>> Earth. A 4.5-billion-year-
old planet, still evolving.
As continents shift and clash,
volcanoes erupt, and glaciers
grow and recede, the Earth's
crust is carved in numerous
and fascinating ways, leaving
a trail of geological
mysteries behind.
In this episode, Krakatoa, one
of the deadliest volcanoes in
the world.
More than 100 years ago, it
erupted with such devastating
fury that it wiped itself off
the face of the Earth.
In the process, it sent out
the loudest sound in recorded
history and killed more than
36,000 people. And now, this
deadly volcanic beast is back.
Geologists investigate one of
the world's fastest-growing
volcanoes to hunt for clues
that will tell them if, and
when, Krakatoa will explode
once again with the same
cataclysmic force.
As they prize apart the rocks,
the answers they find will be
another piece of the puzzle of
How the Earth Was Made.
S01x03 Krakatoa Original Air Date on February 24, 2009
-- Sync, corrected by elderman -- -- for addic7ed.com --
Krakatoa is one of the most
dangerous volcanoes the world
has ever seen. When it
exploded apart in 1883, the
blast was heard over nearly
ten per cent of the Earth's
surface. It was a worldwide
clarion call, announcing the
awesome power of volcanoes.
The site of this monstrous
eruption lies between the
Indonesian islands of Java and
Sumatra, in a channel known as
the Sunda Straits.
Today, a new volcano has
staked its claim in exactly
the same spot. It's called
Anak Krakatau, meaning "the
child of Krakatoa."
Right now, it's in the middle
of a new and extremely
dangerous phase.
Dr. Charles Mandeville
traveled here to see if the
child will one day be as
deadly as its parent--to see
if history is about to repeat
itself. The stakes are high.
At risk now are the one
million people of Java and
Sumatra who live within 50
miles of the volcano.
>> Oh, wow. Look at that.
We've got a little explosion
going on. I've kind of been
following this from the
internet, from my office, but
it's actually good to kind of
see the thing, uh, live again.
I've noticed in coming here
that, uh, the volcano itself
has grown possibly as much as
250 to 300 feet since the last
time I've actually stood on
its crater, back in 1990.
>> Growing at a rate of 12 feet
a year, the 1,033-foot volcano
is both one of the
fastest-growing and youngest
volcanoes on the planet.
This remarkable footage shows
its explosive birth in June
1927, when it first broke
through the sea floor and
erupted out of the water.
Its rapid growth is clear
evidence that this new volcano
is extremely active, but will
it be as deadly as its parent?
These eruptions are always
accompanied by a series of
ground-shaking tremors.
For geologists, these small
earthquakes are evidence that
this volcano is entering a
more destructive phase.
Seismographs have been buried
deep on Anak's slopes to
record this underground
activity. But these small
quakes are not the only sign
of a dangerously active
volcano. A more subtle clue is
right beneath Mandeville's
feet.
>> Black sand beaches are very
common in volcanic areas.
Uh, the minerals and the glass
fragments that comprise the
ash that the volcano erupts is
typically dark charcoal gray
colored, and usually, these
materials don't stand up to
weathering over long
protracted periods of geologic
time, but you find them in
relatively fresh, pristine
form when you are near an
active volcano.
>> Anak Krakatau is rarely
completely quiet, but the
level of activity in 2008
shows that the volcano has
become unusually violent.
To discover just how much of a
threat it could pose in the
near future, volcano
detectives must turn to their
history books to learn what
made its parent Krakatoa so
destructive. This is a story
that has fascinated geologists
for over a century.
>> What got me switched on to
volcanology was the 1883
eruption, I learned about this
at school, and I remember
thinking how incredible that
an island could just blow
itself into oblivion. You
know, what was going on?
What was that all about?
What was special? You know,
how does that happen? And
could it happen again
elsewhere on Earth?
>> Before it exploded in 1883,
Krakatoa was an uninhabited
island with three jagged
peaks, covered in lush
vegetation. It was part of the
Dutch East Indies, a thriving,
bustling hub of international
trade. Indonesia's wealth of
minerals and spices attracted
many Western traders,
journalists and geologists.
Their reports provide
first-hand accounts of what
happened before and during
Krakatoa's deadly and shocking
eruption. There had been no
hint of volcanic activity in
anyone's memory. No one had a
clue that Krakatoa was about
to blow. Beneath its green and
placid surface, Krakatoa was a
time bomb waiting to explode.
>> So the first idea the
locals would have got that
anything was--anything strange
was happening on their island
would have been in May 1883.
Earthquakes, earth tremors.
>> These tremors reached as
far as the capital Batavia,
more than 100 miles away.
Few suspected that the island
of Krakatoa, seen on the
distant horizon, was to blame,
and that these earthquakes
were the first clue to its
deadly potential.
Then, on May 20th, 1883,
Krakatoa announced that it was
no mere island.
One of Krakatoa's three peaks
exploded with extreme force,
shooting a plume of ash
hundreds of feet into the air.
But after these initial
fireworks, the activity
appeared to cease. The local
population breathed a sigh of
relief. Thinking it safe, the
governor of the Dutch East
Indies sent a research party
of geologists to the island in
late May, where they observed
the scorched landscape and
smoking crater with amazement.
Their meticulous report gives
modern-day geologists the
first clue as to what lay
behind Krakatoa's immense
power. A key discovery was a
layer of pumice one foot deep
that covered the island's
shores. This pumice is the
solidified lava that comes
from the heart of a volcano,
and it's riddled with bubbles.
These bubbles suggest to
geologists that Krakatoa is a
stratovolcano.
>> And those volcanoes tend to
be the classic volcanoes that
you see in textbooks, they're
very steep-sided, like sort of
sharp, almost triangular type
mountains.
>> These are the most
dangerous types of volcanoes
on Earth. They are fueled by
molten rock called lava,
known as magma when it's
underground. The magma that
flows though these volcanoes
is like liquid dynamite.
>> Stratovolcanoes are
dangerous because of the sorts
of lava that they erupt, and
the lava that comes out of
stratovolcanoes is very sticky,
viscous lava, and the danger
there is that sticky lava
often contains large amounts
of gas.
>> The bubbles inside the
pumice discovered on Krakatoa
in 1883 show that the magma
was once packed with explosive
gases. Because the magma was
so sticky--a term describing
its thickness and resistance
to flow--the gas could not
easily escape.
>> And the formation of gas
bubbles in the sticky lava
can be powerful enough to
actually rip the lava apart,
and, in the process, you
actually tear away the volcano.
The whole thing becomes--becomes
explosive and you produce very
dangerous volcanic activity.
>> Krakatoa's magma had
another deadly property.
>> PETFORD: In some situations,
the lava can become so sticky
that it sort of freezes up and
congests or chokes up the
volcano, it forms a kind of a
plug or a seal. What will
happen is that, over time,
more magma is coming up and
being trapped beneath that
plug. At some--some time in
the future, the pressure will
be so great that there'll be
so much magma wanting to get
up that you'll just rip the
plug apart, and that can
produce, again, a catastrophic
volcanic eruption.
>> This is exactly what
happened at Krakatoa on May
20th, 1883.
>> From then onwards, over the
summer it--it quietened down a
bit, but this was really the
kind of calm before the storm.
>> The investigation into
Krakatoa's deadly potential
has produced important
evidence. The frequent
earthquakes on Anak Krakatau
today indicate the volcano is
still dangerous.
The pumice from 1883 reveals
that Krakatoa was a
stratovolcano, its sticky,
gas-rich lava making it
dangerously explosive.
Krakatoa's eruption in May
1883 was spectacular, but
beneath the surface, Krakatoa
was refueling. An even greater
eruption was gathering force
out of sight and out of mind.
Anak Krakatau is one of the
fastest-growing volcanoes in
the world. Geologists are
investigating its threat to
the region. They have turned
to the past to uncover what
made its parent so deadly.
In 1883, exactly 100 days
after Krakatoa first blew, the
volcano showed its true power.
This final phase of eruptions
began at six minutes past one
on the afternoon of August 26th.
All three volcanic peaks
erupted simultaneously,
hurling dense clouds of ash
and smoke an astonishing 17
miles into the sky.
>> The eruption of Krakatoa
was one of the--the biggest
volcanic events of the last
few hundred years, and it
would have been, to people
observing it, it would have
been like the--the--the
beginning of the end of the
world, if you like.
>> The power of this eruption
was immense, like a giant jet
engine aimed skywards. The air
quickly became choked with
tons of thick black ash,
blotting out the sun.
>> So the temperature, because
of all the ash in the
atmosphere, would be stifling,
and if you were very near, on
the, for example, the west coast
of Java, you--you'd be getting
the ash in your throat and in
your eyes. It would have been,
you know, a real vision of
hell.
>> And a nightmare that showed
no signs of ending, Byhe
next morning of August 27th
1883, Krakatoa's three craters
had been raging for more than
14 hours.
Then, sometime between 5:30
and 10:02 a.m., the land was
deafened by a series of four
huge explosions.
The noise was so loud, it
could be heard over 2,000
miles away in the Australian
desert near Perth.
The third was the loudest
recorded noise in history, the
equivalent to 200 megatons of
TNT, 13,000 times the size of
the bomb that destroyed
Hiroshima.
What created this awesome
explosion? The hunt for
answers takes geologist
Charles Mandeville
to the jagged island of
Rakata. This tiny island is,
in fact, a part of the
once-mighty Krakatoa.
>> The record of what the
volcano did from May 20th to
August 26th to 27th is here
represented on the islands by
the layered deposits that we
see preserved in the jungle.
This is a goldmine for a
volcanologist trying to
reconstruct the events that
took place here, because each
one of these deposits tells us
something particular about
what the volcano was doing.
>> This pumice was thrown out
of the heart of the volcano in
1883. Mandeville believes that
it holds the key to
understanding the forces that
destroyed Krakatoa.
>> What I have in my hand is a
mixed pumice or streaked
pumice. And what it represts
is that we had two magmas
mingling in the conduit of the
1883 eruption of Krakatoa.
>> The stripes are proof of
the two types of magma inside
Krakatoa. The lighter band
represents the cooler,
gas-rich magma that was
present during the earlier
eruption in May. This eruption
only partially emptied the
magma chamber. By August, this
void was filled from deep
below by searingly hot,
dark-colored magma.
When these two magmas
mixed together, it was
a lethal cocktail. The intense
heat of the dark magma caused
the huge amounts of gas within
the light magma to expand.
>> The magma chamber that was
holding this mixed bag became
overpressurized to the point
where it exceeded the rock
strength of the roof rocks
above it, and when that
happens, you can get really
rapid ascent of magma to the
surface.
>> When this magma exploded
from the surface, it ripped
apart tons of rocks with an
ear-splitting blast.
This mega explosion caused the
loudest noise in recorded
history. The striped pumice on
Rakata proves that magma
mixing was the trigger.
But Krakatoa wasn't just the
loudest volcano in history.
It was a killer.
Because Krakatoa itself was
uninhabited, some of the
volcano's first victims were
at Ketimbang, a village on the
southern coast of Sumatra.
But Ketimbang is on the
mainland, 20 miles from
Krakatoa, and separated by the
waters of the Sunda Straits.
How these people fell victim
to the deadly ashes was a
mystery. To uncover the
answers, we have to return
to the scene of the crime,
Rakata, and to these imposing
white cliffs. They may seem
part of an ancient landscape,
but these 200-foot white
cliffs were laid down in a
matter of hours. They are
what's left of a raging
torrent of hot gas and rocks--
a terrifying force of nature
known as a pyroclastic flow.
>> Pyroclastic flows travel
extremely quickly, so you
can't outrun them. They're
also extremely hot, several
hundred degrees centigrade, so
they will, if you're caught in
the middle of one, they will
incinerate you instantly.
>> Perhaps the most famous
victims of a pyroclastic flow
lie at Pompeii, the Roman
settlement that was utterly
destroyed during the eruption
of Vesuvius in Italy in the
year 79. The perfectly
preserved remains of the
people here are testament to
the power of these fiery
avalanches.
>> And most people die not
because of hundred percent
burns, but because they inhale
the gases which are so hot
that they just destroy
the--the air passage and the
lungs instantly, and so after
two breaths, you're dead.
>> The sheer size of the cliffs
at Rakata have led geologists
to estimate that the
pyroclastic flows thrown out
by Krakatoa were an amazing
2,800 feet high. But the
victims of this deadly torrent
were on the other side of the
Sunda Straits. What happened
next was truly astonishing.
>> Pyroclastic flows are--are
ground-hugging. In other
words, they--they follow the
ground surface as they go
down. But they also have a--an
upper part which is very rich
in gas, so it's low density.
Now, when a pyroclastic flow
hits the sea, the dense bit
carries on down onto the ocean
bed, but the gas-rich but
still very hot bit goes
hurtling across, scooting
across the top of the water,
there's virtually no friction
between the gas and the war
so it can travel a very long
distance.
>> Over 2,000 people at
Ketimbang perished from the
burning debris that could not
just walk on water but run, at
amazing speeds of up to 200
miles per hour across 20 miles
of open sea.
The investigation into the
Krakatoa volcano has
pinpointed the extraordinary
force that ripped the island
apart.
Striped pumice is proof
that magma mixing created
the vast explosion.
Two hundred foot cliffs
on the island of Rakata
are evidence of vast,
pyroclastic flows.
Big enough to cross the ocean
and claim the volcanoe's
first victims.
But contemporary reports show
that most of Krakatoa's
victims were not killed by
these deadly avalanches, but
by a very different force of
nature.
August, 1883 Krakatoa's
second and most deadly
eruption. More than 2,000
people were killed by
searingly hot pyroclastic
flows. But there was worse to
come. These gigantic boulders
are on the shore of Anjer in
Java, 22 miles away from
Krakatoa. They are a crucial
clue to what the volcano did
here, and a stark reminder of
what could one day happen
again. They are made of coral,
which can only grow
underwater. So, some immense
force unleashed by Krakatoa
must have put them here.
These shattered bricks are
another piece of the same
puzzle. They are all that
remain of a lighthouse that
once was one of the sturdiest
buildings on the Java
coastline, but no match for
Krakatoa.
>> I'm standing at the top of
the new lighthouse in Anjer,
120ft above sea level, built
two years after the eruption
of Krakatoa in 1883. The old
lighthouse down there is
nothing but a trace of bricks,
because it was wiped out by a
large tsami.
>> Eyewitness accounts detail
the exact height of this
terrifying wave.
>> Difficult though it might
be to comprehend, the momentum
of that wave would have taken
the water up to the level that
I am now standing.
>> Krakatoa's death throes had
triggered a massive wall of
water that now raced towards
the shore at Anjer.
>> I don't ink anyone living
along the shores of western
Java or southern Sumatra would
have known about the tsunami
that they were about to face,
and, certainly, nobody would
have been able to survive
those sorts of wave heights.
>> The power of the wave can
be seen in this 600-ton block
of coral that was ripped from
the sea bed and smashed the
lighthouse to pieces. Still
here today, it provides some
of the clearest evidence
of the immense power of
Krakatoa's 1883 eruption.
The same wave that shifted
this boulder also destroyed
houses, villages and
transport, leaving nothing but
twisted wreckage behind.
The mighty wave even picked up
and stranded a Dutch steamer,
the Berouw, two miles inland.
This immense tsunami claimed
the lives of more than 34,000
people.
>> It's quite possible
that those people who
lived in the villages in
western Java and southern
Sumatra thought, "Well, the
volcano's out there somewhere,
it's an island, so it can't
possibly affect us here."
But of course the--the
eruption itself triggered the
tsunami, which meant that the
water adjacent to the volcano
was--was being displaced right
across to where they lived.
So you know, that--that
feeling of safety was--was
sadly misplaced.
>> For modern-day
investigators, the puzzle was
how fire and water had
combined to wipe out an entire
region. The evidence came from
the shattered remains of the
volcano itself, Rakata
island, part of one of
Krakatoa's three original
peaks. Its sheer vertical
cliff face tells volcano
detectives about Krakatoa's
final moments.
>> When you have a very large
volcanic eruption, you
evacuate a lot of magma, it
leaves behind, effectively, a
hole, so quite often the crust
just collapses down into that
hole and that leaves behind
what we call a caldera.
>> Krakatoa had ejected such
vast amounts of burning magma
and rock, it could no longer
support itself. Drain away the
water and we can see how it
collapsed, creating an
immense caldera.
>> So this cliff behind me
marks the edge of the 1883
caldera. Under the boat, this
water depth is about 40 times
as deep as most of the area
around us. Uh, the scale of
this collapse is pretty big,
it formed a caldera that's
about three miles in the
north-south direction by about
five miles in the east-west
direction.
>> This immense collapse has
only occurred once in recorded
human history. The combined
weight and power of Krakatoa's
awesome pyroclastic flows and
this huge collapse was more
than enough to trigger the
tsunami.
The riddle of just what had
caused Krakatoa's tremendous
tsunamis had finally been
solved.
When the smoke had cleared and
the waters receded from the
most devastating eruption in
recorded history, the island
of Krakatoa had vanished.
In total, Krakatoa had killed
36,417 men, women and children.
It was, without doubt, one of
the most dangerous volcanoes
in history.
But while investigating the
1883 eruption, scientists
discovered ancient lava flows
hidden in the jungle and on
the sea bed.
This deadly volcano had struck
before. But when scientists
dated the lava flows, they hit
a problem. Radiocarbon dating
was only able to place the
eruption to between the first
and 13th centuries--a spread
of 1200 years.
Scientists needed more
information in order to try
and shed light on a new
Krakatoa threat and help the
hundreds of thousands of
people living in the area.
The trail of evidence at
Krakatoa had gone cold...
literally.
Because, thousands of miles
away from the sweltering heat
of Indonesia, in the frozen
wastes of the Antarctic,
scientists recently discovered
a critical clue to Krakatoa's
explosive past.
>> Well, ice cores are
cylinders of ice that we drill
from the ice caps in--in
Greenland and Antarctica.
You can look at things like
volcanoes, erm, any material
coming from the surrounding
oceans will make its way to
Antarctica, where we can
detect it in the ice. You
might imagine that we see the
dust and the ash from a
volcano, but, in fact, very
little of that from the big,
erm, Indonesian type volcanoes
ever makes it to Antarctica.
So what we do see is--is
sulfuric acid, big volcanoes
spew out a lot of sulfur
dioxide into the atmosphere
which is oxidized into
the sulfuric acid, which
we then measure in the ice.
>> The sulfuric acid cannot
be seen in the ice cores with
the naked eye, but can only be
detected back at the British
Antarctic Survey's lab, where
the cores are kept at a
continuous minus 13 degrees
Fahrenheit.
>> So this is a--a piece of
core from Antarctica. This
is a piece from James Ross
Island, it's about 10,000
years old, this ice. What
we're doing now is measuring
the volcanic signals, and what
we see is very, very distinct,
clear electrical pulses that
come from the sulfuric acid
from the volcanoes, so very
quickly, we can see all the
volcano signals throughout
the--throughout the whole core.
>> One of the strongest
signals found in the ice cores
is from the 1883 eruption of
Krakatoa.
>> What we can see from the
1883, er, eruption, we can't
see the ash, but we can see a
very large peak in sulfuric
acid, in fact it's one of the
biggest peaks we've got in the
last thousand years. It's such
a big peak, in fact, that we
use it to date the ice cores,
because it's like a reference
horizon that we can see there.
>> Each ice core is like a
diary of the Earth's climate.
Each layer of ice represents
one year. In the same way that
we can count tree rings,
scientists can count back each
layer of ice to determine the
exact date of any eruption.
Counting back from the 1883
signal, there is a huge spike
in the sulfuric acid levels
in the year 535. This is clear
evidence of an enormous
eruption during the dying days
of the Roman Empire--
an eruption far greater than
Krakatoa's in 1883.
>> We are now beginning to
come to the conclusion that,
yes, there was a large
volcanic eruption in 535.
In fact, it looks one of the
biggest ones on the record, in
terms of how much sulfuric
acid it put into the atmosphere.
>> The ice cores tell us a lot
about this mystery volcano.
Its eruption was so enormous
that its impact was global.
Its date falls exactly in the
middle of the timespan of the
lava flows around Rakata.
Could it be Krakatoa?
The clues seemed to fit.
If they are the same eruption,
this is evidence that Krakatoa
has a far more deadly past
and, potentially, a far more
deadly future.
>> Can we tell whether it's
come from Krakatoa? Now,
that's more difficult, we can
see it in Antarctica and we
can see it in Greenland, so
that tells us it was probably
somewhere mid-latitude, so
somewhere round about the
equator, maybe, so it's a
possibility, but we cannot
really pin it down at the
moment.
>> Despite this uncertainty,
there is no doubt of
Krakatoa's capacity for
destruction.
The steep cliffs at Rakata
show that Krakatoa collapsed
to form an enormous caldera,
triggering a deadly tsunami.
And yet ice cores from
Antarctica suggest that
Krakatoa may have exploded
before with even more force
than 1883.
To discover what originally
created not only 1883
Krakatoa, but also the current
Anak Krakatau, scientists will
have to travel even further
back in time, some two million
years.
The source of Krakatoa's
awesome power remained a
mystery to scientists for
centuries.
One clue is its location.
Indonesia contains more
volcanoes than anywhere else
on Earth.
>> Indonesia's a jackpot for
volcanologists, simply because
the evidence of volcanic
centers that may have lasted
several million years are
available and ready for
observation and study.
>> Incredibly, there are 21
of these "fire mountains" on
the island of Java alone--an
area the same size as New York
State.
The National Park of Tennger
Bromo in east Java is one of
Indonesia's most active
volcanic zones.
>> To view a landscape like
this is actually humbling,
because it tells us that there
are forces at work that far
exceed anything that mankind
can construct.
>> But why there should be so
many volcanoes in such a small
area, no one could explain.
A key discovery was that
Indonesia lies adjacent to the
notorious Ring of Fire, a
chain of volcanoes stretching
around the entire Pacific
Ocean.
In the 1950s, American
geologist Harry Hess began
research into the
groundbreaking hypothesis
known as seafloor spreading.
This laid the foundation for
plate tectonics.
Plate tectonics is based on
the idea that our planet is
not a perfect and unbroken
sphere. It's composed of eight
major tectonic plates that
jostle and jar against one
another. These plates are
driven by heat from the
planet's core.
Here in Indonesia, the plates
collide faster than almost
anywhere else on Earth.
The volcanoes here are created
when the heavier oceanic plate
is pushed under the lighter
continental rock.
This is subduction. When the
rock is pushed deeper, it
melts to produce magma.
Over thousands of years, it
builds up into a vast magma
chamber, many miles beneath
the surface of the Earth.
Eventually, the pressure of
the extra magma becomes too
great for the Earth's crust.
The magma forces its way up to
the surface in a storm of hot
ash and boiling lava.
A volcano is born.
In the case of Indonesia, this
is a nation constructed almost
entirely from volcanoes.
>> Most of Indonesia is, in
fact, composed of volcanoes
that initiated from somewhere
down below sea level, rose up
to sea level and then grew as
islands and amalgamated to
form bigger land masses that
now comprise the Indonesian
nation.
>> Using the theory of plate
tectonics, scientists can
rewind the clock.
45 million years ago, the
Australian plate started to
move north rapidly. The island
chain of Indonesia began to
emerge from the ocean
at the point where the two
plates collided. Vast numbers
of volcanoes exploded as the
Australian plate was pushed
deep into the bowels of the
Earth. Krakatoa was a product
of these same forces, and it
was two million years ago, as
our early human ancestors were
taking their first tentative
steps, that the volcano was
created.
>> So the fact that under the
Sunda Straits of Indonesia you
have all these processes
taking place 70 and 80 miles
down below the surface made it
inevitable that a volcano like
Krakatoa came into existence,
but also had a catastrophic
eruption.
>> What made Krakatoa so much
more dangerous than hundreds
of other volcanoes in
Indonesia only became clear in
1988. Scientists discovered
that large clusters of
earthquakes were taking place
beneath the Sunda Straits.
Earthquakes are common along
plate boundaries, but this
amount was off the charts.
This major clue would enable
scientists to finally identify
the killer factor in Krakatoa.
Beneath Krakatoa, in the
middle of the Sunda Straits,
the subduction zone contains a
kink. This twists and rips the
Earth's crust, and provides
even more material to fuel
Krakatoa's hungry magma chamber.
>> Where you have those kinks,
two things could happen.
Firstly there might be a
greater chance of earthquakes
because the kink itself
actually starts to tear or
rip, and secondly, where the
kink is might generate more
melting, and it's the melting
that takes place in the mantle
that ultimately leads to the
lavas that are erupted from
the volcanoes at the surface.
>> Finally, the origins of
Krakatoa had been revealed.
Hundreds of volcanoes in
Indonesia show that the
country lies on a volatile
plate boundary. Unusually high
numbers of quakes show that
Krakatoa lies on a deadly kink
within this zone.
But can scientists now use
this knowledge to predict
Krakatoa's future? A
prediction that is today more
important than ever,
because the volcano is back,
and it's getting bigger
every day.
Today, these shattered islands
are all that remain of the
cataclysmic 1883 Krakatoa
eruption.
But a deeper understanding of
this event is now more
important than ever, because,
out in the Straits, a new
threat is growing.
Krakatoa is back, in the form
of Anak Krakatau, Indonesian
for "child of Krakatoa."
And that child is now an
angry teenager.
Like a phoenix from the ashes,
Anak Krakatau is growing
directly over the site of the
original Krakatoa volcano,
leading scientists to conclude
it's being fed by the same
magma chamber deep beneath the
Sunda Straits. This deadly
heritage means that Anak could
potentially be one of the most
dangerous volcanoes on Earth.
But just how immediate is this
threat?
Since its explosive beginnings
in 1927, Anak has erupted
frequently and violently.
As one of the fastest-growing
volcanoes on the planet, this
1,033-foot-high mountain bears
watching.
Predicting exactly when
another major eruption will
happen is difficult, but there
are clues. Underground tremors
are a sure sign that the magma
deep within the volcano is
starting to move.
>> We have seismometers
stationed on the volcano that
tell us when rocks are
breaking, not just at the
vent, but in the subsurface,
heralding the arrival of new,
fresh magma into the edifice,
into the cone.
>> These details are
transmitted via radio signals
to the monitoring station
on the mainland, which is
operated 24 hours a day.
They have a simple scale to
measure the threat, running
from one to five. Anything
above a three, and they go on
red alert.
At the moment, it's hovering
around the danger zone, a
level three.
The type of magma within the
volcano is another way
geologists can judge the
potential of a major eruption.
But the magma itself is
impossible to test, as it lies
several miles deep within the
Earth. The next best clue is
to look at what has been
literally thrown out of the
volcano...
lava bombs.
>> I've got my hand on a
basaltic andesite scoria bomb
that was probably blown out of
a vent about three quarters of
a mile from here, and you can
imagine, to be hit by one
of these would not be a good
situation. These can actually
range up to things that are
the size of refrigerators and
television sets, and
there--thereby making them
even more lethal, particularly
when they are traveling at
120 miles an hour.
>> Mandeville anyzes these
rocks made up of basaltic
andesite, which will give him
a clue to the makeup of the
magma deep underground.
>> Part of what, uh, this
composition tells me is the
composition of magmas
being erupted at Anak are
unlike what was typically
erupted at, uh, the 1883
eruption of Krakatoa, which
was much more silica-rich and
much lighter in color,
typically light beige to
almost white.
>> The more silica in the
magma, the more viscous, or
sticky, it is. And that's what
contributed to Krakatoa's
explosive eruption in 1883.
The explosive gases were
trapped in the magma and
pressure had been building up
over time. Fortunately, the
dark color of the lava bombs
from Anak Krakatau are
evidence that the magma is low
in silica, and the explosive
gases have yet to reach
critical 1883 levels. But this
is not a permanent state.
>> Over the years, a magma
like this can, in fact, evolve
into something that was that
explosive.
>> As Anak Krakatau grows, the
magma will certainly become
thicker and stickier. As in
its parent, once the magma
gets too sticky, the vent
could become blocked. The
silence could signal disaster.
It means that pressure could
be building up inside. Too
much pressure, and Indonesia
could suffer another
cataclysmic explosion.
More than 100 years of
investigation into Krakatoa
has helped unlock the secrets
of its past and provided
scientists with strong
evidence that Anak Krakatau is
following in its footsteps.
The pumice from 1883 suggests
that Krakatoa was a deadly
stratovolcano.
The stripes in the pumice show
that the massive 1883 eruption
was triggered by an injection
of superhot magma. It was this
that blew the volcano to
pieces. The remains of vast
pyroclastic flows that were
over twice the height of the
Empire State Building, plus
the immense caldera, show the
massive scale of Krakatoa's
1883 eruption. But most
ominously of all, the position
of Anak Krakatau near the
deadly Ring of Fire directly
above a kink in the subduction
zone means that a future
massive eruption is inevitable.
>> A lot of the Anak Krakatau
activity that we now witness
today is actually almost a
continuation of the volcanic
activity that took place back
in 1883. We could have another
eruption here on the scale of
the 83 eruption of Krakatoa.
>> The 1883 eruption of
Krakatoa may be the most
famous, but it is a geological
certainty that it won't be the
last. Krakatoa is on the rise
again--dynamic proof that the
Earth is never at rest.
-- Sync, corrected by elderman -- -- for addic7ed.com --