This is our planet, the Earth.
It's a remarkable, ever-changing world, full of natural wonders.
But there's more to Earth than this, much more.
Because our planet is unique in the solar system,
perhaps even in the universe.
Four and a half billion years
have made it a world of extraordinary landscapes
and a home to life.
My name is Iain Stewart and I want to show you
how our planet works.
I'm going to explore volcanoes.
They're terrifyingly destructive.
But they're also the most fundamental force on the planet.
Volcanoes are part of a global system
that continually reshapes our world.
They hold the key to the origins of life on Earth.
They saved the planet from possibly the biggest crisis it's ever faced.
And they've even formed a partnership with life
that keeps our planet habitable.
Ethiopia, eastern Africa.
This is the Afar region, bandit country.
So I've hitched a lift with the Ethiopian military.
I' m off to one of the hottest and remotest places
on the surface of our planet,
to see the most powerful force on Earth in action.
We've got plenty of equipment because ahead of us
there's some serious climbing.
We've touched down on a dry, brittle surface of recently cooled lava.
I've come all this way to see one of the most remarkable volcanoes
anywhere on the planet.
It's called Erta Ale.
The name means smoking mountain to the local Afar people.
It's reckoned that the lava lake has been active for at least 90 years,
making it one of the longest known eruptions.
But no one's quite sure
because it's only been properly studied for the last 40 years.
I've been lucky to see a lot of volcanoes in my time
and I've never seen one
that has a permanent lake of molten lava in its crater.
But there's another reason why this volcano is very special.
And to see that, I need to get down into the crater
and see the lava up close.
- Sit back, sit back. - After, after.
Okay.
That's it. That's good.
It's close to a 100-foot drop to the terrace below.
I've waited until sunset to take a closer look
because the lava is at its most spectacular at night.
This is as close as I can safely get.
Oh, wow. Look at that. That is magnificent.
I mean, it's taken us a hell of a journey to get here,
but that makes it all worth it.
I' m standing on the edge of an active volcano,
right next to a big pool of molten lava.
What makes this lava lake more than just pure spectacle
is that it's a window that allows us to look deep into the Earth
and it helps us understand the forces that shape our planet.
Just take a look at the motion of the lava lake speeded up.
It wells up on one side of the crater and forms a dark crust as it cools.
Then this crust moves across the surface of the lake
driven by the churning action of the lava below.
Finally the crust sinks back down.
This process of molten rock
churning away below the surface affects the planet on a global scale.
But the Earth's heat does far more than simply fuel volcanoes.
It continually rebuilds the planet's surface
and it created the conditions for life on Earth to begin.
To understand where our planet's immense inner heat comes from,
you have to go back four and a half billion years.
This is the time of our planet's birth.
you may not recognize it, but this is the Earth.
Little more than a few pieces of rock colliding as they circle the Sun.
But these impacts produced immense amounts of heat,
as did underground radioactive decay.
Eventually, when the outer layers of the planet cooled,
these powerful sources of heat were trapped in a huge, hot core.
The centre of our planet is around as hot as the surface of the Sun.
This is the source of Earth's vast heat energy.
And it's what fuels volcanoes to this day.
Earth's hot core has been continuously releasing
unimaginable amounts of heat since its formation.
Even after four and a half billion years, there's still plenty left.
Volcanoes are the most obvious examples of the Earth's inner heat in action.
But this inner heat also continually reshapes
the surface of the whole planet.
It creates a restless, constantly changing landscape.
Iceland is a great place to see exactly how the planet's inner heat
is able to transform the surface of the Earth.
Magma usually lies many miles beneath the surface
but here, in Iceland, it's much closer.
And that has a dramatic effect.
Sulphurous fumes and bubbling hot pools with hundred-degree-plus temperatures
hint at the power that is just beneath the surface.
There are naturally heated pools everywhere on the island,
which makes going for a dip something of a national pastime.
But the people here might not be quite so relaxed
if they knew exactly how the water gets heated.
Just 12 miles beneath Iceland
is a vast column of super-heated rock called a plume.
It's over 100 miles wide and at least 370 miles deep.
Created more than 50 million years ago,
the plume is sustained by heat continually rising up
from Earth's hot core.
This giant plume does more than just warm up Iceland's hot springs.
It also created Iceland itself.
In 1963, there was an event that showed how it must have happened.
A volcano, just below the sea's surface, blasted its way out of the water.
A new island, Surtsey, was born.
This is what Iceland must have looked like more than 50 million years ago
when it first burst above the surface.
Iceland owes its existence to the plume of super-heated rock beneath it.
But it's also shaped by the Earth's inner heat
in another even more dramatic way.
This extraordinary rock face at Thingvellir shows how.
From the air it's clear just how unusual this rock face is.
It's a crack in the Earth's surface that runs as far as the eye can see.
But even this is just a small part of something far bigger.
To the left is a gigantic slab of the Earth's crust,
which runs unbroken for over 4,000 miles,
from here, under the Atlantic
across the USA, all the way to California.
It's what's known as the North American Plate.
The Earth's surface is broken up into seven vast chunks called plates.
They're so enormous they can carry an entire continent,
even extending under the ocean.
Strip away the Atlantic and the long boundary between two plates
that runs along the ocean floor is exposed,
until it rises above the waves,
and cuts through Iceland,
to eventually join up with the rock face at Thingvellir.
These sheer rock faces were once joined together
but driven by the churning force of molten rock beneath them,
the land was split apart.
It happens because hot rock from the Earth's interior rises up.
Near the surface, the rock spreads sideways in two directions.
It begins to lose heat.
Eventually, the much cooler rock sinks back down.
Through this spreading process,
the Earth's crust is very slowly dragged apart
and it's this that ultimately causes the land masses to move.
225 million years ago,
our planet was unrecognizable.
All the continents were joined together
in a single super-continent called Pangaea.
As the plates moved, this super-continent broke up.
New oceans formed as continents drifted around the globe.
It's this that has created the world we know today.
But the churning heat beneath us means the plates never stop moving.
In the distant future, our continents may once again
be reunited in another giant super-continent.
This is what happens when the plates move apart.
But when they collide, the results can be even more dramatic.
The collision of the Earth's plates is responsible
for the most spectacular mountain ranges on the planet.
Like the Southern Alps in New Zealand.
These stunning peaks run 300 miles along the west coast,
forming a dramatic spine down the island.
Tens of millions of years ago,
the collision of the Pacific and Australian plates
created the New Zealand we know today.
Along the collision Zone, the land was buckled
and a line of mountains rose up.
New Zealand's mountains are around five million years old.
That may sound ancient,
but it's just a geological blink of an eye.
Yet even in this short timescale, these peaks have grown into giants,
many over 10,000 feet high.
All the great mountain ranges formed in this way
as the planet's inner heat forced the continental plates to collide,
crumpling the surface of the Earth.
The European Alps,
the South American Andes,
the Himalayas of Central Asia.
They're all relatively young, born out of recent collisions between plates.
Sometimes you can actually see their growing pains.
Earthquakes are a horrific force of destruction.
Entire cities can be wiped out at terrible human cost.
They happen with the Earth's plates push against each other and get stuck.
Stress builds up until it's suddenly released.
In October 2005, a devastating earthquake
hit the western Himalayas in northern Pakistan.
Much of the area around the town of MuZaffarabad
was completely flattened.
But satellites measuring the height
of the surrounding land before and after the earthquake
revealed that something else had happened as well.
The red and yellow colors
show how the hills close to the epicenter
had actually risen as much as 1 6 feet during the earthquake.
From earthquakes to mountains, geological forces are shaping our world.
They have helped build the Himalayas
into the greatest mountain range on Earth,
soaring reminders of the power of our planet.
Despite their size, mountains are continuously under attack.
And the force that can eventually destroy the highest peak
is nothing more than water.
Mountains create the very rain that attacks them.
The higher the mountains are pushed up,
the higher the air is forced to rise to cross them.
So the air cools and condenses into clouds, which produce rain.
And it's surprising just how effective the power of water can be.
And forward!
Bring it down!
Hold on!
This gorge is hundreds of feet deep.
It was carved out by New Zealand's Shotover River
relentlessly wearing away at the mountain range,
and it's still getting deeper.
As rivers erode the rock,
they also carry vast quantities of silt from the mountains down to the sea.
It happens on a massive scale.
In South America, the Amazon River carries away
over two billion tons of the Andes every year
and deposits much of the sediment in the Atlantic Ocean.
And on the Indian subcontinent,
the Ganges River that starts high in the Himalayas
grinds away close to a billion tons of rock every year
dropping millions of tons almost 1, 900 miles
down the river in the Indian Ocean.
If it wasn't for the movement of the plates building new mountain ranges,
water would eventually erode away all the land on our planet.
It's hard to imagine, but if the plates should ever stop moving,
our planet would become a water world.
It may take an unfeasibly long time,
but eventually the land would be worn down and washed out to sea
and Earth would be covered in a vast ocean.
So it's thanks to the collision of the plates continually pushing the land up
that we've still got terra firma to stand on.
Our world is constantly reshaped by a never-ending battle
between the geological forces that push the land up
and the forces of erosion that wear it down.
But the Earth's inner heat
has made a profound difference to our planet in another way,
perhaps the most important way of all.
It began around four billion years ago.
This is Rotorua in the North Island of New Zealand.
It's one of the most volcanically active places on the planet,
possibly similar to Earth millions of years ago.
To us, the young Earth would have been a hellish place.
But ironically, this volcanic activity helped create the right conditions
for the most important change in the history of our planet.
Volcanoes provided the surface of our young planet
with warmth, water and a potent cocktail of chemicals.
And it was this combination which inadvertently prepared Earth
for an utterly remarkable event.
No one's sure exactly how it happened,
but around four billion years ago, our planet saw the birth of life.
These pools have a unique chemistry
that is very similar to what would have existed on the early Earth.
Bruce Mountain has studied these pools for many years.
He's going to show me how the first life on Earth might have begun.
We don't have a time machine to take us back so the only thing we can do
is look at things that we think are similar to what they were like.
And these hot springs are very, very close
to those that would be found on the early Earth.
So what's the temperature of this water?
Well, the water's 75 degrees Celsius,
so you' d definitely get burned if you put your finger in there.
And it's full of hydrogen sulphide, which is quite poisonous.
There's a bit of arsenic in the water as well.
Surely there can't be anything living in there. What am I looking at?
There's billions and billions and billions and billions of organisms
living in that water, and they form these orange fibres.
For the microbes living within the orange fibres,
these toxic chemicals within the water are a rich soup of nutrients.
Pools like this were very common on the early Earth.
Fed by volcanic activity,
they may have provided all the right chemicals needed
for the emergence of life.
MOU NTAIN : Deep down below us, there's a body of magma that's very hot.
Now, the magma itself is giving off gases like
carbon dioxide and sulphur dioxide
and that provides the food for these bacteria to grow.
So the volcanoes are like a supply chain providing all this stuff?
They' re the heat engine that drives the whole process.
STEWART: Volcanic pools like this
are one possible place where life might have begun.
But there is an alternative theory,
as volcanoes created other places where life could have started.
Like hydrothermal vents.
These too are the result of volcanic activity,
but they are found in the deepest parts of the oceans.
Today, they support an extraordinary diversity of life.
But four billion years ago,
it's thought that the combination of high temperatures
and rich chemicals that the vents produced
might have stimulated the emergence of life.
But the role of volcanoes went beyond just kick-starting life.
They have played a critical role in nurturing and protecting it, too.
During Earth's infancy,
the Sun wasn't burning as brightly as it does today.
In fact it was about 30% cooler.
With a dimmer Sun bathing the planet in weaker sunlight,
Earth was actually in danger of freezing.
It was volcanoes that provided the young vulnerable planet
with a way to keep warm, but not in the way that you might think.
Earth wasn't warmed up by all that hot lava spewing out,
but by an extraordinary gas that volcanoes pumped out.
And that gas was carbon dioxide.
Today we think of carbon dioxide as a dangerous gas,
causing havoc through climate change.
But actually carbon dioxide has always been vital to our planet
because it traps heat in the atmosphere that would otherwise be lost to space.
To see just how critical carbon dioxide is for Earth,
take a look at our neighbors.
Mars is a frozen wasteland
with an average temperature of minus 60 degrees.
That's because its atmosphere
doesn't have enough carbon dioxide to keep it warm.
At the other extreme, the temperature on the surface of Venus
is hot enough to melt lead, not simply because it's a bit closer to the Sun,
but because Venus has an atmosphere
with thousands of times more carbon dioxide than Earth.
The early Earth was much more volcanic than it is today
because its core was so much hotter.
This provided enough carbon dioxide to compensate for the weak Sun.
Volcanoes prevented the young Earth from freezing over
and so early life was able to survive.
But even this was not the end of what volcanoes have done for life on Earth.
About 600 million years ago, they also helped trigger
a great evolutionary leap in Earth's history.
Shark Bay in Western Australia
is home to some of the oldest life forms on Earth.
These strange domes are made up from layer upon layer of bacteria.
They're called stromatolites.
For most of Earth's long history,
this was the most advanced life on the planet.
For around two billion years,
stromatolites ruled our world unchallenged
and there was nothing to suggest that this was ever going to change.
But Earth and the stromatolites were to face a catastrophe,
perhaps the most serious crisis life has ever faced.
Around 700 million years ago, our planet started to cool.
It was the beginning of an Ice Age.
No one is quite sure why it happened,
but it seems that our entire world was plunged
into an interminable winter.
Some scientists have called it the time of snowball Earth
because the whole planet may have appeared as an icy ball.
Others believe that the Earth was cold but not completely frozen.
Travel out to Jupiter and you can get some idea
of what Earth might have looked like.
Europe is one of Jupiter's moons. A frozen landscape
that might mirror parts of Earth millions of years ago.
But knowing what Earth looked like
doesn't convey just how terrible the conditions would have been.
A blizzard high in the Alps in mid-winter is as close as I can get.
Today the average surface temperature of the planet
around the world is 1 5 degrees Celsius.
700 million years ago, it was much colder.
That average surface temperature plummeted to minus 50,
5-0 degrees Celsius.
Most of the Sun's heat was reflected back to space.
It looked like the Earth might never heat up again,
but clearly something happened.
It was volcanoes that came to the rescue.
They erupted with tremendous force,
even blasting through the ice sheets that covered much of the planet.
It must have been an extraordinary time.
The nearest we've experienced was in 2004
when an eruption was filmed
bursting through an ice sheet in central Iceland.
This is what would have happened millions of years ago,
but on a global scale.
The heat from volcanoes would have melted holes in the ice,
but that's not what saved our planet.
It was the tons of carbon dioxide gas it released that did the trick.
As volcanoes continued to erupt,
levels of carbon dioxide steadily built up in the atmosphere.
Until around 630 million years ago,
the layer of carbon dioxide became so thick
that it trapped enough heat to release the planet from its endless winter.
At last, a thaw began.
Fierce storms pounded the planet
and Earth's cold and slushy climate began to warm.
In just a few hundred years,
temperatures would rise dramatically.
and Earth would never be the same.
Fortunately, over time our planet's climate stabilized
and Earth slowly returned to normal.
Volcanoes had set the stage for a dynamic new era.
In South Australia, there's evidence for what happened
to the evolution of life after Earth's long winter.
Five hours' drive out of Adelaide,
paleontologist Jim Gehling is traveling to see some of the rarest
and most ancient fossils in the world.
We' re going to a secret location in the Flinders Ranges.
It's the place where you can get a look at the very first fossil evidence
of complex life on Earth.
STEWART: The area Jim's visiting was once at the bottom of the sea.
600 million years ago,
the oceans were the only place where life could be found.
But a warmer Earth brought change.
For a billion years, all that the Earth had seen
was microscopic single-celled creatures. The best they could do was to form
these domes of slime, which we call stromatolites.
Stromatolites were the Earth's dominant life form.
Were it not for the violent climatic changes triggered by volcanoes
at the end of the snowball era, they might still rule the planet today.
Instead, new life forms arose.
We see a revolution in the history of life.
We see a sudden increase in size and complexity of the single cell creatures
and soon after, you find impressions on rocks
of the very first large creatures,
the oldest multi-cell creatures, the Ediacara fossils.
STEWART: These fossils may represent
the most important leap forward in the history of life on our planet,
but that doesn't mean they're easy to spot.
This is a very old surface and if we clean it off
and then push this putty onto the surface,
- you can actually see the impression... - Look at that.
... of a thing called Parvancorina.
You know, it looks like somebody's signet ring.
- It's like a trademark. - Exactly, yeah.
And that's really all the fossil is.
It's the impression of this soft-bodied creature
as it was preserved instantly on the sea floor
about 560 million years ago.
These are nothing like the fossils I' m used to.
I mean, that... I would never, ever have spotted that.
Parvancorina wouldn't attract much attention today,
but this animal had made a gigantic evolutionary leap.
Unlike single-celled microbes,
this was a complex creature with a head, skin and internal organs.
Under here we can actually see the imprint of quite a large creature,
at least the size of your hand.
This is Dickinsonia and it has got the finest segments
that you can actually believe.
Once you get it at the right angle
you can actually see the details of these body segments.
There are about three there. There's another one, there.
It's like it was impressed there yesterday.
Every little detail is preserved on these sands.
It's beautiful.
Dickinsonia could grow to over three feet long.
It's thought they lived on the sea floor
soaking up nutrients through their skin.
Here for the first time we' re seeing life
that's become multi-celled, it's large.
These are the creatures that gave rise to the life that we know today.
For two billion years,
our planet had been dominated by stromatolites.
Complex multi-celled life exploded into many new shapes and sizes.
Emerging from the sea, animals and plants
went on to conquer the land and the air.
Volcanoes had created the conditions for a great evolutionary leap forward.
But the planet's powerful volcanoes had one further role to play
in the story of life on Earth.
A role still vital to the survival of complex life.
It involves an amazing alliance, a partnership between volcanoes and life
which regulates the temperature of the planet.
It may be hard to believe,
but working together volcanoes and life fine-tune the Earth's temperature
by controlling the amount of carbon dioxide in the atmosphere.
This extraordinary process begins in an unlikely place.
The oceans, with tiny creatures called plankton.
They may be individually microscopic
but they're so abundant that when they come together
they can be seen from space.
Every year they proliferate into huge blooms
that color the ocean green.
The oceans absorb carbon dioxide from the atmosphere
and plankton use this carbon for both photosynthesis and to make their shells.
When the plankton die,
they fall to the sea floor and here, over thousands of years,
their shells are slowly transformed into rock.
In this way, huge amounts of carbon dioxide,
the very gas that keeps our planet warm,
are removed from the atmosphere.
So if that was the end of the story,
our planet would have run out of carbon dioxide
and steadily got colder and colder.
But fortunately, a special type of volcano doesn't allow that to happen.
They're called subduction volcanoes.
Where plates in the Earth's crust collide,
the rock on the sea floor containing carbon from the plankton shells
is carried deep into the Earth.
This is called subduction.
As it descends, this layer of rock is heated
and melts, releasing carbon dioxide.
This gas is returned back into the atmosphere during an eruption.
The remarkable cycle is complete.
It's uncanny how life and volcanoes
keep just the right amount of carbon dioxide in our atmosphere,
keeping our planet at a comfortable temperature.
But this process that has sustained all life on the planet
comes at an enormous cost.
Subduction volcanoes are the most powerful on Earth.
you can see just how explosive they are
by looking at one of the most famous eruptions ever recorded.
On May 18th, 1980,
Mount St Helens in the Pacific Northwest was ripped apart.
Within minutes, over 100 billion cubic feet of the mountain
slid down into the surrounding countryside.
Since the eruption, Mount St Helens has been fairly quiet.
But inside its vast crater a giant cone of rock is growing.
Forced up by pressure from beneath,
Mount St Helens is building for another eruption.
The irony is that subduction volcanoes are so highly explosive and destructive
because they're so gassy,
yet it's the release of the gas that's crucial to the Earth.
That's the key to recycling back into the atmosphere
the carbon that's locked in the rocks below.
The whole elaborate system works a bit like a thermostat,
maintaining the right temperatures for life.
Ever since our planet formed four and a half billion years ago,
Earth's inner heat has been continuously struggling to escape.
In fact, you could say that the whole history of the planet
has been driven by the immense heat trapped inside it.
No force on Earth is more dramatic
more destructive, and more violent than volcanoes.
They're the life force of our planet.
This is our planet, the Earth.
It's unique in the solar system, perhaps even in the universe.
My name is Iain Stewart
and I want to show you how our planet works.
I'm exploring the atmosphere.
The atmosphere creates our climate
and protects us against the cold hostility of space.
And it provides oxygen to fuel our bodies.
Our atmosphere is full of contradictions.
It's immensely powerful and yet it's incredibly sensitive.
It's destructive and at the same time it protects us.
It's essential for all life and yet it was created by life.
Without it, the planet would be utterly uninhabitable.
I've come to South Africa for something very special,
a personal tour of the atmosphere.
I' m going to take a ride on a jet, but not just any jet.
This one is one of the fastest planes on the planet.
And, more importantly, it flies high, very high.
This plane is an English Electric Lightning"
a legend from the 1960s,
and South Africa is one of the few places where they're still flying.
My pilot today is Dave Stock.
You' re going to feel like you' re strapped onto the front of a missile.
I don't know if I like that or not.
Part of me likes it and part of it terrifies me.
Look at that!
STOCK: The last of the great Cold War fighters.
"If the canopy does not open... "
Things like that you really don't want to read, really.
How's the helmet?
It feels nice, yeah.
We humans are perfectly adapted to survive at ground level,
where the air has all the right conditions for life.
It's the right temperature, right pressure
and it's got the right mix of gases.
Down here, there's plenty of oxygen about,
but after about three kilometers the air's so thin,
if you didn't have this mask, you' d slip into unconsciousness.
I' d better put it on.
MAN ON RADIO: 121, continue your approach. Flight information...
STEWART: The atmosphere that surrounds our planet
is made up of four key layers, each very different.
Although I'm above the clouds, I'm still at the very bottom,
in a layer called the troposphere.
It's a narrow band,
usually more than six miles thick.
The troposphere is a rich soup of oxygen-rich air.
It's unstable, chaotic and unpredictable but life depends upon it.
And in just a couple of minutes, I'll be leaving it behind.
And now I'm 40,000 feet above the Earth.
STEWART: We're approaching 45,000 feet
and we` re about to cross an invisible boundary in the atmosphere.
We're leaving behind the first layer the troposphere,
and entering the stratosphere.
A very different place.
Here the air is stable and exceptionally dry,
so there's virtually no weather.
The stratosphere is home to the ozone layer
which reduces the amount of lethal solar radiation reaching the Earth.
We've reached 50,000 feet.
Nearly 80% of the mass of gases that make up the atmosphere are below me.
But almost 50 years ago, one man went much, much higher than me,
and he experienced the atmosphere in a completely different way.
On August 16th, 1960,
long before man had set foot on the Moon,
military pilot Joe Kittinger
took a solo journey to explore the heavens.
Not in a rocket, but in a giant helium balloon,
to determine the risks of high-altitude bailouts from air or spacecraft.
The balloon took Kittinger over 19 miles into the stratosphere.
That's twice the height that I reached.
Then Kittinger did something astonishing.
He jumped! This is the actual moment.
He fell to Earth
reaching a speed of almost 620 miles an hour
and yet he had no sense of speed.
KITTINGER I had no ripple of the fabric on my pressure suit
and it was a very weird sensation.
I had no visual reference of anything
so I thought I was really suspended in space.
STEWART: Kittinger had fallen at great speed
as he plunged toward the troposphere, thick with clouds,
floating over a New Mexico desert.
Finally, he opened his parachute.
His jump remains the longest freefall in history.
Just 15 minutes after he jumped, Kittinger was back on the ground.
Falling from the upper reaches of the stratosphere,
Kittinger had plummeted through 99% of the atmosphere's mass.
KITTINGER Fifteen minutes before, I had been at the edge of space
and now, to me, I was in the Garden of Eden.
We really don't appreciate what a beautiful planet we have.
STEWART: Although Kittinger had jumped from high in the stratosphere,
he still didn't reach the furthest edge of our atmosphere.
Above the stratosphere are more protective layers
so wispy and tenuous that they barely exist,
but are vital for our planet.
About 30 miles beyond the stratosphere
lies the third layer the mesosphere.
It's this layer that helps protect us from meteors.
When we see a shooting star
it's actually a meteor burning up high in the atmosphere.
The mesosphere is also home to a strange phenomenon
called noctilucent clouds.
They're thin, wispy clouds that can only be seen in the summer at high latitudes.
Beginning at nearly 50 miles high,
there's the fourth layer the thermosphere.
Here, the atmosphere is so thin that beyond 50 miles
we approach the beginnings of space.
The space shuttle orbits the Earth in the thermosphere.
It's also where nitrogen and oxygen
interact with the Sun's lethal solar wind,
creating the aurora around the Earth's poles.
There's another way of looking at the atmosphere.
If you could unwrap the atmosphere from the surface of the Earth
and put it all into a ball, this is what it would look like.
Its weight is equal to a layer of water 34 feet deep, covering the Earth.
The layer that we spend our lives in, the troposphere, is just a narrow band.
It's a finely balanced mixture of different gases essential for life
but it also has a physical presence.
To understand the troposphere we live in,
you have to think of it not just as gases, but also as a fluid.
In effect, we live at the bottom of an ocean of air.
Just like water air has turbulence.
These clouds are formed as the air creates eddy currents
flowing around the tips of mountains.
Tornadoes are like giant whirlpools.
And just like the ocean, the troposphere even has waves.
This cloud in Queensland, Australia,
is one of the largest waves in the world.
It can reach to over a mile high.
It's a solitary tropospheric wave
that combined with the humidity in the region
takes the form of a visible cloud.
As the air cools, it condenses to form a cloud
that rolls inland at 2 5 miles an hour
visible evidence of the ocean of air above us.
And just like any fluid, the atmosphere has a weight.
It presses down on each of our bodies
with a force of over 1 4 pounds per square inch.
The only reason that we don't collapse in a heap
is because the air inside our bodies balances the pressure outside.
We' re like lobsters walking on the sea bed,
oblivious to the weight of the fluid above us
because we' re so adjusted to it.
And if you're still in any doubt about the fluid nature of the atmosphere,
some people can even surf on it.
Admittedly, it's a little trickier than traditional surfing,
which is why it's best left to an expert like Troy Hartman.
Troy isn't just falling vertically through the air
he can move horizontally, too.
The sky is Troy's ocean.
Whoa!
Once you come to terms with the idea that the atmosphere is a fluid,
you realize it has some extraordinary consequences.
One of them is that Earth's atmosphere
is capable of shaping the surface of the planet,
even cutting through solid rock.
I' m on my way to a very special place,
a place where you can really see how powerful the atmosphere can be.
Only a few people every day are granted the honor
of walking the three mile path to get there.
But there's a good reason for that.
This rock formation in Arizona
is one of the most precious geological sites on the planet.
Wow! Look at this.
It is so beautiful.
It's like being inside a giant sculpture,
a geological piece of art.
These rocks in Arizona are known as The Wave. And it's easy to see why.
These giant curvaceous shapes look as if they've been carved out by water.
Instead they've been sculpted by a different fluid motion,
the wind.
As it buffets the sandstone rocks, the wind picks up grains of sand,
and becomes a giant scouring pad, .
scratching away at the rock surface and etching out these lines.