ITALY'S SUPERVOLCANO, 2015

[Music] in 79 AD at the height of the Roman Empire a great Cataclysm struck the Italian peninsula the mountain of Vesuvius near present-day Naples erupted killing thousands and destroying the cities of Pompeii and Herculaneum the only surviving account of the event comes from two letters by a Roman magistrate named Pliny the Younger to the historian Tacitus these letters described exactly what happened in the days before and during the eruption it was the first time in history a detailed account of such an eruption had been given explosive volcanic eruptions like Vesuvius are now known as plinian eruptions the Romans did not realize that this was a volcano they knew about volcanoes because Etna had erupted many times in Roman history but they didn't know about Vesuvius and in less than 24 hours the city of Pompeii was buried under many metres of volcanic ash and the city of Herculaneum was swept away by pyroclastic flows the explosion was about the size of the eruption of Mount st. Helens in 1980 and Mount st. Helens we calculate had an energy released the equivalent of 24 megatons bear in mind in the case of both Mount st. Helens and Vesuvius that would be 24 megatons of energy released over a period of about 24 hours as opposed to a nanosecond with a hydrogen bomb when the eruption of Vesuvius began in AD 79 a created of cloud of volcanic ash that rose at least 50,000 feet into the atmosphere though prevailing winds carried this to the southeast and this dropped a large blanket of volcanic ash on the city of Pompeii over a period of about 18 hours we know that about a thousand people died in the city as volcanic ash started to pile up it placed a great deal of weight on the rooftops of the houses and eventually the the roofs collapsed Mary and the people underneath Pompeii was basically buried under more than 30 feet of volcanic ash the city disappeared as bad as the ash cloud that destroyed Pompeii was it was only the beginning as the people in the nearby city of Herculaneum would soon find out as this volcanic ash cloud continued to erupt for hours eventually it got to the point that the eruption could no longer propel the ash high into the atmosphere and the cloud collapsed producing pyroclastic flows and these pyroclastic flows were mixtures of extremely hot gas and volcanic ash with temperatures on the order of 500 or 600 degrees Fahrenheit now Herculaneum was better positioned initially because the prevailing winds carried the volcanic ash cloud away from Herculaneum but Herculaneum was subsequently buried by these pyroclastic flows so it's a very different story for them in Herculaneum the kind of preservation is different imagine concrete coming at you at temperatures of 500 to 600 degrees incinerating everything but subsequently preserving everything beautifully in Pompeii on the other hand the people were encased in much more porous volcanic ash and over the centuries their corpses decayed their bones were dissolved and what we were left with were casts without any preservation of the people in many respects Herculaneum is better preserved but it is much harder to excavate because of the difference between the styles of eruption that covered them it is estimated as many as 16,000 people died in the eruption of Mount Vesuvius in 79 AD part of the reason for such a tragically high number was the volcano itself although the Romans did not know that Vesuvius was an active volcano they were well-acquainted with the benefits that active volcanoes provide there was rich agriculture on the flanks of the volcano in fact Pompeii and the region were famous for the wine that was produced there was also deposits that the Romans discovered that we now today called pots Ilan it's volcanic ash that when mixed with lime produces a concrete that will set underwater this is one of the great discoveries of the Romans the abundance of fertile ground and other resources around Vesuvius has led to a dense and ever-increasing population around the volcano and although Vesuvius has not repeated an eruption on the scale of devastation and loss of life as the 79ad explosion it is far from quiet Vesuvius remains quite active since AD 79 Vesuvius has erupted about 36 times most recently in 1944 with the large population living around Vesuvius the Italian authorities are very concerned about the status of the volcano however there's much more volcanic activity in the area and the threat extends far beyond just Vesuvius the greatest concentration of people in the surrounding area is in the city of Naples locally known as Napoli Nopalea is probably one of the most important places in the world for studying active volcanism more than 3 million people are threatened by possible eruptions from Mount Vesuvius and another volcanic center that few people outside of Italy know about named copy Flegrei copy Flegrei is Italy's supervolcano you can think of it as Italy's Yellowstone it's not 12 kilometers in diameter that's much smaller than Yellowstone but on the other hand it's much more active and more threatening we call these super volcanoes calderas because what they are is big basins the eruption is so big that no edifices produce the explosions be erupted anywhere from 300 cubic kilometres to more than a thousand cubic kilometers of material and what you're left with is a big Basin that we call a caldera copy Flegrei has produced several very large eruptions one that we know about occurred 30,000 years ago released 300 cubic kilometers of volcanic ash about 15,000 years ago a major eruption released between 30 and 50 cubic kilometers of volcanic ash that we call the Neapolitan tuff that would be 30 to 50 times the eruption of Mount st. Helens the Neapolitan tuff is widely distributed around the Bay of Naples that forms yellow cliffs and it's used in building stone a lot in the city of Na Polly today incopy Flegrei the ground moves dramatically because magma is injected continuously at depth causing the ground to rise and then the ground will subside as the magma cools and shrinks the earthquake activity is extreme probably a third of the population of Na Polly lives actually inside the caldera itself so the risk posed by an eruption from campi Flegrei is - not just the City of Na Polly but really southern Italy as all the long occupation of the area around Vesuvius and compy Flegrei has met many generations of people have been living under threat but it's also provided scientists with an unusual window into the study of its volcanic history copy Flegrei is one of the first places where scientists were able to recognize and document significant uplift and subsidence of the earth's crust they could do this because in the bay apart slowly there are roman columns that have been burrowed into by mollusks the Romans didn't build the temples in the ocean they built them on dry land so that dry land above sea level had to subside so that sea level came up and then those mollusks could burrow in there and then the land had to rise up again when the land would subside the columns would drop down beneath sea level mollusks was burrow into them and then when magma intruding at depth and the surface of the earth was pushed up again these columns would be emergent and the mollusks would die this is all since the Romans this is a couple thousand years and so we can see those mollusks today and track over centuries the rise and fall of pots well eBay as a result of the restlessness of the copy Flegrei caldera if you have these columns that were raised up and lowered down within the span of time of a couple of thousand years imagine multiplying that by earth time and you can then imagine how mountains form valleys form oceans form it was very enlightening the contributions of copy Flegrei have not been only to science over the centuries other disciplines have been influenced by its unique nature so copy Flegrei is also host to a very active geothermal system one of these that is quite renowned as sulphate era this is something that has been known and described since the time of Dante in fact it's thought to be the inspiration for the entrance to hell these hydrothermal systems are produced by groundwater circulating down to depth where it becomes heated by the heat released from the magma beneath copy Flegrei once it's heated it comes back up toward the surface and is released as superheated steam you can imagine hot gaseous emissions coming out of the ground above the boiling point of water and reeking of sulfur this is exactly the sort of thing that Dante would imagine going into hell and this is what you have at solfatara the intense energies contained under Vesuvius and copy Flegrei have led many in the past to make wild speculations about their nature and causes but today scientists have a much firmer understanding of what's actually going on under the ground at the monitoring center for the Italian National Institute of geophysics and Volcanology and Naples the entire area is watched 24 hours a day Vesuvius itself has 18 seismic monitoring stations and seven infrasound microphones working around the clock it is the most sophisticated and accurate geophysical during system in the world today we don't have to look at the columns of ancient Roman ruins to measure how the earth is responding to the volcanic forces that are acting on it now you can measure how fast the surface is rising what the heat flow is you can measure those things directly we can actually see and in a sense feel the earth rise as it rises and as it falls and as the heat flows through it despite all the advanced hardware and data being collected at this and other monitoring stations volcanoes can still be wildly unpredictable volcanologists would still benefit from a closer look at the interior of an actual volcanic system coincidentally such an opportunity presented itself a relatively short distance away dr. Jim quick is a volcanologist at Southern Methodist University in Dallas Texas for 16 years he spent summer studying the geology of a mountainous region called Valse Asia in northern Italy in 2009 he released his findings on an extraordinary discovery the Valse Asia area of northern Italy sits in the foothills of the Alps it's a very special place because of the collision that occurred between Europe and Africa it's the collision that produced the mountains we call the Alps when continents collide it's a slow-motion event that takes place over tens of millions of years but the results can be quite dramatic now in the case of northern Italy in the val Stasia area we actually have the boundary between africa and europe exposed there it's called the ensue brick line this collision would be occurring against Africa and Europe and as a result of that collision along the ensue brick line the crust of the African plate is tilted and bringing up progressively deeper and deeper rocks as you approach the ensue Burak line now of course at the same time erosion is occurring you're building mountains but you're also wearing them down through erosive processes and so what we see now today cuts through the original crust that had been tilted and uplifted what makes it even more special is at the very top of this tilted section of rocks we have a caldera a supervolcano something the equivalent are similar to a copy Flegrei or a Yellowstone but much older this caldera is about 285 million years in age and we know that that's when it formed because we can date the rocks using the decay of uranium to produce lead everybody is familiar that uranium is a radioactive and when it does decay it produces a certain specific isotope of lead looking at the ratios of these isotopes we can calculate the age of the minerals that host them so we know that this system was active in about 285 million years ago and beneath it is a magnetic system exposed by this tilting as well it's the only place in the world where such exposures exist what's particularly interesting about this is what you can see in the field when you look at the rocks it's what the geophysicists imagine exists at depth beneath Yellowstone beneath copy Flegrei when they look at their seismic data they see a magma chamber perched at a depth of about 4 or 5 kilometers that's feeding the eruption and then beneath that as a much deeper larger volume of magmatic rocks that's providing the heat that drives the whole system this is at a depth of more than 20 kilometers and in Valse Asia we see this whole section beautifully displayed and we could look at the relationship of these rocks and gain a better understanding of how these systems work you're actually walking through the depths of the crust of the earth and actually seeing the kinds of minerals and rocks that are formed from each composition of magma and each temperature and pressure and that's anime same thing to see it's like walking down towards the center of the earth dr. quicks discovery provides a first-hand look at the deep interior plumbing of a supervolcano it will further research on the prediction of volcanic events not only at Vesuvius and campi Flegrei but other geophysical hotspots around the world it may also help in discovering ways to channel these volcanic forces more effectively toward human consumption such an endeavor is already underway and has been for many years again in Italy in a place called larderello the larderello area of Italy is interesting geologically because of the large hydrothermal systems that are there larderello really got started being exploited to produce boric acid a product that you can produce from volcanic muds but with time was realized that these systems produce steam that had enough energy that you could drive turbines and generate electricity in 1911 the first geothermal plant in the world was produced in larderello using that technology and that plant is still active today the larderello geothermal complex powers more than 30 power plants generating more than 700 megawatts of electricity which is a significant contribution to the power grid of Italy there in Italy is the first place it was done and if you look now it's all over the world everywhere there's high heat flow there is someone trying to take advantage of the hot springs to use the energy of the earth to produce electricity since plenty the Younger sent his letters to Tacitus people have sought to understand the immense forces behind the eruption of Vesuvius why did it erupt when will interrupt again the monitoring of activity at Vesuvius and campi Flegrei is allowing scientists to see in real-time the ever changing nature of a living volcanic system dr. quicks discovery of the caldera at Valse asia is giving scientists an understanding of a supervolcano to depths previously thought impossible the larderello complex is allowing geophysicists to capture a portion of this energy for public use it is hoped that the amassing of all this data will not only help volcanologist detect and predict the next eruption of Vesuvius it could help in understanding the behavior of other volcanoes around the world it could also assist geophysicists in finding new and better ways to harness this fantastic resource for the benefit of everyone as humans we need to understand the earth how its plumbing works how its heat is distributed and what it does how we can make life better by using the resources of the earth in a responsible way we must understand the earth so that people can have a better life [Music] you

Channel: ISEM at SMU

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Id: 96026QEl-44

Length: 19min 44sec (1184 seconds)

Published: Thu Jul 20 2017