[narrator] 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...
[man] This is a belch
from the guts of the Earth.
[narrator]
...a volcanic storm
that can bring down
a jumbo jet.
[pilot] KLM 167, WE HAVE
A FLAME OUT, ALL ENGINES,
AND WE ARE DESCENDING NOW.
[narrator] 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.
[narrator]
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.
[narrator]
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.
[narrator] 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.
[explosion]
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.
[Ferrell] 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.
[narrator] 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.
[Browne] Airplanes
cannot see ash clouds,
doesn't appear on radar.
[narrator] 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.
[pilot] WE ARE
IN A BLACK CLOUD,
HEADING 1-3-0.
KLM 167, WE HAVE
A FLAME OUT, ALL ENGINES,
AND WE ARE DESCENDING NOW.
[Browne] 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.
[narrator]
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.
[pilot] KLM 167 HEAVY,
WE ARE DESCENDING NOW.
WE ARE IN A FALL.
[narrator] 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,
stranding ten million people.
[explosion]
On Earth, the ash
from volcanic eruptions
can reach into the stratosphere
and alter the weather
across the planet.
[woman] This is an ash slope
formed by an explosive
volcanic eruption.
Fuego has had
many of these eruptions,
and what we see here
is coarser material
than what we get
in the stratosphere,
but if a volcano spews out
a lot of very fine ash
and it goes
into the stratosphere,
that can have
an effect on climate
because some of that ash
will block sunlight.
[explosion]
[narrator] The finer particles
rise with the wind column
and can reach 20 miles
into the Earth's stratosphere
and spread out to cover
thousands of square miles.
The ash cloud is
like a heavy blanket,
preventing solar radiation
from penetrating the atmosphere
and causing the Earth to cool.
[Lopes] Explosive eruptions can
have major effects on weather.
We call those volcanic winters.
[narrator]
Volcanic winters
are one of planet Earth's
secret weather anomalies.
June 15th, 1991,
the Philippines.
In the 20th century's
second-biggest eruption,
Mount Pinatubo ejects
ten billion metric tons
of pulverized rock and ash,
killing nearly 800 people,
most of whom are crushed
under collapsing roofs.
Global temperatures fall
by an average of 1.3 degrees
over three years.
The eruption stalls
the Pacific jet stream,
causing massive rainfall
in some areas
and drought in others.
Catastrophic flooding
of the Mississippi River
in 1993 is blamed
on Pinatubo.
[explosion]
Volcanic ash can alter
the climate around the world,
but at the site
of the eruption,
it creates bizarre
and violent weather phenomenon,
a volcanic secret
that scientists are
just beginning to unlock.
[thunderclap]
Volcanoes spawn
wild weather on Earth.
Sometimes they can even launch
an electrical storm
unlike anything
in the solar system.
It's called volcanic lightning.
[Browne] Volcanic lightning
is a very localized form
of volcanic weather.
[thunderclap]
[narrator] Scientists
on Earth have tried
to explain this phenomenon
for years,
but its secrets
are not given up easily.
March 15, 2009.
When Alaska's
Mount Redoubt erupts,
scientists record
the volcanic lightning storm
using a very high frequency
antenna
positioned near the cone.
What they find
is mind-bending--
more than 7,000
lightning strikes
over a single
70-minute eruption,
but what secret force
is at work
creating this hellish display?
[thunderclap]
[Browne] So, as this
ash material and gas
is rapidly ascending
through the atmosphere
at very high speeds,
hundreds of miles an hour,
ash particles
are being pulled apart,
and it's generating
this positive and negative
electrical charges
which then stimulate
lightning strikes.
[thunderclap]
[narrator] Higher
in the plume,
multimillion-volt
lighting bolts discharge
much the same as those
in a typical thunderstorm.
Supercooled water droplets
get charged with electricity,
and a massive
electrostatic discharge
rips through the ash cloud.
These photos of Iceland's
Eyjafjallajokull in 2010...
[thunderclap]
...capture the split-second
lightning bolts...
[thunderclap]
...each one traveling at more
than 220,000 miles per hour.
[explosion]
Lightning is just one
of the volcanic secrets
being decoded by scientists
on planet Earth.
[airplane engine]
April 4, 1982.
After several days
of massive eruptions,
Mexico's El Chichon volcano
spews more than 500 metric tons
of volcanic ash
into the stratosphere,
approximately the same amount
as Mount St. Helen's
two years earlier.
Mount St. Helen's produces
no detectable cooling effect
on the planet,
but amazingly, El Chichon
triggers a volcanic winter.
How could two eruptions
of the same size
have such different effects
on the weather?
The secret weapon
is invisible.
[Ferrell] What we see
right here behind us,
this gas, this is about as close
as you would want to get
unless you had a gas mask.
These are fumes coming
from the guts of the Earth,
chemicals, sulfuric gas,
very, very dangerous stuff.
[narrator] Scientists
are just beginning to discover
the once-secret role
of sulfur dioxide gas.
[Browne] Those tiny sulfur
particles essentially act like
lots and lots
of little mirrors,
and when that sunlight
comes into the Earth's
upper atmosphere,
those small mirrors reflect that
sunlight back out into space,
which prevents the sunlight from
reaching the ground surface,
which results in
a cooling effect to all of us.
[narrator]
Mount St. Helen's
put out one megaton
of sulfur dioxide;
El Chichon, 13 megatons.
The reason for this difference,
El Chichon's magma
built up inside limestone,
a rock that's loaded
with sulfur dioxide.
Mount St. Helen's magma
was housed
in very hard igneous rock
with virtually no gas.
Sulfur dioxide
seeps to the surface
in hot springs
around the world.
Volcanologist Brandon Browne
studies locations
like Hot Creek in California.
[Browne] Well, what we're
looking at here
is a high concentration
of volcanic gases.
It has that particular smell
of rotten eggs
indicative of
high amounts of sulfur,
hydrogen sulfide,
and sulfur dioxide in the gas.
[narrator] Big eruptions
can churn out
massive amounts of gas.
Humans burning fossil fuels
release more
than 20 million metric tons
of sulfur dioxide each year.
The 1991 Mount Pinatubo
eruption
released that same amount
in one day.
The gas cloud circled
the Earth in three weeks
and remained in the atmosphere
for more than one year,
leading to a volcanic winter,
but there are secret volcanoes
far more massive than Pinatubo
hiding on planet Earth
with the power
to destroy civilization.
Guatemala's imposing
Volcan Fuego
is a daily reminder
that volcanic weather
plays a big role
in the long-term forecast
for planet Earth.
[Ferrell]
When this angry thing goes,
there's an eruption,
the first thing you do
is you feel it in your chest,
then you hear it.
These things remind us
that we're very small.
[narrator] But there are
much bigger volcanoes
than the 1,200-story-tall
Fuego,
and these secret beasts
can't be seen
on the surface
of the Earth.
[Kaku] We like to think
that the Earth is solid
underneath our feet,
But we don't realize
that there are
hidden, sleeping
super-volcanoes
right underneath the crust
of the United States of America,
in California.
[narrator]
In central California,
a sleeping giant reveals
small signs of its presence.
[Browne] We're looking
at California's
Long Valley Caldera,
the site of one of the largest
volcanic eruptions
in North American history.
The eruption ensued
in such a way
that so much magma was
withdrawn from this eruption
that the ground
we see in front of us
dropped down two miles,
forming this giant depression.
The catastrophic super-eruption
occurred 760,000 years ago,
but we still see signs today
of volcanic unrest.
[narrator] On the western rim
of the caldera
sits Mammoth Mountain,
one of America's
largest ski resorts.
The ancient caldera's
volcanic vents
steadily pump out
sulfur dioxide and other gases
above its popular slopes.
In nearby Hot Creek,
scalding-hot sulfur springs
are a smoking reminder
of the volcanic superstorm
that erupted
more than
a half-million years ago.
[Browne] In these smaller pools
off to the side,
where a lot of this new
hot water is coming in,
temperatures right here
are 186,
and they're as high
as 200 degrees
in the pool opposite the creek.
So temperatures this high,
these are certainly
scalding conditions.
Dozens of people have actually
been killed at Hot Creek
because of these
unpredictable explosions
or geysering events that occur.
[narrator] The Long Valley
Caldera eruption
blew more than 150 cubic miles
of molten rock
into the atmosphere...
[explosion]
...2,000 times the magnitude
of the Mount St. Helen's blast,
but Long Valley is not
America's biggest
super-volcano threat.
That beast slumbers beneath
one of America's biggest
national parks.
The Yellowstone super-volcano
has erupted three times
in geologic history.
The next eruption could produce
a 100-year-long volcanic storm.
[Browne] Should
Yellowstone Caldera erupt again,
we would have
enormous quantities
of ash and volcanic gas.
Current estimates
are on the order
of billions of metric tons,
which would circulate the globe,
and that affects everything,
from the plants we grow
to the way we live.
It's going to affect
the whole Earth for decades
and potentially
hundreds of years.
[narrator] Residents
of Hawaii's big island
don't have to wait
for a future super-volcano
to change their weather.
Their secret storm
is a choking volcanic gas
that has the potential to ruin
the forecast in paradise.
Having erupted more
than 60 times since 1823,
Kilauea,
on Hawaii's big island,
is one of the most active
volcanoes on Earth.
It is a sulfur dioxide factory,
pumping out some 2,000 tons
of gas per day
during frequent
sustained eruptions,
enough to fill
100 Goodyear blimps.
This creates
a secret weather hazard,
a volcanic smog known
to locals as "vog."
[Browne]
"Vog" is a mixture
of volcanic gases and smog,
and it's just a local term
that people in Hilo
and the big island of Hawaii
refer to as their own kind of
unique volcanic air pollution.
Sulfur dioxide mixes with
water vapor in the atmosphere
and little dust particles,
and it acidifies
the air that people breathe.
So it causes irritation
to their eyes and throat
and nose
when they're breathing.
[man] Sulfur dioxide
in higher concentrations
will actually bond with water
to form sulfuric acid.
You and I are carrying water
in our lungs
and on the surface of our eyes.
So "vog" is something
we monitor for regularly here
at Hawaii Volcanoes
National Park.
[narrator] When Hawaii's
trade winds slow or stall,
health warnings
force residents inside
to escape the acidified air.
Sometimes evacuations
are ordered.
"Vog" has been blamed for
thousands of premature deaths
on the big island.
While volcanic weather
can threaten life,
it may also have been
the driving force
that created it.
[explosion]
[Kaku] Astronomers believe
that volcanic activity
could be the missing link
that explains
why we breathe air
and why we have water
in our oceans.
It turns out
that outgassing from volcanoes
creates carbon dioxide
as well as water vapor.
Water vapor then condensed
to form our great oceans,
and the air we breathe,
much of it was
primordial carbon dioxide
coming from volcanoes
that later changed to oxygen.
So we have an irony here.
On one hand,
volcanoes, in some sense,
are the giver of life,
the giver of the oceans,
the giver of the atmosphere,
the very air we breathe.
However, volcanic activity
could also wipe out
life on the planet Earth.
[narrator] With half
a billion humans living
within 25 miles
of active volcanoes,
it's wise to keep an eye
on the secret threat
of volcanic weather.