Professor Colin Wilson - The Life and Times of Supervolcanoes (2018)

at this point I'd like you to join with me and welcome professor Colin Wilson to his talk the life in times of super volcanoes what I would like to do during the course of this talk is to give you a snapshot and an overview of the sort of work that I've been doing over the years that I was very pleased to receive the Medal named after this gentleman behind me and tell you a little bit about the life and times of super volcanos and so there are four aspects about which I want to cover what is a supervolcano how the people like me study such events what have we learnt and where are we at at the moment in our understanding of them so to start off with a supervolcano is a volcano that's seen a super eruption okay what's a super eruption well this isn't in any of the Allyson Holst's recipe books at least so far as I have seen but you take 10 to the 15 kilograms of molten rock in one go of magma and you sling it out over the landscape and that's a very hard figure to envisage so I've tried to put it in more human human terms when it's fluffed up as pumice and ash as it inevitably is that's about three point seven meters of debris over the whole area of the country or its equivalent to about 350 Wellington harbours coming out in one go or it's enough to bury the super city under a kilometer of debris and for some reason that analog seems to get the most applause south of the Bombay Hills not sure why anyway so super-eruptions is ideal with them there are other types of major large-scale eruptions that have occurred during earth history which I'm not going to be dealing with but super eruptions inevitably involve what we call explosive activity the magma the molten rocket depth contains gases dissolved in it exactly the same way as the bottle of coke you buy from the dairy as gases dissolved in it and in exactly the same way when you take the lid off the bottle of coke and the gases froth the drink up and sometimes bring it out all over the kitchen this happens with volcanoes as well so this is narahari during its latest phase of activity I hasten to add I arrived in the country in 1978 and it has done nothing since and I am trying to work out who I apply to to get my money back because it's just not good enough so the materials emerge from the summit fragmented and shattered it's hot it mixes with the air and there are two fates for it one is to mix with enough air to heat the air to become buoyant just like a factory chimney plume like a hot-air balloon to rise to great heights really big eruptions it might go to 40 or 50 kilometers high this one is quite modest material that's too dense to rise in the air is forced to travel downwards sideways as a kind of liquid a pyroclastic flow or pyroclastic density currents so those are the two major styles of explosive activity and they give rise to two major kinds of deposit that are the sort of materials that I have studied in my work the high blue this is an example of the deposit from a hype room from ruapehu in 1996 covering postdoc colleagues car that's a ladder for those of you of vintage memory and the brown is not rust that's actually paint and you can see the ashes draped over the bonnet you can see the shadow of it on the ground so for deposits are very very widespread driven by the winds but very generally rather thin the flow deposits are controlled flow down so they're thicker they're less extensive but obviously can build up to great thicknesses 200 plus meters even in historic events and in particular the deposits that contain a lot of pumice frothed up very silica rich magma a called ignimbrite which is a very peculiarly New Zealand term coined by Patrick Marshall in the 1930s who was a professor at the University of Otago to describe the big eruptive units in the central North Island and this New Zealand world has actually now in the last 20 or 30 years conquered the world so even Americans use this term so how many super eruptions have we had well as you go back in time in geological history we start to lose detail so for the purposes of this talk I'm just going to restrict us to the last 2.6 million years which is what we call the quaternary period this is when we've had ice sheets at North and South Pole we've had the rhythms of glacials and interglacials so for geologists this is recent times and we've had 12 sorry 10 examples - in the US from Yellowstone of which Americans are inordinately proud and quite rightly so it's a splendid place and we've studied one of those in detail one from Eastern California at Long Valley there's one in the middle of godforsaken nowhere altiplano western Argentina that's very little study there's only been one series of works that Toba in Sumatra and the younger of the two that have come from Toba about 74,000 years ago is the great granddaddy of all of these ten probably around total of 5000 cubic kilometers of magma it's by far the biggest of them and then here we are dear little old New Zealand tucked away in the South Pacific at the bottom end of this structure the Tonga Kermadec arc where the Pacific plate subducts underneath the Australian plate we have four examples within the top of volcanic zone so we stand tall on a world scale and within New Zealand all the young or the potentially active volcanism is in the North Island there are a few hisses and boos from the South Islanders but I reassured them by the fact they have the Alpine Fault to play with so they're equally well off up here at these centres Auckland com'ere Bay of Islands there is erupted the least silica rich magma vessels black in color very fluid very runny there is Earl's of it pouring out of the Earth's surface at Kilauea at the moment the East rift eruptions over the last few months he must have seen pictures of his basalt and they're very nice volcanoes but nobody would really take any notice of them were it not for the fact that in their intelligence the Aucklanders have got the biggest city in the country smack on top active volcanic field if you add a bit more silica to your magmatic mix you create a rock called andesite it's a little more sticky a little more viscous more explosive events and often somewhat larger eruptions and with that you build magnificent cone volcanoes like tera na ki tongariro nara ho itself hikari this is the classical rock of up systems so who are there island is its own little private Idaho I won't go into that in any detail but then within this area of the toka volcanic zone that leads down from here we have this area outlined from Takano to corral at 120 kilometers long by 60 kilometers wide that is unique on earth it's about the same size as Yellowstone put out about three times as much magma that has slightly less geothermal activity at the present day and this zone is strange because by far the biggest volume of material thrown out is the most silica rich sticky magma we call rhyolite and because it's so sticky it's often gas-rich most of the eruptions are highly explosive liquid magma that you see often you know in the forming these combs here or forming lava close at Auckland is much subordinate so you don't build majestic cones you build dumpy lumpy mountains like Tarawera or herro herro or naga tahoe at Rotorua instead most of the material comes out fragmented is widespread and in the case of these volcanoes the biggest eruptions are so large that at the end of the eruption the magma chamber below the surface is drained the ground collapses in to form what we call a caldera so these are a strange in member kind of volcano called caldera volcanoes where basically they're just giant holes in the ground now in filled by more younger debris and of these caldera volcanoes these are the ones we've identified so far undoubtedly there are more they tend to cover their own tracks with their own debris and of these three of them manga Kino Fokker Maru and top row itself are the super volcanoes so the eruptions that define these super volcanoes there's four of them as I mentioned too from manga Kino which is long long inactive this one the younger titi you will actually have seen the products of this eruption whether you know it or not because this is a new era stone that's the deposits of this eruption and for some reason in all my travels doing geology and giving these talks I see it constantly forming the walls of banks and public lavatories for some reason or other it's the popular building stone for a lot of public buildings this one in here the kidnappers I'll show you a little bit of information about this later very few people know about it's not very obvious in the landscape but it's a massive eruption this one in here the FACA maru from the center here is biggest of them probably around two-and-a-half thousand cubic kilometer very very substantial most of the Waikato dam schemes are built on the rock from that particular eruption and then topo with near ruin or eruption at twenty-five and a half thousand years ago is the youngest and this is the youngest super eruption on planet Earth so we're up there with the best and so along with the spectrum of volcanoes there's a spectrum of volcanologists I just want to show you two in member types here there's the gung-ho types and yeah they're valuable do you go in you're observing you're collecting material and informing us about what's going on at the present day and the gung-ho of the gung-ho with this couple Morris and Katia craft and their work their films they went to places I don't actually give a stuff about the health and safety at Work Act I know what I'm comfortable with in terms of health and safety in the job I do they went way beyond my comfort zone many times and collected movies and films but they're louvers and films convinced people to evacuate from volcanoes when eruptions were threatening and between them they've saved probably thousands to tens of thousands of lives so the work is not without its value but it's not without its perils and in 1991 this volcano in Japan was erupting a magma that's a bit more sticky than andesite but not quite up to rhyolite it's called a site it was putting out liquid magma at the surface to produce a dome that was then collapsing to produce pyroclastic flows that came down and the crafts were there to do their filming I just want to show you a little bit of footage pillaged from a documentary with the sound killed to show you here's the dome collapsing and instead of tumbling down as just big blocks of rock it breaks up it's hot it's gas charged and so it breaks up into a material that's capable of flowing like a liquid down the stream valley with the dust cloud coming off it that's a small one in there this is a bigger one I hope you noticed the lurch on the camera as the operator somehow let go and seems to run away I'm not quite sure the steadiness of the camera suggests no one was behind it at this point and so you see that air it's heated the air and the mesh tire has taken off up into the atmosphere and it leaves behind the deposit landscape and the sad thing was that underneath there were the crafts another volcanologists called Harry Glickman and forty Japanese journalists and civil defense workers there they had misjudged what the volcano was capable of doing and so there is a second type of volcanologist to which i'm a card-carrying member cruel people call this the school of the cunning cowards we go in afterwards we go in after the eruptions to see what has happened and try and reconstruct what's happened and build the forensics of eruptions because there's basically a very limited range of eruptions you can watch and survive and certainly for every super eruption and even most explosive eruptions if you're close enough to the vent to watch the action your life is in imminent peril and this is not a good mode of career advancements at least not so far as I'm concerned and my own experience of the fewer options I have watched is that you're not sitting there with your notebook taking nice detailed notes and observations and measurements you're just sitting there with your mouth open going Wow trust me it's like that and the third point here is that the sort of magma that creates super eruptions and super volcanoes produce this rhyolite magma a very sticky silica rich magma it's actually quite rare in historic events you can't just phone home and say oh sorry dear can you put the tea in the oven there's a rhyolite eruption going on down the road I'm just off to have a look at it no in the last 150 years we've only had four examples on planet Earth strange as it may sound this one up here the biggest of them 1912 novarupta in Alaska spent many weeks up there working on this eruption trying to link the scanty eyewitness accounts with what you see on the ground to ground truth what our geology knowledge tells us with what we can actually limit and block out with human observations the other three examples this little one in Papua New Guinea is virtually unknown and unstudied and then two more recent ones in Chile have been extensively studied including by people out there they're relatively small in volume but we've learned an enormous amount about the dynamics of how such eruptions operate so we have a limited amount of eyewitness material that we can link to our geological observations and go in afterwards and make sense of things but when you start working on the deposits of super eruptions or even intermediate sized eruptions you start to realize that you're dealing with another whole world that the deposits from these eruptions so that's the bishop tuff that's the one from Long Valley 150 meters of material this is the huckleberry Ridge tuff both of these have studied a lot you start to get to grips with eruptions that are just orders of magnitude bigger to give you some example the largest historic eruption that we know of in the last sort of five hundred to a thousand years is Tambora in 1815 in Indonesia if repeated today it would devastate a large part of the Indonesian economy the biggest super eruption we know of only seven four thousand years ago is a hundred times bigger than that so my colleagues up the hill who study earthquakes Iraq them I say you've got it easy guys because even in my lifetime we've seen earthquakes around the world Japan in 2011 was the latest example that are just about as big as any you can get on earth short of a major meteorite impact or something like that the Earth's crust its outer brittle shell simply isn't strong enough to maintain the stresses that would produce earthquakes much bigger than we've seen in the last few decades so with earthquakes you're working within a known range of parameters when you're trying to understand their hazards and how to mitigate them with these events know you're thrown onto another world and to give you an idea of that I want to show you a series of images to give you an idea of the scale of what the big eruptions are like so here's narahari again there's the flows the tip of them there I like to take the students there and say Majan you're there watching that come towards you what would you have done half of them say I think it'd have been quite safe I promise you you'd of being safe tiny million cubic meters you can envisage a million cubic meters it's not that bad this is another scale up this is Mount st. Helens in 1980 beautiful symmetrical cone there was an intrusion of andesite inside that cone mulched the side out it was an earthquake the side of the cone fell away so what you see there in the dust is actually two and a half cubic kilometers of mountain heading downhill at high speed and the magma inside the volcano bursts out is this directed blast event that knocked out about 600 square kilometres in a few minutes killed 57 people and that's what it does to mature Douglas fir forests that's what it does to meet a diameter Douglas fir trees that's starting to look quite impressive but it's only about 1/10 of a cubic kilometer of magma you move up a scale come back to New Zealand and this is the area of prime North Island real-estate knocked out by the pair elastic flow at the height of the latest explosive eruption from tawa about 20,000 square kilometers taken out in approximately 10 minutes little by the way the flow went through two rang at about 250 meters per second we can work that out from the height of the mountains it climbed all around the area that's around 30 cubic kilometers of pumice ash you move up another notch to the kidnappers eruption the fall deposit is immense it goes out to mid tasman sea goes out three four thousand kilometers into the Pacific but the flow deposits are amongst the most widespread on the planet - named after cape kidnappers here but it fell into the sea at Gisborne a poder key there's 12 meters of it underneath the Tauranga harbour oh and at South Auckland if you go to the golf club but why you coupe and look across you'll see cliffs five meters of England right from this eruption on the source area yes they drilled this back in the early 2000s for geothermal energy didn't get anywhere because three kilometres below the surface they still weren't out of the deposits of this eruption 1.8 kilometers thickness material from this eruption in the hole left behind you then go up another notch into the really big ones this is the huckleberry Ridge tuff a magnificent beast of a huge challenge i've ground myself to a halt studying it so I have to now write all this stuff up the full deposit one of three super eruptions in the western US that area that they've marked on is the obvious full material about 10 to 15 centimetres thickness enough to bring your house roof down over one to two million square kilometers the flow deposits not quite so widespread but still immense 150 metres thick down here the hole left behind 90 nice sixty kilometers and in the oil wells of Louisiana coast here sixty meters of material that's been reworked five thousand kilometres down the river systems draining the area that's big my I think it's safe to say this if repeated will cause more damage to the US economy and Donald Trump is going to do I think and so how do we get to grips with these things these are events really beyond imagination even for people like me who are familiar with them it's very hard to get your brain around them and so this is a personalized approach others will use other systems but in essence my approach is divided into two parts above-ground reconstructing these eruptions if you can see them erupting you're gonna die therefore everything is based on what you can pick out afterwards using physical methods using observations to build up the picture of the eruption and how it went about its business and then by collecting material from the different deposits I want to get to grips with what lay beneath at that time in what we call the magma chamber and one of the things that has come out of work done on large eruptions over the last twenty to thirty years is a general consensus that the magma bodies that drive rhyolite eruptions like these ones most of that body consists of material called mush and if please when the weather warms up you go down the dairy and you see those big tanks full of slush crystals with the paddles going through them that's ice water mush these are crystal melt much much more viscous they don't generally erupt they're too sticky to gas-poor but they are kept hot and stirred by less silica rich magnus coming in from below and passing the heat on and then every now and again something triggers the melt held in the mush to accumulate into what we ruptal magma or a melt dominant body and it's this material colored yellow here that's what actually feeds the eruptions so what we try and do is by sampling that material is get to grips with the processes the timings that go on down in here prior to past eruptions so in the physical sense you all can do forensic Volcanology it's actually startlingly easy to do you just need my mentor George Walker managed for his whole career with a notebook a tape measure a spade a scraper and a car and created whole new worlds for people in understanding and what it tells you is that it's not uniform there still is a perception that the bigger the eruption that bigger the bang you know little ones just cuts away but the big ones lay wastes of the countryside and you probably have seen that Yellowstone movie where you know people are screaming and there's this cloud coming it's actually much more interesting than that the fact you have layers tell you the eruption is not uniform something else is controlling the eruption it's not down to sheer size there are other things going on the size of the particles changes from coarser to finer it tells you it's fluctuating what's causing that fluctuation that's the story within a single eruption and each eruption is different and tells the different stories like a book go down the Wellington library and just pokum pull the book out at random they're all books but they're all different they're all telling different things when you start to look at the longer term and you include radiocarbon dating what you find is the history of volcanoes like topo a built up of these long periods of boredom during which time soils form trees grow humanity does it stuff interspersed with these periods of pure terror which are eruptions themselves so each eruption tells a story and then the stack of eruptions tells a story and in particular topo yes you can see long time breaks evidence by better form soils supported by radiocarbon dating but here's two eruptions c and d from different vents different chemistry's the field geology tells you that they're different eruptions yet between them is just this dusting of pink of windblown dust and a little bit of disturbance by tree some vegetation growing back up through the older eruption before the second one came in that's probably around 10 to 20 years but most now to put it in human analogues if I told you you're going to win the lottery in 1,200 years time you just blank thank you if I said you were going to win the lottery in ten years time when your ears perk up and you think oh maybe we can afford that nice boat maybe we can afford this this is the message is that when you look at the histories of volcanoes like topo you start to see that the volcano isn't this thing that's long dead and screams into life then goes dead for thousands of years it can react and revive itself what time scale sort of direct interest is humanity the order of years two decades and so you build up the picture at topo and you sample the material through so each eruption has its own story of uniformity or diversity and the composition of what's erupted and then by working through time you can build up a picture of how the volcano itself is behaving through time and so we collect pumice lots of pumice my department manager and senior technical manager roll their eyes when they remind me of how much material I have stored in nicks Avenue but this stuff is to me is wonderful because I can just sit there and look at it and it tells me stories it tells me physical store is how the pumice and the crystals are dispersed these are pictures these are thin sections of pieces of pumice the white is the glass the black is the bubbles the shape the size the number of the bubbles tells you a huge amount of information about the dynamics of how that little tiny chunk of magma came to the surface that we can build into pictures of the rates of magma rise the explosiveness of the eruption and all the dynamics going on in an area where you cannot possibly even today put any observation or equipment it will be destroyed so there's physical methods that we can use this lump here is one of my favorite pieces of pumice because it reminds me of that gorgeous vanilla and chocolate ice cream you know ripple ice cream so our vanilla is good quality rhyolite 74% silica with crystals in it that we can study 70% cocoa fineness lint swiss chocolate is 58% silicones it mingled in here and up here is the milk chocolate with hokey-pokey pieces which are crystals growing in it three magnets completely different origins yet here they are come together in a piece of pumice you can hold in your hand there are stories there that's another whole sequence of lectures won't go into but it's to show you that by looking at the chemistry of the material as well as its physical characteristics we build up a picture but to do chemistry you need equipment you enter the realm anyone here doing industrial design or thinking of getting into industrial design please if you do can you work on these people I'm sick of beige and gray equipment I want colorful equipment it's boring being in the lab a lot of the time so these are four pieces of kit that we've used very extensively in the work electron microprobe this tells us about the major composition of our crystals or our melts are frozen melt down to a spot size of two microns so we can really get into detail inside those premises inside those crystals that tells us about the major element this thing here this is a laser quite a fancy one better than the one they tried to do James Bond in with that blasts a 50 micron wide by 20 micron deep hole in your mineral or your glass takes the material puts it through the black box on the right and that will give you the concentration of every element from lithium to uranium with the exception of a few in about two minutes so you can look at the trace elements they're tiny small amounts of elements to a scale of 50 microns the scanning electron microscope we use this to take pictures of the minerals in what's called cathode or luminescence you shine an electron beam at your mineral and certain minerals particularly zircon which is the one we've used a lot of the light comes off it it's very very weak you wouldn't be able to see it yourself but you can detect it magnified to produce pictures of the textures and structures inciting mineral and in particular this gargantuan machine I'd love to have one of these but I don't think the Provos would come up with five million us and three full-time staff positions to support it with this we analyzed our cans and this uses instead of electrons this uses ionized oxygen to chip away at your sample instead of blasting a hole like a laser this caresses it 30 microns across 2 microns deep in about 20 minutes and what you can do is so stupendous you can measure the isotopes of a huge range of elements including uranium and lead to date the mineral as first pointed out or this gentleman and so we take this toolkit that we have available to us and we apply it to the minerals and the glass within the rock I want to show you what we've done with the ruin or eruption there is another four minerals that I could have talked about but a the talk will go so long Robin would hustle me off the stage and be I've got to try and persuade somebody at least to come up to Vic and study the stuff in some more detail so this is the picture we get off the scanning electron microscope this is cathode a luminescence of zircon tiny crystals barely see them in the palm of your hand but they have enormous ly complex and rich histories and with these we can date them because they soak up the rhenium and thorium which are radioactive minerals and decay eventually to lead we can measure these with the ion microprobe and work out the age of the crystals quite stunning degrees of precision when considering you know what's in there this one in here is actually one of my favorites it's not a mineral you charge off down to the rock and gems show and say I want author peroxy and give it to me now it's a very dull mineral for most purposes but when you slice it through it has a lot of history to it in the Illinois events and the crystals 90% of the crystals have two parts to them separated by that red line the inner part we can analyze and find that that must have come from the deep mush part of our Magnus system the outer part from its composition and zonation and the fact it's got glass all around it grew in that melt dominant erupt ibadi so the red line represents an event in the history of that crystal when it's height from depth in the mush along with the melt to start to build the melt dominant body if we take pictures using our electron microprobe in different elements if we use aluminium you can see the picture of that is fuzzy you can see the detail that we can pick up in normal light if we take the picture in magnesium it reminds me of color TV in the 70s when I was a kid it's all blurry and slightly wonky colors the blurriness is because magnesium has moved in the crystal structure if we know the temperature at which the crystals held which can estimate we can work out the time of when that crystal and others will hiked out of its nice cozy little nest deep in the crust and spat into a melt dominant body ready to go all over the landscape plugger Clay's a very common mineral shows the same thing a core that's experience unhappiness and then a rim and here you can actually see the growth sounds exactly like tree rings probably not annual but not far off and the darker to lighter shade tells you you can trace the way in which your erupt will melt body is changing in composition and temperature with time until the point when it's quenched by the eruption and then finally these funny little blobs in here are not gas bubbles they're melt bubbles they're melts trapped by growth of quartz and in doing so that traps in all the volatile phases the water the carbon dioxide the fluorine the chlorine the sulfur that were dissolved at depth and holds them in all through the eruption process we can measure their abundances and then work out of what depth those inclusions were trapped so we can work out where in the crust this melt dominant body where the crystals group was actually accumulating so each mineral gives us a slightly different facet of the overall story and the overall story embarrassing to say is that every one of the six super eruptions have studied plus all the smaller ones we've studied they're all different in the same all of you I take it are human you have a head two arms two legs but every one of you is different and unique the same is true for volcanic eruptions the size isn't everything in volcanic eruption so if we go back to above-ground to the layering that we saw in the Aurora no eruption by looking at this site and many hundreds of others through the central North Island we build up a picture that says these gradients represent time breaks and in particular this one down here the first layer is this pale colored one and you can see here the bugs something has burrowed it into the soil it's missing at a number of locations this indicates a time break of the order of probably three to six months not years because the deposits still preserved and the nearest data logger I can give you which in Auckland is a very painful one is to imagine the eruption has started and then a little man with a clipboard comes up and says excuse me do you have resource consent for this eruption oops I've got resource consent no we don't have good resource and said okay let's get resource consent and in Auckland the laughter is bitter because getting resource consent in three to six months is nigh on impossible but the point is made something is controlling this something is saying hang on you might have 530 cubic kilometers of magma gas charge 700 mm how much eighty centigrade but stop what is that that could be find out and the extremer of this and the two examples have studied in the u.s. one the bishop tuff as far as the geological evidence allows it looks like it started and finished within the space of about a week no mucking around no hesitancy just go on the other hand the huckleberry Ridge tuff in total occupied probably around 30 years three major spasms separated pair them by months another pair by decades but just imagine this how would you plan for this how would you forecast this in advance how do you get to grips with these things behaving in such a diverse way with your own eye we found the clue and the clue comes in the deposits which is all we have to go on so here's the first full deposit second third so these there's ten phases in total and a nail and I went through and we saw all this material for an analysis and we found that most of the material colored green here was of a composition had minerals in exactly the same as pumice you find all the way through the rest of the eruption so that's the main magma but then we found a small percentage of what I've colored in blue here and you could see it in the field it's different it's got different minerals in different characteristics the fieldwork tells you has to have come from the same vent at the same time as the green magma but it's foreign where's it come from it appears to have come from up here because identical magma has erupted at the surface on three occasions up here and the magma system below here is probably what's fueling the whole war Akito hara geothermal system at the present days this is still a live system will be it not highly active and it looks at the time of the eruption as though magma from this system decided to go on a holiday back to its barracks and went 10 to 15 kilometres along to erupt from the rule no event starting up here at the north end of the lake the only way we can explain this is if we take recognition of the setting which is a rift setting the Earth's crust is pulling apart in this area on average about 8 to 10 millimeters a year and at the time of this eruption it looks as though there was a major rifting event that both open the vent up for the green magma that underlay this whole area and allowed the blue magma to come trucking in and join in the fun the stress is then reversed shut the thing off shut off both systems there's then a time break the stresses have to build back up again and then the eruption resumes after that break of several months again magma can come in and then it jumps over to this eastern side and then we lose the detail because the whole area where the lake is now is starting to break up and vent so what this tells us is that you may have 530 cubic kilometers of magma you may be at 70 780 centigrade and full of gas but the tectonics the external stresses around the volcano control you it's really quite alarming for a volcanologist to have to get to grips again with structural geology but we have to and the point is that it's yes we monitor the volcanoes but it's not just the volcanoes we should be monitoring it's the setting it's the context of the volcanoes is equally important and the suspicion is that a lot of eruptions not just supervolcano ones with modest to medium size the same controls are there it's just that here because of the freak presence of that foreign magma we can pick the process up and see it happening and this idea that tectonics has a control is seen on a bigger scale on a longer time scale here's the history of eruptions from Oak attina up here and topo and Mara which is the area just to the north down here and for example at one stage a katana was putting out a big batch of eruptions this thing called the mango nee subgroup big pumice eruptions a repeat of the bigger ones of these would put a big dent in any government spending plans at that time topo was deathly quiet there's a magnificent soil a long long period of border going on down there there's then a couple of little minor hiccups and then the big one by big I mean look at the scale this is six times bigger than everything else on that diagram put together oh Katina doesn't do anything at that time that we can pick up in the geological record but it changes personality this is your wild teenager tearing up and down the road and souped-up cars this is your stay at home at five pipe and slippers family married man the eruptions are much more uniform in size one of the features that anybody who knows the areas a lot of it has come out to produce these mountains Hera Hera Mara tere dome and Terra where are particularly so a lot more liquid magma reaching the surface so somehow these two volcanoes on a geological timescale are talking to each other not sure whether it's with skinny or two degrees or spark but they talk so somehow between the two of them they are linked the only way they can be linked is tectonic Li and for this reason we in the work we're doing now are considering basically this whole area not as a single supervolcano but as a supervolcano system because it's clear that things don't happen independently the other message from this and it's very pertinent to the sky behind me here is that a super eruption defines a super volcano as a Nobel Prize to find that guy's career but it doesn't limit what you can do and one of the things that I want to come back to with topo in particular it's just how enormous lis diverse the eruptions are tiny little beasts that we barely have a record of interspersed with super eruption what's going on here to come back to that a ruiner event this is what our crystals tell us we date these circles we can work out that the overall magma system that underground chamber of mush and material came together in the form which eventually gave rise to the eruption about 80 to a hundred thousand years before the eruption no great surprises there but what are boring but beautiful orthopyroxene tell us is that that event the redline event when the magma is being hiked out of its deep roots and accumulated in the reservoir ready to go rampant over the landscape took at most 600 years most of it inside a hundred years at its height the volume of molten rock the size of narahari is being shifted to shallow depths every year I'm sure that if that were to be repeated today we would pick it up we would notice but there's no record of past information that we have the feldspar complements that so actually that little lump in there is a piece of great Waikiki that's had a very long and exciting history and come up to the surface but what the plagioclase tells us which is equally startling is that that melt dominant body that huge body was actually cooling quite rapidly but something of the order of between a tenth and a half a degree centigrade a year which doesn't sound like very much but what it means is that within one to two thousand years you'd have lost that body there would have been no super eruption and this is quite scary because what it says to us is that this volcano is generating these melt dominant bodies and probably doing it regularly but not all of them form eruptions you have to have a marriage between tectonics and the volcano you have to have the bed made ready the pillows there the chocolate on the pillow if the tectonics isn't in the mood nothing will happen the maca will cool off astonishingly fast because all the heats being sucked out by hydrothermal systems if the volcano sorry if yea the volcanoes in the mood the tectonics not it just goes back if the tectonics isn't hey let's let's go and the volcanoes is not tonight I have a headache then nothing will happen it's got to be a marriage between the two if we could understand how the two get on we would get a lot further and the final thing is that the melting Cluj UNS tell us that that huge body of magma was only about three and a half to six kilometers below the surface the big drill rigs that are used for the geothermal systems at the present day will go to 3.2 kilometers you can bring in a rig that will go deeper it's a bit more expensive but you could have drilled into this thing in principle so this is a cartoon although it's a complex cartoon for general audience it's a simplification for geological audience so I hope you'll forgive the garish colors in essence what some controlling features one is that the greywacke only goes to about fifteen or sixteen kilometers depth so if we get evidence of greywacke being involved we know what levels in the crust we're dealing with the system is fueled by basalt in vast quantities that's the primary magma coming up from depth coming up from the subduction zone but basalt is denser than greywacke so it's forced to pond and stop hand on its heat to evolve to become more solicit less dense before it can rise further into the crust so there's a zone ation here whereby you get silica rich raya lights up here and the bath salts will track down here so this is like a car factory down here is all the steel the aluminium the glass the plastics coming in preferably tariff-free up here is your brand new BMW series 7 could pay ready to hit the road the big challenge for us which is what we're tackling now is to understand what goes on in that volume there and how it operates and how you can get such a stylish Irate of magmatic production going on here's our trappin factory for those with long memories of East Europe in 1988 or 89 when the wall came down and trappings became hot property Odle system just working away here that joined in the fun it's derived with the BMW so we can build up quite detailed quite complex pictures of the past behavior of these magmatic systems is the where it really gets challenging is the present day there's toka volcano beautiful place love it up there so the obvious questions I'm asked every time I give talks up there okay when's the next direction got to be how big is it going to be what's going to happen and here's the challenge and it's a challenge everybody has to share the geological record since zero no event is that there are 28 eruptions there may be a few more maybe a few less but there's many many eruptions some of them absolutely tiny I cheerfully go up there and drink a gin and tonic in a deserted bar somewhere watch the whole thing go off there's one or two others that have big enough that you just say bye and you're gone like 232 ad and so how do you forecast this if you treat the magma the system as a strong magma chamber the idea is it's like pumping up a rugby ball you pump it up and you pump it up and then when it finally ruptures the longer you pump for the bigger the bang but you should see a relationship between the size of the eruption and what we call the repose period the period of boredom before the eruption there is no such relationship if you deal with the period after the eruption it's like a system you've flushed it it's the time taken to refill the system again no relationship how do we deal with this that's a real challenge so at the present day the studies of past events and in particular this was work Simon Barca did words me as a student this is the area encompassed by the vents for the last twenty five thousand years as the geology allows you to say this is actually the collapse area for the 232 Airedale eruption and these are the vents that have been active in the last two-and-a-half thousand years and this is the modern system so our mineral work suggests a vertical dimension here our vent positions suggest a horizontal dimension so at the moment there's something between 200 and a thousand cubic kilometers of mush that Lake losing heat at 200 megawatts through or a McCain Geary's every now and again it accumulates a body of melt dominant material uniform composition so it's a repetitive thing and the strong suspicion we have is that it's generating these melt dominant bodies much more frequently than we see as eruptions again basalt they're the filtering the solicit systems here our northeast dome system is still potentially active as well and a topo every few years two decades there's a bit of unrest and on average and this is not a reliable figure to predict every thousand years in eruption what does this mean what's going on and Sally Potter at G&S has made a study of the unrest events at Topal I don't necessarily agree with some of her conclusions about the causes that's part of what work we're going to try and do over the next few years but in essence the volcano is like your partner in bed you go to sleep at half 10 you get up at half 6:00 is it quiet no they snore roll over they pull the duvet off you they put cold feet on you the volcanoes do exactly the same thing there's periods of inactivity nothing happening and see four decades at a time there's minor unrest this earthquakes was up to moderate unrest and she's labeled this as moderate unrest I'm not sure at the time you'd have agreed with this assessment because over a period of several months in 1922-23 the area on the north side of the lake misses at for Kaipo bag for those of you know the place dropped by three point seven meters relative to lake level and one event this was a Department of Internal Affairs fishing lodge and the on in one of the events the caretaker parent it was looking out of the window towards the lake of watching it rise towards him he was dropping two meters in one go down towards the lake how would we react to that nowadays is it tectonic or is it magmatic how could we tell how do we get to grips with this who's putting the chocolate on the pillow that's what I want to know that's what everybody wants to know in the future so at the moment we have this big project started up which is designed to try and get to grips through this challenge my work is very much at the hard core geological end we have social scientists we have eerie representatives on because part of the problem with topo is the perception is a supervolcano it's gonna erupt panic yeah there need not be panic the chances of eruption are small but we have to understand unrest and we have to get to grips with what the magma is doing now that's geophysics what processes happen during unrest episodes how do we get to grips with these snoring's these turning overs these pulling the do they are I'm particularly interested in this question every eruption will have had a period of unrest assured of that well they will not come without warning but not every period of unrest results in eruption okay where's the tipping point where's the point of which you push that big red button to civil defense to Regional Council's to government and say it's gonna go and how much time do you have once you've made your mind up do you have an hour ten hours ten years we don't know because we don't know the processes so there's a whole bunch of things going on there and it's I hope there'll be the chance for some new public talks about the work we we're trying to bring out of this so anyway I am just the front person for a whole bunch of people family yeah Thank You colleagues student colleagues the funding and support agencies over the years landowners particularly a way around like torpor and of course the sponsors for the tour this this has been quite a journey over the last seven eight weeks so you're number 22 on list and 23 by popular demand from the Royal Society 24 by popular demand from my support team in the department are we can't be bothered to register would you give the talk up here okay so this back to go I hope you've learned a little bit about what I do I hope you've understood that there's still enormous challenges to come but it's an exciting area to work in it's a fun area to work in so thank you [Applause]

Channel: RoyalSocietyNZ

Views: 5,122

Rating: 4.7802196 out of 5

Keywords: New Zealand, NZ, volcano, volcanoes, supervolcano, supervolcanoes, science, geology, eruption, Taupo, natural hazards, fire & emergency, Royal Society NZ, Royal Society Te Apārangi, GNS Science, EQC, Victoria University of Wellington

Id: sl0vPnmTBUU

Length: 57min 46sec (3466 seconds)

Published: Fri Oct 05 2018