EGU GIFT2017: Living in a caldera: The case of Campi Flegrei, Italy

thanks a lot and good morning everybody and I wish to thank Carlo for giving me the opportunity to talk to you today on volcanoes in fact it would be impossible to talk about the Mediterranean region without talking about the volcanoes in the Mediterranean region and among the many volcanoes we have campi Flegrei in Italy the one that is giving us more concerns and we'll see why and we'll see the magnitudes of the concern that can't be for a gave us today and we will also see something of the some of the activities that we do in order to deal with that and we will conclude that it's much more what we don't know with respect to what we know unfortunately yes so this way yeah okay first of all calderas what is a caldera it is a volcanic structure which is definitely different from stratovolcanoes stratovolcanoes is the kind of volcanoes we are used to think at when we talk about volcanoes if you ask your baby or kids to draw a volcano it will do probably something like these but this is just one kind one type of volcanoes there are also calderas which are very different in shape calderas are characterized by large depressions quite often filled with lakes or if the volcano is in the sea the sea can invade the depression and we can have an island like in Santorini in Greece which is a remnant of the borders of the caldera and what see was the formation was the dynamics of formation of calderas caldera they form after large eruptions in fact calderas they mark the largest eruptions ever cured on earth so calderas are the place where large eruptions did occur in the past and when you have a large eruption like this one you can have there the magma which is sitting somewhere inside the crust is brought out of the system very fast and if that's too fast the system cannot react we liberate and it collapses down there is a significant pressure decrease here so that all the system collapses down when that happens huge materials of materials are erupted in a short time and that gives origin to what we call the ink memorize eruption evening Brady corruptions which again are the largest eruptions we know on earth and after that the system is like this one there is a large depression quite often in China new eruptions occur from this place so the depression can be partly or completely filled with new volcanic material or it can have a lake like in these are the case here because volcanic ash are impermeable they don't allow the water to go away and so they produce an impermeable layer where the water can accumulate producing a lake the best way calderas form and if we look at caldera this is a example of campi Flegrei we can see here the ring like structure of the of campi Flegrei following the collapse of the structure and many other here many other craters and smaller calderas marking the activity occurred after the lodge caldera-forming eruption after the eruption that produced this depression here we have many many other eruptions which partly fill the caldera depression while the other parts are incomplete the gray is under the sea and that's the case for Yellowstone which is also Nava calderas caldera and the size of caldera can be very variable at camp if regard we are the round 12 kilometers in diameter but we can go up to 50 or even more largest caldera we know our family 80 kilometers in diameter so they are really huge very big structure and if you because they are so large if you if you walk in a caldera you might not have the impression that you are inside a volcano but that's where you are those people there they live in beautiful places this is comfy for a Naples but they shoot and partly they are aware that they live inside the volcano not close on the to the volcano not on the volcano they live inside the volcano and that's the case for Yellowstone which is a very nice very beautiful environment but still if you walk here and there you see the signs that this is actually a volcano the vasila solfatara crater in campi Flegrei which is characterized by very large flows of bullet of gasses coming from the from the magma which is still sitting below campi Flegrei and it is the very famous Old Faithful geyser in Yellowstone which is also produced by the heat due to the magma which is below the system okay so just to have an idea how big are the eruptions which form calderas here we have the companion ignimbrite eruption in campi Flegrei which formed because there are about 39,000 years ago 39,000 years ago might seem a lot but in geological terms it's more like like seeing a few hours ago so it's really now and we have here some or some some events that may happen like landslides tornado this is the ear Ashima bomb and this is the energy which is expressed in terms of tones of T and T okay so this is about 10 between 10,000 to 100,000 tons of tnt and this is the eruption of mountain talents which was relatively small eruption and here we we are at 10,000,000 to 100,000,000 so it's 1,000 times larger than one year Ashima Bob and fishing forget to the companion ignimbrite eruption we are what another 1000 times larger than that 10 billions to 100 billions tons of TNT equivalent so this is 1000 times larger than the Year assume a bomb and it is 1 million times larger than the Euro scheme abomb an eruption like that one produces energy which is as large as the impact with an asteroid so the only fact is that the impact with an asteroid is a recurrence of 100,000 years while caldera-forming eruption are more frequent than that on earth it is just to give you an idea in terms of volumes erupted these are the volumes of the product from the largest historical eruptions ok so the largest historical eruption is a Tambora eruption in Indonesia in 1815 50 cubic kilometers of magma and we can go down here we have some of the most famous eruption here this is the Vesuvius eruption in Italy in 79 BC which produced which killed about five thousand people in Pompeii and gave us this beautiful archeological remnants DFT Krakatoa eruption in Indonesia in 1883 which someone says it inspired the moon cream or moon cry because the volcanic ash which was spread over the atmosphere and all around the globe gave form animals particularly red sky and that inspired moon for his celebrated picture and this is the Tambora eruption as I told you in 1815 which produced the eel without summer in 1815 in Europe there was no Sun there was no harvest and for here the harvests were very poor that caused heavy Fanning that mass immigration so there was really a large-scale event with global implications these are all caldera-forming eruption the biggest eruptions we have an historic time they were caldera-forming eruption so calderas are associated to the largest eruption we know on earth and if we have to defeat the companion ignimbrite eruption on the same scale we have to reduce it down because it would be like this this is the companion ignimbrite eruption as big as these compared to what we have seen up to now which is down here some of you may remind IFE habla yaku eruption from iceland in 2010 which caused the shutdown or f-fly operations of a Europe for J's and caused billions of economic loss and that eruption sits somewhere here it's a vanishing point at the very beginning of this scale so that's really nothing in terms of the scale of the eruptions you can imagine what some like this might be it will be something with a an impact at the global scale with consequence which will be very large not only nearly not only in Europe but on the global scale okay of course campi Flegrei they also produce much smaller eruption we have seen many craters inside the large depression of the caldera and those eruption can be much smaller so if we go back here this is Canberra 50 cubic kilometers this is 300 cubic kilometers most of the eruptions were all of the eruptions of the last 5000 years of activity at campi Flegrei are less than one cubic kilometer but an eruption like this one which is the largest eruption of the last 5000 years at Contra gradient yeah no Montes spin eruption this one will be a complete disaster that's still quite big it's as big as the mountain talents eruption apart from the fact that Mountain talents ease in a remote area there is nothing around that why here we are in the city in Naples and would see that in a few moments this is the last eruption at campi Flegrei the mountain of eruption which occurred in AD 1538 a very small eruption as you can see but still on the run like this one would be a real problem in the area and that's because 500,000 people lives inside the volcano live inside campi Flegrei you can see here from this picture this is all campi Flegrei and completely gray and bigger than that and the same city of Naples is sitting inside a large part of the city not old city if sitting inside campi Flegrei okay and this puts lowly city which is also very large it is the mountain of eruption the last eruption in 1538 you can see here it produced this new mountain mountain model means new mounting exactly that and you can see how urbanized if the area is the area around that this is a picture showing the eruption in the 16th century still there were houses towns not the situation as to J of course in fact all the area here is heavily urbanized there are about three million people exposed to volcanic hazard from three major active volcanoes which are counties a gray here a caldera this is very famous Vesuvius volcano and Ischia Islands which is also an active volcano which rapid last time in medieval times okay so it's three active dangerous volcanoes and three million people living there with a density of urbanization which in many places is comparable to that of Hong Kong so it's really a huge problem it's probably the highest three volcanic risk situation in the world what kind means what are those kinds of hazards that are expected when you have a volcanic eruption well a volcanic eruption is different from an earthquake I'm from Toronado because the kind of process process is producing hazard and risk very many very many and very different you might have a lava flow eruption you can see here depicted some lava flows and there is a problem but it is probable this is certainly the lowest risky kind of volcanic activity because lava flows are slow and you can just go away while they are coming they destroy everything of course by they very rarely kill people but if you have an explosive eruption like the one that we see here instead of having lava flows you have a mixture of gas and fragmented magma the fragmented magma is what we call pyro class and that's Tommy's volcanic ash free crystals coming from the magma it's a mixture of pieces of magma which are fragmented because of the very high speeds of ejection along the volcanic boundaries this volcanic ash can go up into the atmosphere up for tens of kilometers up to 50 kilometers in very large eruptions and then it's spread over by the winds in months and challenge in 1980 the eruption of Mount st. Helens produced ash that travelled eastwards and after one month they came back a both months and Terrance so they did round two the words were okay and the ash which is spread over into the atmosphere will fall somewhere producing a full of ash which accumulates on the ground and that may create huge problems for the population and also cause the collapse of roofs so it's a very dangerous source of volcanic risk but the most destructive kind of volcanic activity pyroclastic flows this mixture of gas and ash can go up into the atmosphere if it becomes less dense that the atmosphere surrounding this but in some cases can be denser than the atmosphere so what it does it go up for a while then it collapses down and it forms avalanches of hot gas and pyro class which are called pyroclastic flows or someone else called them density kara volcanic density currents which is the same and this pyroclastic flows can travel to speeds above 100 km/h they have hundreds of degrees of temperature they can cause very large impact they have a very large dynamic pressure so they cause destruction of everything you cannot brace absolutely everything is destroyed if you are sitting there when a pyroclastic flows goes there is no way to escape that and there are many other services of others but I'm not getting into all of them just to show you some pictures of what I say this lava flows from very famous Edna volcano in Sicily a digit instead an eruption like this one this is Pinatubo in the Philippines in 1991 this is the largest volcanic eruption of the last century and this to cut this column here reached nearly 40 kilometers into the stratosphere okay like this one and you can see the effects of the accumulation of ashes on the ground so ash is accumulated on the ground that can completely shut off any kind of human activity in the territory and the coast deaths because of respiratory problems and they can also cause collapse of the roots as I told you and this is pyroclastic flows I hope it works this is per clastic flows formed yes that's good formed in Montserrat you can see here what they look like this is an avalanche of hot gases and pyro class going everywhere they can also travel on the sea for a while and they completely distort destroy everything when a caldera formed like in campi Flegrei that's the major kind of activity that you have pyroclastic flows like this one that can travel for very large distances and we will see something about judged so pyroclastic flows is what produced complete destruction in montalais in Martinique in 1902 you can see here the city of some pier 25 thousand people killed and this is again Pompeii in Vesuvius in AD 79 destroyed again by pyroclastic flows so past the situation's Naples and Vesuvius to J so if we had five thousand six thousand people who died here now we have millions of people who live here and there is Naples and on the other side we have County through grey and you can you can understand how big is the problem in this area this is a completely urbanized industrialized areas largely industry some many many people living there well getting back to campus a grey this is the eruption which caused the first formation of the caldera the companion ignimbrite eruption 39,000 years ago that I already told you and it is the area where so loud of ash is found today the red dots are all places where we can find in the field deposits from the fallout of volcanic ash from the volcanic cloud and you can see how large is this area okay this is here open this is Russia we are in Russia this is so agrees and whatever so an impact which is really huge and once again here in yellow this country for a here we are looking at the companion region Posey's here this is Vesuvius campi Flegrei yeah and in yellow we have the deposits of the pyroclastic flows and this is about 120 kilometers all the major cities in the companion region then eventually no caserta Nopalea of course which is here Salerno would be reached by pyroclastic flows even eruption like that one should occur in the future so you can imagine how how big will be the destruction and that's not the only big eruption which occur that can't be theoretical fifteen thousand years ago another large caldera-forming eruption producing huge pyroclastic flows formed that's the yellow tough eruption this is the yellow tops in Naples these are the deposits from one single eruption one single eruption produced all these so you didn't have that and a few days after that you have the city which is gone completely covered by cans and turns up to more than 100 meters of material produced by a volcanic eruption that's what we're talking about and that's campi Flegrei unless or Futaba crater that I already showed you campi Flegrei they are an active volcano there is a huge emission of volcanic gases securing there most of that comes out from lava Tara and another place which is very near very close to forfeit era which is called pisher le those are the two areas where the gases come out with the greatest energy at campi Flegrei and that creates another series of problems because gas is escaping from the ground as long as they can escape everything is fine everything is ok but if instead for some reason the ground is filled so that the gases cannot escape any more pressure can accumulate below the ground and a phreatic explosion like this one this is not compass regret fortunately but a faradic explosion like this one they appear and that's very very dangerous because three attic explosions they are a very superficial process very shallow process and they are very very difficult to predict to anticipate in fact most of the volcanologists go around on volcanoes they died because of phreatic explosions because they are nearly impossible to anticipate and that's also a problem and you can see here the magnitudes of the energy which is released that can't be for a through the escaping gases this is a thermal image of campi Flegrei in red you can see the hottest parts of the solfatara crater here and this is instead the area where the carbon dioxide flux is greater this is Russell Fatah and it especially that I was mentioned knew there are about 2,000 tons per day of carbon dioxide which is released by campi Flegrei the amount of carbon dioxide which is released only by campi Flegrei is larger than the total amount of carbon dioxide released by the volcanic Iceland by the entire Iceland which is entirely volcanic but the carbon dioxide which comes out from here is larger than that and this corresponds about 100 megawatt of thermal energy which would be a large geothermal arge energy plant one hundred megawatt is relatively large and you can see here the temperature of the aquifer which can go up to 90 degrees but thirdly the temperatures can be larger than that and in the picture le area here they we measure up to 120 degrees in the indy in the in the gases okay so going back to volcanic ash what do we do in order to deal with that kind with that thirds of risk of course we volcanologists work through the Civil Protection Department in Italy in order to quantify the hazards make plans help them to make emergency plans and this is an example what we do with volcanic ashes and I think it's useful to understand because we can introduce here the thirds of uncertainties and some of the activities that ver technologies do in order to understand volcanic eruptions and volcanic hazards well as always geologists start from the fields and the lines that you see here can be raised here the lines that you see here represents what we call ISO pucks they are lines they represent contours of volcanic deposits having the same thickness okay so first of all we reconstruct what volcano did in the past and we get a picture of its history what it needs based on the fundamental principle of geology which is the principle of actually that says that if something occurred in the past it may also cure in the future so first of all we go and see what what happened in the past and we construct a picture of the size of the magnitude of the past eruptions and the areas of dispersions and so on and so forth and from a picture like that we can get an image of the probability of having fuses that means lava flows or explosive small medium large or very large eruptions and this K here phase that for example the probability of having a large eruption would be full percent if a new eruption should occur in the future and very large which is something comparable to a caldera-forming eruption is less than 1% if an eruption should occur in the future which is not not a littlie it is it is important it is a large probability set consider that if you construct a nuclear power plant the accept acceptance probability of having troubles with jets must be lower than 10 to the minus 6 1 out of 1 million and that's 7 out of 1,000 so it's 1,000 times larger than the security parameters we will apply for a nuclear power plant but still if we consider that together we see that with 90 more than 95% probability the eruption will be medium or smaller than that and we start to get a picture of what we get there is another problems with calderas differently from central volcanoes central volcanoes they have a very clear structure with the central conduits and the probability of having an eruption from the central event is very high instead with calderas we can have an eruption nearly from everywhere inside the caldera we don't know where when the next when event will form it depends on manufacturers it could be everywhere as all of these credits here testify after the caldera-forming eruption we had an eruption from er1 from you or from you or from you or from here and others from other places so with calderas we also have a large uncertainty related to the place from where an eruption will occur so we have to construct a probability map for vent opening which is this again on the past history and on the investigation of the structure of the volcano where the wake zones are that may favour the essence of magma and we need a distribution a probability distribution of winds and that's because as I said volcanic ash if they are pushed by prevailing winds and therefore the accumulation of volcanic ash depends very much on where the winds are blowing and that in turn depends on the season in certain season the prevailing winds are westwards or they can be eastward so we get a picture and we can have a distribution map for a summer eruption or winter eruption and stuff like that and once we have all of this information we can use all of it together with numerical codes what is numerical codes it means that we write the equations which govern the process we write conservation of mass conservation balance of momentum balance of energy forces where this comes out to be a complex system of equation that we can solve with a computer we put in there the conditions that we we imagine they could be effective during the next eruption of course we don't just select one set of conditions but we select many each one as we associated with its probability so we have a vent from here with its probability of M from here for its probability a win like this one wind like this one the probability of having a small and medium large eruption all of that combined provides a mesh full-out hazard map which is a probability map we define here saying that the probability of having an accumulation of ash which exceeds a critical threshold which is known to cause roofs collapse here is 1% here is 5% us 10% and so on and so forth so this is the kind of map which is then used by Phillip protection in order to define the hazard of zones and undefined there emergency plans and the same we do with pyroclastic flows of curves with pyroclastic flows things a bit much a bit more complex because we have to deal with the policies and which with process which were really very complex and this is this is a result of a numerical simulation so it's solution of equation it's not just a cartoon it's not a movie it's no world is may it's a solution of equations describing the dynamics occurring inside inside a mixture of gas and higher class which may erupt at campi Flegrei and whatever you see here these are pyroclastic flows traveling along the ground you can see this one here advancing toward the pot slowly herb or the pot soil area I'm clearly destroying everything here so we can use we can again make a number of this simulation with different size of sorry I have to stick here the different size of expected volcanic eruptions and see what are the areas which are expected with which are expected to be impacted and as you can see here which we can obtain maps like this one we don't only see the areas we also see the timing here we see the concentration of ashes from point to point and their distribution in time we see the distribution of any other risky factor like concentration of ashes like temperature like dynamic pressure and so on and so forth and we can get a picture and all of that goes to Civil Protection and they of course take this complex information they simplify it and they transform in hazard map with areas which are subject to different risks the red area here again to this campi Flegrei directly discomfiture gray the red area is the area which is subject to the risk by pyroclastic flow invasion the yellow area is the area where ash accumulation on the ground is expected to be enough to go through the collapse or to cause serious dangerous serious problems to the population we should still sit here when an eruption comes and so that's that's where all the information we can get we can construct goes into and of course the big problem with campi Flegrei is a program of preparedness that means that we should be able to anticipate a next volcanic eruption which is really a big problem everyone knows that we cannot predict earthquakes but at the same time everyone knows that we can somehow predict volcanic eruptions or at least we can deal with that we can deal with prediction of volcanic eruption although prediction is a bad word and we shouldn't use that we should use forecast because prediction is a deterministic deterministic meaning it means that we know what's going to happen instead we don't know uncertainties still dominate the system what we can do is to make projection into the future and make forecast the same way as atmospheric scientists make weather for us there is a probability associated to rain tomorrow it may rain if that probability sigh but it may also not rain because the uncertainties are large and if the uncertainties are large in a system like atmosphere that we can observe from top from below from me though we measure at any point we observe in real-time if the uncertainties are large there you can imagine how large the uncertainties can be in a volcanic system which is at least as much complex as the atmosphere but much of that is outside our direct investigation we cannot directly investigate the magma below the the ground so we don't know what's happening down there we only have an indirect information coming from our network of instruments which are placed on the ground or in BO holes and we we get many signals and we need to invert the signals to try to understand what's going on at kilometres of depth which is very different from the atmospheric sciences where you observe directly the atmosphere from time to time so uncertainties dominates our volcanic forecasts they are really dominating and if they dominate there are even more dominating vocal dara'a calderas are systems which are very very difficult to understand and the reason for that is that we also know the story we often observe unrest dynamics unrest dynamics means that the volcanic moving is doing something is inflating deflating escaping gases something is happening so we Unruh we observe unrest dynamics at calderas so large that if we observe them as a stratovolcano almost certainly there will be an eruption following those unrest dynamics instead with calderas we observe many things happening matters of the formation huge amount of gases escaping or a lot of seismic swarm seismicity everything going on but no eruption follows while some other times we would self much lower Cygnus nothing seems too much warring and an eruption happens so calderas are really very very difficult to understand and that's the that's a message for a casting the occurrence of an eruption a caldera is much much more complex than for stratovolcanoes for central Vulcans the calderas are really complex and it is an example from campi Flegrei what we are looking at here is the position the vertical position of two points in campi Flegrei so this is one point in time we go here from 1905 to nearly today ok so this is about 100 years one century of measurements this is one specific point and this is one other specific points and we see that in time up to the 50s campi Flegrei worth subsiding we're going down slowly and slowly in fact subsidence at camp it's gray has dominated since the Roman times slowly and slowly and slowly all the campuses the ground that can't be for grey has been going down and down and down like this like here but Jen in the 50s something new happens and the ground started to go up you can we can see it's here and here this point here at the beginning of last century was built oh sorry was below the sea level and then this is the sea level you see and then in time you went down down then in the fifties it started to rise then the walls again subsidence then at the end of the 60s again the rise Jana gained nothing or earth nor subsidence and then again at the beginning of the eighties a large rise of the ground and then again subsidence and we'll see where we are today so from the sixties on from the sixties on something new with from the fifties on sorry something new have occurred at campi Flegrei campi Flegrei are today a volcano in an unrest face something is happening here that we need to understand in order to try to forecast the possible occurrence of the next eruption I've told you that this point the sea level this point here was below sea level and that subsidence dominated since the Roman times and we can see that because in front of pot slowly this is put slowly in the center of campus a gray and we can see here the remnants of villas from the ancien trailmen's which are 2j below the sea level because what this pointing out in time for appear above the ground and then it went down down down down until it was submerged it was below the sea level this is the sea repeal temple it's very famous it's a non ciients Roman market and it's located in front input slowly close to the harbor of portfolio this is a picture from the 50s this point here is in fact the point in the therapure floor okay so the therapure flow was submerged in the 50s and you can see here it was invaded by the sea and this is the same picture taken today well a few years ago here when the therapure temple was completely out of the sea level so really huge movement securing and it is about 70 years of unrest which are going on at campi Flegrei we should toll it with a total uplift of the ground of 3.5 mailers so if one guy from the 1930 of 1940 should come there and look at campus array it will find that Rehan write-up of 3.5 meters it wouldn't recognize the coastline it's very much different from from there and of course this movement this at least cause a lot of damages and these are this is a picture from summer 1983 summer 1984 from 1980 to 1984 there was the last big rise of the big uplift of the Florida was showing you and many buildings were seriously damaged by that in fact there was a big concern that an eruption may occur at that time but it was also be concerned because tens because thousands and thousands of earthquakes and big ground uplift what were seriously damaging the buildings and 40,000 people were taken away and relocated somewhere else and this is again just to show you the dominance subsidence since the Roman times it is the largest picture of the Roman villas and if you go down here and dive you can see it stuff like these these are the Roman villas which are 2j below the sea it's beautiful it's it's another small Pompeii yep again so coming back to what campi Flegrei are doing what kind of signals they are giving us this is the 8284 crisis which is concentrated here and it is what happened up to 2000 Oh 8 I will show you the rest of the story in a moment so what we see we see that the red blocks here are the number of earthquakes okay so we see that we have earthquakes at campus a gray we had earthquakes only at specific times when there was bigger price the blue line is the if the color is the floor if the position of the floor so it's the uplift this is a big uplift in the 80s and then everything went down and there were small up rises here another one here another one here and every time the terrain goes up there are new earthquakes occurring and also there are other signals which are the dull and the Green Line which is the composition of the gas which is ejected which is emitted from solfatara crater this composition is expressed here as the ratio between carbon dioxide and water in the volcanic gases and we see that when we have uplift of the ground we have earthquakes and large increase of the amount of carbon dioxide in the gases than degrees then we have earthquakes uplift and large and again increase of carbon dioxide and again and again so clearly the volcano is telling us something the volcano is speaking there are signals that we interpret I don't get into the interpretation and the physics and the models that lie behind all these but you can imagine how how many investigation how many studies how many models have been constructed based on that in order to try to understand what's really going on adept at campi Flegrei and this is the entire story up to today practically today of the deformation so we had a bigger prize here than subsidence for many years but then after with a new millennium something new happens there is a new trend going on now we are not subsiding anymore but we are rising up with the trend which is very different from what you will in the past we have served very large a price here very restricted in time but high rates uplift here here here now we have a lower uplift rate which is continuous in time going on and on and on and a bit increasing in rates you see the curve is going a bit like this so there is a new trend in the formation and again giving us troubles because we have to understand what that means there is a satellite picture of again showing a deformation at campi Flegrei uplift that campi Flegrei this pathology this campi Flegrei and the different colors here show different magnitudes of the at least so we can see that the uplift is maximum in the middle of the caldera which correspond to virtually area and then there is a lower uplift here here and here so the entire caldera is going up like this and all of the caldera the green area we don't have any ground movements so it's the caldera which is going up and up okay so this is our images they are rather images made with the satellite it this is a principle which is based on interferometry those of you who know interferometry may understand how it works there is a satellite sending a rather signal and it it goes over the same place after about 15 days there is a new signal there if the ground moved the signal which is coming back is no more in phase with the old signal there is a faith a displays in the face so oops sorry haha yep I was joking with this there is a displace in the face and you can play with that and make interferometric pictures and understand how large is the phase shift and how that translates in terms of ground movements that's the principle of insa and this is under this what I was saying that the line the coastal line has change significantly in red here we see the cultural line before the 50s and in orange we have the beach before the 50s and everything we see here is come out of the sea from the fifties to today but it's a it's a rising it's a place which is really rising out of the sea okay of course we need to understand what's going on down there and we make a lot of investigation in order to do jet geophysicist geochemists volcanologist numerical modelers are all getting into their big signs in order to try to understand how the underground of campi Flegrei looks like and what the processes might be down there and post sorry and this picture here shows some of that I don't get into any detail of course but these are the results of what we call seismic tomography which is a metal with emissive based on seismic waves in order to reconstruct the mechanical characteristics of the ground at different depth and we can combine that with gravity anomalies which is another method which allows us to see what's the distribution of the density of the terrain have different depths below the ground we can combine all of that in order to get pictures of the underground structure compass array and that allowed us to discover that at the depth of about eight kilometers below campus array there is a mass film there is an area with a significant amount of melt of magma if you like which is present there select this one this is a cartoon showing the results of this investigation so at about eight kilometers below campi Flegrei the magma is there and it is a lot of magma because it's at least 30 kilometers by 30 kilometers probably one kilometer thick that means about 1,000 cube kilometers of magma which is really of melt zone which is really a lot a new investigation which is again based on two seismic tomography what different with different techniques there is seismic attenuation there is a t too much see here attenuation seismic attenuation tomography with this method we go and see how the seismic waves are damping down from place to place it's a different technique which allows to put in evidence better areas which where fluids are hostage so we can see what's the structure of gasses what this distribution of gases and water below the campi Flegrei but also with this technique here we could identify what we probably what we think it is probably magma at a lower depth of only three to four kilometers so a large mass on here probably magma sitting at three to four kilometers right below post slowly in the center of the caldera and this might have been responsible for the unrest that we are observing for the large uplift of the ground since the fifties everything is a nice may because we don't have any certainty about this there are only hypothesis models and that we continuously test okay so from all of that a picture comes out like in this cartoon where we might have a magma chamber at about eight kilometers depth a very large magma chamber actually and a fill intrusion at about three three to four kilometers of depth below campi Flegrei below post slowly that's the picture that many people believe it's true many others question that it's not universally accepted of course but i would say that most people now believe that's the case and we can we can work with that we can transform this tuned here into a simplified picture that we can use for numerical simulation for investigates what kind of processes might occur if the system would be like this one and this is a simple schema decision which is adequate for doing numerical simulations here we have a large magma chamber at about eight kilometers depth up to down to nine which is hosting a volatile rich magma volatiles are very very critical in what can occur on eyes you know because it's the volcanic gases that cause the magma to rise and produce eruptions so and the kind of processes in magma is such that if you have magma coming up here this magma will unavoidably become depleted in gases in time so we have an intrusion here three kilometers which hot magma which is depleted in gases and volatile gas rich magma sitting down there and there are somehow connected that's a simple scheme and we can use that for numerical simulations what we are looking at here is a zoom in this area we simulate the entire system of curves but in order to see what happens here I just make a zoom of this area here so this is a shallow magma chamber this is what we call a dyke the dyke is connecting the shallow chamber with a bigger chamber and there is gas rich magma sitting here so what happens in time is something like this this is again solution of equations describing the physics of the system and we can investigate how the process goes on the process of rejuvenation of a magma chamber by volatile rich Magma's okay so what we see here is plumes of volatile rich magma getting into the chamber the time is very much accelerated here since when we started speaking nearly two hours have passed by of real time of so we are accelerating time in order to see what's going on and we can we can see that if the situation will be like this one probably this is the kind of processes that may occur in a chamber can we can we see that in signals do we have some hints that may tell us that this is really going on and that's not a part of the story that's what we need to to understand so we can move from magma dynamics to ground movements we can take all the forces which are generated on the boundaries of the system because of this process of convection going on we have convection mixing of magma movements these are closing forces that distributed here we calculate those forces we project we use we simulate the transmission of those forces into the rack system and we see okay we see what kind of movements we might have on the ground so we can see what kind of thickness we might have on the ground if we if this process would be true we would see something like that do we see that we can go back to the fields and compare our synthetic signal with the real signal and see whether there are similarities or there are no similarities and in this specific case as you can see the blue lines if the computers ground displacements the black lines is what we observe and there are good similarities so there are reasons to believe that we have something like this below campi Flegrei we are shallow chamber which is periodically rejuvenated yeah so we can do a lot we have a lot of science to put in there and the volcano observatories out to a very high tech places where a huge seeing huge number of signals are continuously recorded analyze the very very high tech systems all volcanoes are covered with instruments but still uncertainties dominate still we don't know what's going to happen and this is an example from rubbles caldera in Papua New Guinea ax okay from very this is also a caldera big caldera as you can see here this is see invaded by the sea and in the 90s in 1994 the world's an eruption in this caldera but let us see the history of this eruption what happened is that starting from the 70s the ground was at least in more and more and in the eighties he was uplifting very fast and very a lot so the people were very scared also because they were the blue the blue lines here is the number of earthquakes there were a lot of earthquakes in correspondence with these huge ground at least and there were no notes more than not small earthquakes there were large earthquakes larger than magnitude seven you've seen yesterday that magnitude seven is a big earthquake and nothing happens many people flee many people escapes from the area spontaneously they went away from the front cities there but then nothing happened so they came back and they stayed there the ground was not an uplifting anymore it was continuously uplifting but certainly nothing comparable to all of these and nothing comparable to these there were nearly no earthquakes until when small uplift here in a short time small earthquakes magnitude 5 not magnitude 7 100 times smaller than these more or less and suddenly an eruption occurred so once again this is what calderas do you can see a lot of thickness you can see big changes but then nothing happens and then you see nearly nothing compared to what you already saw and then eruption can't and that's the big problem with calderas I put here the history of deformation campi Flegrei which is not in scale of course but just to show that encounter forget also we saw in 8284 a bigger place and then subsidence in this case and then now we are sitting here we are sitting in a place where we have small ground uplift it's not very different from the one so who knows what's going to happen that's the case and just to tell you just to show you how complex can be the calderas this is another example from oak mock illusion our credit is in Alaska okay and again we have designed here show again the position of the ground periods with inflation apprised of the ground then nothing happens status eruption it's big influence re big inflation again then Manning happens everyone will be scared here no scared here instead eruption comes after yeah I should I should preach just other examples and just Charlie well this is an example mixing up manacled errors and you can see here that caldera they can get into an eruption following many different trends this is the intensity of indicators how big are the things that we observing and we have everything even cases were in eruption follow the period with everything was slowing down and John was smoothing down and down we did not serve nearly anything and then eruption started and these are all cases when eruption occurred these are all cases of unrest that calderas where nothing happened and again the trends are superimposing one to the other so we don't have any clear clue to understand what's going on with calderas for occur circled eras are characterized by digging certainties and that's why we are talking a lot of uncertainties and relying on probability estimates instead of relying on predictions that we are not able to do we have to deal with uncertainties and probabilities and that's some of the best we can do to j with system which are its complexities and we that i've finished thank you [Applause]

Channel: European Geosciences Union

Views: 53,615

Keywords: education, teachers, conference, science, cool, mediterranean sea, mediterranean region, earth science, geosciences, vienna, teaching, school

Id: HuoMiUXf1YY

Length: 59min 31sec (3571 seconds)

Published: Wed Jul 05 2017