Enormous Volcanic Eruptions

what's the biggest rupture in Earth's history what's the biggest volcanic event and that's what I'm going to talk about today the interest of course is that there's really only two natural hazards which can create a global catastrophe one is of course a large meteor hitting the earth will acid it in the Cretaceous to lead to the demise of the dinosaurs but also a very very large eruption much bigger than if you like modern societies experience it also has the potential for creating a global disaster well firstly let's have a look at some of the what goes on in the earth with regard to volcanism those 551 historically active volcanoes and in fact before 2010 there were five hundred and fifty because Mount Sinabung in Indonesia ruptured in 2010 and it hadn't had an historic eruption before so in fact you will see that in the next line there's from over 1,500 active volcanoes quaternary volcanoes which still seem to have a potential for eruption so because we've only got 550 historically active volcanoes it's really quite common that volcanoes that have had no activity in recorded history will start up and as roughly about one every two years somewhere on earth a new volcano erupted sutures never we didn't know it had any record of before on the whole was about 50 eruptions every year around the the earth it varies a bit sometimes it's 30 sometimes it's 60 but on average it's about 50 and as I mentioned one volcano erupts every two years which has had no historic eruption the economic cost can be very high locally and sometimes more regionally when the eruption in Iceland took place and a lot of ash stopped aviation flying across Europe in fact around the world but I guess some of you might have been caught out by that and aviation commercial aviation was shut down and that costs several several million dollars sir hundreds of millions of dollars I should say to the aviation industry as well as a lot of inconvenience to passengers and important point about eruptions very large eruptions can affect global climate that's a theme I'll return to but very large eruptions can create not just local but regional and global effects because of the pollution they create and vulnerability to volcanic eruptions and in fact all natural hazards increasing partly as a result of a population growth but also because of globalization and increase in infrastructure so the volcanic risk although the rate at which volcanoes erupt around the earth doesn't appear to change very much where with time the vulnerability or the risk that does well let's just start off with some facts and figures how do we measure the size of a volcanic eruption there's two measures one is the amount that's erupted in oftenly either as a volume or a mass and that's called the magnitude it's a bit like the scale for earthquakes ISM the magnitude scale for volcanoes and we can measure the we can measure the magnitude either by volume and you'll see for the eruptions we're talking about we're thinking about many cubic kilometers so keep in mind what a cubic kilometer keep one kilometer by one kilometer by one kilometer how much material is in that that's a huge amount of material and we'll see that some of the the greatest volcanic eruptions have erupted hundreds even a few thousand cubic kilometers all in one eruption sometimes the actual magnitude scale is based on converting that volume into a mass in kilograms and the Makarov show very many formulas but this is a bit like the earthquake scale but the magnitude is essentially the logarithm of the mass eruptive how many kilograms have erupted plus plus seven and the rate of eruption it is another measure of how big an eruption is intensity and that's volume per second or mass per second and I'll just give you an example of what we're talking about a fairly important eruption in the 1980 was the eruption of Mount st. Helens in the United States and during that eruption it was quite a big explosive eruption it's tiny compared to what we're going to discuss later in this lecture but that erupted 10,000 cubic meters of magma every second now a destard a rough calculation before I started this lecture that this lecture theater seems to be about 15 meters wide maybe 20 meters deep and several meters high so it's maybe two or three thousand cubic meters of volume in this lecture theater and Mount Saint Helens was erupting something like three or four times greater than that volume every second and it did so for several hours so that's a measure of intensity it's the rate at which things happen either volume per second or a mass per second and a super eruption is which is a cut a term coined by the media by the BBC they had a program a few years ago is a magnitude 8 eruption or greater and I'll come to explain that a little bit more detail next so what we're going to be talking about this evening is the very biggest volcanic eruptions on earth and I'm going to start with a the biggest eruption but one of the two biggest eruptions of the 20th century on the bottom left you'll see a picture of Mount of Mount Pinatubo and this is the crater formed by the 1991 eruption of Mount Pinatubo and that crater is something like just over three kilometers wide and it's one of the two biggest eruptions of the 20th century and it erupted five cubic kilometers of magma and that's roughly 25 times greater than Mount st. Helens erupted in 1980 so it gives you a bit of a it is also similar to the Sioux vyas in AD 79 when Pompeii was buried and volcanic deposits that was another I guess famous eruption so Pinatubo somewhat similar in size about five cubic kilometers and it had a magnitude six and a half so that's pretty big if we go to one of the biggest eruption of the last thousand years on earth we come to a volcano called Tambora in Indonesia which erupted in 1815 I'm going to talk about this eruption eruption later and the effects it had but this created a crater this is a crater about six kilometers in diameter and the reason of course you get these huge craters is that so much material is erupted out of the earth there's basically not exactly a hole but there's it's it's actually erupted out and then the earth basically collapses into the space which this magma originally occupied within the crust and that's why we get these large holes so they that crept the size of the crater is a sort of measure of the size and in tempo in 1850 NASA say one of about two very very large eruptions in the last thousand years had a mag erupted a volume of 45 cubic kilometers and that's getting pretty big and that was a magnitude 7 eruption and then we going to leap right up to one of the in fact the biggest eruption of the last a hundred thousand years on earth which is Mount Toba it's in Sumatra and it erupted 74,000 years ago it's the largest eruption on earth in the last hundred thousand years and this is just about the biggest not quite the biggest but very close to being the biggest known volcanic eruption in Earth history and that created a whole a criminal normos crater and this crater is about a hundred kilometers in this direction and about 30 kilometers in that direction because the 3500 cubic kilometers of material erupted all in one go and the mid where that magma came from underground collapsed in on itself and formed this gigantic crater you can see Tambora the one of the biggest eruptions the last 1,000 years on the same scale so that's this crater here and you can see just how huge the Toba called here it's these craters often call calderas how big it is it's a biggest volcanic crater on earth and again just for comparison we're talking about hundreds of times bigger than the biggest eruption of the last a hundred years so that's giving you a sense of how big volcanic eruptions can get just a little bit about the what happens in these eruptions just to say that the reason that volcanoes are so explosive is that underground a few kilometers or so underground where you've got molten rock it can dissolve volcanic gases like carbon dioxide and water to quite large amounts so it's the same as basically what happens when you make fizzy water or champagne you're dissolving carbon dioxide in a liquid under pressure and when we relieve the pressure of course the the bubbles come out and if they come out if there's a lot of the gases dissolved in the liquid then we get an explosive flow so in a volcano typically we've got about five percent water water's the main propellant or ingredient and it's dissolved a few kilometers under the earth molten rock dissolves of something like five percent water if that magma comes to the Earth's surface as it did in Mount Saint Helens versus 1980 it expands dramatically the water comes out forms bubbles and the bubbles of the gas expands by about a thousandfold very very rapidly and the result of that is a very high speed typically at going at one or two or 300 meters per second that Jets and fragments the magma into fine volcanic ash and that's what you see here in Mount st. Helens and this material is going up a high in the sky and that's what also happens in the super eruptions too now there's two things that again perhaps just to waiver comparison that's Mount st. Helens 1980 and as I mentioned already ten thousand cubic meters per second is what you're seeing here of the rate of eruption and so it erupted at about point two cubic kilometers over several hours so it's pretty impressive but if you saw from the previous slide it's a tiny little eruption compared to the biggest eruptions on earth now as to things that can happen when this stuff explodes into the atmosphere one is it lacks a bit like a bonfire or a factory chimney hot volcanic ash of hundreds and hundreds of degrees centigrade mixes up with cold air and heats the air and makes it expand as how a bomb for the the plume above a bonfire works or above a factory chimney you've got hot material which heats up the air and makes it go high and in a volcanic eruption there's so much material that it can go up to 20 30 40 kilometers height in case amounts and Helens it went up to nearly 20 kilometers high and it go and then spreads volcanic ash and dust and gases into the upper parts of the atmosphere the other thing that can happen is that it that that there can be so much ash that it jets out of the volcano but it doesn't really mix with enough air and it collapses and flows down the side of the instead flows down the side of the volcano or something we call a pyroclastic flow and this is the really definitely the thing you want to avoid if you're around a volcano because they are deadly they contribute about almost 40% of fatalities around Kanak eruptions so what I'd like to do is I'm going to show you a short film and I want to just take a little bit of a deviation away from the main theme by showing you a film of a number of films you can download these from the internet for free that we've produced by a Bristol by funding from the World Bank and what these films are designed to do is to tell the public who live around volcanoes what a pyroclastic flow one of these flows is like and why they shouldn't be anywhere near one when they happen it's only about a two and a half minute long film it's on YouTube and on Vimeo you can download all the films for free there's about sixty four of the films actually and I'm just showing you one but to tell you what a pyroclastic flow is like and you may recognize the voice it's dr. Ian Stewart from Plymouth University who often is the compare on the number of BBC science programs [Music] pyroclastic flows are one of the most deadly of volcanic hazards they are rapidly moving avalanches of hot rock dust and gas that flow down the sides of a volcano and into surrounding valleys it can climb up and over ridges and high ground they are dangerous because they flow much faster than a person can run and often faster than a car so for those in their path there's little chance of escape what makes them especially lethal and devastating is that they're extremely hot during the day they appear gray and ashy but at night they can be seen glowing red-hot they destroy and bomb anything in their way death or severe injury is certain for those caught by a pyroclastic flow there are two main ways pyroclastic flows before sometimes a volcano explodes and forms a fountain of hot pulverized rocking deaths that frost rapidly rises into the sky and it falls back forming pyroclastic flows which raise those sides of the volcano [Music] other times instead of an explosion sticky lava ugh a volcano and piles up around the site pyroclastic flows can then form by parts of the lava collapsing although pyroclastic flows normally move down valleys extremely hot fast-moving billowing clouds form above them which can spell out of Bali's this means that even people on high ground are not safe pyroclastic flows normally travel to distances of 5 to 10 kilometres from the volcanic summit but in the biggest eruptions we reach much more than 20 communities volcanoes that have interrupted for many decades or even centuries may appear peaceful but when they awaken the eruptions are often very loud and exclusive scientists can detect that a volcano is reawakening and are able to provide some warning and advice to evacuate which is the only protection from pyroclastic flows that I hope gives you some sort of idea about the phenomena that happened during volcanic explosions and I think from the film you can see you saw glimpses of material going up very high into the atmosphere and some material collapsing down over the volcano after what during the explosion and flowing down the sides of the volcano and that's what the pyroclastic flow is like now by comparison the pyroclastic flows that we've had in historical eruptions like I'll give you an example ad 79 which buried Pompeii Pompeii's buried under pyroclastic flow deposits and there are body casts that have been found there underneath the pyroclastic flow and those flows probably went about maybe 10 15 kilometers away from Vesuvius so it's quite a big eruptions but what happens in one of these much bigger eruptions and I'm going to give you the story of taupo in new zealand 180 ad and it's about the most violent eruption it's not the biggest in terms of magnitude but in terms of the intensity it's extraordinary if those of you have been to New Zealand so we'll know Lake tout the beautiful Lake Taupo on the North Island and this is the map of the pyroclastic flow which formed in the 180 ad eruption from Lake Taupo so Lake Taupo such a violent volcano that it never forms a great big peak like Fuji or for su vyas it just forms a depression a crater and that's what makes tappers another example of these of this and it's an extraordinary event you can see that it went from the scale that's 50 kilometers you can see it went almost 80 kilometers in all directions and you can see on this map that these are mountains in the North Island of New Zealand taupo lake tap itself is a depression and some of these mountains go up to about 1500 meters high this pyroclastic flow was moving so fast it flowed over these mountains and went on the other side and a colleague of mine from Wellington University Colin Wilson he estimates that this volcano erupted 15 cubic kilometers in 15 minutes and that's with is something like 20 million cubic meters per second so just an extraordinary leave violent event so if you imagine the film that collapsing explosion just imagine it on a gigantic scale that's what happened in taupo in 188 a.d if you superimpose that map on the centre of london if we if we run that fortunately britain doesn't have any active volcanoes but if taupo was in the middle of london this is how far the flow would have spread and it would have covered this area in something like 20 meters of volcanic hot volcanic ash and from the ability of the flow if you've got a flow which is going along and it meets an obstacle like a mountain or a building if it's going slowly it will flow round the building or round the mountain but if it's going very fast it'll flow over the mountain and that's what Colin did he mapped these out and he found bits of the deposits on top of the mountains to show they definitely got there and you can work out on a very simple energy balance but the flow speed must have been about 800 kilometres per hour so an absolutely extraordinary event so that's the most violent now of course it would be terrible news for any any local area if there's a big volcanic eruption clearly as local devastation from pyroclastic flows but the issue that's of greater concern if you like for us is the global pollution that eruptions of this kind can create and I'm going to give you the example of Mount Pinatubo Philippines and you might remember five cubic kilometer that it erupted five cubic kilometres and I told you that it was the one of the two biggest eruptions of the 20th century there's Mount Pinatubo and that red line here is the Philippines that's Luzon and there's Mount Pinatubo is down there and that gray object this is a space photograph is the cloud that formed from the eruption of Mount Pinatubo in 1991 on the 15th of June and at this stage it's something like 600 kilometers diameter so what's happened is it's put so much materials the atmosphere that is spreads almost like a gigantic hurricane and spreads out and forms a huge 600 kilometer diameter cloud a little bit later this is an infrared picture of this same cloud now it's got to about 800 kilometers diameter and the colors adjust the temperature at the hotter at the top of the cloud it's an infrared image but that the main thing to get out of this image really is just how huge these clouds are now within three weeks this is an image from a satellite of which detects sulfur dioxide so it's very normally there's very little sulfur dioxide in the atmosphere Ness we have a factory that's poor coal burning or something like that we get acid or a but in volcanoes do we also get colossal amounts of sulfur dioxide and the importance about this sulfur dioxide is that it reacts with water in the atmosphere and forms tiny little droplets of sulfuric acid that we call an aerosol and this image shows you a satellite picture of the earth and where it's all red around the creek equator that's detecting enormous amounts of sulfur dioxide that ring the earth within three weeks of this eruption so it had so it had a it spread around the equator and then over the next several months this pollution this sulfur dark side here reacted with water and formed softly big acid droplets in stratosphere and it spread all around the earth I should have mentioned by the way that this cloud got to 35 kilometers so well into the Earth's stratosphere so this is a stratospheric pollution event so that's pretty impressive let's now look at another example I'll come back to Pinatubo later it's one where we've actually got a lot of measurements we go back to 1850 eruption of Tambora in Indonesia we mentioned that that's 45 cubic kilometers and there are about 60,000 deaths directly from the pyroclastic flows and from famine and there's some archaeological sites very much like Pompeii around the volcano that have been excavated by indonesian archaeologists and they've found just like pompeii they found buried villages and the importance of this event at 45 cubic kilometers so it's much bigger than Pinatubo so it had a much much bigger global pollution event and 1816 one 1816 I should say was the year with called the year without a summer and let's just talk a little bit about the effects of this aerosol so here we've got the volcano we pump into the atmosphere enormous amounts of ash and the one I'm going to concentrate on is Sophia is sulphur dioxide and this reacts with water to form sulfuric acid and these tiny little droplets do two things one is that they scatter sunlight away from the earth so when we have one of these eruptions the earth gets basically covered in a mist of sulfuric acid and that bounces solar radiation away from the earth and generally everything cools down so big effects for then a few years after one of these big eruptions is global cooling it's often called a volcanic winter the other effect which is a bit more subtle but if we look at this diagram we can see this that this mist of pollution or in the stratosphere bounces some heat away but it'll also absorbs heat it stops the Rays getting to the Earth's surface so the near surface of the earth the atmosphere cools a lot but actually this region swarms a bit and this warming affects the circulation of the global atmosphere and I'll show you some of the effects of that a little bit later well let's go back to 1816 the Great Famine it's quite famous for as I say for being the year without the summer and some of you may know that Mary Shelley went to Geneva in this dark dismal summer of 1816 and was since I'm not sure with inspired was right the right word but wrote Franken to the famous book Frankenstein a sort of a very sinister Gothic thriller I guess and also another in terms of sort of arts Turner some of the the Turner painted some of his wonderful landscape sort of sunsets in this period because as you'll see later the pollution of this sulfuric acid produces magnificent sunsets for a year or two after eruption and that too inspired to turn in some of his paintings we can look at some of the quotes here in Lancashire Plain UK the coldest July in 192 years record this is Geneva Switzerland where Mary sure I guess with Switzerland where Mary Shelley was the coldest summer and in the period 1753 to 1960 in May in the USA in July ice froze as thick as window glass and in Ireland for the harvests entirely fell from the badness of the weather so those are a number of quotes around the world showing that this eruption that eruption Indonesia had truly global effects one of the really interesting stories about this is that if you know New England and the typical New England landscape in Connecticut or Massachusetts you probably didn't appreciate that that landscape was to some extent produced by this eruption because what happened was in in 1816 the farmers in New England started to plant their crops and then in May there was a snowstorms and Frost's in New England and the crops of course failed so then replanted the crops and then in July those are not more snow storms and Frost's and into August Salewa 'the a series of Frost's and snowstorms highly unusual in the in the middle of the summer in New England and the crop and basically thus the farmers many of the farmers escaped as attention migrated to the east their Bandhan their farms and if you go in the New England forest you'll see some old walls and things from the abandonment of the farm so it never really recovered they found much better farmland in the east so it led to a migration of farming communities in New England you can see the effect of this is in the u.s. of the of that crop failure this is the price of wheat in dollars it been ate in 1816 reaching about three times almost two or three times the if you like the sort of average so to led2 big food price hikes in Europe and in North America this is of course not a measurements but this is the temperature change global temperature change in 1816 or the early 19th century these are from Kuta model so they're not measurement they're not measurements but they're estimates and they're consistent with this kind of a politic observations and you'll see that the computers estimated something like between 1 and 2 degrees global cooling and that's quite a lot because you only need four degrees ku global cooling sustained and we'll have a nice a well of another Ice Age so one or two degrees cooling around the planets is actually quite a big deal okay well explain this map in a moment but just go back to Pinatubo 1991 it produced this global pollution effect and as I mentioned what happens is this sulfuric acid pollution gets into the stratosphere it gets heated and then it moves towards the poles and the sulfuric acid actually rains down in Antarctica and then in Greenland and North Pole because of a change of circulation so it's not just that as cooling there's a change brilliant very dramatic change to the way the earth the Earth's climate works on the weather that takes place after it and you can see here this these are maps of the summer after the Pinatubo eruption in June 1991 so it's in 1992 and you can see here is the observations temperature changes so this is basically if it's blue it means it's colder than average on the map if it's on orange II colors it means it's warmer than usual so you can see from this map this is what we actually observed a year after Mount Pinatubo and you can see that lots of places get definitely get colder quite a lot colder some and you'll see that the east coast of the United States gets three or four degrees cold up and or up into this part of camp and you can see this effect which must have affected people in New England in 1816 you can also see that there are some places which actually get a bit warmer so it's a bit of a mixed picture now these as I say these are the I should say the observations on the top so get warm zones and cold zones and these are the results of a model now the reason this is scientifically important is you probably know that the predictions of global warming are there's a lot of emphasis put on globe what's called global climate models you run the models to find out what the climates going to do over the next few decades with more and more carbon dioxide going into the atmosphere and so a volcanic eruption is a wonderful experiment on how these models perform so what they did after Penner tuba the climate scientists ran their model of the Earth's climate and they put in the pollution from Pinatubo to see what the model would predict and this is the model and that's the observations and although there's not a it's not exact you can see that overall the patterns that the global climate models that we put a lot of stock on in terms of predicting what's going to happen with global warming really worked rather well and that's scientifically why big volcanic eruptions are of huge interest not just to me as a volcanologist but to climate scientists so you can see these effects now there's something else that happened and it's a bit of a subtle one under again a graph this is something that's a very famous graph of the carbon dioxide content of the atmosphere against time from a measurements at in Hawaii this tells us how much carbon dioxide you can see back in 1960 we had about 320 poppers called parts per million or that's the concentration and we're about now we're approaching 400 so we've increased the amount of carbon dioxide in the Earth's atmosphere dramatically and you can see it going up and the this bumping around as seasonal effects but you can see it in except inexorably increasing and of course that's why people so many scientists are worried about global warming of these greenhouse gases going up inexorably but something very interesting happened at about the time of Pinatubo 1991 and if you look at this quite carefully which a number you can find that actually the rate at which the all of our fossil fuel burning that the co2 was going up in the in the Earth's atmosphere actually was about half normal in the two or three years after Pinatubo and it's written that this may have been there's a number of theories for this but the one of the best bets is that the volcanic ash from Pinatubo fell in the ocean it's got lots of nutrients and a lot of the bugs in the ocean like those nutrients they grow shells calcium carbonate shells in the ocean and they suck carbon dioxide out of the atmosphere so it's a possible explanation of something that happened after Mount Pinatubo so again it's another effect another one I won't illustrate but there was a that eruption also caused a no significant ozone hole over northern Europe in the following year again to do with the chemists the chemical pollution effects okay well what is going to happen to us if there's a super eruption and some colleagues are in the met office have done the same kind of calculations they've run their models of what would happen if Mount Toba eruption of the scale of Mount Toba happened again and it's not very encouraging I think it's best way of putting it this is the predicted temperature changes during the Northern Hemisphere summer and if you're look at these colors the darker the blue the colder it gets and if you look at this scale this area in the middle of the content of the of the continents would get down to minus 24 lower than normal so that would not be very good news for food production around the world there's an other interesting feature that I just want to draw your attention to is where would it be a good place to be if there was a super eruption and you'll see that Britain's not too bad and the reason for that is the this signal is much stronger in the interior of continents than it is next to the ocean or in the ocean because the ocean provides an ameliorating effect at war it stops it getting quite so cold because the oceans got a lot of heat and keeps things not quite so cold so we see that Britain is actually not a bad place to be if we look in the winter we get again one of these surprising results that actually the North Pole gets a lot normal warmer than normal and that's because of this the effects of this pollution the sir on the atmospheric circulation it's one of the things of course in the nineteenth 870s and 80s people were very worried about the same effect with a big nuclear war it would be the same effect but for rather different reasons it would be again a huge amount of pollution associated with could produce what's what was called a nuclear winter and a lot of scientists worked on that particularly in the sort of Cold War period okay let's now talk a little bit about how often these happen now to get how often these big events happen what you need to do is you crater a database you look at all the volcanoes that are erupted in this way and what we did at Bristol is we've created a if you like a record and inventory of all the volcanoes we know about and all the sizes of the eruption and we've got a database of about 1,900 records of very large eruptions from about 480 volcanoes now this is a bit of a scattergram but bear with me this is today and this is 10,000 years ago so this lower bit of the graph is 10,000 years of the last 10,000 years of Earth history and this upper axis is the eruption magnitude so remember six spin a tube over six-and-a-half Tambora seven and Tobi's way off the scale if you look at this record you'll see that the number of dots as you go back in time get less and that's because the geological record gets poorer as we go back in time we don't preserve such good records and we have to correct for that you'll notice that the bigger dots the bigger eruptions don't show such a big effect as the smaller eruptions because the bigger eruptions leave behind big craters that i've shown you and big thick ash deposits of volcanic ash so that we have a better record of the bigger ones than the smaller ones so what we do is I work with a statistician in Bristol Chuck called John T Roche and we essentially interrogate that data and produce something which is basically you've heard of the Richter scale for earthquakes the bigger the earthquake the less frequently it happens and we do the same for these volcanoes and so this is magnitude against what we call the return period or the the time that and when we do this analysis interruption like Tambora in 1815 happens we we think that roughly every 500 years and then if we want to look at how many times a super eruption will happen then it's every we get a number of abouts every 17,000 years it's not it's certainly not very accurate it could be quite a bit less or quite a bit more but it's something of the order of 20,000 years let's say so we don't have to worry too much about super eruptions at the moment our chances of you being personally involved in a super eruption why while you're on earth is probably well pretty low and remember twenty thousand years is sort of much more than recorded history so they're rare events on a human time scale okay so how can we get a better record and this is the last bit of last graph I'll show you is I mentioned that when you get this pollution the aerosol it the circulation in the earth takes the pollution and it dumps it on the poles and it dumps it in Antarctica which is very convenient because it then produces a beautiful record of volcanic activity on earth and if what you do is you go to Antarctica and you take a drill core and you get the ice out and inside the ice is the these little droplets of sulfuric acid from each eruption drop down and you can measure these they've created conductivity of the ice and so you can rep measure them and this is the last from a nice record in Antarctica this is the last two hundred thousand years of Earth history and every red spike is a very big eruption Tambora is somewhere about there so an eruption about Tambor is just about enough to get in this record and you can see going back 200,000 years there are some very big spikes and that fits in quite well with us our rough estimate that we are getting one of these we think one of these very big spikes is one of these super eruptions and we're trying to identify which ones and we can see that this idea of them happening every roughly 20,000 years seems to be borne out by the record and the Antarctic ice cores so the final discussion point is where's the next one going to be and so where would you go to find the next super eruption well you probably wouldn't go to the places that have all had one recently and this is Mount Mazama in Oregon and that's what it looked like before the eruption quite a big volcano and in six thousand seven hundred years it had a magnitude 7.3 so it's a bit bigger than Tambora something similar to Tambora and it's produced the famous crater lake in Oregon a very beautiful place to visit so what we would probably do is not think that crater lake was such a likely place we'd probably think we'd like to look for a volcano which look more like this what did the volcano look like before it had one of these really big eruptions so where would you go you'd go sue well at least we could go to Turkey which is not a place you'd probably think about volcanoes but we've got recently a collaborative grant with between the UK in the Turkish Science Foundation to study with Turkish colleagues the ten active volcanoes of Turkey which includes Ararat where supposedly Noah's Ark ended up the one that we've been working on we're going to work on all the Turkish volcanoes to assess their risk and it's surprising it turns out Turkey is a surprisingly high volcanic risk and that's what we're working with in our Turkish colleagues and during this project we found this volcano and I'll show perhaps just go back it's this yellow dot here is one called I just dug it lives near the city of Chi Sri here or it's a next door to the city of Chi Cerie and this is a volcano that we think from the geological record looks very like what a volcano looks like before it has one of these massive eruptions this is our team of Bristol University and a Geological Survey of Turkey colleagues on our jess's that went the highest peak and the highest peaks the middle east goes up to about 3700 meters it's an absolutely spectacular beautiful volcano and what we've been able to this is a photograph image of it from space it's a huge volcano just look at the scale this is 20 kilometers it's a gigantic strata volcano which has got a history that suggests that is brewing up for one of a very big eruption that red dot deadline is from an old caldera from a past very very large explosive eruption and what we've been able to find is BCE I and the summit are all really quite large eruptions which happened about seven or eight thousand years ago and we believe that those we interpret this as evidence that this volcano is far from a daughter extinct now the thing about Turkey is that the volcanic risk is not going up because the volcanoes becoming more active is going up because of population growth and this is one of the towns which was a literally a village of a couple of thousand people in the 1950s and it's now a town of a hundred thousand people it's built on very young pyroclastic float these all this mucky quarry stuff are the para clastic flow deposits which as a geologist I can recognize as pyroclastic flows and we found that these are erupted something like seven or eight thousand years ago and the new city or the town of Diwali is built on that but even more concerning is the town of Kai Suri I suspect if you asked where were the ten biggest fastest growing cities in on the earth at the moment I suspect almost everybody would think China was on that list and that's true about 410 of the five of the lot ten fastest-growing cities are Chinese cities three of them are in Turkey and so Turkey is going through prodigious urbanization and this is is a slope on the outer sides of that volcano and the town of Chi Surrey which was 50,000 people in 1950 is now 1.2 million people and the growth is 5 percent per year it's a very dramatic economic and social changes going on to set Turkey that's one of the biggest industrial estates in Turkey which is also built on pyroclastic flows from very recent eruptions and this is one of the favored areas for industrialization in Turkey because this is an area which at supports President Erdogan very strongly so they seem to have had a lot of benefits like large industrial estates and these are tower blocks each with a probably a couple of hundred people there that are going up on the plains this flat ground is actually very young pyroclastic flow deposits so they're building up basically on the same sort of stuff which got into Pompeii in AD 79 so we're seeing the volcanic risk going up very greatly and we're working with our Turkish colleagues to understand that and all so to start talking to authorities and citizens around the volcanoes about the in the basically what they would do were there to be a volcanic eruption or how they should plan for that so risk is pretty pretty high in this area okay so that's um I'll finish off with this nice watercolor of the Krakatoa in 1883 another very big eruption when the bigger the nineteenth century and some of the beautiful sunsets that were created by all that pollution and all to bring the lecture to an end now you

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Keywords: Gresham, Gresham College, Education, Lecture, Public, London, Debate, Academia, Knowledge, stephen sparks, volcanology, volcanoes, eruptions, super eruptions, University of Bristol, sinabung, volcanism, magnitude, tambora, pinatubo, toba, mount st helens, taupo, New Zealand, philipines, Indonesia, volcanic winter, great famine of 1816, mauna loa observatory, LaMEVE, ice core, caldera volcanoes, mount mazama, crater lake, turkey, erciyes dagi, deverli, pyroclastic flow, kayseri, W. Ashcroft, Krakatau

Id: 0hUVoAo2Lws

Length: 49min 36sec (2976 seconds)

Published: Tue Nov 27 2018