"The high Andes of Bolivia" "In the 16th century rumours of fabulous wealth drew Spanish adventurers to this lonely place." "What they found here exceeded their wildest dreams." "A mountain of silver... they called the Cerro Rico." "To the Spanish the Cerro Rico was a gift from God." "The amount of silver won from this mountain alone" "Was truly fantastic." "Perhaps up to 60,000 tons of silver has been won, enough to finance the entire Spanish empire, and indeed the Western World." "It is estimated that perhaps just as much remains." "So that this mountain, Cerro Rico, can truly be said to be the richest silver mine in the world." "As over the centuries prospectors followed the trail of silver and also gold, it led them to rich deposits all round the great Pacific Ocean." "In fact, you might call the rim of the Pacific" "'The Ring of Gold', but it's more usually called 'The Ring of Fire' because all round the margin of the Pacific Basin associated with the mineral deposits, there are huge chains of volcanoes." "At first sight, there might not seem to be any connection between volcanoes and mineral wealth, but in fact there is, and that link is a clue to one of the most puzzling mysteries about the earth." "How did the dry land - the continents on which we live - how did they form?" "Only one third of the Earth's surface is dry land." "Most of the planet is covered by water" "John Dewey is a geologist" "Who has spent his career looking at the rocks on land, trying to understand their origin." "Those on the west coast of Scotland hold a special interest for him:" "they're the oldest in the British Isles." "I think you have to remember that prior to about thirty years ago, geologists had been mapping the continents and making very detailed geological maps, over a period of perhaps a hundred years, including a beautiful map of this area" "made in the last century with exquisite details of all the rocks;" "but of course there was no ready explanation to explain all these rocks and geological relationships." "When John Dewey first came here over 30 years ago, many geologists still saw no distinction between the rocks on dry land, and those beneath the sea." "But that soon began to change." "As scientists explored the oceans, they started to realize that the veil of water concealed a fundamental difference between the continents and the ocean floor." "Unlike the continents, the deep ocean floor consists almost entirely of rocks of only one type." "What's more, scientists worked out that this rock had all been produced in the same way - all erupted by undersea volcanoes that ran down the middle of the oceans." "It was a beautifully simple picture." "In contrast, on the continents we see a very, very different kind of story." "These rocks have suffered an immensely complicated history over a very long period of time, in such a way that these bands, light and dark bands, have been folded, swirled together, squidged and squashed at very high temperatures and pressures" "in ways that are typical in many many parts of the world, the kind of thing you see in the continents but never in the oceans." "How had rocks like these been created?" "Unlike their ocean-going colleagues, land geologists lacked a simple theory that could explain the origin of the continental crust." "In those days, we didn't have it:" "we were simply groping in the dark." "The first glimmer of light came from the same region that had enriched the Spanish Empire... in the high Andes of Bolivia." "Each year the people who live at the foot of the Cerro Rico celebrate the source of their prosperity." "But for many years the region has also attracted scientists like Rodney Grapes and Leonore Hoke from New Zealand." "Top it up" "This year they're being joined by two British geologists Rick Thomas and Catrin Jones." "The team are heading for an area which for thirty years scientists have suspected may hold the key to how the continental crust is formed.." "OK, so where are we heading?" "I think really we've got to go straight towards that big volcano because there's nothing else that's gonna give us so good a bearing." "So that's 3.10." "We've got...?" "behind us, to the right." "We've got this distinctive volcano." "Yes that's this one here." "...what is it - 3.10?" "We'll have to rely on your bearing then." "OK, well then let's go." "Their journey takes them across the Salar, a dry salt lake... part of the vast Altiplano... a 4000 meter-high plateau in the middle of the Andes." "There are the odd pot-holes, but I think it's the best road in Bolivia - you go flat out, 120 kilometers, if the car makes it." "You're still going at sixty are you?" "Yeah, well." "Enjoy the view." "Between them and the Pacific coast lies their goal - a chain of active volcanoes, the highest in the world." "As they near the volcanoes, the team start to see signs at the surface of tremendous activity deep below them." "I'm familiar with the volcanoes in New Zealand, and it's a real thrill to come here to the Andes, where you can see so many more of these volcanoes, very similar to the ones we have in New Zealand." "The rock that's erupted from these volcanoes is in fact called Andesite, after the Andes, so if you like this is the home of the Andesite." "Not just the volcanic cones, but the entire landscape here is made of andesite and other volcanic rocks." "Since the 1960s, scientists studying the growth of the continents, like Rick Thomas, have been working out how this happens." "Volcanoes in the Andes are notoriously explosive." "They can eject tons of ash and fragments of volcanic rock into the atmosphere." "The reason for this behaviour is a surprising one." "The liquid rock at depth contains a lot of water, and that water's happily dissolved when it's down deep;" "as it comes close to the surface, it froths up the magma, the liquid rock, and it causes it to explode, just like when you uncork a champagne bottle:" "same sort of thing's happening here." "Froths up and what we get is fragments of rock which are full of bubbles within the rock and you get lots of these pumices which you can see here." "If you'd been here during one of these eruptions, you'd have seen vast billowing clouds in the distance coming towards you, kilometers away, but in a minute or so, because they travel so fast " "hundreds of miles an hour quite easily - they would have engulfed you." "and this ash cloud would have just blasted on down the valley and just filled most of what we can see of that plain." "As the clouds of ash and pumice settle, they compress together to form new rock layers." "Over time these layers gradually build up." "Water is the key to this process and it's the water that's attracted the team to this remote spot." "Straight ahead of us, is Ojagwe with its fumarole on top." "Yes, a nice conical volcano, that, actually, and you can..." "Leonora plans to collect a gas sample from the active fumaroles at the summit, which are continually producing steam and other vapours." "...quite clearly the fumarole there." "As you come down the right shoulder, and you just might be able to make out Irruputuncu." "And that's where we're heading." "Back in the Sixties, scientists searching for the origin of the continents realised that the explosive process they could see building up the landscape here was not confined to the Andes:" "it was happening elsewhere too." "Matthew Thirlwall has collected rock samples from volcanoes all over the world." "Of the thousand or so active volcanoes in the earth at the moment, some eighty per cent produce these highly explosive eruptions." "This is a sample of pumice from the Andes, but we can find almost identical pumice in several other places on earth." "Here we have pumice almost exactly the same, with these gas bubbles in it, from Mount St. Helens in Washington State, and this is a typical example of Andesite, the characteristic rock in these areas." "And you can see- find almost identical Andesites in several other recent eruptions - for example, here we have a sample from Mount Pinatubo in the Philippines:" "very very similar samples with some four thousand miles of Pacific between them." "In fact, geologists soon discovered that most of the volcanoes that surround the Pacific Ocean produce the same type of rock, in the same explosive fashion." "We're completely safe from these eruptions in England, but if you happen to live anywhere near the edge of the Pacific Ocean, you can almost certainly drive within a day to one of these Andesitic volcanoes." "So the volcanoes of the Ring of Fire are all basically similar." "Hundreds of them are continually erupting in an extraordinary arc that runs up the western coast of the Americas from Patagonia all the way to Alaska..." "And then continues all the way around the Pacific Basin." "It dawned on scientists that in the process, the volcanoes were building up a ring of Andesitic rock all around the Pacific." "And then they discovered a link between these rocks and those which make up the continent as a whole." "As they analysed thousands of samples, from all over the world, a surprisingly simple picture emerged:" "though the rocks looked different, they were made from basically the same ingredients." "And indeed their average composition hardly varied at all from continent to continent." "Even more significant, this average composition was essentially the same as that of the volcanic rocks in the Ring of Fire." "If one were to take all the continental crust of the whole world, grind it up, then measure its average composition, it would be very very similar to that of these rocks, and it would consist of three basic minerals:" "the very translucent mineral is quartz, the rather milky mineral is feldspar, and the dark green mineral is hornblende." "And then if one goes to the Andes and looks at the volcanoes, and indeed looks at the rocks injected deep in the crust beneath the volcanoes, one has the same general composition as we find here, of quartz, of feldspar and of hornblende." "And of course that immediately begins to give one an inkling that possibly these rocks were formed in the same way." "And not only that but much of the continental crust must have been formed in the same way as we see in the Andes in the present day." "So perhaps the continents had all been created by volcanoes like these, building up the crust over geological time." "But, what was creating the volcanoes themselves?" "And how could something happening around the Pacific explain the rocks in Scotland?" "All this was a complete mystery." "But then the Ring of Fire provided another vital clue." "The region was periodically rocked by earthquakes." "In 1964, a major one struck Alaska." "I was leaning in my cabin getting a cigarette, and all of a sudden it started shaking." "We was evidently right over the epicenter." "These big sand spouts were shooting up in the air." "You can't believe how that boat shook and rattled." "It was scary." "Could I have your attention please?" "Alaska Airlines Flight 61 will be arriving now." "The day after the earthquake, a US government geologist flew in to investigate what had happened." "George Plafker is still working in the region." "I was in Seattle attending a geological conference when the earthquake struck." "From the initial reports, we realised it was a major disaster and a great earthquake, and it was in my field area." "We got some clothing together and we took the next flight up to Alaska." "Our mission was to assess the damage." "And of course as a scientist I was interested in trying to figure out the cause of this earthquake." "Unknown to George at the time, understanding the cause would have global implications." "But his immediate problem was just getting around:" "the earthquake had affected a vast and remote region." "When we first came up, all we had heard was that the roads and railroads were cut and that there was a great deal of land sliding and wave damage in the coastal areas." "There was a big... water out there, between this island and that mainland over there." "I said: 'oh, my gosh: tidal wave', and I just kept running " "I didn't even look back." "Amongst all the stories of eye-witnesses, confusing reports of sea-level changes were also emerging." "Some witnesses claimed the sea level had dropped, others that it had risen." "George's hunch was that something fundamental had happened to the land itself, and that working this out would lead him to the cause of the earthquake." "He decided to examine the shore-line in detail." "This is what we had to do to get around this shore-line." "And it was here that he made his first remarkable discovery." "This water level is a little bit below mean high-tide." "Mean high-tide normally reaches to about the top of this rock, and you can see these barnacles on the rock and seaweed which grow up to that level." "Let me show you something fascinating now." "Here is a line of dead barnacles and this line is about six feet above the living barnacles." "When I came here in 1964, some of these barnacles were still alive." "George realised that during the few moments of the earthquake, the land here had been jacked up six feet." "What was more, George had found a way to measure accurately land level changes over the whole enormous area affected." "He visited hundreds of small coves and inlets, following the line of barnacles." "That big..." "wheel going down the track means it's all up and down, He ain't coming back, so I'm moving on," "I'll soon be gone." "You are flying too high for my little old sky, so I'm moving on." "That big loud whistle as it blew and blew," "Said hello to the south land, we're coming to you when we're moving on," "Oh hear my song..." "Now there are thirty two feet above the level at which barnacles live at the present time." "Spent all of the summer of 1964 and most of the summer of 1965 studying a stretch of coast more than 500 miles from one end to the other." "It's to find my home, so please listen to me, 'cause I got a pretty mamma..." "Where the shore-line was uplifted, plants soon colonized the new land." "Portage is about 270 degrees..." "But when he flew north west, further inland, it was a completely different story." "...go across Naked Island..." "Before the earthquake," "Portage had been a thriving rail stop." "But George learned that it was now being flooded at high tides, and icebergs were floating up the river into the town." "We were stood over there where the railroad station used to be, and watched these icebergs slam into the bar building and bounce off;" "they'd slam into the houses and go crunch." "That night, the water came in to the top of the bar where people sat to drink, and was clear up to there." "And old guy that worked or us stayed in the bar that night;" "the rest of us all fled across the street, and we all go back over to see if he's all right." "And of course he was:" "he was drunk." "George realised that in this region, land had gone down, nearly two meters at Portage." "The subsequent inundation of sea water, killed large tracts of pine forest." "When George plotted his measurements on a map, he found that a striking picture emerged." "Along the coastal regions, an area about the size of Great Britain had risen during the earthquake up to 12 meters, while further inland another vast area had gone down about two meters." "That was something that was absolutely new and different:" "nobody had ever seen anything like that before probably on the face of the earth." "George Plafker had discovered movements of the earth's crust on a totally unprecedented scale, that accounted for the huge landslides and the tidal waves." "What he still had to explain was why parts of the Alaskan crust had risen, whilst other parts had sunk." "And the explanation he came up with changed our view of the earth for ever." "When George was working on the geological effects of the Alaskan earthquake of 1964, we already knew big tiits of the ground and movements of the ground, and indeed earthquakes were the result of slip on faults, and perhaps the best example in the world" "that has been best studied is the San Andreas fault in California." "And here we have a couple of rather nice slides, where a large segment of the fault is slipping along, so quite naturally," "George was looking for a similar kind of structure, a steep break in the a earth's crust along the Alaskan region, to explain the 1964 earthquake." "But in Alaska there was no sign of a large fault cutting the surface." "Despite all of our efforts, we didn't find such a fault." "Now this was a major puzzle and something that bothered me for a long time." "But then George started to look elsewhere." "Finally, after much thinking about it," "I realised that the fault we were looking for actually underlays the entire region of uplifted subsidence, and that we couldn't see it because it came to the surface out to sea." "George's insight was that the fault was underground, sloping gently beneath the entire region." "Oceanographers had known for some time about a mysterious deep trench in the sea floor about a hundred kilometers offshore." "George was convinced that this was where his gigantic fault reached the surface - under water." "So if I draw a cross-section of Alaska " "I come from the north, do the land, across the volcano and down gradually, steeper and deeper, then down into a deep ocean trench, and I'll draw the sea in a blue wavy colour like this." "What George found, you remember, of course, was that the great Alaskan earthquake of 1964 was produced on a fault plane dipping gently under Alaska like this, with this sense of motions, that is the underpart was slipping down under Alaska in that way." "And of course this is very important because if one projects that fault out along its length, lo and behold, it projects to exactly the position of the oceanic trench." "So we can connect the trench directly with this plane of earthquakes." "A major fault like this would have caused repeated earthquakes and George realised it was what happened between earthquakes as the crust was squeezed that could explain why some places had gone down while others had risen." "I have here a model, very simplified representation of the continental margin of Alaska." "This represents the fault." "For several centuries between earthquakes there is gradual compression and uplift of the area above that fault, and at the time of an earthquake it slips suddenly, causing uplift on the seaward side," "and subsidence in the area where there was a fault." "And this land movement was not a one-off event." "When he looked," "George found signs of past earthquakes engraved in the landscape." "This series of steps was created as the land was repeatedly jacked out of the sea every few hundred years by a sudden movement on the fault." "But it was what was happening beneath the fault that was really significant." "George suggested that with this sense of motion, the whole of the Pacific Ocean floor is slipping, flowing down along this inclined plane underneath Alaska." "And of course the expression of this are intermittent earthquakes about every seven or eight hundred years." "If you keep on adding up each few meters of slip that generates the earthquake then over a long period of geological time this was suggesting the whole Pacific Ocean floor was flowing down along this inclined plane underneath Alaska." "Only then did George Plafker and his colleagues realise the full significance of the ocean trench off the coast of Alaska." "Because this trench circled virtually the whole Pacific margin, it suggested that the entire floor of the Pacific Ocean was sliding back beneath the surrounding continents, sinking back into the Earth's interior." "And this was just part of an even bigger picture." "Geologists had already discovered that the sea floor was being continually created along the mid-ocean ridge- the volcanic mountain chain that ran up the middle of the oceans." "The ultimate fate of this sea floor was obvious now." "As it was being created in the middle of the oceans, so it was being destroyed at the trenches at ocean margins in what scientists called subduction zones." "And this was happening all over the planet." "Together the ocean trenches and the mid-ocean ridges formed a network of lines, boundaries that divided the globe into vast, slowly moving regions - the plates." "It was an extraordinary revelation - geologists suddenly realized that the entire surface of our world was in constant motion." "And so the theory of plate tectonics was born, and scientists started thinking about the earth in a completely new way." "And it's really quite an extraordinary idea, but remarkably simple." "The surface of the earth consists of a number of rigid plates that are moving relative to each other;" "and this map here shows these plates in different colours." "And the Pacific region forms a huge plate which um is moving relative to the Australian plate in the New Zealand region, and sliding past the North American plate in California." "The continents move with the plates." "Throughout geological time, they have completely rearranged themselves, sometimes coming together and sometimes splitting apart, opening and closing oceans, re-shaping the face of the earth." "What had begun with a line of dead barnacles ended with a new view of our planet." "Plate tectonics suddenly arrived as a marvelous theory because it was able to suddenly explain lots of things we weren't able to explain many years ago." "Back in Bolivia, scientists began using the theory of plate tectonics to explain the origin of the Ring of Fire." "Leonore Hoke and the team believe that it can also throw new light on the growth of the continents." "They know that deep beneath their feet, ocean plate is sinking into the earth's interior." "Now it's very interesting because we have volcanoes round about in the position where the subducting oceanic plate is 100 to 120 kilometers below the surface where we are here now." "And that's where we have volcanoes:" "and we know from looking at the volcanoes that they produce a lot of molten rock and they produce a lot of fluids like water." "Geologists suspect that some of this water comes directly from the sinking ocean plate and may explain why the volcanoes are here." "Leonore plans to test this idea by collecting a sample from high on the volcano." "Well, this is my blue barrel which contains all the sample equipment which I need, and there are all sorts of things in it like this gas mask which protects me from noxious gases, funnels to collect gas bubbles with," "it contains this tubing which I need, and it contains these containers, and I pack them with at sea-level in New Zealand, oops, they pop when you open them because we are really at high altitude here." "And here are these special glass containers um into which I will suck the gas they evacuated, and the gases will tell me an awful lot about processes which gave rise to formation of these volcanoes- volcanoes and processes which happen at great depth." "Are we ready then?" "Como se llama...?" "Benito Velo" "Benito." "Leonore." "Benito." "Se Catrin." "Como estás?" "OK?" "It's six a. m." "on the Bolivian border with Chile." "Leonore, Catrin and their guide are on their way to their chosen sampling area." "They're heading for the crater, the most dangerous place on the active volcano:" "Irruputuncu." "The climbers are following a rarely used footpath, made by locals to collect sulphur from the summit." "They are climbing to nearly 6000 meters." "At this height oxygen levels have almost halved making it difficult to breathe." "It's hard work isn't it?" "Yeah." "Biting wind." "Sulphurous smell's getting stronger as well." "Well, we're getting closer to the fumarole." "Yup." "Another hour or so." "Brilliant view." "That's really the reward of it, isn't it?" "Yeah." "Its' amazing." "Feel like a bird up here." "The higher they go, the steeper the climb, as the sticky volcanic rock has built up the slopes of the crater." "After 4 hours they're within sight of their goal." "This is the solid material that the volcano's made from." "It's dark, almost black." "But covering all these rocks is sulphur, which is coming from the gases that are coming up from the craters behind me." "Beautiful yellow crystalline material." "The gases are also containing water, and that water is pervasively reacting with the rock, and changing it, so we get this crumbly white material." "It's this water, together with other gases rising through the crater, that Leonore has come to collect." "I'm taking a condensate sample:" "that means I'm collecting the steam and I guide it through this glass container which is immersed in snow, and that cools the steam, and I'm collecting the water at the bottom of it, and you will see later" "on there's quite a lot of water in this steam." "I'm having a look now how much water there is:" "I dig it out of the snow." "It's great to get out of that hot steam:" "it's hundred and twenty degrees." "But what I've collected here is some water:" "you can see it in here." "There's quite a lot coming out of this fumarole." "Now the chemistry of this water will tell us where this water's coming from and it will be analysed back at the lab." "There's yellow all over it." "Covered with sulphur." "... your eyes and things." "It was kind of like Hell." "The devil was about to pop his head out any minute." "OK, time to go." "Mm, it's still warm." "Back in Wellington, New Zealand," "Leonore heads straight for her laboratory." "Here I've got the sample" "I collected on top of active volcano in Bolivia, so let's see what's in it." "She's about to measure the composition of the sample to get an insight into the events taking place deep below the volcano." "You can measure the different gas components in the sample, and it contains helium, it contains argon, it contains CO2, it contains nitrogen and many other gas components." "But it's the concentration of nitrogen which catches her attention:" "it goes almost off the scale." "That's good." "I have quite a high signal coming from the nitrogen." "Nitrogen is the most common gas in air." "But the proportion in the sample is far too high:" "it suggests a completely different source." "Leonara turns her attention to the water in the sample." "We can also measure the isotypes of these gas components by using a mass petrometer" "By analysing the atoms in the water," "Leonore is hoping to test a startling idea." "She suspects that some of the water in the sample might come from the sea." "If so, it would support her growing conviction that the nitrogen could be coming from dead marine organisms known to be nitrogen rich, buried in the sea floor." "Could the flask from Bolivia contain a sample of the Pacific Ocean?" "The hydrogen is very close to the hydrogen isotopes of sea water." "So that suggests that some component within that water is probably sea water." "So we can say from that that a lot of that nitrogen is biogenic nitrogen, produced in ocean sediments and released during the subduction process." "So the journey up the volcano has yielded an amazing result - high up at the summit are traces of marine life and the Pacific Ocean itself, which have completed a long and extraordinary journey through the Earth." "Good climb?" "Excellent." "The whole story's contained in one glass flask." "You suffered with me!" "And of course a large part of this cyclic process explains the origin - origins of the continents because we now see that lovely link between the origin of volcanoes and the oceanic trench." "It's a beautifully linked system." "We now have the picture of this flux of wet rock, oceanic material coming into the subduction zone, carrying a lot of water with it, getting hotter and hotter and eventually it gets so hot that the water is expelled and that water will arise into the mantle" "above and will act like anti-freeze:" "it will trigger melting." "So water is the key to the Ring of Fire." "As the ocean floor sinks into the earth, water is squeezed out of the rocks." "Like scattering salt on an icy road, the water reduces the melting point of the surrounding rocks and so they start to melt." "This molten rock rises to the surface, to erupt as a line of volcanoes." "But these volcanoes are like the tip of an iceberg." "Only a small proportion of the molten rock ever reaches the surface." "Most of it is building the continental crust beneath our feet." "The surface volcanoes are merely the surface manifestation of a huge process of the addition of new hot material to the crust." "And if this has been going on for some considerable period of time, which we know it has, you can actually make very large amounts of continental crust in this way." "There's a huge volume of volcanic material being added to the crust." "Below us, we can imagine more molten rock pending underneath you at some level." "As you drive along, you're witnessing the growth of continental crusts." "It's quite an exciting thought." "Here is a place where for millions of years the continent has been growing, and it's going to continue probably for many more millions of years." "But as the plates have moved through out geological time, the places where the continents grow have shifted over the Earth." "Britain's ancient crust was built up in the same way by volcanoes " "450 million years ago." "As Matthew Thirlwall explains in the Lake District." "Everything we see over here was produced by big eruptions." "Below us, there's something like eight thousand meters of volcanic rock." "We can tell from the andesitic composition of the rocks, that there was almost certainly a subduction zone beneath the Lake District, with an ocean to the north, and an oceanic plate coming down beneath the Lake District, beneath Wales," "beneath Ireland and so on." "And the crust in this area almost certainly grew as a response to that subduction." "Worldwide, the composition of the continental crust is andesitic, right the way back through time." "Subduction zones were the sites of continental crust formation, not just at the present day at the Ring of Fire, but right the way back until the earliest parts of earth history." "As the continents have grown, another legacy has been left behind:" "the mineral wealth with which we have forged civilization." "The Cerro Rico itself used to be an active volcano some 16 million years ago." "And the much older volcanoes in the Lake District have also brought up their own rich dividend:" "copper." "In the 19th century, this area provided much of the copper for the burgeoning Industrial Revolution." "The link between volcanoes and mineral wealth is another consequence of water moving within the earth." "The connection is that the hot rocks at depth mobilize water, and that water circulates around the hot rocks, dissolves, leaches metals from the volcanic rocks, forces cracks up to the surface, transports the metals up in these cracks," "and then deposits them as the pressure drops." "It's really lucky that that's what's actually happened because if the metals were not deposited in these veins it would take something like the whole mountainside to work to produce a single copper pipe." "The volcanoes provide the workable deposits." "The people of the Cerro Rico have long believed the silver is a gift from Patja Mama their god of the earth." "In some ways, they've been proved right." "Scientists now see how, as the plates of the earth move, creating the land on which we live, our planet also yields up its wealth." "Subtitles:" "Thor"