How the Earth Was Made: The Most DANGEROUS Geological Mysteries *Epic Marathon*

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] [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] [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 [Music] 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 [Music]

Channel: HISTORY

Views: 20,702,840

Keywords: history, history channel, history shows, history channel shows, the history channel, documentary history channel, history documentary, documentary, history channel full episodes, documentaries, history channel documentaries, How The Earth Was Made, marathon, History marathon, How The Earth Was Made marathon, how the earth was made, how the earth was made marathon, marathon on history, earth, planets, proceess, History Channel, History Channel marathon, full episodes

Id: BRSkRlPa5_E

Length: 222min 37sec (13357 seconds)

Published: Sun Jun 18 2023