraordinary lattice

of quartz and mud perforated

with strange cavities.

>> It looks like a honeycomb,

like something's eaten away

at it. Clearly some strange

geologic process has

concentrated and hidden

the gold in the rock.

>> Scientists realized if they

were going to solve the puzzle

of how gold came to be hiding

in these rocks, first they

would have to understand

where the rocks came from.

A clue was found

in the 19th century by

cattle rancher Absalom Lehman

in the eastern reaches

of Nevada.

>> In 1885, Absalom Lehman

stumbled upon a hole

in the ground, and with rope

and lantern, he lowered himself

in the Earth and discovered

this beautiful cave system

with some of the most

spectacular cave formations

in the world.

>> The solid foundations

of this cave are made

of a messy mixture of mud

and calcium carbonate shells.

They are the remains

of tiny sea creatures,

evidence that Nevada

was once covered

by an ancient tropical sea.

>> For millions and millions

of years, creatures with shells

composed of calcium carbonate

began to rain down through

the ocean and accumulate

on the sea floor forming

this calcareous ooze.

Later, this ooze hardened

into a sedimentary rock

called limestone.

>> These extraordinary

structures in the cave

were formed when water eroded

the huge limestone bed

that sits underneath Nevada.

And back over at the Carlin

Trend, scientists noticed

that the gold ore was made

of a very similar type of rock.

They figured out that

the Lehman Cave limestone

and Carlin Trend gold ore must

once have been the same rock.

>> This is fresh limestone.

This is gold ore.

Clearly something happened

to change this rock into

this spongy gold-bearing ore.

Well, the clue is

in the chemical reactivity

of this limestone.

If I put dilute hydrochloric

acid on this limestone,

note how it fizzes.

Very reactive.

The acid is eating away

at the rock.

Now if I put the acid

on the spongy gold ore...

no reaction. The fluid

is soaking into the rock

like a sponge.

>> Scientists concluded

the reason Carlin Trend gold ore

did not fizz is that

it had already been attacked

by an acid.

Beneath the bed of limestone

at Carlin is a gigantic

vertical crack.

Geologists now believe

that a blast of hot, acidic

gold-rich fluid was once

forced upwards from deep

within the Earth.

It streamed through the crack,

drenching the limestone.

The acid ate into it,

leaving a spongelike

muddy framework behind.

And in the cavities, it dumped

quartz and the most minute

sprinklings of gold.

>> It's only been very recently

that scientists have been able

to use even more sophisticated

imaging equipment--microscopy--

to image down to the scale

of individual atoms.

>> Magnified 100,000 times,

tiny specks of submicroscopic

gold can be seen embedded

in the rock.

Zooming in further

a staggering 4 million times,

the gold particle

Is finally revealed.

This fleck of gold is only

5 nanometers in diameter,

one-millionth the size

of a pinhead, and each tiny

white dot is an individual

gold atom.

>> These ordinary-looking rocks

have produced 65 million ounces

of gold from a single crack

in the Earth known as

the Carlin Trend, and it's made

the United States the fourth

largest gold producer

in the world.

>> Scientists investigating

how Nevada's gold ore formed

have found a spongelike

rock structure, suggesting

that something ate away

at the limestone,

and gold ore not reacting

with acid, evidence that

an acidic fluid had already

attacked the limestone,

showering it with minute

particles of gold.

Similar Carlin type deposits

have since been discovered

yielding a further

35 million ounces of gold.

Yet these discoveries

may only be the tip of the iceberg.

Geologists are now using

state-of-the-art equipment,

hoping to unlock millions

of ounces of American gold

trapped deep beneath

the Nevada desert.

>> Throughout world history,

over 5 billion ounces of gold

have been recovered by man,

and almost 1/10th of this

has been found in California

and Nevada, adding up

to a staggering $280 billion

worth of bounty.

>> How much remains

is anyone's guess.

There is no reason not to

assume as much gold exists

as has been mined in the past.

But geologists, prospectors,

explorationists have found

the easy gold.

>> In the past, prospectors

and geologists homed in

on this easy gold by following

geological clues exposed

on the surface.

But vast areas of Nevada

are covered in a deep layer

of mud and gravel that has been

eroded from the surrounding

mountains. Geologists believe

hoards of gold still lie

concealed beneath this layer

of gravel, unseen by anyone

for millions of years.

Finding all this buried gold

in an area covering

110,000 square miles

is no easy task.

But one man has the ability

to see under the ground,

using pioneering technology.

>> I've got gold in the hills

around me.

I've got good reason to believe

that there's gold beneath me

in the rocks, if I could just

see through this sand

and gravel.

This little piece of equipment,

I believe, is going to help me

figure that out.

[machinery whirring]

>> The geo-probe is drilling

not for rocks,

but for groundwater,

200 feet below the surface,

and it's this groundwater

that holds the key to finding

Nevada's hidden gold.

>> If there's a gold deposit

concealed by the sand

and gravel, the groundwater

will interact with it,

and you'll pick up clues.

>> Traces of metals associated

with gold seep into

the groundwater, clues that will

lead Hodges to the secret

location of the gold deposit

deep below the surface.

>> Imagine an iron bar rusting

in a bucket of water.

The trace metals are going to

come out of that rusted iron bar

and are going to be disseminated

in the groundwater, and you

would be able to sample

that groundwater and tell

that there was an iron bar

somewhere nearby, just as we're

going to be able to sample

this groundwater and know that

there's a gold deposit

somewhere nearby.

So in a sense, it's like

the deposit of gold

is creating a scent.

>> If Hodges can latch on

to a whiff of this scent,

he can track it back

to find the gold.

Once the drill

is deep enough, Hodges

pumps out the groundwater.

[pump whirring]

>> Ok. I think I've got

enough sample now.

Somewhere in this bucket

of muddy water, I believe

we've got some clues.

>> This is no ordinary

pickup truck.

It's a state-of-the-art

mobile laboratory.

Hodges measures how many

trace metals are in

the groundwater,

and the scent here

is particularly strong.

>> And it's telling me

that I've likely got

a lot more trace metals.

Arsenic, antimony, mercury,

copper, lead, zinc are the kinds

of trace metals that are often

associated with gold deposits.

And it looks to me like we're

moving in the right direction.

>> In the same way

the old-timers traced the gold

up into the mountains,

Hodges tracks the increasing

concentration of trace metals

in the groundwater.

>> It's like a little childhood

game of hide-and-go-seek.

Am I getting hotter,

or am I getting colder?

And that makes it a science.

>> The net is tightening

around the gold deposit.

The scent is strongest in this

4-square-mile target zone.

But it's still too large an area

to begin test-drilling for gold.

To focus in further,

Hodges needs to literally

see inside the Earth.

>> Well, this instrument here

is a gravitometer,

and it has the ability

to measure how dense the rocks

are beneath this point.

Just as there's a landscape

here on the horizon behind me,

there's a landscape

in the bedrock underneath me.

>> Multiple readings

from the gravitometer

create a secret treasure map

of the terrain submerged

beneath the surface gravel.

From this rock density map,

Hodges can pinpoint the likely

location of the gold deposit.

He has found a suspect gas

in the Earth over a mile long

and 250 feet below the surface.

It's a good sign, as gold

is often found deposited

in deep cracks. It's time

to start drilling for gold.

The diamond-studded drill

probes the crack and extracts

a cylinder of bedrock.

This is the first

in a sequence of test drills

along the crack, and the results

are tantalizing.

>> After all this traveling

around, I'm finally able to see

the rocks for the first time.

These rocks have been

out of view for millions

of years, and to me,

it's one of the most exciting

things about this line of work.

I get to look at these rocks

before anybody else has ever

seen them, and I could compare

them with the rocks that I've

seen elsewhere in the mountains.

In this piece of core,

I see several different kinds

of fragments of rocks.

Some of them are quartz.

Quartz we know is good for gold.

>> Hodges could be on the verge

of a massive gold strike,

adding to his tally

of 30 million ounces

discovered so far.

>> Reaching down into the Earth,

pulling out a sample that says

there's gold in it and realizing

that you've done it.

And in a sense, it connects you

with those old-timers,

the same spirit of the old west.

It's exciting.

>> It's pioneering geologists

like Hodges who will find

what's left of America's gold.

Scientists and prospectors

investigating how gold

is concentrated around the world

have found gold in heavy black

sands, evidence that rivers

concentrate gold on the inside

bends...

Parallel beds of broken,

altered rock, proof that

gold-rich fluid was squeezed

from California's mountains...

Multicolored layered outcrops

show that ancient hot springs

deposited gold quartz veins

in Nevada...

And spongy gold ore,

evidence that an acid dumped

minute sprinklings of gold

in the rock.

The Earth does not relinquish

her gold treasure easily.

Man's irresistible urge to find

gold is the driving force

which helped pioneer

the science of geology.

Investigating how gold is

concentrated across the world

is not just the story

of metal and mining...

It's an epic tale that has

revealed how the Earth is

dynamically changing to this day.

And over billions of years

of the planet's history.

Living proof that the Earth

is never at rest.

-- Sync, corrected by elderman -- -- for www.MY-SUBS.com --