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 leading a
trail of geological Mysteries behind
[Music]
in this episode an investigation into
California's San Andreas Fault
greatest fault line on Earth
800 miles long this ugly scar on the
landscape has spawned earthquake after
earthquake
but for now it waits quietly deep under
our cities
building up stress to strike once again
[Music]
San Andreas fault is one of the most
dangerous geological features
on Earth
[Music]
California's greatest cities and
millions of her citizens live in
constant peril
since records began there have been 13
large earthquakes along the San Andreas
Fault
[Music]
and now America's geologists her Rock
detectives a warning of a potential
disaster
damage has been done
in the fall of 2008 more than 300
scientists calculated what a major
earthquake would do to Southern
California
we've been conducting a special study of
a magnitude 7.8 earthquake on the
southern San Andreas fault large enough
to potentially damage tall buildings
firework will be very significant
the definitive scientific report
presented to politicians was code named
ShakeOut
forecast thousands of deaths and
billions of dollars of damage in the
city of Los Angeles
which makes it crucial to investigate
the most important question
when will the next big earthquake hit
the San Andreas Fault
the latest preparations for disaster are
the climax of an investigation that
started more than 100 years ago
in the aftermath of the great San
Francisco earthquake of 1906.
the earthquake struck on a Wednesday
Just Before Dawn
the ground shook violently for 45
seconds igniting fires that raged
unchecked for the next four days
28 000 buildings a tenth of the entire
city were destroyed and more than three
thousand people one in every hundred of
the population were killed with a
magnitude of 7.8 it's in the top 20 of
North America's strongest ever
earthquakes
the scale of the great San Francisco
earthquake shocked the nation
but no one understood what had made the
city Shake
foreign
Native American myths explained
earthquakes as shocks from a battle
between warring spirits
Latter-Day explorers couldn't understand
the shocks that destroyed their mission
buildings
one Spanish missionary wrote
the Earth shook around me from
explosions under the ground
300 years later and science has still
made little progress refugees in the
ruins of San Francisco still blamed
earthquakes on mysterious underground
explosions
so just three days after the earthquake
the state of California asked one of the
world's most famous geologists Andrew
Lawson from California State University
to investigate what had destroyed the
city
he and a team of 25 scientists began
collecting damage evidence in the City
and surrounding Countryside
there were roads that had buckled
rail tracks that had twisted
the most startling evidence of all
that came near the town of Bolinas in
Marin County to the North of San
Francisco
this picket fence had an eight-foot Gap
in the middle
before the earthquake it was a solid
boundary fence dividing two fields
but when he recreated what had happened
Lawson realized that the land had jolted
apart and torn the fence in two
plotting the evidence on a map around
San Francisco revealed a surprising
pattern
because connecting the dots drew a
straight line
and at every point the Earth moved the
same way on the coast to the north
Inland to the South
this line of weakness was the culprit
they were searching for
South of San Francisco the suspect line
ran underneath a lake the Laguna De San
Andreas
so now the earthquake perpetrator at
last had a name
Professor Lawson who a decade earlier
had identified cracks in the earth here
as a harmless Rift now re-christened it
the San Andreas Fault
in modern day San Francisco the
buildings the roads and the railways
have long since been repaired
but if you know where to look evidence
of the 1906 Quake can still be found
geologist Charlie Paul follows in the
footsteps of Lawson's team seeking signs
of the Havoc from 1906.
he finds it on the Cliffs at muscle Rock
12 miles south of San Francisco
the cliff is not here by accident
there's a very good reason why this
Cliff is here half a mile or so of the
shore face apparently fell off in the
1906 earthquake and if you look down
below us there's a big rotated block
that's near the present day Shoreline
and it is just in Board of the San
Andreas fault the San Andreas fault is
about a quarter of a mile offshore here
and of course that's one of the major
crustal Junctions on this side of North
America
thank you
modern computers can now Trace how
damage waves spread out across the city
and that pinpoints where the Quake
originated along the San Andreas
[Music]
it was offshore about two miles out to
sea from the Golden Gate Bridge
so to continue tracking the fault the
investigation must head out to sea
Marine geologists use remote operating
Vehicles many submarines to map the sea
floor
what you'd see is subtle variations in
the topography or topography that would
not naturally line up
so there might be a line on the ocean
floor that is higher or lower on one
side and you can use various techniques
to determine that this actually is a
fault instead of some other process
running South across the seabed the San
Andreas finally runs out of ocean and
hits the land
this broken line of rocks stretching in
from the sea marks where the San Andreas
hits land 12 miles south of San
Francisco
muscle Rock and we're essentially
standing on the San Andreas fault right
now and if there was an earthquake I
don't know it would happen right here
but I wouldn't want to be here
this Pacific Coastline where Cliffs
crumble slowly into the sea is the
boundary between two of the Earth's
massive continental plates
separated by the San Andreas fault two
vast separate blocks of the Earth's
crust lie directly alongside each other
here the continent of North America lies
slightly on top of the adjacent section
of crust which holds the Pacific Ocean
the join can be seen where these lower
darker rocks are overlaid by
light-colored sedimentary rocks
these rock types differ by by more than
100 million years in Age Two Rock bodies
that are not similar in any way have
been brought together
the fault line was exposed to geologists
when the cliffs collapsed here in the
1906 earthquake
but back then nobody understood how and
why the two different types of rock were
next to each other
until around 40 years ago when the
answer was finally revealed by the
theory of plate tectonics
[Music]
the theory showed that the Earth's crust
consists of separate moving plates on
which the oceans and continents sit
[Music]
around 200 million years ago the heavy
Pacific ocean plate collided with North
America and started sinking underneath
the lighter continent
[Music]
professor of geophysics Mark zobach
studies that process called subduction
in his laboratory at Stanford University
for many millions of years prior to the
existence of the San Andreas fault the
Pacific Plate was subducting beneath
North America the oceanic plate was
diving down and that process went on for
well well over a hundred million years
so a tremendous amount of activity was
occurring
as the Unstoppable force of one plate
met the immovable object of the other
they were forced to change direction
about 20 million years ago the play
motions were such that the Pacific Plate
had to start sliding North with respect
to North America and now you know that
the principal motion is this sliding
process between the two plates and 20
million years ago the San Andreas fault
was born it was the moving place that
crushed different types of rock together
just as here at mussel Rock
at last the investigation knows what it
is dealing with
the San Andreas fault is 800 miles long
emerging from the seabed north of Point
Arena in Northern California and running
down to the Salton Sea in the south
evidence is coming together
Clues from the 1906 earthquake such as
the picket fence that was torn apart
prove that the land was moving
connecting the dots identifies the
straight line of the San Andreas Fault
and muscle Rock uncovers different
plates of the Earth's crust on either
side of the fault line
but investigators still need more
information about how often the San
Andreas has spawned earthquakes in the
past
might help them answer the all-important
question
when will the San Andreas strike again
to discover when the San Andreas fault
will strike again the investigation
needs to know about ancient earthquakes
that have struck along the fault line
[Music]
but there's an immediate problem so here
in California it's a particular
challenge some of the earliest written
records were from the missions and from
the early explorers so only dating back
into the 18th century here other parts
of the world we have an earthquake
history going back millennia
the investigation moves 350 miles south
of San Francisco to a desert where the
San Andreas may have been active for
thousands of years
there's crucial evidence here about
earthquakes from ancient times
this Creek used to flow straight across
the San Andreas fault here but several
earthquakes formed a Natural Dam where
the San Andreas fault wedges up here in
front of me that created a small pond
and now we're looking at the dry
sediments of that pond that record the
history of earthquakes and that tells us
quite a great deal about the past
behavior of the San Andreas Fault
some of the clues are so small that HUD
nuts detective work gets him down and
Dusty among tiny cracks inside the fault
sometimes we can find out about the past
behavior of the San Andreas Fault by
looking at the tiniest details
at the bottom of this small ancient Pond
mud sediments collected above a fine
line of Pebbles
then an earthquake shifted the land
upwards on one side of the vertical
fault line
so this layer was originally flat and
then in a subsequent earthquake it was
broken like this along this tiny
fracture strand of the San Andreas fault
but finding proof that this is the site
of an ancient earthquake is only part of
the story
hudnut needs to know how long ago it
happened
the bare rock layers are no help in
dating his find but just above the
fracture line of the Rocks he has found
the evidence he needs
here a bush was burned by a prehistoric
wildfire and that remnant of carbon is
why you see this black stain on the side
of the trench wall
the key to unlocking the age of the
Rocks is carbon 14 known as radiocarbon
its molecular structure means that
carbon 14 is a more unstable isotope
than other forms of carbon it's absorbed
by growing plants then radioactively
decays at a known rate after the plant
dies so measuring carbon 14 in
vegetation burned in a wildfire reveals
how long ago those plants died and dates
The Rock in which the carbon is found
and through this we can reconstruct the
evidence of the past earthquakes
radiocarbon dating has proved that
earthquakes have been happening along
the line of the San Andreas for
thousands of years
the particular small earthquake
investigated by hudnut for example is
around three and a half thousand years
old
it happened at a time when the last
woolly mammoths were dying out in North
America
the investigation moves to an even more
remote desert spot the Carrizo plain 160
miles north of Los Angeles here lies a
dried up riverbed which takes an unusual
course
thank you
coming down off the hills the creek bed
takes a sudden sharp turn to its right
a few hundred feet later it makes an
equally odd 90 degree turn to the left
the creek crossed the line of the San
Andreas Fault but early geologists were
mystified
why did it Bend in this way
the scientific Pioneers were limited to
studies on the ground
nowadays hudnut has an advantage he can
take to the air
foreign
[Music]
where it cuts through the Carrizo plane
it almost looks like a scar and it was
caused by repeated earthquakes in the
past
along the long line of Hills marking the
course of the San Andreas HUD nut spots
the puzzling bends that he's seeking
along the fall through here that would
be awesome oh there's a great angle see
that right angle offset Channel with the
elbow in it right there that's a classic
one right there
PUD nuts aerial view of the creek bed
shows that the river once flowed
straight on across the fault
but little by little a series of
earthquakes along the San Andreas
dragged the creek away from its original
course
recreating how the land had moved showed
hudnut that the two parts of the creek
had traveled more than 300 feet apart
so if you imagine the North American
Plate is fixed and the Pacific Plate is
moving through the northwest
the Wallace Creek site records that
offset because the channel is straight
across the fault but it's been offset
Through Time
earlier investigators had already
radiocarbon dated the land on each side
of the faultier revealing that it took 3
000 years to change the Creek's position
so knowing the distance and the time it
took to do it let's hudnut calculate the
average speed with which the two land
masses are moving past each other
300 feet in three thousand years
[Music]
one foot per decade
just over an inch a year
but this was never a steady sliding one
inch a year movement the reality was a
series of sudden small jumps whenever
tension built up enough between the two
moving plates to overcome friction
between the rocks and rip the land apart
with an earthquake
it's an important moment for the
investigation
knowing how fast the land is moving not
only reveals the stress that's building
up but also the risk of an earthquake
the San Andreas fault is giving up its
secrets
Clues from a long dried up Pond revealed
the sight of ancient earthquakes
carbon from a prehistoric fire provides
the dates
Ben's in a riverbed prove how fast the
plates are moving along the San Andreas
but now the investigation has a new
mystery to solve
the land along the San Andreas is moving
one inch every year causing earthquakes
then why as one small town along the
fault line never had any
[Music]
the investigation has discovered how
fast the land is stretching and
straining along each side of the San
Andreas Fault
which should help establish when that
ever increasing stress will snap the
land apart in the next major earthquake
but there's a problem
one part of the fault line just doesn't
fit the pattern
the small town of Hollister is unique
along the San Andreas fault system
it's never had an earthquake
the investigation is going to find out
why
Hollister has a population of 37
thousand
nothing here is quite the way it should
be
there are plenty of Clues suggesting
that the land must be moving here
thank you
sidewalks with cracks in
curb Stones way out of line
and walls that are bent out of shape
walking through the Hollister we can't
see anything that man has built that was
laid out in a straight line may have a
jog in it every year it changes a little
bit and it's a progressive thing
the clues add up to one clear conclusion
and without any earthquakes the Earth in
this town in the heart of the San
Andreas system still slides
imperceptibly slowly and effortlessly
along
in in one sense the damage that you see
here associated with the creeping is uh
is clearly sort of under control but as
a geologist if you start playing that
out for tens of thousands or hundreds of
thousands or millions of years the
consequences of that become enormous
for many years the creeping ground that
moved without earthquakes remained an
unsolved mystery
[Music]
but then the investigation moved 100
miles south to another small community
where the land also creeps along
[Music]
the village of Parkfield has a
population of just 37 people and a
bridge which spans right across the San
Andreas Fault
Bridge separates the Pacific Plate on
one side
from the North American Plate on the
other
the bridge railings have started to bend
I'm right now on a Pacific Plate
on the west side of the San Andreas
Fault
and you know the the San Andreas comes
off the flank of that hill and right
across that field right under the bridge
and then right over by the corner of
that building or that fence post and
then on off to Middle Mountain
the movement here around the bridge is
strikingly similar to the slow creeping
ground of Hollister
but there is one important difference
here in Parkfield every couple of
decades or so this Village does have
earthquakes
they're just little Tremors but they're
big enough to be recorded on earthquake
monitoring seismographs
that's why the village proudly boasts of
being the earthquake capital of the
world
but it's perhaps more accurately called
the earthquake study Capital because
scientists are fascinated by the fact
that earthquakes here follow a
predictable pattern
elsewhere earthquakes always strike
without warning the toll of death and
destruction made worse because nobody
knew they were coming
so scientists are desperate for any
clues that might help predict when an
earthquake could happen
and here in Parkfield the earthquakes
happen with astonishing regularity on
average every couple of decades or so
[Music]
minor Quakes happened here in 1857 1881
1901
1922 1934 and 1966.
after the 66 earthquake investigators
set up a network of monitoring
instruments to see if the fault gave any
warning before the next earthquake
arrived
they expected it sometime between 1988
and 1993 but it was late and months of
waiting stretched into years
but still the scientists waited
until finally in December 2004 the
long-awaited earthquake arrived and was
caught on film from a now slightly worn
and damaged camera
the earthquake movie may not have seemed
that impressive but the instruments
collected a mass of information
[Music]
the data didn't after all help with
earthquake prediction but it did
pinpoint where the earthquake started
Underground
which told investigators where to look
next
deep down under the Park field
Countryside
starting slightly to one side of the
fault the aim was to angle in and stab
into the very heart of the San Andreas
[Music]
of drilling long cores of rock were
extracted from the exact spot where the
earthquake occurred
this was the first time the team leader
geologist Mark zobach had ever seen
rocks from the center of the San Andreas
what we're looking at here are cores
from the act of San Andreas fault from a
depth of about two miles so for the
earth science Community these are like
moon rocks as we were trying to exhume
these cores we had a great deal of
drilling difficulty the San Andreas
fault was literally fighting back
after nine weeks of attempting to
recover the course in the middle of a
huge lightning storm almost a scene
directly out of Hollywood with the
thunder and lightning these cores came
to the surface
and so it was a tremendous feeling of
satisfaction the lightning and thunder
just made it that much more dramatic
and we're all wearing gloves we didn't
want any oil from our fingers to affect
the core
and the the rule was that you touch the
core as little as possible
I'm not gonna wait for you guys
block the reality was we couldn't help
ourselves and uh
um it was just such a remarkable thing
to be actually looking at the San
Andreas fault for the very first time
then we all got to touch it a little bit
buried within the rock cores they found
a vital clue about the way that land
slips along the San Andreas
they found serpentanite
sir Penn Knight is an unusual rock type
it was originally formed at the base of
the ocean crust and it zoomed up onto
the continent but the reason that
serpentinite is so interesting is that
serpentinite is very easily altered to
talc it allows the rock to slide at very
low Force levels it's Falcon powder is
very slippery
talc's crystalline structure of soft
sliding flat plates makes it one of the
slipperiest Rocks known to science
[Music]
so Tau could well be a key mineral in in
deciding how the fault is actually
working in in central California we see
that the secret of the slipping San
Andreas fault is actually the Rocks
themselves
the talc explains the tiny earthquakes
of Park field nobody's yet drilled to
investigate the rocks at Hollister but
scientists suspect the talc is present
there too
cracks in the wall show the land Creeps
in Hollister
and a bend in the bridge reveals the
same creeping ground in a nearby town
Rock cores extracted from the fault
contain serpentinite
leading investigators to the softest and
slipperiest mineral talc which
lubricates some parts of the fault
the investigation is having success but
one crucial question remains to be
answered what will the San Andreas fault
do next
the investigation into the San Andreas
fault is trying to predict when and
where its next major earthquake will
strike
so far the only certain prediction is
the far distant future of the San
Andreas
2 million years ahead if the plate
movements continue to follow their
pattern Los Angeles will end up becoming
a suburb of San Francisco
but predictions on a shorter time scale
are more difficult
if you were to ask the question
can we predict earthquakes my answer
would be no because I know what your
question really meant is you know can we
predict that an earthquake is going to
occur on a certain fault at a certain
time that we can specify in the future
and we cannot do that but there are many
things we can predict we can predict
which faults are likely to produce the
big earthquakes we can predict how big
the earthquakes are likely to be and we
can even predict the probability of the
earthquake occurrence over some period
of several decades
predictions are most crucial where the
San Andreas runs to the south of LA
here in the Coachella Valley desert
geological evidence of earthquakes
stretches back 1500 years and more
and they follow a regular pattern
major earthquakes strike here with
monotonous regularity every 200 years
but the latest one is long overdue there
hasn't been an earthquake here for more
than 300 years
that's a concern because parts of the
San Andreas fault system runs straight
from here towards the city of Los
Angeles
The Faults will transmit earthquake
shocks in a straight line towards
California's biggest city
geologist Yuri fiaco regularly monitors
how the ground moves on either side of
the fault line
he lines up his GPS equipment precisely
over a series of metal pegs fixed into
the ground
foreign
is crucial for estimating how fast the
fault slips at depths and what is the
rate of accumulation of strain in the
crust in other words how close the crust
is brought to failure by a slip of the
faulted depths the repeated Ultra
precise measurements reveal that land
here on the surface hardly moves at all
this is a problem because deep
underground the stresses and strains are
still building up the fault is moving
adapts at the Fairly high speed and this
deformation is growing and growing and
growing with time
miles underground the Deep fault is
moving at more than an inch a year
which tells fianco that in the century
since the last quake the surface should
have shifted 300 inches 25 feet or more
but it hasn't so sooner or later
Something's Gotta Give
and fialco knows what that something
will be
the Rocks themselves
and one example is
this type of rock which is called
granite or this is in fact the rock out
of which most of the Earth crust is made
a microscope reveals the crystalline
structure of the granite the crystals
make the Rocks tough but they have a
hidden weakness
the bonds between them may suddenly
crack under stress
basically once this material solidifies
it is able to
crack and be sheared on the fold surface
and the brittle behavior of these rocks
is what lies behind the physics of
earthquakes
granite rocks underlie all of the San
Andreas fault but right here the Rocks
Under greater stress than anywhere else
because it's so many centuries since a
major Quake occurred
and now we're over the 300 year limit
and so it means that the strain the
amount of strain that has been
accumulated on the fault at this point
is very close to the maximum strain that
this fault has ever seen through its uh
geologic record and this is a fault that
is capable of generating great
destructive earthquakes
fialko believes the coming Quake could
be the big one that people have been
talking about for years
facts could be horrific because of the
population density of Southern
California
when the last huge Quake occurred 300
years ago Los Angeles was just a tiny
Spanish mission Community with fewer
than 100 people
now it's America's second largest city
with almost 11 million people living in
the earthquake vulnerable metropolitan
area
people who live in California probably
experience a smaller and moderate size
earthquake every year few things moving
in your house but it's really actually
kind of fun there is no major
destruction people just go on with their
life much bigger events on the other
hand are quite a bit different story
with the threat to Los Angeles becoming
ever clearer the investigation is
nearing its conclusion
data from repeated GPS measurements in
the desert reveal evidence that stress
is building up
while examination of the rocks of the
crust show they may not take the strain
for much longer
all the evidence points towards a
potentially huge earthquake building up
Southern California
and new experiments suggest the coming
Quake could be far worse than anyone
that ever imagined
there is new urgency in the
investigation into the San Andreas fault
as revealed by recent evidence compiled
by 300 of America's most respected
scientists
they warned that Los Angeles will be
devastated if a major Quake strikes
along the southern section of the fault
line
while there hasn't been a major Quake
for hundreds of years even small ones
can still be deadly
like the Northridge Earthquake which
struck this LA suburb in 1994.
rupturing along an offshoot of the main
San Andreas fault the Quake was only a
magnitude 6.7 considered moderate on the
scale of earthquake measurement
but it still killed 72 people and
injured 12 000 more
and new evidence suggests Mother Nature
might have a lot more in store for Los
Angeles
scientists have long known that
earthquakes generate several distinct
sets of waves
they travel at different speeds each
spreading damage and destruction out
from the epicenter
modern city buildings in earthquake
prone areas like California are
engineered to cope with such waves
Now new research by geophysicist
Professor Ares rosakis suggests that the
San Andreas may offer a new and even
more deadly threat
razakis researches how earthquakes
rupture along straight-line faults just
like the San Andreas where it approaches
Los Angeles
he creates his own mini earthquakes
representing the San Andreas Fault by a
hairline crack in a thick transparent
block
this special material shows up internal
stress lines when it's lit by a laser
and the earthquake is triggered by a
tiny explosion
three
two one zero
the load has dropped
and the explosion was big enough that we
even have a crack
an ultra high-speed camera capturing 10
million frames a second reveals a
startling and newly discovered
phenomenon
this Frozen picture reveals stress lines
speeding along the mini San Andreas in
the milliseconds after the explosion
the cone to the left of this Frame is a
previously unrecognized type of shock
wave racing along the rupture line from
the earthquake Center
on a microscopic scale it looks and
moves exactly like the sonic boom
produced when a supersonic aircraft such
as Concord breaks the sound barrier
because we also see Mac cones lines that
are emitted from the Rapture tips eyes
from the tips of moving airplanes
and just like a sonic boom it can be
dangerous
the same sense that we hear the sonic
boom from the Concord you're going to
feel the sonic boom from the Rapture the
danger comes because many high rises
just aren't built to cope with extra
stress from this newly discovered type
of shock wave so if you are an old
building for example
you'll take one way you would like to
murate some damage
and very soon after that you will get
very strong ground shaking because of
other types of waves coming also
the high speed ruptures that razakis
calls super sheer happen where faults
run in a straight line
which might help explain a 100 year old
mystery surrounding the great San
Francisco Quake the natural disaster
which launched the entire San Andreas
investigation
the overwhelming damage in San Francisco
has long seen surprisingly out of
proportion to the 7.8 magnitude of the
quake
and there's a particularly straight
section of the San Andreas approaching
San Francisco
so many scientists now believe that the
damage was greater than expected because
the 1906 Quake had traveled at Super
sheer speed
of Greater concern to Modern Emergency
Services is not what happened a century
ago but what could happen tomorrow
because there is a similar straight
section of faulted ground heading
straight towards Los Angeles
and if a super sheer earthquake develops
on that line then the consequences could
be disastrous
all of the investigation's warnings
about the San Andreas came together in
the fall of 2008 with the biggest
earthquake drill ever held in California
if this earthquake would have happened
in reality there was there would have
been buildings coming down we know that
there would be no water now in certain
areas that's what this exercise is all
about
but what are the real chances of Los
Angeles soon being hit by a massive
earthquake
frightening the best scientific
consensus now warns that there's a 99
chance of a major quake in Southern
California within the next 30 Years
to better understand the threat to La
the geologists produced their study
jointly with experts in charge of the
city's disaster planning
and none of them doubt that the big
Quake is coming
it really isn't even a question of if
anymore
the shaking is going to be severe for
two to three minutes
and then it's going to stop
and then you have that moment of silence
that often happens before you start
hearing the car alarms and all those
other sounds that you have in a disaster
like this the study estimates that a
major earthquake in the LA metro area
would cause 2 000 deaths 50 000 injuries
and 200 billion dollars of damage
you're gonna have conflagrations
developing tens of blocks will be on
fire the water lines has ruptured there
is no coming out of
the that's the kind of nightmare
scenario that we're looking at
this Specter of disaster to California's
people and cities motivates the search
to unravel the secrets of the San
Andreas Fault
all the evidence is finally in
the damage reports from the 1906
disaster show the false 800 mile path
the different types of rock at muscle
Rock provide clues to how the fault was
created 20 million years ago
the riverbends prove how fast the land
is moving
the mineral Tau explains why some parts
slip without major quakes
the brittle granite rocks reveal a
threat to Los Angeles
and recent lab experiments uncover new
and more dangerous earthquake shock
waves
but one goal has eluded The Rock
detectives who study the greatest fault
line on Earth
when will the sleeping San Andreas come
to life once again
it could be any time
the only certainty is that nothing is
certain in the ever-evolving story of
how the Earth was made
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 the Marianas Trench the
deepest point on Earth is explored
its sheer walls cut seven miles into the
Pacific Ocean
the mystery of what created this deep
dark Chasm takes science detectives on
some of the most dangerous Dives ever
attempted
deep into the abyss
scouring the ocean floor scientists
uncover a strange undersea world of
fiery mountains
bizarre mud volcanoes
and the largest geological structure on
Earth
discoveries from this unique Underwater
World will revolutionize our
understanding of the powerful forces
that shape not just the trench but the
Earth itself
hidden deep beneath the waves of the
Western Pacific lies the Marianas Trench
deepest point of all the oceans
the first step on the Journey of what
created this mysterious scar in the
Earth's crust and how it continues to
mold the planet takes us back to 1872.
when a British research vessel HMS
Challenger set out on the first ever
mission to map the ocean floor
throughout most of recorded history men
just assume that Beyond a certain level
the sea was pretty flat pretty dead
fairly lifeless
they weren't expecting to find anything
very interesting
for four years the Challenger
crisscrossed the oceans covering seventy
thousand miles
a third of the distance to the Moon
the crew plumbed The Depths every 140
miles using a total of 249 miles of rope
and hundreds of pounds of lead weight
it was tedious back-breaking work but at
the time it was the only way to measure
the depth of the ocean floor
good
when they got to the Western Pacific 200
miles off the island of Guam the crew
routinely lowered the Rope for a
measurement
but the weight kept on dropping and
dropping
it's a big surprise
nobody thought the ocean was this deep
so all of a sudden we've got scientists
saying why is that
[Music]
thank you
eventually the weight struck the bottom
at
4475 fathoms
nearly five miles beneath the ocean's
surface
the scientist would be going wow we
found something and what does it mean
is it a little hole is it a big hole
what kind of feature is it down there
there's a whole lot of questions you get
when you find this one spectacular
reading
the Challenger Expedition marked the
birth of modern oceanography and
provided the first crude map of the
ocean floor
it showed how the ocean floor gently
slopes away from the land and then
plummets thousands of feet into vast
flat Plains
but the Western Pacific is different it
drops off again into the Five Mile deep
hole a hole that blew right out of the
water the long-held belief that the sea
floor was flat and featureless
and it spawned a mystery
because nobody could understand how this
strange underwater feature came about
it would be 75 years before any answers
emerged
it took a revolutionary new technology
sonar to push the investigation forward
to the next crucial stage
foreign
was first developed in the early 1900s
and then perfected during the 1940s to
detect submarines lurking in the Deep
[Music]
the system works by pumping sound waves
through the water
the waves bounce off solid objects and
are reflected back to a detector
by measuring the time it takes for the
sound waves to bounce back scientists
realized they could build a remarkably
accurate picture of the world beneath
the waves
the world's major Navy spend a lot of
time and effort developing submarine
hunting technology
then the hydrographers Discover that you
can use this to chart the bottom of the
sea and it's an awful lot cheaper and
easier than using large numbers of
sailors pulling on ropes
in 1951 a British Navy research ship
returned to the deep hole found by the
Challenger Expedition
but this time they were armed with
sophisticated new sonar equipment
and the results were amazing
detailed sonar Maps revealed that the
deep hole in the Pacific Ocean Floor
isn't a hole at all but part of a
massive trench 30 times deeper than the
Empire State Building is high
it runs twice the length of California
1500 miles from the southeast of Guam to
the northwest of the Mariana Islands
people were probably astounded by what
they were seeing because clearly the
ocean floor had enormous changes in
relief was very mountainous in some
places had great deeps in other places
to a geologist this would be extremely
exciting
even within the trench itself there are
remarkable variations
at its southern end lies the greatest
surprise of all
the floor drops down another two miles
to its lowest point
a staggering seven miles beneath the
waves
scientists had discovered the deepest
part of the oceans
even today it is the lowest known point
on the planet
they named this part of the trench the
Challenger Deep in honor of the ship
that discovered it
to get a sense of just how deep trenches
are if we take the height of Mount
Everest
we would still have about a mile of
water above us before we get to the
ocean's surface
but how the Marianas Trench was formed
remained a mystery
investigators decided the best way to
find the answer was to dive to the
bottom of the trench
to see for themselves the lowest point
on the planet the Challenger Deep
but they faced a major problem
at the bottom of the trench they would
have to contend with pressure a thousand
times stronger than at the surface
that's the equivalent of being squeezed
on all sides by the weight of 50 jumbo
Jets
to demonstrate the effects of such
pressure scientists use a dummy head
today what we're going to do is actually
put one of these styrofoam wig heads in
the pressure chamber
and expose it to the pressure we would
see in the Marianas Trench that's about
16 000 PSI
a human skull would be crushed to a pulp
but the rubbery head will only have all
the air squeezed out
wow that's smaller
and here's what the original size was
just for comparison
quite dramatic pretty Stark difference
between something that hasn't been seven
miles deep in the ocean and something
that has glad I'm not going there
at the Mariana Trench human life is
impossible
we're not equipped to resist those kinds
of pressures
and so it's necessary to protect humans
from that type of an environment
the challenge to Engineers was how to
accomplish this
in 1953 Swiss scientist Auguste Picard
designed the Trieste
a pioneering vehicle that could
withstand the crushing pressures
[Music]
the submersible was dominated by a
50-foot long Hull filled with light
Aviation gasoline and Lead weights to
control buoyancy
slung underneath it was a tiny six-foot
spherical cabin with five inch thick
steel walls
finally after seven years of
modifications and man test Dives no
deeper than three and a half miles
The Trieste was ready to attempt the
seven miles to the bottom of the trench
the commander of this perilous
undertaking was U.S Navy lieutenant and
deep sea Explorer Don Walsh
I know the astronauts that go through
this all the time why do you have to be
there why can't we just put up a robot
to do things
you've got to be there because that's
what we do
only a few officers and scientists knew
about the risky Mission which was
launched in January 1960 from the
Western Pacific island of Guam
Guam in those days was kind of a
Backwater it was just right for us
because we were trying to do this
project sort of out of sight because we
weren't too sure it was going to work
the Navy just didn't want to be
embarrassed by a failed science
spectacular
Walsh was the son of The Trieste
designer engineer and oceanographer
Jacques Picard
two men would spend the next nine hours
squeezed inside the cramped sphere
and we had 20 cubic feet of space inside
that's about the same as a household
refrigerator
and the temperature was almost that cold
inside
it was a drama
the Marianas Trench is one of the most
remote inhospitable places on Earth
in January 1960 two deep sea explorers
Don Walsh and Jacques Picard plunged
into its depths on board the submersible
The Trieste
at a speed of just three miles per hour
they began their slow descent into the
Twilight Zone
by three thousand feet the darkness was
total
the only illumination was from the
trieste's powerful lights
The Depths we're operating at it was
always black
the only thing that Lit Up The Abyss was
the bioluminescence from animals and
Plankton
like fireflies they carry their own
light sources with them
encased in their five-inch thick steel
sphere Walsh and Picard quickly passed
their test dive record of eighteen
thousand feet
everything appeared to be going to plan
at the rear of the cabin the crew were
protected by a double layer of glass
two hours into the dive the outer pain
cracked
we had a great big bang
we didn't know what it was we're about
20 000 feet and we looked around and
checked everything
every square inch of their tiny
life-supporting capsule was fighting
back eight tons of pressure
with the outer pain broken the only
thing between the men and instant death
was a single pane of glass if the inner
window had cracked we would have been
instantly dead maybe even before we knew
it
but incredibly the inner pain remained
watertight
Walsh and Picard decided to continue The
Descent
after a tense claustrophobic four hours
and 48 minutes they approached the
bottom of the trench only to be startled
by movement on the sea floor
just before we landed we saw a flat fish
about a foot long
and that's a bottom dwelling fish so if
you see one there are others
nobody expected to see life at these
crushing depths but it meant the
Explorers had reached their goal
foreign
the very bottom of the Marianas Trench
the depth gauge with a reading of 35 800
feet nearly seven miles below the
surface confirmed the sonar findings
used inside their bubble of breathable
air the two explorers were closer to the
Earth's center than man had ever been
we took a self-portrait
that's the picture that you see
so we're going to do it and we did it
but there was work to be done
Walsh and Picard wanted to make detailed
observations of the enormous Trench
Unfortunately The Trieste stirred up a
cloud of fine powdery sediment from the
sea floor that obscured their View
it's like being a bowl of milk at that
point so realizing we're not going to
see anything we decided going back up to
the surface
off the island of Guam the priest
surfaces after a descent into the
Marianas Trench after nine grueling
hours underwater Walsh and Picard
returned to the surface on January 23
1960.
and officially entered the record books
for the deepest dive of all time
to this day their extraordinary feat has
never been repeated
the mission was a success
but the mystery remained
geologists still didn't understand what
could have formed the immense Trench
if they couldn't find the answer inside
the trench they would have to look
elsewhere
perhaps there was something somewhere on
the ocean floor that might explain the
trench's origins
throughout the 50s and 60s a team of
geologists led by Princeton's Harry Hess
compiled sonar data from all of the
world's oceans
it was as though they had pulled out a
giant plug to drain away all the water
and expose the ocean floor
their Maps revealed that the Marianas
Trench is just a tiny fraction of a
network of enormous underwater Canyons
stretching right around the planet
but that wasn't all
running parallel to the trench on the
other side of the Pacific the map showed
a giant underwater mountain range the
East Pacific Ridge
and this too is part of a Global Network
a forty Thousand Mile long chain of
mountain ranges that ring the globe like
the seams of a baseball
to make the largest geological feature
on Earth
it was a major development in the
investigation one that scientists hoped
might explain the trench's formation
The Next Step was clear investigators
needed to understand whether there was a
connection between the trench and the
East Pacific Ridge
the Breakthrough came from the
unlikeliest of sources
during the Cold War the U.S built a vast
network of underground seismometers to
pick up atomic bomb testing around the
world
inadvertently the seismometers also
detected naturally occurring earthquakes
when geologists plotted these on a map a
pattern emerged
[Music]
the earthquakes were clustered along the
ocean's ridges and trenches
it was a discovery that transformed our
understanding of the Earth
geologists realized the friction that
causes earthquakes comes from movements
that must be occurring deep Beneath The
Ridges and trenches
with this great investment in seismology
it became possible to locate very
precisely where earthquakes had occurred
and it was these things the precise
location the depth and the motion that
really gave the outlines of plate
tectonics
it was the birth of an extraordinary new
Theory
solid layer of rock the crust on which
the land and ocean sits is broken up
into a series of vast slabs the
geologists call tectonic plates
it's these plates that are moving
grinding past each other
and triggering earthquakes
the underwater ridges and trenches sit
on the boundaries between tectonic
plates
the East Pacific Ridge and the Marianas
Trench lie on opposite edges of the
Pacific Plate
journey to discover what formed the
Marianas Trench is accumulating
additional evidence
The Trieste dive to the bottom of the
trench
and confirmed that it is the deepest
point on the planet
sonar Maps then revealed the East
Pacific ocean ridge running parallel to
the trench
to solve the mystery of the Marianas
Trench investigators needed to find out
exactly what was happening at the East
Pacific Ridge and that meant exploring
these vast mountains eight thousand feet
under water
thank you the pieces of the Marianas
Trench puzzle are falling into place
with the knowledge that it lies on the
western edge of the Pacific tectonic
plate
on the opposite side of the plate lies
the East Pacific Ocean Ridge
part of an enormous chain of underwater
mountain ranges that ring the globe to
create the largest geological feature on
Earth
scientists had a hunch that this
colossal Ridge might help explain how
the trench was formed
and they found a major clue halfway
around the globe where the ridge passed
beneath the middle of the Atlantic Ocean
during the Cold War the U.S Navy
developed a new technique to spot Soviet
submarines
they scanned the Seas with a tool called
mad a magnetic anomaly detector which
could pinpoint steel hulls lurking in
the Deep
but they stumbled across something else
running parallel on either side of the
ridge they found strange Stripes of
magnetic rocks alternating positive and
negative away from the ridge's peak
seriously Mid-Atlantic Bridge coming
down through here almost perfectly
symmetric on either side of that are
these white and black stripes these have
often been called zebra stripes foreign
geologists know that the Earth is like a
giant magnet with a north and a South
Pole but the magnetic poles aren't fixed
every 300 000 years or so the magnetic
field suddenly flips 180 degrees
when the field flips a compass that was
previously pointing North will swing to
the South
this reversing of beerus magnetic field
is a very interesting and exciting but
very puzzling phenomenon for
geophysicists to explain
scientists think this reversal explains
the stripes either side of the ocean
ridge
in the 1960s geologists discovered that
molten volcanic rock known as magma
swelled up from deep underground to
create the ridges in the Atlantic and
Pacific
as magma Wells up between the tectonic
plates it pushes the sea floor up and
forms the Colossal mid-ocean ridge
thousands of feet high
when the rock is hot and molten its
magnetic minerals line up with the
north-south direction of the Earth's
magnetic field
as the magma cools the minerals are
locked in position
these rocks act as a permanent record of
the magnetic poles location when the
Rocks were formed
more and more magma is forced up the old
crust is pushed away from the Ridge and
Records the reversals in the Earth's
magnetic polarity
if you have reversals of magnetic
polarity then the seafloor acts sort of
like a tape recorder and Records these
changes in magnetization then the
pattern of magnetic stripes allows
people to calculate the speed at which
the plates are moving apart
[Music]
zebra stripes are proof that over time
the sea floor in both the Atlantic and
the Pacific is spreading away from The
Ridges at a rate of more than two inches
a year
a geologist needed proof that magma
created The Ridge
if red hot molten rock is forming the
enormous mountain range in the Pacific
the surrounding water should be warm
foreign
1977 a team of scientists set out to
discover whether this warm water really
existed
Dudley Foster was the pilot for these
historic Dives it's been an exciting
occupation because you're on cutting
edge of science new discoveries all the
time
every Cruise there's a new group of
scientists with new scientific
objectives and there's the exploration
and the discovery
and that's really what puts the thrill
in the job
for weeks the crew scanned the undersea
mountains without success
and then they hit the jackpot
a bizarre pillar of Rock
spewing hot toxic gas
and we saw the water was sort of
shimmering sort of like a bubbling in a
glass teapot or something
we stuck the temperature probe in there
and measured 38 39 degrees Fahrenheit
which was really amazing because the the
ocean is a huge heat sink
so to see something warm like that was
kind of startling
in these pillars of rock the Expedition
had found the heat from the magma
surging up from deep inside the Earth
it wasn't warming the water evenly along
the ridge it was channeled up through
strange hydrothermal vents
when you make these discoveries you
don't know how significant they are
true significance of them maybe take
several years to appreciate
and this was one of those times
[Music]
for the investigation into the Marianas
Trench these vents are a decisive piece
of evidence
[Music]
they confirmed that magma is continually
creating new crust at the Pacific Ocean
Ridge
and magnetic zebra stripes proved that
old crust is pushed away from the ridge
towards the other side of the Pacific
Plate towards the Marianas Trench
but this presents scientists with a
puzzle if new crust is being created at
the ocean ridge and the Earth isn't
expanding then the old crust must be
disappearing somewhere else
the reason that there's not getting
bigger with seafloor spreading is
because the same amount of seafloor is
being destroyed in the Pacific
something in the Pacific Ocean is
devouring the sea floor
all the evidence points to Marianas
Trench
in the hunt to discover what formed the
Marianas Trench scientists now know
crust created at the ocean ridge is
being devoured somewhere and by
something in the Pacific Ocean
they suspect the Marianas Trench is
involved
would come not from the trench
but from these
the Mariana Islands
chain of volcanoes that break through
the ocean's surface 200 miles west of
the trench
scientists noticed the island chain
mirrors the trench's exact shape
this led them to think the trench was
responsible for the Island's creation
if you see pictures of the Mariana's
Trench it's curved and the line of
volcanoes that it generates is curved
exactly parallel to it
geologists believe that the trench
formed the volcanoes via a process
called subduction
[Music]
subduction occurs where two tectonic
plates collide as they grind past each
other the heavier plate is pushed
beneath the lighter plate
the descending plate is forced down into
the Earth's intensely hot interior
called the mantle
it takes with it water and sediment
built up over millions of years
volcanoes form above subduction zones
not because the Earth is hotter there
but because this is where we're taking
the water that once was in the ocean
it's taken into the mantle and gets
sweated out causes the mantle to melt in
this magma is what then Rises and erupts
explosively out these volcanoes
the water in the sediment forces magma
to swirl up and push through the plate
above
and when it breaks the surface it
creates volcanoes like the volcanoes
that form the Mariana Islands
it was subduction that formed the
islands west of the trench
and gave investigators the Breakthrough
they'd been looking for
because here at last was a process
powerful enough to create the Marianas
Trench
as the descending plate Dives down it
digs into the mantle
here the colliding plates form a trench
a giant crease in the ocean floor
it seemed that scientists had finally
explained how the trench was formed
there was just one problem
a very large problem
around the world subduction zones cause
violent earthquakes and catastrophic
tsunamis
we know subduction is happening because
of the active earthquakes and these are
the most devastating earthquakes
this is the earthquake that generated
the tsunami in Sumatra
also the other very large earthquakes in
Alaska and Chile
the Marianas Trench the deepest
subduction zone in the world hasn't
caused the devastating earthquake since
records began in the 17th century
investigators needed to know why
Ah that's that's uh the sixty Thousand
Dollar Question
they hope the trench's shallower Western
Edge might provide the answer
here they found an intriguing chain of
underwater Hills two miles below the
surface of the sea
Engineers drilled down into the hills
and collected core samples
and when the scientists analyzed the
samples they discovered the hills were
actually volcanoes
and they spewed out not lava
but mud
the fine powdery mud is made up of a
soft type of rock that has been ground
up in the subduction zone
it seemed this soft rock might explain
why there have been no major earthquakes
at the Marianas Trench
everybody has a sense of what a volcano
is but not all volcanoes erupt igneous
rocks there's some volcanoes that erupt
mud and a certain kind of unusual kind
of mud in the Marianas is made out of
serpentine and Serpentine is a very weak
Rock and it can be scratched with a
knife or something like that
investigators realized the grinding
plates crush the soft rock to form a
lubricating mud that prevents large
earthquakes
then the mud bubbles up to the ocean
floor where it forms the strange mud
volcanoes found along the trench's
western edge
other parts of the world like the Andes
or maybe Indonesia you've got two plates
that are grinding together and one of
the plates is quite strong and it takes
a big earthquake to rupture that plate
interface but if these rocks are weak
like they are in the Marianas where
you've got these serpentinites those are
very weak and it doesn't take much
energy at all to get the two plates to
Glide one past the other
at last geologists had discovered what
created the Marianas Trench
[Music]
50 million years ago the Pacific Plate
slipped under the edge of the Philippine
plate
as it bent and dived into the Earth's
mantle it formed the Colossal Marianas
Trench
and the plate is still moving
like a giant conveyor belt the Earth's
crust travels slowly across the Pacific
Plate from its birthplace in the East
Pacific Ridge to its graveyard ten
thousand miles away in the Marianas
Trench
today the Pacific plates movement can be
tracked in real time
has come from GPS technology where we
can actually put a transmitter on an
island and come back year after year and
actually follow it moving a few
centimeters a year towards the trench
devouring the crust at a rate of three
inches a year about as fast as a human
fingernail grows
every four million years it swallows an
area the size of the United States
by consuming the crust created at the
Pacific Ocean Ridge the ravenous
Marianas Trench is the world's largest
recycling plant
but there was one remaining and major
piece of the puzzle to find
scientists still didn't know why it is
the deepest trench on Earth
they suspected the age of the sea floor
at the bottom of the trench May provide
the answer
it turns out there's a really strong
relationship between the age of the
seafloor and its depth in the water
in 1999 a team of deep sea Drillers
returned to the trench to collect core
samples
one great thing about drilling station
crust is we actually got pieces of it
so we're holding our hands here the
material that's actually getting
subducted at the Marianas Trench and it
turned out to be 170 million years old
so we can say with confidence that's the
oldest ocean floor before it's getting
swallowed up in the mantle at the trench
why is this piece of rock the oldest on
the ocean floor
the sea floor at the Marianas Trench is
so old because it's been so long since
it was born so it was born in the
equivalent of the Eastern Pacific today
and it's just been going on longer than
than any other place in the oceans
before it's been subducted
the Pacific Plate is the planet's
largest tectonic plate covering an area
11 times the size of the United States
oh
when crust bubbled up at the ridge 170
million years ago it was light and
buoyant
but as it traveled ten thousand miles
across the plate it cooled and became
Compact and dense
over millions of years the dense crust
got heavier and began to sink into the
mantle below
scientists realized that because the
crust at the Marianas Trench is the
oldest ocean crust it's also the
heaviest and so has sunk deeper into the
mantle than any other area of ocean
crust
here at last was the explanation for the
trench's extraordinary depth
the picture of the Marianas Trench is
almost complete
the investigation into the Marianas
Trench has one final puzzle to solve
at the trench's southern end the sea
floor plummets a further ten thousand
feet
into a seven mile deep Chasm called the
Challenger Deep
it's the lowest point on the planet
but so far scientists have been unable
to explain why this one section of the
trench is so deep
now they believe the shape of the
descending tectonic plate May hold the
answer
the Challenger Deep In addition is a
little bit deeper because of some
peculiarities relating to how the slab
that's going down is behaving
a narrow slab of crust has torn away
from the Pacific Plate's descending Edge
well it's basically got to do with how
the slab pushes The Mantel out of the
way
where you have a narrow slab like you
have at the Challenger Deep it can sink
almost vertically because the mantle
that it's trying to displace can move
around out of the way
investigators have finally unraveled the
mysteries of the Marianas Trench
the process they've made a discovery
with implications that stretch far
beyond the trench itself
studying the ocean ridges LED geologists
to believe that magma welling up at The
Ridges was pushing the plates apart
but the exploration of the Marianas
Trench has changed this idea forever
people used to think that maybe the
magma would kind of push the plates
apart and that idea is largely
discounted now
[Music]
as the ocean crust travels from the
Pacific Ocean Ridge to the trench it
changes from a buoyant red hot magma
into a colder denser and heavier crust
the Plate's Leading Edge becomes so
heavy that it drags the rest of the
plate along behind it
said the trenches are sinking down into
the mantle and pulling the plates apart
at the ridges and the magma just
passively fills in the gaps
[Music]
the investigation into the Marianas
Trench has revolutionized our
understanding of how the Earth's plates
move
we now know a worldwide network of
subduction zones drag tectonic plates
around the globe
powering the movement of continents over
millions of years
and moving the very Earth we stand on
trenches
the Pacific Plate is the fastest moving
of the nine major plates on the planet
because it is surrounded by dozens of
destructive trenches like the Marianas
they are consuming the ocean crust
faster than the ocean ridge can produce
it
over millions of years the Pacific Plate
will shrink until sometime in the
distant future the largest ocean on
earth will disappear Australia will
crash into the United States reshaping
our planet
perhaps one day downtown Seattle will
compete for Real Estate with a suburb of
Sydney Australia
and all because of subduction zones like
the Marianas Trench
but for all its significance man has
only ever dived to the bottom of the
trench once
and there are no immediate plans to
return
imagine asking someone
what is the Flora and Fauna of
California and saying that someone spent
10 minutes there picked up two ants come
back and said they've sampled California
that's probably how well we know the
Marianas Trench
[Music]
less than five percent of the world's
oceans have been explored
but only by returning to the ocean's
very deepest reaches will we fully
comprehend the incredible forces that
recycle and rebuild our world
the way I like to think of it is that
ocean exploration leads to new research
questions
and if we don't have exploration we
don't even know the right questions to
ask
it is now known what a geological wonder
the Marianas Trench is
since this deep chasm in the Earth's
crust was first discovered with a length
of rope and a lump of lead more than a
century ago evidence has piled up
a record-breaking dive to the lowest
point on Earth
giant undersea mountain ranges with
bizarre magnetic zebra stripes proof
that the ocean crust is spreading
towards the hungry Marianas Trench lined
with slippery mud volcanoes which
prevent devastating earthquakes
and the planet's oldest ocean crust the
reason that the Marianas Trench is the
deepest point in the oceans
in the darkest and most remote place in
the world scientists have added to their
knowledge about the powerful forces that
contribute to the dynamic story of our
planet
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
killed more than 36 000 people
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
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 10 percent 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 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
live again
[Music]
I've noticed in coming here that 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
1033 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 very deep on
unacked 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 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're near an active volcano
Anna Krakatoa 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 switch onto 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 and 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
foreign
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 time I do the local sort of
got that anything was anything strange
was happening on their Island would have
been in May 1883. the 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
on May 20th 1883 Krakatoa announced that
it was no mere Island
of krakatoa's Three Peaks exploded with
extreme force
shooting a plume of Ash hundreds of feet
into the air
[Music]
but after these initial fireworks the
activity appeared to Cease the local
population breathed a sigh of relief
thinking it's 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
Shores
this pumice is the solidified lava that
comes from the heart of a volcano and
it's riddled with bubbles
these bubbles suggest a geologist that
Krakatoa is a strata volcano
and those volcanoes that 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 through
these volcanoes is like liquid Dynamite
Strada volcanoes are dangerous because
of the source of lava they erupt and the
lava that comes out of strata volcanoes
is very sticky viscous lava
and the danger there is that the 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 this
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 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 but
what will happen is over time more magma
is coming up and being trapped beneath
that plug
some sometime in the future the pressure
would be so great there'd be so much
Magnum wanted to get up that you 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
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 a knack
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
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
and at krakato 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 parents 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
was one of 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 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
it's a 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
your eyes it would have been a real
vision of hell
and a nightmare that showed no signs of
ending
by the next morning of August 27 1883
krakatoa's three craters had been raging
for more than 14 hours
then sometime between 5 30 and 1002 am
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
thirteen thousand 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 ricotta
this tiny island is in fact a part of
the once Mighty Krakatoa
[Music]
the record of what the volcano did from
May 20th to August 26 to 27th is here
represented on the islands by the
layered deposits that we see preserved
in the jungle
this is a gold mine 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 streak pumice and what it represents
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 over pressurized 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 ricotta 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 ketembang
a village on the southern coast of
Sumatra
but kettenbang is on the mainland 20
miles from Krakatoa and separated By the
Waters of the Sunder 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
acoustic flights 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
but most people die not because of 100
Burns but because they inhale the gases
which are so hot that they just destroy
the the air passage in the lungs
instantly and so after two breaths
you're dead
the sheer size of the Cliffs at ricotta
have led geologists to estimate that the
pyroclastic flows thrown out by Krakatoa
were in Amazing 2 800 feet high
but the victims of this deadly torrent
were on the other side of the Sunday
Straits
what happened next was truly astonishing
power classic flows are ground hugging
in other words 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 flows Hits the Sea the dense
bit carries on down onto the ocean bed
but the the gas rates but still very hop
it goes hurtling across scooting across
the top of the water there's virtually
no friction between the gas and the
water so it can travel a very long
distance
over 2 000 people at Kevin bang 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
100 foot Cliffs on the island of Rakata
are evidence of vast pyroclastic flows
big enough to cross the ocean and claim
the volcano'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
[Music]
these gigantic Boulders are on the shore
of any year 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 on-year 120 feet 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 tsunami
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'm now standing
krakatoa's death throws had triggered a
massive wall of water that now raced
towards the shore at an year
I don't think 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
power of the wave can be seen in this
600 ton block of coral that was ripped
from the seabed 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 baru two
miles inland
this immense tsunami claimed the lives
of more than 34 000 people
possible that those people who lived in
the villages in in Western Java and
Southern Sumatra thought well the
volcanoes out there Somers in Ireland so
it can't possibly affect us here but of
course 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 ricotta
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 in 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 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
[Music]
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 seabed
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
[Music]
scientists needed more information in
order to try and shed light on a new
Krakatoa threat
helped the hundreds of thousands of
people living in the area
[Music]
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
ORS cylinders of ice that we drill from
the ice caps in in Greenland and
Antarctica if you look at things like
volcanoes any material coming from
surrounding oceans 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 in fact very
little of that from the big Indonesian
type volcanoes ever makes it to
Antarctica
so what we do see is sulfuric acid a big
volcanoes that spew out a lot of sulfur
dioxide into the atmosphere which is
oxidized into this 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 piece of core for
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 through the other throughout the
whole core
one of the strongest signals found in
the ice cores is from the 1883 eruption
of Krakatoa
what we could say from the 1883 eruption
we can't see the ash but we can't 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 cause because it's like a
reference rise than 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 time span of the lava flows around
Rakata
could it be Krakatoa
the clues seem to fit if they are the
same eruption this is evidence that
Krakatoa has a far more deadly past
ually a far more deadly future
can we tell whether it's come from
Krakatoa that's more difficult we can't
say it in Antarctica and we can't see it
in Greenland so that tells us it was
probably somewhere mid-latitude so
somewhere around about the equator maybe
so it's 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 ricotta 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
anakrakatau scientists will have to
travel even further back in time some 2
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 is 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 Jabba alone
an area the same size as New York State
the national park of Tanga 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
[Music]
a key Discovery was that Indonesia lies
adjacent to the notorious Ring of Fire a
chain of volcanoes stretching around the
entire Pacific Ocean
[Music]
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 jossel 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 Sun The
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 Sunder 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
larvas that 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
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
[Music]
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 1033 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
details are transmitted via radio
signals to the monitoring station on the
mainland which has 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 event 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
they're thereby making them even more
lethal particularly when they're
traveling at 120 miles an hour
Mandeville analyzes these rocks made up
of basaltic andesite which will give him
a clue to the makeup of the magma deep
underground
part of what this composition tells me
is the composition of magmas being
erupted at anarch are unlike what was
typically erupted at 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 anaka 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
provided scientists with strong evidence
that anak krakatau is following in its
footsteps
the pumice from 1883 suggests that
Krakatoa was a deadly strata volcano
the stripes in the pumice show that the
massive 1883 eruption was triggered by
an injection of super hot magma
it was this that blew the volcano to
Pieces
[Music]
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 Krakatoa 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 1883 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
Earth
a four and a half billion year old
planet
still evolving
continents shift and Clash
volcanoes erupt and Glaciers grow and
recede the Earth's crust is carved in
numerous and fast ways
leaving a trail of geological Mysteries
behind
in this episode the 450 million year old
geological history of New York City is
explored a metropolis pockmarked with
strange rocks
haunted by Footprints of ancient giant
reptiles
in line with a vast curtain of
solidified lava
scientists investigate the evidence for
fiery volcanoes
massive floods
and ice sheets four times as high as the
Empire State Building
the clues to understanding New York
City's geological past provides a window
into the formation of the Earth itself
foreign
the investigation into New York City's
geological history begins here
with Manhattan's Rocky outcrops
rocks are Clues to how the land was made
and how its geology helped it become a
dense thriving pulsating City
they're scattered all over Manhattan
poking through the surface of parks and
through the concrete between the
buildings
some squashed between two apartment
blocks are the size of a whale
they are the extraordinary survivors of
ancient times
most importantly they are the surface
tips of the bedrock in which Manhattan's
buildings are anchored
[Applause]
gigantic skyscrapers stand in two
clusters in downtown and Midtown
in the section between the buildings are
lower
the clues to the shape of Manhattan's
familiar Skyline are the Rocks beneath
the surface
a leading expert on the rocks in New
York is geologist Charles magarian
the entire history of the development of
the Earth's crust is emblazoned in the
Rocks beneath us the Rocks here in New
York City Harbor and ancestry that dates
back over a billion years of time
magarian is searching for evidence to
show how the city's Bedrock was made
[Applause]
at Inwood Hill Park in Upper Manhattan
he's found an extremely hard piece of
the Bedrock known as Manhattan schist
to the untrained eye it's just a piece
of Rock
but to magarian this is his first clue
the rocks that we're looking at right
here are rocks of the Manhattan schist
formation and these rocks are very
severely deformed and the structures
here in this rock is a structure that
comes up like this bends around and
comes back down on itself as such and in
three-dimensional view it's a structure
that looks something like this a very
very tight fold with a plunge towards
the South here
these are rocks that were very very
strongly deformed over protracted
periods of time and it's the same
Bedrock that occurs over much of New
York City
this tight fold in the Rocks suggests
New York's Bedrock was formed under
great pressure
to confirm this hunch magarian takes a
sample to the lab for detailed analysis
radiometric dating proves this rock is
about 450 million years old
The Rock has even greater secrets to
tell
it contains a kaleidoscope of minerals
which opens a window into the ancient
world to me minerals are like the
instrument cluster in your car they tell
you everything about how your car is
running
[Music]
agarion uses a microscope with polarized
light to view the minerals
examination tells us the former depth
regime How Deep The Rocks were they tell
you the age of the Rocks they tell you
everything you want to know about the
development of the Earth's crust
what's striking about these samples is
that the minerals inside are elongated
it is a clue that these rocks must once
have been crushed by Massive forces
and the colors support this Theory
under the polarized light the sample
from Inwood Hill Park shows up blue
this comes from a mineral called kyanite
which forms at Great depths
its conclusive evidence that this rock
was compressed deep under the surface
rocks forged at these depths are much
harder
ideal for a city's foundations
but what gigantic weight was on top
magarian believes there is only one
answer
The Rock was once buried under the
crushing weight of a chain of massive
mountains
the minerals that we find in the Bedrock
units of New York City
tell us that the rocks of New York City
were formerly buried when they were
formed under very high pressures
and that those High pressures indicate
that these rocks formally were produced
at depths of 20 to 25 miles and probably
the mountains were as high as the Alps
are today
but even the most impressive Mountain
chains can survive the ravages of time
the Rocky Mountains for example millions
of years ago they soared nearly six
miles into the sky today erosion has
halved their size
[Music]
the same process happened in New York
rain wind and Ice War the ancient
mountains almost flat
but the microscopic crystals found in
the Rock in Manhattan testify that they
existed in the past
did the mountains form
the answer lies in the way the Earth's
crust moves
a network of interlocking individual
pieces makes up the Earth's surface
geologists call them tectonic plates
over millions of years they Collide and
break apart to form different continents
450 million years ago the Earth's
surface looked completely different
North America was much further to the
South
North America was tilted 90 degrees
clockwise from its present orientation
and it was straddling the equator as
such the climate was tropical the east
coast of North America was really
experiencing Club Med conditions
the weather may have been awesome
ancient east coast was heading for
trouble
the plate beneath it was moving
the East Coast was on a collision course
with ancient West Africa
450 million years ago they collided
the impact Unleashed geological chaos
under intense compression the land was
forced upwards to form a soaring range
of mountains the Collision that took
place is the most fundamental and
impressive mountain building event to
affect the east coast of North America
All That Remains are their stumps
stumps that form the Bedrock a modern
day New York
the Collision that built up the ancient
mountains also folded the Bedrock into
dips and Rises
these folds are responsible for the
shape of Manhattan skyline
the city boasts two clusters of
skyscrapers in downtown and Midtown
here the hard Bedrock that formed deep
underground was forced up it is now
close to the surface and provides solid
Anchorage for the high-rise buildings
in the dip in the middle The Rock was
folded down
the area is filled with loose sediments
less suitable for skyscrapers
when the Bedrock is at the Earth's
surface where it's actually exposed then
it's pretty easy to build tall buildings
because you can root them directly into
Solid Rock however in areas where the
Bedrock is deep and covered by glacial
sediment in those cases it's very
difficult to build 12 buildings because
you need to root those buildings either
into solid rock or build concrete
abutments both caissons that can support
tall buildings
New York's deep history is beginning to
take shape
building up from Tiny crystals in the
Rock scientists revealed how New York's
Bedrock was formed under the crushing
weight of a massive ancient mountain
range the result was hard Manhattan
schist a perfect foundation for the
city's skyscrapers
but New York City still had a long way
to go
the colliding plates created an enormous
land mass the last great supercontinent
called Pangea
New York was now trapped in the center
but somehow it made it back to the coast
beyond the city's streets is evidence of
huge volcanic eruptions mass extinctions
and continents torn into pieces
clues that could explain how New York
became one of the world's great Maritime
cities
[Music]
investigators are piecing together how
New York City's unique geology was
formed
much of its early success is a trade and
commerce Center is owed to its deep
water Harbor
and its location at the coast
[Music]
but 450 million years ago things were
different
the area of New York City was landlocked
embedded in the heart of a huge
supercontinent
how did it get to the coast
the investigation fast forwards 250
million years
in a quarry in New Jersey 25 miles
Northeast of Manhattan paleontologist
Paul Olsen Unearthed the first of a
string of clues that could explain how
New York City reached the coast
a giant fossilized footprint
this is the footprint actually the mud
that filled in the footprint of a
four-footed crocodile relative that was
the dominant carnivore during the late
Triassic you can see the toes here have
little pads on them and here's the
handprint and these animals would have
been in this case about the size of a
modest crocodile but some of them became
much much larger the size even of a
T-Rex
[Music]
um
the footprints are from a huge
crocodile-like creature called pasta
sukis
first appeared on the Earth around 230
million years ago
then some 30 million years later its
Footprints suddenly vanished
but pasta sukis wasn't alone
half of all land animals perished at the
same time
the fossil evidence proves it to be one
of the biggest mass extinctions ever
recorded
the evidence for this mass extinction is
that we have lots and lots of fossils
right in this area and what you see is
especially in the in the reptile
Footprints you see one group of forms
the forms that are related to
crocodilians disappear
whatever cause the mass extinction must
have been a catastrophic event
Olsen had a hunch that the mass
extinction was somehow related to New
York's return to the coast
the ancient area of New York sat on a
line of great weakness
a plate boundary where two continents
joined to form the supercontinent Pangea
and it was unstable prone to earthquakes
and volcanoes
Olson's quest to find the evidence for
the natural disaster that finished off
post-asuka's 200 million years ago
a band of dark Rock above the footprints
in the New Jersey Quarry caught his eye
it was Basalt The Smoking Gun Olsen was
looking for
Basalt is a volcanic rock
it forms when hot lava erupts onto the
surface and cools
did the volcanoes that forged this
Basalt trigger the mass extinction and
also rip Pangea apart
on its own
the evidence that the Quarry was
unconvincing
the layer of Basalt is only a few feet
thick
prove Mass lava flows caused this Global
catastrophe scientists needed
corroborative evidence
oh
high above the Hudson River geologist
Matt Goring follows another lead
he's studying the Palisades a dramatic
geologic feature that hugs the Hudson
River beginning across mid-manhattan and
running into Northeast New Jersey
they too are made of basaltic rock the
same Rock implicated in the mass
extinction of land animals
but the Palisades are on an altogether
different scale
the Palisades are a sheet of basaltic
magma about one thousand feet thick it's
about 40 miles long so it's a very
prominent set of cliffs that run all the
way up the west side of the Hudson River
here is proof of massive volcanic
activity
flooded out of ruptures in the Earth's
crust and covered ancient North America
in a mild deep sheet
the lava cracked as it cooled
the vertical ruptures formed regular
pencil-shaped columns
these distinctive rock formations have
been known to geologists since the 19th
century
intriguingly they appear on both sides
of the Atlantic in North and South
America Europe and Africa
geologists suspected that their presence
pointed to the spot where Africa and
Europe separated from America
but that was just an unproven Theory
until the 1950s when scientists
developed a revolutionary technique
called paleomagnetism
now they could study the magnetic
properties of rocks
many rocks including Basalt have a
distinctive magnetic signature
formed as The Rock is born
tiny crystals inside the rock act like
Compass needles
when the magma that forms the rock is
fluid the crystals align to the Earth's
magnetic field pointing North
as The Rock solidifies the crystals
freeze forever locked in that fixed
magnetic alignment
as continents move and the Rocks travel
the crystals end up pointing in a
different direction than North
Goring and his team investigate the
magnetic signature of the Palisades
[Applause]
to get a sample they bore into the Rock
with a water-cooled drill
they measure the exact orientation of
the crystals today with a compass
when they offset this reading with
Magnetic North they can calculate the
original location of The Rock
one of the youthful things that you can
do with this rock is you can take it
back in the lab and measure its magnetic
orientation and that magnetic
orientation will be when this rock
crystallize or solidify 200 million
years ago so this rock would have
minerals that would be pointing in some
other direction other than North today
when scientists compared the magnetic
orientation of the Palisades with the
other Basalt outcrops around the
Atlantic they discovered they formed at
approximately the same latitude
not only did the rocks have the same age
they were also born at the same location
for example 200 million years ago New
York and Morocco were Neighbors
geologists had all the proof they needed
they could now confidently piece
together what happened
with a global volcanic disaster
about 200 million years ago North
American Africa began to pull apart from
each other
there were gigantic lava outpourings
these lava flows erupted along very long
cracks in the Earth's crust that would
have produced Fountains of lava
extending thousands and thousands of
feet into the atmosphere
they're covered an almost inconceivably
large area
roughly 4 million square miles
from Southwestern France
Southwestern Brazil
from New York to Central Mali in Africa
this area was covered in ponded lava
flows that in some places ended up being
nearly a mile thick
mechanic eruptions led to Soaring
temperatures
half of the plants and animals died
postasuchus didn't stand a chance
as enormous forces tore Pangea apart a
giant sea formed between the separating
land masses
the Atlantic Ocean
the city of New York was now at the
coast
[Music]
200 million year old Footprints beneath
a layer of Basalt and the Palisades
towering above the Hudson
provide evidence that Pangea split apart
to create the east coast of North
America
story of New York City was far from over
after being built by fire the region was
about to be overcome by another
destructive force
scientists are piecing together the
story of New York's violent geological
past
250 million years ago the Atlantic Ocean
opened up leaving the area of New York
on the coast
but the maritime City still had a long
way to go
[Music]
there was no deep Hudson River Channel
it was nothing but a small stream
what forces transformed it into the wide
river capable of carrying heavy
Freighters far inland
a clue to how the Hudson Valley was
created is the strange Boulders that are
scattered throughout Manhattan's Central
Park
some of them weigh several tons
but they're strangers to these parts
totally unlike the surrounding rocks
geologist Charles magarian investigates
where they came from
Boulder is a boulder from the Palisade
sheet on the other side of the Hudson in
New Jersey
you can see it's very nicely polished
compositionally it's totally different
than the surrounding Bedrock which is
Manhattan schist and the Manhattan
schist here is very rich in Mica this
rock has no light-colored Mica in it
whatsoever
the Palisade sheet is located to the
west and north of us
for 40 miles along the Hudson River
something immensely powerful must have
moved the boulders such a great distance
magarian knows the answer is ice
scientists have noticed a similar
phenomenon four thousand miles away in
the Swiss Alps
glaciers grind their way across the
landscape they gouge out lumps of rock
and carry them along in the base of the
ice
these rocks act like sandpaper and carve
out deep scratches
when the ice melts it leaves the
boulders behind
[Music]
magarian is convinced the same thing
happened in Central Park
ice moved the Palisade Boulders and
carved out grooves in the Bedrock
underneath
this Bedrock exposure in Central Park
shows the profound effects of glaciation
in the form of these spectacular glacial
grooves that move up the outcrop and
show this pattern where glaciers grabbed
huge Boulders and those huge Boulders
acted like tools to produce these
scratches
to magarian the rocks in Central Park
are compelling evidence that New York
once was covered in ice
over millions of years growing and
receding ice has repeatedly turned North
America into a frozen wilderness
but the grooves on the rocks in New York
don't tell the full story
destruction caused by the ice points to
a gigantic glacial event that would
dwarf the future Metropolis
find out the extent of the ice magarian
traveled to Bear Mountain some 50 miles
north of New York City
again the clue was in the rocks
he found glacial marks similar to those
in Central Park
what we're looking at here are chatter
marks chatter marks are very diagnostic
features of glacial erosion they're
produced by Boulders embedded in the
base of a thick sheet of glacial ice
those Boulders impinged on this Bedrock
surface polishing it smoothing it off
and then plucking pieces of rock off as
the glacial ice moved over with the
boulders embedded in the base
the gouges in the Rocks could mean just
one thing the glacier must have been
thousands of feet thick
in this case although we're standing at
an elevation of about 1280 feet above
sea level the glacial ice sheet covered
bare Mountain as if it weren't even
there
scientists have found identical chatter
marks on nearby Peaks up to a mile above
sea level
it was unmistakable proof a glacier at
least one mile thick ground its way
across these mountains
did this same ice sheet also plow
through Central Park
another nearby rock face provided the
answer
the feature that we're looking at here
are a series of subparallel glacial
scratches and grooves these are again
are produced by the glacial ice sheet
Dragon Boulders across this very durable
Granite surface it's kind of polished
the surface and in addition it's
produced these rather subtle uh but but
but obvious when the lighting is right
striae or grooves in the Bedrock now if
we measure the orientation of these
these uh
these come out about North 20 degrees
west just about identical in orientation
to the stri that we measure at Central
Park
it's significant evidence that the ice
sheet that covered Bear Mountain also
flowed over the surface of Central Park
proof that New York City was covered by
a glacier four times higher than the
Empire State Building
just imagine glacial ice a huge thick
ice sheet over a mile thick exerting
tremendous pressure on the surface and
sculpting the surface into the landscape
that we see today
the ice sheets crushing weight bulldozed
everything in its path and cut through
the remains of the ancient mountains
before the ice arrived the Waters of the
Hudson River had gently cut down through
the landscape to form a v-shaped valley
but a mild thick Glacier takes no
prisoners
it gouged out the sides in the bottom of
the river valley and turned it into a
U-shaped riverbed
the Hudson River was now navigable for
big ships
the picture of modern day New York was
almost complete
long grooves in the rocks and Central
Park showed scientists that a vast ice
sheet flowed over the eroded remains of
these mountains and marks and glacial
striations on Bear Mountain proved this
ice sheet was at least four times higher
than the Empire State Building
the ice melted it left a vast Ridge of
debris blocking the Hudson River from
the Atlantic
the final challenge for geologists was
to find out how the ridge was destroyed
and how New York's Harbor opened to the
oceans
[Music]
New York today boasts one of the largest
natural Harbors in the world
but it wasn't always that way
towards the end of the last ice age the
port's wide entrance was blocked
sixteen thousand years ago the melting
glaciers left behind a 220 foot high
wall of debris
the ridge stretched from Long Island to
Staten Island and forced the Hudson
river through a narrow more Westerly
course to the ocean
[Music]
what powerful forces destroyed this rock
jam
the prime suspect was a flash flood
but scientists needed evidence to prove
that such a flood had happened
in the 1960s fishermen made an
unexpected find at the mouth of the
Hudson River
they dredged up a giant mammoth tusk
from the depths of the sea floor
[Music]
herds of these giant beasts roamed The
Plains of North America before they
became extinct at the end of the last
ice age
finding the odd mammoth tusk here and
there is not so surprising
but since the initial Discovery
scientists have found hundreds more
tusks and bones in the mouth of the
Hudson River
it was as though a violent torrent swept
the mammoths away and dumped their
remains off the coast
and there were more clues nearby
huge Boulders resting on the sandy sea
floor
some of them as big as cars
The Boulders must have been part of the
ancient Moraine that once ran between
Long Island and Staten Island
geologist David franzi knows that only a
raging torrent could have shifted them
based on the size of the boulders that
we see here
we know that that flood must have
discharge on the order of 1.5 million
cubic feet per second
that's three times larger than the
largest Mississippi River flood ever
recorded
and all that water had to come from
somewhere
scientists began looking for the source
of this flood a flood powerful enough to
transport huge Boulders all the way to
the Sea
rocks to a geologists are like pages in
a history book for us
erosion oftentimes rips some of the
pages out of our history book so it's
the job of the geologist to put together
a fragmentary record into a coherent
history of the events that happened in
the past
300 miles north of the city in Upstate
New York frenzy tracked what might have
been the flood's path to an unusual
Grove of trees on Covey Hill in the
Adirondack Mountains
the trees are Jack Pines
they are rare in this area where the
soil is usually fertile and deep
[Music]
but on Covey Hill their presence shows
that there is no more than a few inches
of soil on top of the Bedrock
the Jack Pine is essentially rooted
right on the top of the rock surface
here this is a bare Sandstone surface
very little mineral soil and it's
subject to prolonged periods of dryness
during the summertime Jack Pine's
adaptations make it able to survive here
where no other tree species can
[Music]
what happened to the soil
the Jack Pines continue to grow at the
entrance of a long Gorge over 300 feet
wide
usually Gorges like this are cut down
over thousands of years but in this case
the missing topsoil points to a sudden
flood event
a raging torrent must have ripped away
the soil and cut deep into the Rock
in a helicopter frenzy follows the gorge
West
eventually it opens into a vast empty
Basin located next to one of the Great
Lakes Lake Ontario
stretch of the imagination here to
imagine this Valley filled with water
and then with these Hills poking up
through his Islands
sixteen thousand years ago this Basin
was filled with two billion cubic miles
of water a huge Lake geologists call
Lake Iroquois it Formed at the end of
the last ice age
as glaciers receded the Melt Waters
slowly filled up the lake
the ice dams holding the waters weakened
eventually the dams collapsed causing
sudden and devastating flash floods
lake level dropped on the order of 70
feet and about 160 cubic miles of water
were released into the Champlain Valley
catastrophically that flood water would
of course down the Champlain Valley
through the Hudson Valley and ultimately
out into the Atlantic Ocean
the torrent race towards New York City
300 miles to the south then took the
straightest course to the Sea
the flood waters smashed into the
ancient Moraine the huge pile of debris
blocking the direct exit of the Hudson
River
[Music]
the bridge we see behind me spans the
channel That was cut by the flood event
when the flood wave came through it was
of sufficient intensity to over top the
dam and very rapidly cut the channel
Gap that was created by the floods still
exists
it's now a title straight called The
Narrows
today the Gap is spanned by the
Verrazano Bridge
the channel is deep enough for even the
biggest ocean-going ships it's the most
important entrance to New York City's
Harbor
Mammoth tusks and huge Boulders at the
mouth of the river showed scientists
that there was a torrent big enough to
blast a hole through the ancient Moraine
and a channel leading towards the Great
Lakes revealed the source of the flood
it was this flood that created the
Narrows and gave New York a wide
entrance to its port
a unique geology laid down the
foundations for New York City
same forces that constructed it may also
have sown the seeds for New York's
destruction
scientists have pieced together the half
billion year history of New York City
huge mountains volcanic eruptions and
glacial ice shaped the area
but New York's story doesn't end here
the geology that created one of the
greatest cities on Earth also has the
potential to destroy it
experts have been studying the Potential
Threat to the city
we're standing here in lower Manhattan
on one of our major thoroughfares Canal
Street and it's important because in
1821 a category 2 hurricane raised the
water level at the battery 13 feet in
one hour and literally the Hudson River
met the East River and Canal Street was
covered by water in Manhattan was
actually two islands for three hours
until the water receded
New York City is vulnerable because of
its position on the coast
Long Island stretches Northeast at a
right angle from the New Jersey Shore
New York City is nestled behind the
Western end of Long Island
normally the island protects the city
from the sea but when hurricanes
threaten the opposite is true
Long Island becomes a dangerous
liability
hurricanes racing North along the
beaches of the Atlantic coast pile up
huge bulges of water in front of them
they're called Storm surges
hitting the right angle Junction at Long
Island the winds funnel the storm surge
in through the Narrows the gap between
Long Island and New Jersey
the actual apex of the right angle in
New York where all the water being
pushed by a hurricane would be
concentrated and in the distance is the
Verrazano Bridge and all that water is
going to go through the passage we call
the Narrows and it's going to be
accelerated toward New York City where
it will rise to abnormal Heights
experts believe that in the United
States New York is the third most
vulnerable city after Miami and New
Orleans to a hurricane disaster
if it was hit today the consequences
would be serious New York City uh is hit
by hurricanes only infrequently like in
1821 and in 1893 and in 1938 however the
point is that the hurricane that will
eventually hit New York City again will
be catastrophic and what is going to
happen when the utilities are knocked
out what is going to happen when salt
water reaches into the Subways and rooms
the electrical system we're talking
about unbelievable amounts of money to
restore the infrastructure we're talking
about setbacks and delays in Commerce
and Banking and transportation a
catastrophe that's never been seen
Storm surges are not the only threat to
New York's future
earthquakes are also part of the vast
geological forces that shape this area
they are still at work today
some could change the city in an instant
November 4th 1884.
New York City was shaken by an
earthquake that lasted 10 seconds
the Brooklyn Bridge swayed and people
panicked
the earthquake showed 5.5 on the Richter
scale
January 17 2001.
New York City was struck again
this time the Quake was relatively small
only 2.4 but it struck right under 125th
Street
the earthquake in 2001 is the first
earthquake that we could confidently
locate in Manhattan that's its claim to
fame it was felt widely
it's impossible to study the cause of
the Quakes at the surface
the evidence is buried beneath the city
within New York's Bedrock seismologist
Leonardo sieber studies the cause of
these quakes
foreign
tunnel 100 feet beneath the Bedrock
under the East River there is a
ready-made Laboratory
here sieber can study the Rocks up close
and personal
same Bedrock Manhattan is built on
but sieber fears it isn't as solid as
once was thought
New York area
is considered a seismic Zone meaning
there's a cluster of known earthquakes
that have occurred in this setting so we
are a geologists that are eager to
discover which faults are responsible
for these earthquakes
the majority of earthquakes occur at the
boundaries between separate sections of
the Earth's crust the tectonic plates on
which the continents sit
but New York's earthquakes are different
the city is firmly in the middle of a
tectonic plate halfway between the
Mid-Atlantic Ridge to the East and the
San Andreas fault to the West
um
sieber is anxious to discover what's
going on
as he examines the walls of the tunnel
he comes across a possible clue
the long fractures in the Rock are fault
lines that formed when pressure built up
as the tension was released the rock
cracked and shifted
this is felt on the surface as an
earthquake this is an example of a very
small fault
but is a fault that probably did
generate some small earthquakes when one
of these false generated earthquakes
we think that perhaps other faults of
the same family can generate earthquakes
these faults in New York's Bedrock are
evidence that the area was hit by
earthquakes in the past
Eber has no way of knowing if the faults
are still active and dangerous
if a large earthquake hit New York today
the consequences would be catastrophic
a large proportion of New York City
buildings are simply not built to
withstand earthquake shaking
we worry about Transportation tunnels in
particular tunnels that Traverse Rivers
where part of the tunnels are rooted in
Solid Rock and other parts are resting
on soft sediment the oscillation of
these two different materials could
cause severe cracking and fracturing
the infrastructure would be severely
damaged it would take tens of years to
repair the damage caused by such a large
event
the evidence geologists have collected
the story of the creation of New York
City can now be told
Bedrock was formed under a chain of
mountains over a mile high
volcanoes and lava Fields over millions
of square miles split up the ancient
supercontinent and created the east
coast of North America
glacial ice four times as high as the
Empire State Building carved out the
Deep Hudson River
a catastrophic flash flood broke through
the Moraine to form the Narrows and
opened up New York City's Harbor to the
oceans
looking ahead to the distant future
geologists see more challenging times
for the city
in 40 000 years they predict this region
will be engulfed by another ice sheet
and in 250 million years the Atlantic
will start to shrink again
Europe and Africa will eventually crash
back into the American Coast
the fossilized remains of the once great
city of New York will become just
another layer of rock in a vast new
mountain range
a footnote in the immense ever-changing
story of planet Earth
Earth a 4.5 billion year old Planet
still evolving
as continents shift and Clash
volcanoes erupt
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 Loch Ness in the
highlands of Scotland is explored
it holds more water than any other Lake
in Britain
with a Bedrock containing some of the
oldest rocks on the planet
in a landscape that was once part of
America Loch Ness is a lake with an
enduring myth
the Loch Ness Monster
a team of scientists investigate how
Loch Ness was made
Clues they uncover also provide a window
into the formation of the Earth itself
[Music]
deep dark and full of Mystery
this is Loch Ness in the highlands of
Scotland for a thousand years there have
been claims that this vast Lake hides a
strange and terrible secret the fabled
Loch Ness Monster
a mythical Beast suggested by some as a
descendant of the dinosaurs which once
roamed this part of Scotland
Loch Ness would be the perfect hiding
place for a prehistoric monster at 23
miles long and a mile wide this vast
freshwater lake covers the same area as
New York's Manhattan Island
its more than 700 feet deep
but the monster is not the only mystery
that surrounds Loch Ness
in the Hills above the lock there is a
type of rock whose origin baffled
scientists for years
it's a sandstone and it's the start of
the investigation into how Loch Ness was
made
it's known as the old red sandstone and
it's given that name because it's red
and it's a sandstone and it's called Old
because it's about 350 million years old
laughs
the old red Sandstone runs down one side
of Loch Ness
but the most astonishing fact about
these rocks is not their age but where
they come from these rocks actually
belong to my homeland of North America
because these rocks originated on the
North American continent and then have
separated from North America but many
ways this is almost a little bit of home
for me here in Scotland
but how do geologists know that this old
red Sandstone comes from three thousand
miles away on the other side of the
Atlantic Ocean
these rocks are identical in age and
character to the rocks that actually
form the Catskill Mountains and so this
part of Scotland belonged to
Northeastern North America
foreign for more than a thousand years
old red Sandstone has been used for
building castles in this part of
Scotland
but it's also been quarried in the U.S
and used for Brownstone buildings in New
York City
[Music]
under the microscope rocks from both
continents have an identical crystal
structure and chemical analysis has also
proved that they're exactly the same age
how did part of America end up on the
shores of Loch Ness
to answer this crucial question the
investigation must go much further back
in time to look for evidence in the
ancient Bedrock of Northern Scotland
it's here that the story of Loch Ness
begins
the trail starts north of Loch Ness
where the Bedrock comes to the surface
this landscape is full of the
extraordinary mysteries of an
unimaginably ancient past
it's made of a type of rock called
lewisian nice
[Music]
recent Drilling and Blasting for a new
road cut have exposed evidence which
uncovers an amazing chapter in Earth's
history
the long straight lines of the drill
holes left in the rock face
modern radioisotope dating has given
geologists the first clue to
understanding the origin and formation
of these rocks
these rocks are very special to
geologists they're some of the very
oldest rocks in the world we see them in
very few places perhaps a dozen places
across the globe contain rocks of this
age talking about two and a half to
three billion years old
the origin of the gray Lucian nice lies
in the first crust that cooled on the
surface of the Earth
after its formation 4.5 billion years
ago parts of this crust were mixed
together with the earliest sediments
varied re-melted and forced back up
again and again for more than a billion
years
these extraordinary rocks are the result
of that devastating period in our
planet's history
and there's more evidence exposed in
this road cut revealing crucial
information about the early history of
the Loch Ness region this exposure
contains three important pieces of
geological jigsaw puzzle first we have
the gray nice 2.5 to 3 billion years old
secondly we have this black igneous
material which has been intruded into
the area
this is two billion years old
and thirdly we have this pink granitic
intrusion that both intrudes the black
material and the nice and this is 1.8
billion years old
[Music]
this evidence reveals that after the
formation of the Louisiana nice much
younger rocks were then melted and mixed
into the ancient crust
but this process took an incredible
length of time
what we've got here are rocks that
record over a billion years of Earth
history now to put that into perspective
that is almost a quarter of the age of
the Earth recorded in this exposure
this is the Bedrock of Loch Ness it
carries an extraordinary story of a
major part of Earth's history
and there are yet more secrets hidden in
these rocks
it looks very much because of the
temperatures and pressures that these
rocks were under that they've been to
depths of perhaps 50 miles beneath the
earth's surface in the past this
suggests that these rocks have been to
Hell and back two or three occasions
over a billion year period
geologists now know that the only Force
powerful enough to produce this
extraordinary mix of rocks is plate
tectonics
[Music]
plate tectonics is the process by which
the giant plates of the Earth's crust
are driven slowly across the planet's
surface by vast convection currents deep
in the earth's hot mantle
in the Loch Ness region the evidence in
the road cut reveals that incredible
pressures Force the crust deep down into
the Earth where it was melted deformed
mixed together then finally brought back
to the surface
after that for another billion years
this ancient land mass quietly eroded
down to a rough rolling landscape
but this wasn't the green terrain we see
now there was much less oxygen in the
Earth's atmosphere than today and the
surface would have looked like a lunar
landscape desolate and sterile
incredibly remnants of that billion year
old landscaper still preserved today
the clues are revealed in another road
cut where the trained eye can draw
amazing conclusions from what looks like
a jumble of rocks
at this road cut we can see Louisiana
nice which is between two and a half and
three billion years old
but up here we have something completely
different if I go up to this level and
look above it we have horizontally
bedded red sandstones
this Sudden Change in rock type helps to
unravel the mystery hidden in these
ancient formations
they're believed to have been laid down
in a continental environment by Rivers
we've got river systems that laid down
horizontally bedded sedimentary rocks on
an ancient landscape
so this simple outcrop reveals that even
in a world with little oxygen the
ancient Bedrock of Scotland was covered
in rivers a billion years ago and
there's yet another secret hidden here
there is a junction between these rocks
which are almost a billion years old and
the Rocks below are two and a half to
three billion years old this is a major
time gap of between one and a half and
two billion years
foreign
the time Gap revealed here is
extraordinary it shows that after the
traumas of their early formation the
rocks of the Loch Ness region went
through a period of calm which lasted
more than a third of the age of the
Earth
[Music]
the investigation into how Loch Ness was
made has uncovered its first evidence
identical old red Sandstone found on two
continents proves that Scotland and
America were once joined together
some of the oldest rocks in the world
revealed that the Bedrock underlying
Loch Ness was made during the Primeval
creation of the Earth's crust
bedded sandstones lying on the ancient
Bedrock show that Rivers flowed over
this landscape a billion years ago
during a long period of Tranquility
but the calm couldn't last forever
a major Continental Collision was
looming and with it the union between
Scotland and England
[Music]
the investigation into how Loch Ness was
made will next uncover the geological
structures which would eventually create
Loch Ness
the search for evidence begins with a
19th century scientific mystery
in the 1880s geologists in Scotland were
baffled by a sequence of rocks they
found north of Loch Ness
here in a remote Hillside lay the
problem
a huge mass of very old louisian nice
was lying on top of much younger rocks
the 19th century geologists had never
encountered this before in their
experience younger rocks always lay on
top of older beds
then one scientist invented a novel
approach to try to solve the puzzle
a survey geologist back in the Victorian
age 125 years ago mapped this area and
his name was Henry cuddle he went back
to Edinburgh and he worried about what
he'd seen in the field and thought how
do I replicate what I've seen how does
this happen so he built a model and he
attempted then to show using the model
what it was that he saw in the field
cattle's model was simple he suspected
that some Force had squeezed the Rocks
horizontally to make this upside down
sequence so he built an apparatus
containing layers of sand and clay to
test his ideas
[Music]
foreign
[Music]
erhill is using a replica of cattle's
equipment filled with alternating layers
of black sand and plaster of Paris to
try and duplicate cattle's experiment
turning the screw winds the block
forward imitating the horizontal pushing
force that cattle thought was the
culprit
as the horizontal Force increases the
layers are pushed over each other along
a shallow plane which geologists Now
call a thrust fault
and we've got the first thrust appearing
oh look at that another thrusts going in
the experiment showed cattle exactly how
older layers the ones on the bottom are
pushed over and on top of the younger
layers along the plane of the thrust
fault there's some beautiful structures
in here there's a thrustful running
through here which duplicates the white
lab and another one through here and the
final thrust volt which is at the lowest
angle out here towards the left hand
side
a success in terms of a simple model
replicating what we see on the ground
and I can see how cattle and others when
attempting such things began to
understand what it was that they saw in
the field they could replicate it in a
simple crude model but replicate it in a
very successful manner
once cattle and his colleagues
understood the principle of thrust
faults the Apparently illogical sequence
of the Rocks they saw in Northwest
Scotland began to make sense
well the slope represents a thrust fault
what we have underneath it is a bedded
younger quartzite succession which is
Pink
above it the gray rock the rubbly gray
Hillside we see above is the Louisiana
nice again and the surface in between
which is putting older rock the gray
material onto the pink Rock the younger
material is the thrustful just like in
the model that we saw before
geologists now know that a thrust fault
is the Smoking Gun that shows where
continents have collided
but which continents were colliding to
make the thrust faults in Scotland
and how were they involved in making
Loch Ness
the scientists Trail now led them to
another thrust fault the moin thrust
the moin thrust is one of the biggest
thrust faults on Earth
running for 120 miles down the northwest
of Scotland it's mostly hidden from View
but Professor Underhill has found one of
the rare locations where the thrust can
be seen on the surface
this apparently insignificant join
between two Rock layers is the actual
line of the thrust
and it reveals a geological bombshell
the dark layer above the thrust comes
from England
but the surprise lies in the yellow
Limestone below it
just like the old red Sandstone at Loch
Ness this rock comes from North America
this one small piece of evidence has
enormous implications for the formation
of Loch Ness
the amazing thing about this contact is
that it's the meeting point between two
continents so here we are on a wet
Scottish Hillside on a Sunday afternoon
and I am touching the contact between
effectively America and Northwestern
Scotland on one hand and England on the
other as was
425 million years ago
foreign
but how did these two ancient continents
collide
450 million years ago a supercontinent
containing North America and Scotland
lay deep in the southern hemisphere
[Music]
at its margin was an ocean wider than
the present-day Atlantic
on the other side was England and Europe
but the forces of plate tectonics were
slowly pushing the two land masses
together
well around 450 million years ago there
was a major ocean where we're standing
now it was called the iapatis ocean and
it separated America and Northwestern
Scotland on one hand from effectively
Southeastern Scotland and England on the
other hand
now what happened in the 20 million
years after that that ocean closed and
eventually was closed sufficiently that
two continents collided into each other
[Music]
the collision between America and Europe
pushed massive layers of rock over each
other
forcing upwards a range of mountains
higher than the Himalayas are today
still firmly attached to America
Scotland and England became fused
together
but what did this Collision have to do
with the making of Loch Ness
the lock itself provides the most
fundamental evidence
the one thing that's quite striking
about Loch Ness is that when you look at
it particularly from this perspective
you can see that it runs straight almost
straight as an arrow and that
straightness goes on for about 20 miles
and as a geologist that tells me that
there has to be a control on this
topographic straightness because nature
doesn't produce things in straight lines
and so there's a structure here that is
controlling the overall shape of Loch
Ness itself
this structure is the great Glen fault a
major geological fault line formed
during the Continental Collision 425
million years ago
it runs for more than 300 miles right
across Scotland slicing the country in
two
Loch Ness exactly follows the line of
the great Glen fault
the great Glen fault is not a thrust
fault like the moin thrust where
material has been pushed up over it's
not a normal fault where material drops
down vertically it's lateral motion
thank you
the great Glen fault is Scotland's
version of the San Andreas fault it's
just 400 million years older
the great Glen fault is no longer active
but this giant split in the Earth's
crust has been a feature of the Scottish
landscape for more than 400 million
years
it's the foundation of Loch Ness and
without it the lock could not exist nor
could the legend of the Loch Ness
Monster
the investigation into how Loch Ness was
made has uncovered more evidence
the discovery of thrust faults showed
geologists what happens when continents
collide
yellow Limestone from North America
found at the moin thrust proves that
America and Scotland crashed into
England 450 million years ago
and the shape of Loch Ness reveals the
straight line of the underlying great
Glenn fault formed during that
Continental Collision
after the Collision the forces of plate
tectonics drove Scotland South round the
surface of the Earth
now the investigation must follow its
amazing journey
the next step in the investigation into
how Loch Ness was made traces Scotland's
Journey round the surface of the Earth
driven by the forces of plate tectonics
understanding what the environment was
like in the past gives Clues to the
location of Loch Ness millions of years
ago
so the investigation now moves on
to the Jurassic period 165 million years
ago
the trail leads to the Isle of Skye an
island off the west coast of Scotland
at Staffing Bay there is an incredible
piece of evidence which sheds light on
this period in Scotland's past
astonishingly it lay in plain sight but
undiscovered until 1994 when an amateur
geologist made an extraordinary find
on the flat Rocky Shoreline of this
popular Beach he discovered a fossilized
footprint of a giant dinosaur
[Music]
Dr anjana katwa has come to analyze the
details of this remarkable evidence
when you walk across these Ledges it's
just an incredible feeling to think that
dinosaurs walked on the same ledge that
I'm walking on now
165 million years ago this ledge we've
got this wonderful Megalosaurus
footprint
the megalosaur was a 25 foot high
carnivorous dinosaur quite a formidable
Predator during Jurassic times
with some individuals standing as tall
as a football goal post Megalosaurus was
a fearsome monster
but how could something as temporary as
a footprint be preserved for 165 million
years
the footprints are so unique what's
happened is that a dinosaur has traveled
over a kind of sticky gooey mud and
their Impressions have been left behind
that mud is dried off and it's hardened
and then over time windblown sand has
come in and covered that footprint over
and then as further time has developed
we get layers of clay and sand building
up over that footprint and that
footprint becomes fossilized over time
now over a few million years erosion
occurs and those Footprints become
exposed for us to see today
Dr katwa is making a plaster cast of one
of the footprints so she will be able to
examine it more closely
prints so we can take them back to the
lab and have a look at them and
understand how this creature used to
live
as she carefully removes the plaster
cast its shape reveals a 165 million
year old Secret
one thing that really strikes me
actually is the Deep impression that
this front toe is made and how pointed
it is
and this tells me that this dinosaur was
moving at a fast speed and really
pushing down on its front three toes so
we might have been chasing some kind of
prey
[Music]
but Megalosaurus wasn't the only
dinosaur to leave its Footprints in
these rocks only 60 miles from Loch Ness
[Music]
this is the smallest dinosaur footprint
that anybody has ever found in the world
you can actually see it's about the size
of my fingernail and we think it's a
celophysis and it's quite interesting
because the small footprint here which
we think is from a hatchling is embedded
in the larger one here that you can see
what we think this tells us is that the
young traveled with their parents in
groups and that most probably the adults
were looking after the Young
geologists have used the amazing
evidence of the footprints of
coelophysis and Megalosaurus together
with the muddy rocks they were found in
to better reveal the story of Loch Ness
in the Jurassic period
at the time Scotland was still attached
to America
plate tectonics had driven this land
mass much nearer the equator two
thousand miles further south than it is
now
and that had a major effect on the
climate and environment of Loch Ness
back during the Jurassic times a climate
and the environment was very very
different to what we see today there
would have been Lush jungles full of
tropical vegetation and the dinosaurs
would have been living on the edge of
these jungles traveling over Lagoon all
type of wetlands this climate was ideal
for dinosaurs to live in because it
supported a huge ecosystem of wildlife
that they would have predated on
the bones of one more dinosaur have
recently been found on the Isle of Skye
the plesiosaur
but this discovery generated a
completely different kind of Interest
enthusiasts see a strong resemblance
between the shape of the plesiosaur and
some descriptions of the Loch Ness
Monster
could a descendant of the long extinct
plesiosaur really be the source of the
legend
the evidence to unravel the
extraordinary geological history of Loch
Ness is getting stronger the findings of
Megalosaurus and celophysis Footprints
prove that dinosaurs lived in Scotland
165 million years ago and that Loch Ness
was then a subtropical Paradise two
thousand miles further south than it is
today
but about 60 million years ago 5 million
years after the dinosaurs became extinct
plate tectonics would tear Loch Ness and
America apart
the investigation into how Loch Ness was
made now moves forward to a Time 60
million years ago
Scotland and America are still firmly
joined together
the next question is when and how did
they become separated
on the Isle of Skye the landscape is
full of evidence which can unlock the
secrets of this turbulent period in
Scotland's past
at talisker Bay the massive Sea Cliffs
provide the first clue to the events
that devastated the region
they're made entirely of volcanic lava
I'm standing here on a single lava flow
and this nerva flow is only about 10
feet thick but this whole Cliff above me
is made up of lava flaves maybe 150 feet
or more and stretching for miles in all
directions
now these lava phase are composed of
Basil
that's the same type of rock that is
being erupted today from Modern
volcanoes like Hawaii or Iceland
geologists have calculated that these
Basalt lavas on Sky are about 60 million
years old
but where is the volcano which erupted
them
the clue comes from a range of mountains
on the southern tip of Sky the coolant
Hills
it's the type of rock that makes up
these craggy Peaks which provide the
evidence
position is the best salt that's been
erupted onto the surface but there's a
difference the bath salt that was
erupted was cooled very quickly because
it was exposed to the air
geologists call that fine-grained
on the other hand the magma that was
trapped maybe a mile down beneath the
earth's surface that cooled pretty
slowly it was kept warm for quite a long
time and so you've got very large
crystals growing and when you get a rock
with large crystals that's what we call
coarse grained
the large crystals in the gabbro Rocks
give away their origin they tell
geologists that the coolant Hills are
the remains of an enormous magma chamber
deep below the volcano where lava was
stored before being erupted onto the
surface
but how much lava was there
we may be looking now at
the Green Valley but actually all these
hills around here are made up of rocks
that were formed in a series of massive
volcanic eruptions about 60 million
years ago and at that time there were
volcanoes erupting all over Scotland
here we are on sky and this is just one
of those volcanoes
it's now known that an incredible 500
cubic miles of lava was erupted on Sky
alone
that's enough to cover the whole of
Texas with a layer of lava 10 feet thick
this was just the tip of the iceberg
the Rocks themselves reveal that
volcanoes erupted all over Scotland on a
massive scale
the evidence is here huge regular
columns in the lava flows looking like
they've been carved out of the Rock
in reality these amazing formations are
made by gentle cooling of thick lavas
exactly the same type of columns are
found in outcrops of Basalt lava 80
miles away off the west coast of
Scotland
and as far away as the coast of Ireland
150 miles from sky
these lavas have all been dated at about
60 million years old and they were also
part of the same series of massive
eruptions which spread out for hundreds
of miles in all directions
but what was the cause of the eruptions
Dr good enough has found another clue
which points to the origins of these
lavas and their role in the creation of
Loch Ness
this is the Rope he took to another flow
in Hawaii they call it pahui Hui and
what happens is that the lava gets a
thin skin on its surface as it cools but
it's still flowing underneath that skin
and the thin skin wrinkles and gets
pushed forward giving this ropey texture
that we can see here but it's really
quite rare to see them like this in
these old lava flaves but it tells us a
lot about the type of magma that was
erupting from that volcano
[Music]
geologists know that this kind of magma
comes from deep within the Earth it
usually erupts on the surface when
tectonic forces split the Earth's crust
apart is that what happened here 60
million years ago
at that time Scotland was still joined
to North America
continents were being
satanic forces
and that allowed molten rock or magma
from deep within the Earth to well up
and to be erupted from those volcanoes
and eventually that volcanic activity
led to the development of a new ocean
between Scotland and North America the
Atlantic Ocean
so the lavas are the trail of evidence
which show that the opening up of the
Atlantic Ocean began with volcanic
eruptions all over Scotland
[Music]
as magma erupted under the ocean the sea
floor spread out slowly pushing Scotland
and America apart
the birth of the Atlantic Ocean had a
direct effect on the making of Loch Ness
as the ocean grew the huge forces
involved reawakened the 400 million year
old great Glen fault
so faults like the great Glen these are
zones of weakness in Earth's crust and
they're like scars or wounds they can
reopen and in the case of the great
Glenn it was reactivated when the
Atlantic began opening 50 to 60 million
years ago and this is why you see this
feature now present in today's landscape
even though the fault itself is 400
million years old
the massive geological movements
shattered and weakened the Rocks along
the fault
along this line of weakness a river
started cutting down through the
shattered rocks slowly carving out a
valley
for the next 55 million years the
landscape of Scotland weathered and
eroded
the outlines of the mountains softened
and the coastline began to take on its
present shape
Loch Ness became a long river valley
following the line of the great Glen
fault
the investigation is close to uncovering
the final stages in the story of how
Loch Ness was made
huge lava flows on the Isle of Skye
reveal that massive volcanic eruptions
60 million years ago were the start of
the separation of Scotland and America
the sharp outline of the 400 million
year old great Glenn fault shows that
the fault was reawakened as Scotland and
America were torn apart
but there was one final land-changing
event to come
nature wasn't finished with Loch Ness
and it was this event that created the
lake we see today
tracing a violent history that lasted
for three billion years the
investigation into how Loch Ness was
made now moves forward to the recent
past only ten thousand years ago
the final Link in the chain of evidence
is to discover how the wide deep Waters
of Loch Ness were finally made
and whether a descendant of the
dinosaurs could possibly have survived
there to create the myth of the Loch
Ness Monster
a vital clue was uncovered in the 19th
century by one of the greatest
scientific Minds the world has ever
known
Charles Darwin
in 1838 Darwin came to Scotland to
investigate a mystery in the remote
Valley of Glenn Roy about 20 miles from
Loch Ness
for hundreds of years people had been
baffled by three extraordinary parallel
lines which run round both sides of the
valley
strange horizontal Cuts in the hillside
in some places more than 30 feet wide
these parallel roads as they are called
run exactly level for more than 20 miles
what could have made them
Dr Pete Nino is following In Darwin's
footsteps to the glenroy parallel roads
and the story they revealed
the creation was a mystery for a very
long time and initially people you know
just thought they were perhaps created
by Giants a thing of myth or Legend and
then in the in the 19th century a number
of scientists came here including
Charles Darwin and when he saw them he
thought they were exactly the same as
features he'd seen in South America
where earthquakes had uplifted old
Marine shorelines and left them
abandoned higher up from the sea
Darwin was so convinced the parallel
roads were the remains of old seashores
that he published a paper with his
results and the world of science
believed him
but for once Darwin was wrong
in 1840 two years after Darwin's visit a
Swiss scientist named Louis Agassi came
to glenroy
Agassi had spent a lifetime studying
glaciers and the effects of glaciation
on the landscape of the Swiss Alps
[Music]
when he examined the parallel roads
Agassi realized that they were ancient
shorelines but that the valley had been
filled not by the sea but by a
freshwater lake
[Music]
from his knowledge of glaciers in the
Alps Agassi was able to show that a
freshwater lake had once filled the
valley
the lake was kept full by a huge Glacier
which blocked the end of the valley
as the glacier melted and froze again
three times the water in the valley
emptied and filled up to a different
level
carving out the three Relic beaches
initially Agassi wasn't believed because
people believed Darwin and then over
time it became clear that Agassi was
correct and Darwin claiming it was one
of his great embarrassments that he got
something so terribly wrong
which sort of shows that even great
scientists can make mistakes
the evidence that Glenn Roy convinced
Agassi that many features in the
Scottish landscape must have been made
by glaciers
and that led him to the startling
conclusion at the time that the whole of
Scotland had once been covered by Ice
on the mount you make that leap that
what you've got here was created by
glaciers you've instantly got to make
the leap to the fact that we must have
had a very cold climate here in the past
cold enough for Rice sheets and glasses
to to build up this site is a is of
world importance in terms of the
understanding of glaciations and the you
know the fact that in the past ice
covered a much larger proportion of the
planet than it currently covers
this extraordinary investigation LED
eventually to the idea of the Ice Age
periods in the geological past when much
of the northern hemisphere was covered
in glaciers and ice sheets
since agassi's discoveries scientists
have been investigating the role of ice
in making Loch Ness about two and a half
million years ago the global climate
started to cool and since then we've had
a series of repeated glaciations roughly
about once every hundred thousand years
the ice Advanced temperatures plummeted
average winter temperatures were at
least 30 degrees colder than today as
the ice built up it reached
extraordinary thicknesses
the ice sheet over the center of
Scotland would have been three or four
thousand feet thick here in in Loch Ness
it would have certainly been um a couple
of thousand feet thick you might have
seen a few of the highest mountains just
peeking out the top of the ice sheet but
in the main the whole of the landscape
would have just been blanketed by by Ice
but what effect did this vast weight of
ice have on the creation of Loch Ness
the lock itself is difficult to
investigate because it's full of water
but there's another location where the
evidence is clear
just 20 miles from Loch Ness is the
forbidding Valley of Glencoe
Glencoe is a legendary place in Scottish
history as it was here that an Infamous
Massacre took place in 1692 when the
McDonald Clan were murdered in their
beds by the Campbells
the shape of this Valley sheds light on
the way Loch Ness was made
if you could actually drain the water
out of Loch Ness what you'd actually end
up with is a valley with this sort of
shape
and looking down Glencoe you can see
it's a very very steep-sided flat bottom
Valley and it's basically been created
by glasses repeatedly flying down the
valley eroding it and basically gouging
out what was originally a v-shaped value
and turning it into an over deepened
U-shaped valley
Glaciers are extremely efficient at
eroding the landscape they pick up vast
amounts of rock debris which is carried
along at the base of the glacier
with the weight of millions of tons of
ice on top of it this rock debris grinds
away the Bedrock like sandpaper scouring
and deepening The Valleys to a
characteristic u-shape
across Scotland there are hundreds of
valleys with this distinctive u-shape
bearing witness to the huge number of
glaciers which once covered this whole
region
at Loch Ness underwater mapping has
revealed that the lock has this
signature u-shape
it's flat bottomed with very steep sides
in some places only 50 feet from the
shoreline the water is over 500 feet
deep
further proof that Loch Ness was made by
a glacier
there was already a long river valley
which had formed along the line of
weakness created by the shattered rocks
along the great Glen fault
then during the last ice age a giant
Glacier flowed down the valley slowly
carving out Loch Ness
as ice flows down it it scours out
deepens it and over over a series of
glaciations it deepens it to the extent
that it's now you know a lock 750 feet
deep
the investigation is now faced with two
final questions how did Loch Ness fill
up with fresh water and what keeps it
full
loose Rock and boulders found on a huge
Ridge 250 feet high at the head of the
lock could provide the answer
immediately obvious thing about these
large rocks is that they're extremely
smooth and well-rounded and that
indicates that they've been transported
by by water they're also very large this
is very heavy so you need a lot of
energy so that tells you that you've got
a lot of melt water that's carried it
and then subsequently dumped it where we
are now
this evidence combined with discoveries
about climate change shows what happened
here
about ten thousand years ago global
temperatures Rose rapidly the ice began
to melt and the glaciers retreated
glasses down there would have been
eroding Loch Ness bringing up large
amounts of sediment and that sediment is
then being transported in this direction
by the by the flowing ice and also by
flowing melt water
as the ice melted a huge river formed
under the Loch Ness Glacier carrying
with it vast amounts of rock debris
and then what we've got here what we're
standing on is affect the Zone where the
Glasser is now dumping that sediment
millions of tons of rocks created an
enormous plug which damned the river and
stopped the water from escaping
as the ice melted the valley filled up
finally making the lake we know as Loch
Ness
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Loch Ness is only 10 000 years old but
the investigation into its history has
revealed an amazing story
old red sandstone rocks show that
Scotland and the U.S were once joined
together
the shape of Loch Ness is controlled by
the great Glen fault formed when
Scotland and America crashed into
England more than 400 million years ago
fossilized dinosaur footprints placed
Loch Ness near the equator during the
Jurassic period
lava flows reveal that massive volcanic
eruptions 60 million years ago began the
separation of Scotland in America
and the profile of Loch Ness proves that
it was carved out by glaciers ten
thousand years ago
finally creating the Loch Ness we know
today
but what of the Loch Ness Monster
the iconic image is now known to be a
fake
but is there any way that the mythical
Beast could be a descendant of the
dinosaurs
we have two geological facts that tell
us that bachnest cannot be inhabited by
a dinosaur one is the dinosaurs died a
long long time ago in the lock itself
geologically is very young
dinosaurs went extinct 65 million years
ago so 65 million years to 10 000 years
it's a long time distance and there is
no chance at all that you would have
preserved in this law an ancient monster
from times millions of years ago the
Lock's too young
so the geological evidence proves that
Loch Ness could not be home to a
dinosaur that somehow survived there
since the Jurassic
the awesome geological history of Loch
Ness has thrown up many Mysteries
but for science the Loch Ness Monster is
not one of them
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