Secrets of the Earth

We have uncovered

a remarkable planet,

a world of extreme weather,

alien landscapes,

and bizarre phenomena.

It's the most complex system

we know of in the universe.

That planet...

is Earth,

and we are only beginning

to unlock its secrets.

It is a killer cloud

that the weatherman

can't predict...

This is a belch

from the guts of the Earth.

...a volcanic storm

that can bring down

a jumbo jet.

KLM 167, WE HAVE

A FLAME OUT, ALL ENGINES,

AND WE ARE DESCENDING NOW.

On any given day,

at least 20 are erupting

on planet Earth,

and one could turn a good day

into doomsday.

Straight from

the planet's molten core

to the sky above,

volcanic weather

is about to change

the forecast for the planet,

on Secrets of the Earth.

Even from space,

Earth's swirling clouds

are a dead giveaway

that this can be

a stormy planet...

...but look closely.

Another type of cloud indicates

weather of a different kind.

These are volcanic eruptions,

and they have a secret power to

alter Earth's weather forever.

Volcanic weather

is the weather influenced

by the presence

of gigantic volcanic eruptions.

We now realize

that volcanic eruptions

can influence the weather

in ways that we never

appreciated before.

One volcanic hotspot

is the Central American country

of Guatemala,

home to 37 volcanoes.

The most dangerous

is called Volcan Fuego,

or Fire Volcano.

With nearly constant

daily eruptions,

it's Guatemala's

most feared volcano.

Mountain guide Victor Ferrell

has spent years climbing

and observing Fuego.

This is the spine

of the beast,

Volcan Fuego, one

of the most active volcanoes

on planet Earth.

Right now, we're walking

on what we call the knife-ridge.

You've got about a thousand-feet

drop on this side...

...a thousand-foot drop

on this side.

This is a gnarly place to be,

and if you look up ahead,

you can see

the very active cone.

Sometimes it just blows,

no warning.

You just duck and run for cover.

September 13, 2012.

The 12,500-foot-tall

Fuego explodes...

blasting lava rocks and ash

thousands of feet high

and forcing the evacuation

of 30,000 people

from the villages surrounding

the nearby city of Antigua.

If you can imagine

this entire cone blowing apart.

It shoots huge chunks

of lava rock,

sometimes the size of cars,

straight up into the air

thousands of feet

over your head.

This is a belch

from the guts of the Earth.

Volcan Fuego

is one of the biggest.

But it's not

the big chunks of rock

that change the weather.

It's the massive

clouds of ash.

Ash is formed in a split-second

when gases dissolved

in molten rock expand

under extreme pressure.

The force of the escaping gas

violently shreds

the molten rock into ash,

tiny particles

of glass and rock

that are smaller than

the finest grains of beach sand

and harder than a knife blade.

It exceeds the speed of sound

as it leaves that vent, and it

propels ash and this debris

tens of miles

into the atmosphere.

We're sitting

at about 12,500 feet,

going right up to the summit

of Volcan Fuego.

When there's a large eruption,

ash belches out of this volcano.

It can obscure and block

any plane travel

anywhere near this volcano.

A volcanic ash cloud

is the most dangerous form

of volcanic weather

a pilot will ever encounter.

Since 1980, ash

has damaged the engines

of almost 100 airplanes

and has endangered

thousands of passengers.

Airplanes

cannot see ash clouds,

doesn't appear on radar.

Radar can detect

typical clouds

because they contain moisture,

but volcanic ash clouds

are dry,

the secret to why they're

invisible to radar.

December 15, 1989.

An aircraft flies

dangerously close

to the ash cloud from Alaska's

erupting Mount Redoubt.

WE ARE

IN A BLACK CLOUD,

HEADING 1-3-0.

KLM 167, WE HAVE

A FLAME OUT, ALL ENGINES,

AND WE ARE DESCENDING NOW.

The engines that

these large jets are running,

they run at

such high temperatures

that when ash is injected

into those engines,

it stops those engines

from moving.

At 1,800 degrees Fahrenheit,

the operating temperature

of a jet engine

is hot enough

to melt volcanic ash.

After the ash melts,

it resolidifies

and clogs

the engine's compressor,

causing it to shut down.

KLM 167 HEAVY,

WE ARE DESCENDING NOW.

WE ARE IN A FALL.

After

a 14,000-foot freefall,

the pilots are able

to restart the engines

just one minute before impact.

When Iceland's Eyjafjallajokull

volcano erupted in 2010...

...it ejected a massive

ash cloud 55,000 feet high.

Aviation authorities closed

Europe's airspace for six days,