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NARRATOR:
Japan's volcanoes have produced
some of the largest eruptions

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our Earth has ever seen.

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Those volcanoes remain
active today.

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TOM:
It is right now in a very
violent phase of activity.

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It has been building up,
and it continues to build up.

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So we don't know
what's happening next.

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NARRATOR:
Could a series of
earthquakes be setting off

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the country's volcanoes?

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TOM:
There's an explosion!

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Another one, yeah!

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NARRATOR:
And could lead to
a massive eruption.

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[Explosion]

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Nature's power is our planet's
most spectacular show.

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♪♪♪

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♪♪♪

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♪♪♪

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♪♪♪

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♪♪♪

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♪♪♪

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♪♪♪

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♪♪♪

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NARRATOR:
Its beauty makes it
an iconic Japanese landmark...

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but its near-perfect symmetry
belies its destructive nature.

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Mt. Fuji is a
stratovolcano.

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Its last major eruption
was 300 years ago,

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but it is still active,
and one day will erupt again.

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It's a very appropriate symbol
for this island nation.

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Japan is prone to
violent earthquakes,

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and it has more than
100 active volcanoes.

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The country is spread
over three major islands.

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Kyushu in the south
is currently the most active.

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It has several
massive volcanoes,

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including two that are
considered to be among

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the world's top five
most dangerous:

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Aso and Sakurajima.

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Both are serious threats
to the island's population

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of 13 million.

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This is Sakurajima.

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It's located on the
southern tip of Kyushu.

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Scientists pay close
attention to this volcano,

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and for good reason.

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Sakurajima has produced a number
of cataclysmic eruptions

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in the past few centuries.

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The last was in 1914.

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What's especially concerning
is that it sits across

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a narrow strait from
the city of Kagoshima

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and its 600,000
inhabitants.

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A major eruption would put
the city and its people

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in serious danger.

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Volcanologist and photographer
Dr. Tom Pfeiffer

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has come to Sakurajima
just as it's entering

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a new phase of
larger eruptions.

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His timing is excellent.

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Just as he's driving
into Kagoshima,

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Sakurajima erupts.

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[Explosion]

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♪♪♪

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♪♪♪

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TOM:
We're east of Sakurajima,

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which had some massive eruptions
earlier today.

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The whole northern
and western sector is hazy.

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That's actually
the ash plumes.

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Reports say the ash
went up to 17,000 feet.

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That is more than
5 kilometers altitude

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and it's a record number,
I think, for this year.

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NARRATOR:
Tom pulls over to get a better
look at this eruption

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which is sending a big
ash cloud into the sky.

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TOM:
And it's continuing
to spew ash.

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And you see all this haze,
that's all ash

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which is still dissipating
from the large plumes

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emitted earlier.

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Apparently it has been--
it is right now

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in a very violent phase
of activity.

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If you look over
the past months

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it has been building up
gradually.

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It continues to build up,
apparently.

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So we don't know what's
happening next.

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[Explosion]

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NARRATOR:
Sakurajima has been
in a phase of

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nearly continuous eruption
since 1955.

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It normally erupts
once or twice a day.

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But in the past few weeks,

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the frequency of the eruptions
has increased exponentially:

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as many as 10-15
times a day,

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with ash plumes up to
five times larger than usual.

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Scientists still can't predict
the timing of a major eruption.

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But they are afraid that
this volcano is building up

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to something major.

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An eruption similar in magnitude
to 1914 could be devastating.

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It could potentially destroy
the city of Kagoshima.

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TOM:
From here you get the sense of
how close Kagoshima City

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is actually to the volcano.

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Volcanologists know that the
volcano has been inflating

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gradually ever since
the 1914 eruption,

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and it has reached
the same level as it had

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before the last
big eruption.

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NARRATOR:
What that means
is that the volcano

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has replenished itself enough
that its magma reservoirs

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can produce a major eruption,

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something it has done
several times

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over the past 600 years.

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TOM:
So, it is thought that
it might be actually due

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at some point, not necessarily
tomorrow or the next month,

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but in the not too distant
future it could be due

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for another
larger eruption.

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That would clearly
put the city at risk--

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particularly of
pyroclastic flows,

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if you have an eruption
column that rises,

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imagine 15-20 kilometers.

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NARRATOR:
That could be catastrophic
for the city.

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Large eruption plumes can
collapse under their own weight,

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causing a burning hot avalanche
of ash and gas

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called a pyroclastic flow.

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They are capable of
generating tsunamis

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or even traveling
over the water

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on a super-heated
layer of steam,

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burning everything
in their path.

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TOM:
Those pyroclastic flows could
sweep and engulf the whole city.

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To evacuate a large city
like Kagoshima

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is not an easy task,
clearly.

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If you look at the lower slopes
you see this dust floating.

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This is ash from
the recent eruptions

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that has been blown around
the island.

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And people who live there
have that constantly.

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Anything you wash, after a day,
is coated with ash.

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NARRATOR:
Sakurajima means
'cherry blossom island.'

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It was given that fanciful name
because its explosions cover

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the volcano in glowing rocks
that resemble a tree in blossom.

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Even though Sakurajima
is very active,

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travel to the island on which
it sits is still possible.

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After Tom takes the ferry over,
he'll be able to drive

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to the active Showa crater,
which is on the far side.

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But there are hazards.

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Getting there means he'll
have to pass right through

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the ash cloud.

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TOM:
This is clearly where
the plume had passed

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that was produced by these big
explosions earlier today.

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And in fact you can see a lot of
ash covering the leaves.

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Look at the car in front of us
and, you know,

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this ash is everywhere.

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This can be very heavy if
you have to live here

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and this is something
you have every few days.

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But people go on living here
and they stick to their place.

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They don't want
to give this up.

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NARRATOR:
This tourist shop
is as close to the volcano

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as Tom can get
and still be safe.

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The area beyond it
is off-limits.

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TOM:
What we're seeing is
that the eruption is continuing.

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With every few seconds
you see jets of material

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and lightning now
in the ash plume rising.

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And they contribute to this
sustained plume

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that reaches 1-2 kilometers
above the vent, and spreads,

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and all that Northeastern
sector is under ash fall.

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It's quite spectacular,
actually.

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NARRATOR:
This is not typical behavior
from Sakurajima,

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and it's likely attributed
to a new pulse of magma

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coming up from depth
that has lead

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to a more sustained
ash eruption.

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TOM:
Let's hope the wind stays
as it is,

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because we are outside
the ash plume

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and we have a clear view
to the crater.

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This is great.

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Let's pray it
stays like this.

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On the other side,
it's miserable now.

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You have dust in the air
and ash falling,

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and you have to be inside,
lock the windows.

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If you're outside,
you'd better wear a face mask.

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NARRATOR:
Sakurajima's usual eruptions
are a single blast

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that only lasts
a few minutes.

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This one has gone on
for several hours.

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TOM:
The question is,
could this be a precursor

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to a much bigger
eruptive phase?

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I don't dare to say.

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On the long term, maybe.

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NARRATOR:
Although volcanoes can and do
erupt without warning,

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most large-scale eruptions
have a build up phase

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as more magma is pushed
into the system.

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As this is happening, there
are many localized effects,

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like earthquakes,
that can be detected

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by high-tech instruments,
or sometimes even felt

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by the people living
around the volcano.

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TOM:
Before the 1918 eruptions,

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there has been a
very marked increase

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in earthquake activity.

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Visible deformation of the--
inflation of the ground.

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The coastline
visibly changed,

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and things like this
are expected to happen

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as a precursor of another
big eruption,

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which would imply
a much greater volume to erupt.

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By greater, I mean orders of
magnitude greater:

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a hundred times more than
what has happened today.

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NARRATOR:
Before the 1914 eruption,

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the city of Kagoshima
was rocked by three weeks

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of very strong volcanic
earthquakes

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that caused a number
of fatalities.

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The quakes are triggered when
new magma breaks the ground rock

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as it pushes up to
the surface.

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TOM:
What interests volcanologists
to study is actually

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to have a picture of what is
actually happening underneath.

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And understanding what
is happening underneath

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might eventually help
to have an idea

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about what is
going to happen.

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Unfortunately, it is not
very well understood,

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and it is extremely difficult
to be sure and certain

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what is happening.

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NARRATOR:
Scientists don't
fully understand

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what triggers
big eruptions.

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The current belief is that
once a magma chamber is filled,

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as Sakurajima's,
any new large injection

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of fresh hot magma
can reinvigorate

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the older semi-cooled magma
in the volcano's reservoir.

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The heat and pressure
of the new material

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can trigger a
large eruption.

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Eruptions are limited to the
amount of eruptable magma

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00:12:00,620 --> 00:12:03,423
within the underground
reservoir.

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00:12:03,423 --> 00:12:07,794
A big event can virtually
empty that chamber.

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Right now, scientists believe
Sakurjima's chamber

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00:12:11,064 --> 00:12:13,399
has refilled to 90%,

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which makes a larger,
1914-size eruption possible.

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Or it can erupt moderately
like we are seeing here,

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gradually reducing
the pressure within.

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That scenario could mean that
a major eruption is less likely

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since the volcano can't
build up enough pressure.

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NARRATOR:
The other concern is that
these smaller eruptions

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can also open the conduit that
connects to the magma chamber.

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If that happens, the result
is like popping the cork

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on a champagne bottle.

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The eruption can
then sustain itself

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until the magma chamber
is virtually empty.

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That scenario could
happen quickly

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with little very little
advance warning.

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TOM:
Sounds like a thunderstorm
in the distance.

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NARRATOR:
The activity is spectacular,
but today, at least,

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is not the precursor
to a larger eruption.

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Things wind down
as the night goes on.

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But after dark, Tom can see
a glow within the crater.

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That confirms that the magma
is able to push

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00:13:34,547 --> 00:13:38,451
all the way to the opening
of the crater vent.

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00:13:43,289 --> 00:13:46,659
By morning the ash emission
has nearly stopped.

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00:13:46,659 --> 00:13:49,429
It's not over--
the volcano is recharging

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00:13:49,429 --> 00:13:52,799
before it begins
another eruptive phase.

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The cycle that Sakurajima
is going through

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is considered high, but still
in the realm of normal.

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In Japan, the news of
Sakurajima's increasing activity

245
00:14:09,649 --> 00:14:13,786
is watched closely
by an anxious population.

246
00:14:13,786 --> 00:14:17,223
What has touched off public fear
is that several volcanoes

247
00:14:17,223 --> 00:14:19,826
have become active
at the same time--

248
00:14:19,826 --> 00:14:25,098
volcanoes that have been quiet
for decades or centuries.

249
00:14:25,098 --> 00:14:28,167
They're the latest reminders
of just how geologically active

250
00:14:28,167 --> 00:14:31,137
the country is.

251
00:14:31,137 --> 00:14:36,576
In 2011, Japan was rocked by
a major earthquake and tsunami

252
00:14:36,576 --> 00:14:41,180
and the subsequent meltdown
at the Fukushima nuclear plant.

253
00:14:42,081 --> 00:14:44,417
More than 19,000
people died,

254
00:14:44,417 --> 00:14:48,287
and the entire area
was evacuated.

255
00:14:48,287 --> 00:14:50,723
The Tahoku quake was
a national trauma

256
00:14:50,723 --> 00:14:53,392
that has increased awareness
and raised alarm

257
00:14:53,392 --> 00:14:56,796
about the potential of
more natural disasters.

258
00:14:56,796 --> 00:15:01,734
♪♪♪

259
00:15:01,734 --> 00:15:05,538
♪♪♪

260
00:15:05,538 --> 00:15:09,175
NARRATOR:
And in 2014,
50 people were killed

261
00:15:09,175 --> 00:15:13,746
when Mount Ontake erupted
suddenly and without warning.

262
00:15:15,581 --> 00:15:17,517
The eruption sent a
pyroclastic flow

263
00:15:17,517 --> 00:15:21,420
down the mountain,
killing unsuspecting hikers.

264
00:15:22,255 --> 00:15:26,092
On top of that, Hakone,
the volcano closest to Tokyo,

265
00:15:26,092 --> 00:15:29,495
has been raised to
alert level 3 out of 5

266
00:15:29,495 --> 00:15:31,831
after thousands of
small earthquakes

267
00:15:31,831 --> 00:15:35,635
and a sharp increase in heat
was recorded at the summit.

268
00:15:35,635 --> 00:15:38,771
There are fears that
it too may soon erupt.

269
00:15:40,473 --> 00:15:44,677
The Japanese media gives these
stories prominent coverage.

270
00:15:44,677 --> 00:15:46,813
The population wants
to know the government

271
00:15:46,813 --> 00:15:49,582
and its civil defense force
have plans in place

272
00:15:49,582 --> 00:15:52,185
in case of another disaster.

273
00:15:53,619 --> 00:15:56,422
While Tom is
exploring Sakurajima,

274
00:15:56,422 --> 00:16:03,229
a major eruption happens
several hours south.

275
00:16:03,229 --> 00:16:07,266
Mount Shindake, on the
Island of Kuchinoarbujima,

276
00:16:07,266 --> 00:16:11,504
erupts violently, sending a
huge ash cloud into the sky

277
00:16:11,504 --> 00:16:16,108
and triggering a potentially
dangerous pyroclastic flow.

278
00:16:16,108 --> 00:16:19,212
The eruption was caught
on a government web camera

279
00:16:19,212 --> 00:16:21,781
and it shows the sudden
horrifying nature

280
00:16:21,781 --> 00:16:23,983
of the explosion.

281
00:16:31,357 --> 00:16:35,094
This powerful eruption could
have had dire consequences,

282
00:16:35,094 --> 00:16:38,197
but luckily the island
had few inhabitants.

283
00:16:38,197 --> 00:16:42,168
There were only
two injuries.

284
00:16:42,168 --> 00:16:47,173
♪♪♪

285
00:16:47,173 --> 00:16:49,275
♪♪♪

286
00:16:49,275 --> 00:16:52,311
NARRATOR:
Eruptions of this
magnitude are infrequent,

287
00:16:52,311 --> 00:16:54,580
so Tom has left Sakurajima

288
00:16:54,580 --> 00:16:57,450
and is traveling by ferry
to Yakashima,

289
00:16:57,450 --> 00:17:01,287
the island directly across
from the eruption.

290
00:17:01,287 --> 00:17:03,022
If conditions are right,

291
00:17:03,022 --> 00:17:04,790
it will give him
an excellent place

292
00:17:04,790 --> 00:17:07,360
to see the aftermath
of the eruption

293
00:17:07,360 --> 00:17:11,264
and to see how Japan responds
to a volcanic crisis.

294
00:17:12,632 --> 00:17:15,501
Japanese media has descended
on the local police station

295
00:17:15,501 --> 00:17:18,404
that has become the command
center for the disaster.

296
00:17:20,306 --> 00:17:25,645
[Reporter speaking Japanese]

297
00:17:25,645 --> 00:17:29,315
TOM:
Yesterday about this time,
a very large explosion occurred

298
00:17:29,315 --> 00:17:32,818
on the neighboring island
of Kuchinoarbujima.

299
00:17:32,818 --> 00:17:36,255
It was an incredible, large,
unexpected explosion

300
00:17:36,255 --> 00:17:39,492
that forced the evacuation
of the whole island.

301
00:17:39,492 --> 00:17:41,761
We see lots of TV crews.

302
00:17:41,761 --> 00:17:43,362
They're all covering
this story,

303
00:17:43,362 --> 00:17:47,233
which is the headline
all over Japan.

304
00:17:47,233 --> 00:17:51,203
I bet nobody expected
it to be that large.

305
00:17:51,203 --> 00:17:54,540
It produced an eruption
column 9 kilometers high,

306
00:17:54,540 --> 00:17:57,276
which spread out,
and the base of the column

307
00:17:57,276 --> 00:18:00,279
part of the ejected material
immediately collapsed

308
00:18:00,279 --> 00:18:03,249
and caused a violent
pyroclastic flow

309
00:18:03,249 --> 00:18:06,052
which fortunately didn't
go through exactly

310
00:18:06,052 --> 00:18:08,087
the populated area,
it seems.

311
00:18:08,087 --> 00:18:09,722
But it was very close.

312
00:18:09,722 --> 00:18:13,025
It illustrates
a bit the problem,

313
00:18:13,025 --> 00:18:15,494
if you live on an active
volcanic island,

314
00:18:15,494 --> 00:18:18,464
in case of a large eruption
like the one yesterday,

315
00:18:18,464 --> 00:18:21,701
there are not many places
you can go and hide.

316
00:18:24,403 --> 00:18:27,606
NARRATOR:
Tom heads to the lighthouse
at Nagata Cape.

317
00:18:27,606 --> 00:18:31,444
It's the closest point to
Kuchinoarbujima Island

318
00:18:31,444 --> 00:18:35,081
and is the best vantage point
to see the volcano.

319
00:18:35,081 --> 00:18:37,350
But bad weather and the
heavy concentration

320
00:18:37,350 --> 00:18:39,485
of airborne ash
from the eruption

321
00:18:39,485 --> 00:18:42,455
have reduced visibility
considerably.

322
00:18:42,455 --> 00:18:45,591
Tom can't see the volcano.

323
00:18:48,661 --> 00:18:51,130
TOM:
Unfortunately, the
island is, of course,

324
00:18:51,130 --> 00:18:53,299
and it makes sense,
off-limits.

325
00:18:53,299 --> 00:18:55,134
And the weather
is not cooperating.

326
00:18:55,134 --> 00:18:56,702
We can't even see it.

327
00:18:56,702 --> 00:18:58,571
But we gave it a try.

328
00:18:58,571 --> 00:19:00,406
In case there would be
another eruption

329
00:19:00,406 --> 00:19:03,109
you should be able
to see the plume,

330
00:19:03,109 --> 00:19:06,045
and maybe in clear weather
you can even see the island.

331
00:19:06,045 --> 00:19:07,646
It's already quite
a bit of luck

332
00:19:07,646 --> 00:19:10,616
to be in the vicinity
of this event.

333
00:19:11,484 --> 00:19:13,753
NARRATOR:
The media is focusing on
questioning if these volcanoes

334
00:19:13,753 --> 00:19:18,224
are becoming more active
because the of the Tahoku quake.

335
00:19:19,492 --> 00:19:22,762
TOM:
It has always
been questioned,

336
00:19:22,762 --> 00:19:24,730
and many people
tend to think

337
00:19:24,730 --> 00:19:26,665
that there must be
a correlation between

338
00:19:26,665 --> 00:19:29,668
earthquake activity
and volcanic activity.

339
00:19:29,668 --> 00:19:33,205
And in fact, there is
probably some relation

340
00:19:33,205 --> 00:19:36,042
but it's currently not
even well understood.

341
00:19:36,042 --> 00:19:39,211
NARRATOR:
To a volcanologist,
this eruption is another chance

342
00:19:39,211 --> 00:19:42,248
to study the phenomena
up close.

343
00:19:42,248 --> 00:19:45,418
But for a nation still
shaken by the earthquake

344
00:19:45,418 --> 00:19:48,754
and tsunami at Tohuko,
this large eruption

345
00:19:48,754 --> 00:19:52,658
once again raises
collective fears.

346
00:19:52,658 --> 00:19:56,529
Japan is a very
geologically active country.

347
00:19:56,529 --> 00:19:58,564
On a relatively
small landmass,

348
00:19:58,564 --> 00:20:02,168
it has more than
100 active volcanoes.

349
00:20:02,168 --> 00:20:04,837
Japan's abundant earthquakes
and volcanoes

350
00:20:04,837 --> 00:20:08,507
can be explained by the science
of plate tectonics.

351
00:20:08,507 --> 00:20:10,543
The Earth's surface
is broken up into

352
00:20:10,543 --> 00:20:14,246
just over a dozen
large sections or plates.

353
00:20:14,246 --> 00:20:15,848
They are constantly moving,

354
00:20:15,848 --> 00:20:19,652
at about the rate
a fingernail grows.

355
00:20:21,187 --> 00:20:24,090
When two plates collide,
the denser of the two

356
00:20:24,090 --> 00:20:27,326
is forced under the other
and back into the earth.

357
00:20:27,326 --> 00:20:31,764
The place where they meet
is called a subduction zone.

358
00:20:31,764 --> 00:20:35,267
As the denser plate descends,
friction causes stress to build

359
00:20:35,267 --> 00:20:37,536
to the breaking point.

360
00:20:37,536 --> 00:20:40,306
It slips suddenly,
causing an earthquake,

361
00:20:40,306 --> 00:20:43,275
and sometimes a tsunami.

362
00:20:44,477 --> 00:20:47,279
As the denser subducting
plate is forced downwards

363
00:20:47,279 --> 00:20:50,249
into the hot mantle
the water and sediments

364
00:20:50,249 --> 00:20:53,853
that are pulled down with it
begin to boil off.

365
00:20:53,853 --> 00:20:56,188
This lowers the melting point,

366
00:20:56,188 --> 00:21:00,726
and the rock around begins
to melt, creating magma.

367
00:21:00,726 --> 00:21:05,164
The more buoyant magma
rises towards the surface.

368
00:21:06,665 --> 00:21:10,503
Japan is the result of
a major subduction zone.

369
00:21:13,172 --> 00:21:16,675
TOM:
You have to consider that
it is only roughly 50 years

370
00:21:16,675 --> 00:21:19,411
that the whole concept
of plate tectonics

371
00:21:19,411 --> 00:21:21,580
has been accepted,

372
00:21:21,580 --> 00:21:25,317
and it is still a science
really in evolution.

373
00:21:25,317 --> 00:21:30,222
NARRATOR:
For now, it's a theory that
scientists can test against.

374
00:21:30,222 --> 00:21:32,825
TOM:
Right now, of course,
each major earthquake,

375
00:21:32,825 --> 00:21:37,229
each volcanic eruption
provides a new opportunity.

376
00:21:37,229 --> 00:21:38,797
You can test your
previous models.

377
00:21:38,797 --> 00:21:41,700
You have a fresh case.

378
00:21:41,700 --> 00:21:45,304
As science advances
and monitoring techniques--

379
00:21:45,304 --> 00:21:48,207
instruments become more refined,
you have the ability

380
00:21:48,207 --> 00:21:50,776
to measure and
detect more subtle changes

381
00:21:50,776 --> 00:21:53,846
that you would not be able
to see maybe five years ago,

382
00:21:53,846 --> 00:21:57,383
as technology constantly
improves.

383
00:21:57,383 --> 00:22:01,053
But it's not very easy to
establish a rule to say

384
00:22:01,053 --> 00:22:02,254
"We have a big earthquake,

385
00:22:02,254 --> 00:22:05,457
so for sure we will have
volcanic eruptions."

386
00:22:05,457 --> 00:22:10,095
NARRATOR:
At this point it is unlikely
Mt. Shindake will erupt again.

387
00:22:10,095 --> 00:22:13,332
So Tom spends time observing
how the emergency response team

388
00:22:13,332 --> 00:22:16,735
is handling the situation.

389
00:22:16,735 --> 00:22:18,237
Japan has been
sharpening its skills

390
00:22:18,237 --> 00:22:21,473
when it comes to
disaster response.

391
00:22:22,608 --> 00:22:25,344
Within hours
of the eruption,

392
00:22:25,344 --> 00:22:28,314
the island was
completely evacuated.

393
00:22:28,314 --> 00:22:31,317
By the end of the day mobile
command centers had been set up

394
00:22:31,317 --> 00:22:33,786
around the island
to relay information

395
00:22:33,786 --> 00:22:36,388
back to their operation
headquarters.

396
00:22:38,757 --> 00:22:40,593
Tom is with a just
a few members of the

397
00:22:40,593 --> 00:22:44,296
Kagashima Civil Protection
Communications division.

398
00:22:44,296 --> 00:22:46,498
This is the same team
that would be responsible

399
00:22:46,498 --> 00:22:49,134
for an eruption
of Sakurajima.

400
00:22:49,134 --> 00:22:53,272
TOM:
This island is approximately
150 kilometers away,

401
00:22:53,272 --> 00:22:55,241
and it's in a
quite remote area,

402
00:22:55,241 --> 00:22:57,443
so they're doing
an amazing job.

403
00:22:57,443 --> 00:22:59,845
They're showing us the
camera that they had

404
00:22:59,845 --> 00:23:02,047
on the helicopter
who arrived on the scene

405
00:23:02,047 --> 00:23:05,117
just 40 minutes
after the eruption.

406
00:23:05,117 --> 00:23:06,652
Then the main team followed
right afterwards

407
00:23:06,652 --> 00:23:09,054
and is now based here.

408
00:23:09,054 --> 00:23:11,423
And yeah, they are here,
and it shows--

409
00:23:11,423 --> 00:23:15,194
it's quite impressive to see
the level of alertness

410
00:23:15,194 --> 00:23:17,730
of the Japanese authorities

411
00:23:17,730 --> 00:23:21,233
in response to a
volcanic crisis.

412
00:23:27,072 --> 00:23:29,608
NARRATOR:
The teams are equipped
to relay video and data

413
00:23:29,608 --> 00:23:34,680
in real-time back to the
command center in Kagoshima.

414
00:23:34,680 --> 00:23:37,349
All of this can be packed
and loaded on a helicopter

415
00:23:37,349 --> 00:23:39,852
and be on site
within an hour.

416
00:23:39,852 --> 00:23:42,288
Their vehicles are equipped
with generators

417
00:23:42,288 --> 00:23:44,556
capable of powering
a small village.

418
00:23:47,426 --> 00:23:48,560
TOM:
In this case, it was
a small island

419
00:23:48,560 --> 00:23:51,363
with approximately
150 inhabitants.

420
00:23:51,363 --> 00:23:55,501
Now you have to of course
try to imagine what you would do

421
00:23:55,501 --> 00:23:58,871
in the case of an eruption
at Sakurajima of that scale,

422
00:23:58,871 --> 00:24:03,342
where you have 700,000 people
living in the city.

423
00:24:03,342 --> 00:24:05,244
NARRATOR:
The eruption was powerful.

424
00:24:05,244 --> 00:24:08,047
It will likely
be rated a VEI-3

425
00:24:08,047 --> 00:24:11,216
on the Volcanic
Explosivity Index.

426
00:24:11,216 --> 00:24:13,552
The Civil Protection Force
will remain in place

427
00:24:13,552 --> 00:24:17,256
for several weeks in case
there is a secondary eruption.

428
00:24:17,256 --> 00:24:21,327
The response to this explosion
was swift and effective.

429
00:24:21,327 --> 00:24:23,429
No lives were lost.

430
00:24:23,429 --> 00:24:26,398
It's another chance for this
unit to hone its technique,

431
00:24:26,398 --> 00:24:28,300
because in Japan
the question isn't

432
00:24:28,300 --> 00:24:32,404
will there be another
eruption, but when.

433
00:24:32,404 --> 00:24:35,207
TOM:
I think if any country
is really preparing

434
00:24:35,207 --> 00:24:40,212
for worst-case scenarios,
a large explosion of Sakurajima,

435
00:24:40,212 --> 00:24:44,583
Japan is probably the best
prepared on a global scale.

436
00:24:46,518 --> 00:24:50,689
NARRATOR:
Tom heads back to Kagoshima
to explore a sleeping giant

437
00:24:50,689 --> 00:24:53,158
so massive that its
potential threat

438
00:24:53,158 --> 00:24:56,528
is almost impossible
to comprehend.

439
00:24:58,197 --> 00:25:01,300
This is the explosive center
of an ancient volcano,

440
00:25:01,300 --> 00:25:04,103
so massive that
this entire area,

441
00:25:04,103 --> 00:25:08,107
including part of the city
of Kagoshima and Sakurajima,

442
00:25:08,107 --> 00:25:11,043
are sitting above
a giant magma chamber.

443
00:25:14,113 --> 00:25:16,482
Deep beneath the waters
of Kagoshima Bay

444
00:25:16,482 --> 00:25:18,417
is a much bigger menace...

445
00:25:18,417 --> 00:25:21,120
the giant Aira Caldera.

446
00:25:30,295 --> 00:25:33,799
TOM:
The entire city literally
sits inside a volcano.

447
00:25:33,799 --> 00:25:35,534
You can see the cliffs
over there.

448
00:25:35,534 --> 00:25:36,802
It goes all around,

449
00:25:36,802 --> 00:25:40,305
from about 24 kilometers
by 18 kilometers,

450
00:25:40,305 --> 00:25:44,610
a rectangular area,
that is the caldera.

451
00:25:44,610 --> 00:25:48,180
It's probably the worst
place for a city to be.

452
00:25:48,180 --> 00:25:50,115
NARRATOR:
A caldera is a feature
that happens

453
00:25:50,115 --> 00:25:52,718
after an eruption empties
the magma chamber

454
00:25:52,718 --> 00:25:56,422
and the ground above
collapses into it.

455
00:25:56,422 --> 00:26:00,793
The eruption of Aira Caldera
took place 22,000 years ago,

456
00:26:00,793 --> 00:26:02,461
and in the years since,

457
00:26:02,461 --> 00:26:05,364
there hasn't been a
bigger eruption on Earth.

458
00:26:05,364 --> 00:26:09,101
Its effects can be found
all around the bay.

459
00:26:10,636 --> 00:26:13,372
TOM:
This hill, "Shiroyama," means
"white mountain," literally.

460
00:26:13,372 --> 00:26:15,674
Shiro, white;
yama, mountain.

461
00:26:15,674 --> 00:26:18,143
White, you can see why;
it's full of pumice.

462
00:26:18,143 --> 00:26:20,479
The white pieces
of pumice and fine ash.

463
00:26:20,479 --> 00:26:22,147
It's the same material
as pumice,

464
00:26:22,147 --> 00:26:24,216
and darker fragments.

465
00:26:24,216 --> 00:26:26,585
Geologists call this
a non-welded ignimbrite.

466
00:26:26,585 --> 00:26:30,689
It's the result of a massive--
a giant volcanic eruption.

467
00:26:30,689 --> 00:26:32,658
This is just a tiny part
of the deposit.

468
00:26:32,658 --> 00:26:36,328
The whole cliff is probably
100-200 meters high.

469
00:26:36,328 --> 00:26:38,730
It's composed of
this material.

470
00:26:38,730 --> 00:26:41,133
And in fact, this eruption
was so large

471
00:26:41,133 --> 00:26:44,703
it deposited pumice and ash
all over Japan.

472
00:26:44,703 --> 00:26:47,806
NARRATOR:
The eruption was so massive
it was believed to be

473
00:26:47,806 --> 00:26:51,410
200 times the scale of
the 1980 eruption

474
00:26:51,410 --> 00:26:55,280
of Mt. St. Helens
in the United States.

475
00:26:55,280 --> 00:26:58,550
Mt. St. Helens sent a huge
ash cloud into the air

476
00:26:58,550 --> 00:27:01,587
so big that deposits
were found in 11 states

477
00:27:01,587 --> 00:27:04,356
and five Canadian provinces.

478
00:27:04,356 --> 00:27:07,659
It was rated as
a VEI-5 eruption

479
00:27:07,659 --> 00:27:12,164
and one of the largest
in recent times.

480
00:27:12,164 --> 00:27:14,800
Eruptions are measured
using the VEI

481
00:27:14,800 --> 00:27:17,736
or Volcanic Explosivity Index.

482
00:27:17,736 --> 00:27:20,305
They're based on the amount
of material ejected

483
00:27:20,305 --> 00:27:22,574
and the height of
the ash plume.

484
00:27:22,574 --> 00:27:25,511
The scale ranges
from 1 to 8.

485
00:27:25,511 --> 00:27:27,679
VEI-1 is gentle.

486
00:27:27,679 --> 00:27:32,217
VEI-8 is mega-colossal.

487
00:27:32,217 --> 00:27:34,720
Each successive number is
10 times greater in scale

488
00:27:34,720 --> 00:27:36,755
than the previous.

489
00:27:36,755 --> 00:27:41,360
An eruption is classified
from start to stop.

490
00:27:41,360 --> 00:27:44,062
The current eruption phase
of Sakurajima

491
00:27:44,062 --> 00:27:46,265
has lasted more
than 70 years

492
00:27:46,265 --> 00:27:50,302
for a total combined rating
of of VEI-3.

493
00:27:50,302 --> 00:27:53,672
Compare this to
Sakurajima's 1914 eruption,

494
00:27:53,672 --> 00:27:58,644
which lasted just eight months,
was rated VEI-4.

495
00:27:58,644 --> 00:28:02,748
Aira's caldera eruption
ranks as super-colossal,

496
00:28:02,748 --> 00:28:08,020
between VEI-7 and VEI-8.

497
00:28:08,020 --> 00:28:10,322
An eruption of this magnitude

498
00:28:10,322 --> 00:28:13,525
hasn't happened in
recorded history.

499
00:28:13,525 --> 00:28:18,163
The closest is the 1812 eruption
of Tambora in Indonesia,

500
00:28:18,163 --> 00:28:21,099
which was a VEI-7.

501
00:28:21,099 --> 00:28:23,802
That eruption killed
92,000 people

502
00:28:23,802 --> 00:28:27,039
and caused widespread
crop failures throughout Europe

503
00:28:27,039 --> 00:28:29,508
that lasted several years.

504
00:28:29,508 --> 00:28:32,277
The Aira eruption
22,000 years ago

505
00:28:32,277 --> 00:28:36,315
was eight times
more massive than that.

506
00:28:36,315 --> 00:28:38,550
TOM:
This massive giant eruption

507
00:28:38,550 --> 00:28:41,186
or if you want to call it a
super-volcano eruption,

508
00:28:41,186 --> 00:28:45,190
a super eruption,
had a result

509
00:28:45,190 --> 00:28:48,126
that the crust of the Earth
sank several hundred meters

510
00:28:48,126 --> 00:28:51,730
forming what is called
the "Aira Caldera,"

511
00:28:51,730 --> 00:28:58,070
and then a large 24x18
kilometer caldera formed.

512
00:28:58,070 --> 00:29:01,239
This whole city actually
sits inside the Aira volcano.

513
00:29:01,239 --> 00:29:04,109
Aira volcano is the whole
complex, the whole caldera.

514
00:29:04,109 --> 00:29:04,943
We are here on the rim;

515
00:29:04,943 --> 00:29:06,244
we are looking down
onto the city.

516
00:29:06,244 --> 00:29:07,546
This is the crater floor.

517
00:29:09,214 --> 00:29:11,483
NARRATOR:
A super eruption
is fed by the build-up

518
00:29:11,483 --> 00:29:15,387
of a lot of magma
in the volcano's reservoir.

519
00:29:15,387 --> 00:29:18,590
Plate tectonics
explains how that works.

520
00:29:18,590 --> 00:29:20,626
Instead of two plates
colliding,

521
00:29:20,626 --> 00:29:23,161
where one sub-ducts
under the other,

522
00:29:23,161 --> 00:29:26,665
around Japan several smaller
micro plates are being crushed,

523
00:29:26,665 --> 00:29:29,434
twisted, and pulled.

524
00:29:29,434 --> 00:29:32,170
This movement has made the
Earth's crust very thin

525
00:29:32,170 --> 00:29:34,206
under the island of Kyushu.

526
00:29:37,743 --> 00:29:41,513
To make matters worse,
the direction and speed

527
00:29:41,513 --> 00:29:44,816
of the sub-ducting plate has
created a convection current

528
00:29:44,816 --> 00:29:49,121
that is producing an anomaly
called a mantle wedge.

529
00:29:49,121 --> 00:29:51,623
This brings superheated
magma even closer

530
00:29:51,623 --> 00:29:55,160
to the surface, where it
reacts with ground water

531
00:29:55,160 --> 00:30:00,465
to lower the melting point
of the overlying rock layers.

532
00:30:00,465 --> 00:30:04,102
It's the volcanic equivalent
of the perfect storm.

533
00:30:04,102 --> 00:30:07,305
The higher temperatures of
the mantle material allows for

534
00:30:07,305 --> 00:30:11,276
a lot more magma to be produced
at shallower depths.

535
00:30:11,276 --> 00:30:14,346
It creates conditions for
massive eruptions.

536
00:30:14,346 --> 00:30:18,650
This is what's happening
under Japan's Kyushu Island...

537
00:30:18,650 --> 00:30:21,286
and why the island is
littered with active

538
00:30:21,286 --> 00:30:25,257
and very dangerous volcanoes,
including Aira.

539
00:30:26,525 --> 00:30:29,127
Although Sakurajima
appears to be a volcano

540
00:30:29,127 --> 00:30:33,198
within a volcano,
they are one and the same.

541
00:30:33,198 --> 00:30:38,270
Sakurajima is a vent of Aira,
but has its own magma reservoir,

542
00:30:38,270 --> 00:30:42,507
but that reservoir draws
its magma from Aira's.

543
00:30:42,507 --> 00:30:45,143
That is one of the reasons
it can produce large

544
00:30:45,143 --> 00:30:50,415
VEI-4 to 5 eruptions
every 100-200 years.

545
00:30:52,484 --> 00:30:55,387
TOM:
The whole island of Sakurajima
is actually

546
00:30:55,387 --> 00:30:57,723
two overlapping
stratovolcanoes,

547
00:30:57,723 --> 00:31:01,059
An older one, Kita-dake,
to the left,

548
00:31:01,059 --> 00:31:05,130
and the young one,
presently active Minami-dake.

549
00:31:05,130 --> 00:31:09,067
All this has grown just within
the past 25,000 years,

550
00:31:09,067 --> 00:31:12,104
so this is really an
incredibly active volcano.

551
00:31:12,104 --> 00:31:15,507
It is one out of the ten
most active in the earth,

552
00:31:15,507 --> 00:31:17,576
I would say, at the moment.

553
00:31:17,576 --> 00:31:19,778
It is definitely Japan's
most active one.

554
00:31:44,503 --> 00:31:47,606
NARRATOR:
Scientists still don't
fully understand what triggers

555
00:31:47,606 --> 00:31:49,875
a caldera eruption.

556
00:31:49,875 --> 00:31:54,212
This is where the massive
reservoir erupts.

557
00:31:54,212 --> 00:31:58,517
During Sakurajima's 1914
eruption the entire caldera

558
00:31:58,517 --> 00:32:01,119
dropped by almost
two feet lengths

559
00:32:01,119 --> 00:32:05,090
proving that the two
magma chambers are connected.

560
00:32:05,090 --> 00:32:08,093
But the big and
unanswerable question is,

561
00:32:08,093 --> 00:32:12,430
is that enough to
destabilize Aira Caldera?

562
00:32:12,430 --> 00:32:15,467
For the people of Kagoshima,
the good news is

563
00:32:15,467 --> 00:32:18,136
that super eruptions
are infrequent.

564
00:32:18,136 --> 00:32:20,705
Such a massive blast
requires long periods

565
00:32:20,705 --> 00:32:23,809
between eruptions to rebuild
the intense volume

566
00:32:23,809 --> 00:32:27,445
of molten material
within the magma chamber.

567
00:32:27,445 --> 00:32:31,516
That process takes many
thousands of years.

568
00:32:34,820 --> 00:32:38,123
Over the past 300,000 years
there have been several

569
00:32:38,123 --> 00:32:41,493
massive caldera eruptions
on the island of Kyushu

570
00:32:41,493 --> 00:32:46,531
at 20,000-40,000
year intervals.

571
00:32:46,531 --> 00:32:50,569
The volcano that is most likely
to produce a caldera eruption,

572
00:32:50,569 --> 00:32:53,171
and in a more advanced stage
of recharging,

573
00:32:53,171 --> 00:32:56,842
is Aso Caldera.

574
00:32:56,842 --> 00:32:59,845
Aso Caldera is not just
bigger than Aira's,

575
00:32:59,845 --> 00:33:02,747
it's one of the biggest
on the planet.

576
00:33:02,747 --> 00:33:05,450
It is ranked as one of the
most dangerous volcanoes

577
00:33:05,450 --> 00:33:09,654
in the world.

578
00:33:09,654 --> 00:33:14,426
TOM:
This caldera belongs to
the XL class of calderas.

579
00:33:14,426 --> 00:33:16,428
There are not that many
in the whole planet

580
00:33:16,428 --> 00:33:17,429
that have been active

581
00:33:17,429 --> 00:33:20,232
in the past few hundreds
of thousands of years.

582
00:33:20,232 --> 00:33:24,202
Maybe you can count them in
terms of dozens.

583
00:33:24,202 --> 00:33:28,406
NARRATOR:
Aso sits directly over the apex
of the mantle wedge.

584
00:33:28,406 --> 00:33:31,443
Here the crust is also
the thinnest in Kyushu

585
00:33:31,443 --> 00:33:36,314
and Aso has produced four
large caldera eruptions.

586
00:33:36,314 --> 00:33:40,085
Three of them happened within
30,000 years of each other.

587
00:33:40,085 --> 00:33:44,389
On a geological timescale,
that is very close together.

588
00:33:44,389 --> 00:33:47,492
The last one was
90,000 years ago.

589
00:33:51,596 --> 00:33:54,532
Aso also contains a
geological feature

590
00:33:54,532 --> 00:33:56,501
called a resurgent dome.

591
00:33:56,501 --> 00:33:58,837
This is where inflation
from the magma chamber

592
00:33:58,837 --> 00:34:01,239
pushes the caldera
floor upwards,

593
00:34:01,239 --> 00:34:04,476
indicating a charged
magma chamber.

594
00:34:05,677 --> 00:34:08,246
It's estimated that the
volume of new magma

595
00:34:08,246 --> 00:34:11,483
coming into Aso's reservoirs
is so great

596
00:34:11,483 --> 00:34:15,220
that it is capable of producing
a VEI-7 eruption

597
00:34:15,220 --> 00:34:17,822
every 10,000 years.

598
00:34:17,822 --> 00:34:21,226
It has been recharging
for 90,000 years,

599
00:34:21,226 --> 00:34:25,397
so it's capable of something
massive any time.

600
00:34:25,397 --> 00:34:27,332
But over the past
20,000 years

601
00:34:27,332 --> 00:34:30,201
its activity has been
relatively small,

602
00:34:30,201 --> 00:34:35,507
and the impact of its eruptions
has been localized.

603
00:34:43,181 --> 00:34:46,618
There are five major peaks
and 17 cones.

604
00:34:46,618 --> 00:34:52,123
One of them, Mt. Nakadake
is still active.

605
00:34:56,328 --> 00:34:58,663
TOM:
This bluish haze,
it's very typical

606
00:34:58,663 --> 00:35:02,467
if there's SO2 gas present.

607
00:35:02,467 --> 00:35:05,136
That is very typical
if magma is actually

608
00:35:05,136 --> 00:35:06,504
very close to the vent.

609
00:35:06,504 --> 00:35:10,208
So I suspect the eruption
is still going on.

610
00:35:10,208 --> 00:35:12,610
It is just right now
maybe a bit quiet,

611
00:35:12,610 --> 00:35:16,114
but it could produce
explosions any time.

612
00:35:16,114 --> 00:35:18,450
Of course, if a sudden
explosion occurs

613
00:35:18,450 --> 00:35:20,185
it's extremely hazardous,

614
00:35:20,185 --> 00:35:22,287
and in fact,
people in the past

615
00:35:22,287 --> 00:35:26,491
unfortunately have been killed
by projectiles.

616
00:35:26,491 --> 00:35:32,263
NARRATOR:
The SO2, or sulfur dioxide gas,
is toxic and an obvious danger.

617
00:35:32,263 --> 00:35:37,202
In fact, Aso has a history of
small but deadly incidents.

618
00:35:37,202 --> 00:35:40,739
Two people were killed in 1979
from a sudden explosion

619
00:35:40,739 --> 00:35:43,441
that caught everyone
off-guard.

620
00:35:43,441 --> 00:35:45,810
Eleven others were injured
when a rock crashed through

621
00:35:45,810 --> 00:35:49,514
the roof of a
bombproof shelter.

622
00:35:52,650 --> 00:35:54,686
Tourists had been able
to take a cable car

623
00:35:54,686 --> 00:35:56,287
to the crater,

624
00:35:56,287 --> 00:35:59,290
but that was suspended
just over two years ago,

625
00:35:59,290 --> 00:36:02,627
when the volcano alert level
was raised to 3.

626
00:36:02,627 --> 00:36:05,463
Tom is going to get
a rare view.

627
00:36:05,463 --> 00:36:07,399
He has arranged
special permission

628
00:36:07,399 --> 00:36:10,568
with government officials
to visit the active crater.

629
00:36:14,806 --> 00:36:17,675
The current eruptive crater
of Nakadake

630
00:36:17,675 --> 00:36:22,080
has seven vents that have
erupted in historical times.

631
00:36:22,080 --> 00:36:24,249
You can tell how active
a volcano is

632
00:36:24,249 --> 00:36:26,751
by how quickly
it builds new mass.

633
00:36:27,452 --> 00:36:30,822
TOM:
Very large,
extremely active volcano,

634
00:36:30,822 --> 00:36:35,427
Remember, all these mountains
with all these cones,

635
00:36:35,427 --> 00:36:40,265
it's just the central part
of the much larger complex,

636
00:36:40,265 --> 00:36:42,434
and it's only
90,000 years old,

637
00:36:42,434 --> 00:36:45,136
which is in geologic terms
almost nothing.

638
00:36:45,136 --> 00:36:48,706
So for a volcano
it's still very young,

639
00:36:48,706 --> 00:36:50,408
a very young age.

640
00:36:51,676 --> 00:36:55,747
Wow, yeah...
It's a very impressive crater.

641
00:36:56,848 --> 00:36:58,349
You have no idea when
you're down there;

642
00:36:58,349 --> 00:37:00,585
it looks so flat
and harmless.

643
00:37:00,585 --> 00:37:03,221
But this is
actually something.

644
00:37:05,523 --> 00:37:09,294
Wow, yeah, incredible.

645
00:37:09,294 --> 00:37:11,396
Wow.

646
00:37:11,396 --> 00:37:13,431
Okay, we are there.

647
00:37:15,133 --> 00:37:17,402
It's impressive.

648
00:37:17,402 --> 00:37:20,105
The Nakadake crater
is all this, actually.

649
00:37:20,105 --> 00:37:22,607
It goes on over there.

650
00:37:22,607 --> 00:37:25,076
It is more than a
kilometer long in total.

651
00:37:25,076 --> 00:37:28,813
It has seven
different vents,

652
00:37:28,813 --> 00:37:31,316
out of which we see
two here that are active.

653
00:37:31,316 --> 00:37:33,051
You hear the roaring,

654
00:37:33,051 --> 00:37:35,320
so there is a very intense
degassing going on.

655
00:37:35,320 --> 00:37:37,822
Magma is very close
to the surface.

656
00:37:37,822 --> 00:37:41,493
Explosions could actually
occur any time.

657
00:37:41,493 --> 00:37:43,728
Number 2 crater
is also active.

658
00:37:43,728 --> 00:37:45,697
There's a lot of
degassing going on.

659
00:37:45,697 --> 00:37:50,101
It's not so much steam,
but apparently lots of SO2.

660
00:37:50,101 --> 00:37:53,138
This bluish haze
is created by SO2.

661
00:37:53,138 --> 00:37:54,372
We're almost out of
the plume,

662
00:37:54,372 --> 00:37:56,574
but you still can smell
sulfur now.

663
00:37:56,574 --> 00:37:59,210
Wind is swirling a bit.

664
00:37:59,210 --> 00:38:01,246
We're at the edge
of this haze.

665
00:38:01,246 --> 00:38:03,314
So I guess if we were
right in the plume

666
00:38:03,314 --> 00:38:05,617
we'd probably need the
gas mask to breathe.

667
00:38:10,555 --> 00:38:14,125
NARRATOR:
The gases coming off the plume
are deadly.

668
00:38:14,125 --> 00:38:17,262
In 1997, three people
were killed on this spot

669
00:38:17,262 --> 00:38:20,732
when they were overcome
by the noxious gas.

670
00:38:20,732 --> 00:38:23,134
TOM:
Nobody can predict whether
it will just gradually

671
00:38:23,134 --> 00:38:25,403
calm down now in the coming
weeks and months,

672
00:38:25,403 --> 00:38:28,473
or it might re-intensify.

673
00:38:28,473 --> 00:38:30,742
A couple of months ago
you could almost see

674
00:38:30,742 --> 00:38:33,244
constant Strombolian
activity.

675
00:38:33,244 --> 00:38:36,714
At least from the webcam.
I wasn't here, of course.

676
00:38:36,714 --> 00:38:41,819
So you would have seen
incandescent pieces of lava

677
00:38:41,819 --> 00:38:45,323
being ejected, and they
piled up to form that cone.

678
00:38:46,357 --> 00:38:49,527
NARRATOR:
Up until recently,
the crater contained a lake.

679
00:38:49,527 --> 00:38:53,131
But the water boiled off
because of the extreme heat.

680
00:38:53,131 --> 00:38:55,800
Water from the surrounding
hill drains into the crater,

681
00:38:55,800 --> 00:38:59,671
making this volcano
unpredictable.

682
00:39:01,206 --> 00:39:04,676
TOM:
I find this is
extremely impressive.

683
00:39:04,676 --> 00:39:06,211
The contrast couldn't be...

684
00:39:06,211 --> 00:39:08,546
There's an explosion!

685
00:39:09,547 --> 00:39:11,249
Explosion!

686
00:39:12,650 --> 00:39:16,087
This is a phreato, maybe
phreatomagmatic explosion.

687
00:39:16,087 --> 00:39:18,289
You see the ash?

688
00:39:20,525 --> 00:39:22,760
NARRATOR:
The eruption is a result
of ground water

689
00:39:22,760 --> 00:39:26,030
coming into contact
with hot magma.

690
00:39:26,030 --> 00:39:28,299
It flashes to steam.

691
00:39:28,299 --> 00:39:32,070
As a gas it expands to more
than 1,200 times its volume

692
00:39:32,070 --> 00:39:34,305
in a sudden explosion.

693
00:39:34,305 --> 00:39:37,308
Much of the plume
is water vapor.

694
00:39:39,811 --> 00:39:43,281
TOM:
You could probably see
stones being ejected.

695
00:39:43,281 --> 00:39:45,583
This was a very small one,

696
00:39:45,583 --> 00:39:49,254
but well,
that was fantastic!

697
00:39:49,254 --> 00:39:50,722
Another one, yeah.

698
00:40:04,435 --> 00:40:07,272
TOM:
You see the black fingers
of ash,

699
00:40:07,272 --> 00:40:08,806
followed by white steam.

700
00:40:08,806 --> 00:40:12,777
This is very typical for
phreatomagmatic explosions.

701
00:40:15,847 --> 00:40:20,251
[LOUD EXPLOSIONS]

702
00:40:31,129 --> 00:40:32,297
TOM:
It's easy to be
killed here.

703
00:40:32,297 --> 00:40:34,098
If this volcano
was not monitored,

704
00:40:34,098 --> 00:40:35,266
if there was free access

705
00:40:35,266 --> 00:40:38,169
you would have
hundreds of people maybe

706
00:40:38,169 --> 00:40:41,339
on a good day,
walking around here.

707
00:40:41,339 --> 00:40:43,675
And then, of course,
the more people there are

708
00:40:43,675 --> 00:40:45,310
on the rim,
the more likely it is

709
00:40:45,310 --> 00:40:48,746
that during an explosion
there could be an incident.

710
00:40:48,746 --> 00:40:51,849
And during daylight especially
they're not glowing,

711
00:40:51,849 --> 00:40:54,118
you have very little chance
to escape them.

712
00:40:54,118 --> 00:40:56,721
Even the hard hat
would not--

713
00:40:56,721 --> 00:40:58,790
it gives protection against
small things,

714
00:40:58,790 --> 00:41:03,428
but if you have a block
like this the hat is useless.

715
00:41:03,428 --> 00:41:07,732
Imagine this 100 times bigger,
and we'd be in trouble.

716
00:41:10,702 --> 00:41:14,739
For me this was
absolutely amazing.

717
00:41:14,739 --> 00:41:17,675
NARRATOR:
Although the eruption
was small and not threatening,

718
00:41:17,675 --> 00:41:21,446
the situation has now become
unpredictable.

719
00:41:21,446 --> 00:41:24,515
The officials have asked
everyone to leave.

720
00:41:24,515 --> 00:41:27,452
TOM:
The best way to decrease risk
is to limit the time

721
00:41:27,452 --> 00:41:29,287
in a hazardous place.

722
00:41:29,287 --> 00:41:32,457
So we've seen two really nice
small explosions,

723
00:41:32,457 --> 00:41:35,493
so we don't want to risk
to get to a bigger one,

724
00:41:35,493 --> 00:41:37,128
which could happen.

725
00:41:37,128 --> 00:41:38,730
So that's legitimate.

726
00:41:38,730 --> 00:41:42,367
They know the volcano,
and they don't want to go

727
00:41:42,367 --> 00:41:44,635
and take us to any
higher risk levels.

728
00:41:44,635 --> 00:41:47,105
So I completely understand.

729
00:41:47,105 --> 00:41:50,675
NARRATOR:
Large caldera volcanoes work
on a geological clock,

730
00:41:50,675 --> 00:41:52,710
taking tens of thousands
of years

731
00:41:52,710 --> 00:41:56,214
to ready themselves
for a major eruption.

732
00:41:56,214 --> 00:41:58,516
And in those terms,
Aso either be could be

733
00:41:58,516 --> 00:42:01,052
overdue for a
caldera eruption,

734
00:42:01,052 --> 00:42:05,056
or it could still could be
thousands of years off.

735
00:42:05,056 --> 00:42:08,326
Given its size and history
Aso is capable of producing

736
00:42:08,326 --> 00:42:10,461
a massive eruption.

737
00:42:10,461 --> 00:42:13,531
Everything in its danger zone
could be wiped out,

738
00:42:13,531 --> 00:42:16,601
including Kumamoto City,
which is downslope

739
00:42:16,601 --> 00:42:19,637
from the volcano.

740
00:42:19,637 --> 00:42:22,507
In recent history, the only
eruption we can relate it to

741
00:42:22,507 --> 00:42:25,676
is the 1991 eruption of
Mt. Pinatubo

742
00:42:25,676 --> 00:42:27,612
in the Philippines.

743
00:42:27,612 --> 00:42:30,648
It was the largest eruption
to affect a populated area

744
00:42:30,648 --> 00:42:36,154
in the 20th century,
with a ranking of VEI-6.

745
00:42:36,154 --> 00:42:39,824
It caused incredible devastation
to the surrounding area.

746
00:42:39,824 --> 00:42:43,861
The ash fall was recorded in
places as far away as Vietnam,

747
00:42:43,861 --> 00:42:47,698
Cambodia, and Malaysia.

748
00:42:47,698 --> 00:42:50,668
That eruption was an
important landmark.

749
00:42:50,668 --> 00:42:52,703
It was the first time that
scientists were able

750
00:42:52,703 --> 00:42:57,341
to predict the eruption in time
to do mass evacuations.

751
00:42:57,341 --> 00:43:01,546
Because of that, the death toll
was under 1,000.

752
00:43:01,546 --> 00:43:03,614
But if history repeats itself

753
00:43:03,614 --> 00:43:07,385
Aso would be on a
vastly larger scale.

754
00:43:07,385 --> 00:43:10,388
What they'd be looking at
would be 40-50 times bigger

755
00:43:10,388 --> 00:43:14,459
than Pinatubo.

756
00:43:14,459 --> 00:43:19,664
This type of eruption can't be
planned for or mitigated.

757
00:43:19,664 --> 00:43:22,533
The ash fall alone
would be so huge

758
00:43:22,533 --> 00:43:25,636
that it would affect
all of Japan.

759
00:43:25,636 --> 00:43:28,573
Its impact would be global.

760
00:43:28,573 --> 00:43:31,442
But hopefully it isn't something
humans have to deal with

761
00:43:31,442 --> 00:43:33,578
for thousands of years.

762
00:43:44,789 --> 00:43:49,327
♪♪♪

763
00:43:49,327 --> 00:43:52,797
NARRATOR:
Back at Sakurajima, that
volcano's explosive activity

764
00:43:52,797 --> 00:43:56,567
has continued to ramp up.

765
00:43:56,567 --> 00:43:59,237
TOM:
Five to ten years ago
it was maybe an average

766
00:43:59,237 --> 00:44:00,471
of one eruption, two.

767
00:44:00,471 --> 00:44:03,407
Maybe on a good day
there were two per day.

768
00:44:03,407 --> 00:44:06,544
There has been a clear increase
over the past years, though,

769
00:44:06,544 --> 00:44:11,048
so it's not unusual now
to have maybe up to ten

770
00:44:11,048 --> 00:44:14,118
during phases of
elevated activity.

771
00:44:14,118 --> 00:44:16,053
NARRATOR:
It's likely that Sakurajima

772
00:44:16,053 --> 00:44:18,389
is building to
a larger eruption.

773
00:44:18,389 --> 00:44:20,358
And that could mean
something in the range

774
00:44:20,358 --> 00:44:27,465
of a VEI-4 or VEI-5 eruption
in the not-too-distant future.

775
00:44:27,465 --> 00:44:30,401
TOM:
This year alone has
produced more explosions

776
00:44:30,401 --> 00:44:34,138
than last year combined,
and we're only in May.

777
00:44:34,138 --> 00:44:37,508
Nobody can predict what the
volcano is going to do,

778
00:44:37,508 --> 00:44:40,278
but it may be a
long-term precursor

779
00:44:40,278 --> 00:44:44,248
to a major phase of
activity again.

780
00:44:48,686 --> 00:44:53,658
[Explosion]

781
00:45:12,510 --> 00:45:19,317
♪♪♪

782
00:45:19,317 --> 00:45:23,154
NARRATOR:
Tom came to Japan just
in time to catch Sakurajima

783
00:45:23,154 --> 00:45:27,191
at its most spectacular
period of activity in years.

784
00:45:33,130 --> 00:45:36,367
TOM:
Sakurajima has put on
a great show for us.

785
00:45:36,367 --> 00:45:41,272
We've seen tremendous
explosions,

786
00:45:41,272 --> 00:45:43,107
small and large.

787
00:45:43,107 --> 00:45:51,582
This beautiful bay
with fishing boats...

788
00:45:51,582 --> 00:45:54,752
I've never seen Sakurajima
so active before.

789
00:45:54,752 --> 00:46:02,159
[WAVES SPLASHING ON BEACH]

790
00:46:02,159 --> 00:46:04,195
♪♪♪

791
00:46:04,195 --> 00:46:08,332
NARRATOR:
Japan has no choice
but to grapple with giants.

792
00:46:08,332 --> 00:46:11,268
From the sea floor
to its tallest peaks,

793
00:46:11,268 --> 00:46:12,737
the country is at the mercy

794
00:46:12,737 --> 00:46:17,541
of the most elemental
geological forces.

795
00:46:17,541 --> 00:46:20,311
These forces have
created an environment

796
00:46:20,311 --> 00:46:22,079
of staggering beauty,

797
00:46:22,079 --> 00:46:27,284
but they've also caused
devastating disasters.

798
00:46:27,284 --> 00:46:29,787
Science is still on
a steep learning curve

799
00:46:29,787 --> 00:46:32,390
when it comes volcanoes,

800
00:46:32,390 --> 00:46:35,559
but with each new eruption
they are beginning to understand

801
00:46:35,559 --> 00:46:38,329
the incredibly complex forces
that are at work

802
00:46:38,329 --> 00:46:41,465
beneath our
Earth's surface.

803
00:46:41,465 --> 00:46:43,801
Knowledge that is teaching
them how to predict

804
00:46:43,801 --> 00:46:48,272
large eruptions
before they happen.

805
00:46:48,272 --> 00:46:51,075
In a country riddled
with active volcanoes,

806
00:46:51,075 --> 00:46:53,644
some of which erupt
on a daily basis,

807
00:46:53,644 --> 00:46:59,617
life goes on for Japan's
nearly 130 million people.

808
00:46:59,617 --> 00:47:03,187
What else can be done in the
face of such powerful forces,

809
00:47:03,187 --> 00:47:05,723
except watch and wait...

810
00:47:05,723 --> 00:47:08,025
and hope that we learn
what we need to

811
00:47:08,025 --> 00:47:12,396
before our geological
time runs out.

812
00:47:12,396 --> 00:47:17,334
♪♪♪

813
00:47:22,106 --> 00:47:27,111
♪♪♪

814
00:47:27,111 --> 00:47:32,116
♪♪♪

815
00:47:32,116 --> 00:47:37,121
♪♪♪

816
00:47:37,121 --> 00:47:42,126
♪♪♪

817
00:47:42,126 --> 00:47:47,131
♪♪♪

818
00:47:47,131 --> 00:47:52,136
♪♪♪

819
00:47:52,136 --> 00:47:56,540
♪♪♪