When will the next super-volcano erupt?

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1:07So we had an early start this morning to get up at about 4am and we've driven into a massive crater which is filled with a lake. You can hear the water lapping against the shore here and we're getting on a boat and we're going to get on this boat and go into the middle of the lake.

1:32Hello and welcome to CrowdScience from the BBC World Service, the show that goes the distance to answer your science questions, even if it means travelling to an active volcano, which is exactly what we're doing this week. So this huge crater that we're in now, this is actually part of a massive volcano that erupted... Yes, before, thousands of years ago. I'm Anand Jagatia, and I'm on my way to the centre of Tal Volcano, the second most active volcano in the whole of the Philippines. And it's to help us answer this listener question. Hello, I'm Crystal. I'm originally from Sweden, Malmö, but now I live in Florida in the United States.

2:16And my question for crowd science is, when will the next supervolcano erupt? Well this is a cool question and a slightly sort of terrifying sounding one. I don't really think I know what a supervolcano is. What do you understand a supervolcano to be and where did this question come from? Well as I mentioned I'm Swedish and I was watching a program on the history of Sweden and they mentioned that in 536 there was a series of gigantic volcano eruptions. first in the northern hemisphere and then in the tropics. And as a result, Scandinavia had three years of winter because the sun wasn't able to penetrate that gas and ash that the volcanoes spewed out.

3:09Okay, so this sounds like a pretty terrifying ordeal. I mean, it sounds pretty apocalyptic. Exactly. And they reported that about half of the population of Scandinavia perished because they couldn't find food. And it was very, very cold. So I was thinking, well, you know, we still have volcanoes, so they're still affecting us, but it's never resulted in three years of winter. So that must have been way back in 536, a huge explosion, huge volcanoes. So my question would be, could it happen again? And if so, I would really like to know when and where. Thanks, Crystal, for your question. So we need to find out if a volcanic eruption on the scale of the one that happened in the 6th century could occur today.

4:08And if it did, would we be ready for it? To begin our search for answers, let's return to the Philippines, one of the most geologically active countries on Earth. We're motoring across the surface of Lake Tal, a 20-kilometre-wide crater now filled with water that formed after a giant eruption thousands of years ago. In the middle of this lake is our destination, an island made up of dozens of volcanic peaks that rise up out of the waves. So you can see the features. Those are small craters. This is our guide, Paolo Reniva, resident volcanologist at the observatory that's tasked with monitoring Tal Volcano.

4:53It feels so peaceful, it's so beautiful, and yet this is actually an area that's incredibly active volcanically, and there's going to be violence coming up from the middle of the earth here, but yet today it just feels really serene. Yeah, it's calm, peaceful. Today the lake is picturesque and tranquil, But just six years ago, in 2020, the volcano at its centre erupted violently, triggering a full evacuation of the island and its surroundings. So, Paolo, did people used to live on this island in the middle of the lake? Yes, there were around maybe 8 ,000 inhabitants before. Wow. And now? Supposedly, it should be zero.

5:40No one should be permanently staying on the island. In the wake of the 2020 eruption, the island is now considered a high-risk zone and access is tightly controlled by the Philippine Institute of Volcanology and Seismology, or FIVOLTS, the organisation that Paolo works for. They've given us special permission to visit the island. So this is where we start. This is the point. So we are on the almost southwestern sector of the volcano island. So, Paolo, the sand we can see, the mud on the shore, this is black, yeah, so this is ash. The eruption deposit. Wow. This material was spread here from the volcano by a muddy flow of water and ash called lahar.

6:32As we walk across it, Paolo introduces us to someone who's experienced multiple eruptions here, a local fisherman, 72-year-old Rogelito Cacao. He's still allowed to fish in the lake, but he's had to leave his home on the island for good.

6:52I used to live here in the volcano island. I was born and raised here. I was here in 1965 when it first erupted. This place used to be beautiful. We have livelihood here and it was peaceful here, so compared to now that it's now covered in mud and covered in lahar. So it's beautiful here because people have their livelihood here. They do farming, they plant rice, so everybody was happy before the eruption. What was it like in 1965? What happened when the eruption happened in 1965? I was 13 years old then when it erupted in 1965, so we needed to evacuate with my brothers and my father. and then what happened could you tell us what happened in 2020 so on the day of the eruption do you remember what happened so in 2020 i'm a village official so the chief of the village told me to tell my neighbors to evacuate because a tall volcano is about to erupt so when we evacuated here we already experienced some of the lahar but we were not heavily damaged because we were immediately evacuated this place, but there were already lahar flowing from the volcano.

8:07Were you scared? Of course, I'm scared. We were scared. Who won't be scared? It's an eruption, so we were scared. Has it been hard to have to leave your home? It's really difficult because our livelihood is really here in the island, so when we were evacuated and being placed in another island, it's real difficult not only for us but for our livelihood. How do you feel when you come back to this island and you see all the ash covering everything that used to be here? It was real difficult and sad for us because our house was being buried in mud, but more difficult because our livelihood was lost.

8:51Thank you. Thank you. Lovely to meet you. Thank you so much. We say goodbye to Rojalito and begin our trek up to the top of the island. We pass through a kind of natural ravine, and rising up on either side of us are walls of volcanic ash, which have completely buried everything in sight, including the remains of a house. So these are the windows filled with ash. That's all ash? Yes, so it could be totally covered by ash. Well, I mean, from where we're standing, this wall is at least like two or three metres high, completely overgrown now with grass that's like basically just as high as that again.

9:33The entire island was covered by ash. We're walking on top of previously, maybe the top of trees, houses, before. That's what we're walking on now? Yeah, before the eruption. Yeah, yeah, yeah. Maybe now. Wow. It's hard to get your head around. I mean, the power of this volcano to produce that much ash. The sheer amount of material released by this one volcano in a single eruption is truly mind-boggling. But the event that listener Crystal got in touch with us about was even more extreme, creating enough ash to blot out the sun and trigger a volcanic winter that lasted several years in the northern hemisphere.

10:12So what exactly happens inside a volcano or a supervolcano during an eruption to produce such devastating consequences? Well, there's a very simple response of what is a volcano. It's a mountain being sick. This is George Cooper, a volcanologist from Cardiff University in Wales in the UK. In his colourful metaphor, the sick is liquid rock, magma. So it's basically throwing up the guts, which would be the magma, which is stored in the crust beneath the volcano. and that crust is a bit like a series of jigsaw pieces which are all shuffling around. So sometimes those plates collide, one plate is dragged underneath the other and that can form volcanoes at the surface.

11:04In other situations you have those different plates that are pulling apart, allowing magma to reach the surface. So what actually happens when a volcano erupts? So when a volcano erupts, pressure in the magma chamber builds and builds and builds, and then it needs to find an escape. And that often is in the form of a volcano. So when that magma comes out, it can come out in various different forms. Often the magma is fragmented into lots of different pieces, and that comes out as ash clouds. And then in the biggest eruptions, that can also come out as pyroclastic flows. So this is where hot gas, rock and ash travel down the surface of the volcano, quite a long way from the actual vent of the volcano.

11:50And that's kind of the most disruptive form of the volcano. So it can really deposit huge, sort of several metres thick deposits, which would be very hot, destroying homes in the nearby vicinity. So our listener who got in touch with us, Crystal, she is interested in super volcanoes. So what actually is a supervolcano? Is it like a scientific term or is it just a word that people use to describe very, very big volcanoes? Well, a supervolcano is any volcano which has erupted a supereruption. And a supereruption is the largest explosive eruptions on Earth that we have. so unlike a normal volcano which may erupt on average around one cubic kilometer of material a super eruption erupts over 450 cubic kilometers of magma so that's a thousand cubic kilometers of loose pumice and ash so i did a little calculation that's the equivalent of covering the whole of the UK in around four metres of material.

12:57So massively destructive for the country which they erupted in and would also cause global changes as a result of the eruption. So how many supervolcanoes are there on the earth now that scientists are monitoring and keeping an eye on? So I guess the best examples would be Yellowstone in the US, which is being monitored. The other system would be the Taupo Volcanic Zone in New Zealand. And Crystal was, the reason why she got in touch with us is because she saw a documentary about this massive volcanic eruption that happened in around 500 AD in the Northern Hemisphere. What do we know about that?

13:43That time period, it's proposed that there'd be several different volcanic eruptions which occurred within a short space of time. One of those is likely to have been from North America somewhere, and the other has been proposed from El Salvador. And very similar to what would happen in a supereruption is that the ash created from these explosive eruptions travelled around most of the northern hemisphere at this time. Now that caused global climates to change by at least, I think, between 2 and 3 degrees C cooling for several years after those events. So what happened in 536 AD wasn't actually a single super eruption, but several regular volcanic eruptions which combined to produce catastrophic effects.

14:321500 years ago, these volcanic events probably took the world by surprise. But today, scientists all over the globe are monitoring dangerous volcanoes for signs of imminent eruption. So what exactly are they looking for? And to answer Crystal's question, how accurately can they predict when a volcano or supervolcano might next blow its top? That's what we'll be finding out next. This is summer at its peak. Whole Foods Market's Summer Fruit Fest is your invitation to eat the season. Fresh, organic, and bursting with flavor. Start your day with peaches and organic blueberries and yogurt. Build a grazing board with fresh fruit, prosciutto, and artisanal cheese.

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16:00You're listening to CrowdScience from the BBC World Service the show that erupts every week with answers to your science questions I'm Anand Jagatia and I'm in the Philippines to learn first hand how scientists in one of the world's most volcanically active countries monitor the earth to keep people safe

16:22We've been trekking for the last hour to reach the top of the volcanic island that rises from the middle of Lake Tull Up here is a strange, barren landscape where the bleached skeletons of dead trees poke up beneath our feet through huge deposits of fine grey ash

16:44My hat's just blown off, it's quite windy up here we're just about to get to the top of this ridge oh I think possibly over the edge of this ridge will be the inside of the crater whoa it's kind of weird because we've crossed the lake to get to a volcanic island and we've walked to the top of the island and inside that is another lake that is in the middle another crater inside this huge rim. So all the peaks that we could see from the bottom, they're actually the ridges of this crater. And it's right in front of us there. It's actually steaming. You can see the volcanic activity kind of bubbling through the surface.

17:30And all around us kind of going downwards into the crater are these rivers of ash. Paolo remembers what happened on 12 January 2020 when Taal Volcano started to erupt It began that morning with increased seismic activity at the observatory Large amplitude earthquakes are being recorded So we immediately informed the main office that this is the prevailing situation in Taal Volcano Paolo says they soon decided they would have to evacuate the 8 ,000 people living on the island. So at noontime, we at the observatory decided to inform the people here because they could feel the earthquakes. So we told them to evacuate the island.

18:20So the people here initially, of course, had to secure the tourists during that time. So all the tourists, then eventually they evacuated. So in the afternoon when the volcano was already erupting, there were no more people here. So were you concerned when you realised the eruption was happening, that there were thousands of people on this island who live here that could be in danger? Yes. We were very worried because they were our friends. They know us, we know them. They were actually dependent on people, that people must be able to provide sufficient time or warning for them to evacuate. It was thanks to the constant vigilance of FIVOLCS, the Philippine Institute of Volcanology and Seismology, that the thousands of people in danger from the eruption were evacuated safely.

19:17About 50 kilometres away from Tal Volcano, in Manila, are the FIVOLCS headquarters, where they receive monitoring data from volcanoes all over the Philippines. Very cool. Wow, they've got cameras basically fixed on loads of volcanoes to see if they erupt. The first thing you see is a wall of screens with live feeds from cameras trained on volcanoes of interest, including Tal Volcano. Hi, nice to finally meet you. We're here to meet the person in charge of predicting eruptions in the Philippines. So my name is Maria Antonio Bornas. My nickname is Mariton. Everyone calls me Mariton. What I do is that I head the Volcano Monitoring and Eruption Prediction Division.

20:06I've been with FIVOX for 30 years. Mariton and her team have their work cut out, constantly studying dozens of volcanoes for warning signs. Geologically, the Philippines has many active volcanoes. That's around, for now, what we know is 24. We have another 27 or so potentially active volcanoes. but all in all, we have around 300 volcanoes. That includes the inactive ones. Oh, OK, something's happening on the screen behind us. Is something happening? Just as we're talking, some of the staff begin to crowd round a screen from a volcano that seems to be suddenly spewing gas. No, there's nothing. Maybe there's just clouds.

20:47But it's a false alarm. Mariton explains that interruptions like that happen a lot. And she says that the office is often full of the sound of warning sirens, like this one. And that's the alarm.

21:04Also on the wall are screens showing graphs and charts with live data from special monitoring equipment at the volcano sites. And this is what the team uses to try and predict volcanic activity. So for volcano monitoring, the main bread and butter for early warning really is earthquake monitoring, so it's volcanic earthquake monitoring. In every volcano, we will probably have between 10 to 16 seismic stations recording volcanic earthquakes. Why do we monitor volcanic earthquakes? Because these are the signals that are given by magma or its associated processes. For example, if magma starts to intrude from the deep levels of the volcano all the way up, It will have to create a pathway, and that involves breaking rock and letting off gas.

21:59And all of these processes produce signals. They also monitor levels of volcanic gases. So we measure sulfur dioxide. We are also monitoring carbon dioxide in volcanoes that have crater leaks. We can capture them in the water where they could be dissolved or from the lake itself. So a volcano like Tal, because that's got a lake in it, is that where you would potentially be monitoring within the lake the water? You would be monitoring carbon dioxide? Yes, we used to measure before the eruption. Now the acidity is less than one, so it's impossible to do a campaign measurement or even put an instrument.

22:43Because it's too acidic, it would just destroy your equipment. And they can use special satellite data to monitor tiny deformations in ground level caused by volcanoes. This is a really high-resolution GPS, very expensive, and can measure sub-millimeter motion of the ground. So less than a millimeter, the ground will move up or down and you can track that? Then we have other methods. We do have microgravity measurements in Taal Volcano and Mayan Volcano. and this is measuring the slight gravity changes or density changes on the volcano, which can be caused by the introduction of magma or magmatic waters into the volcanic system.

23:28So this is high-level physics. That's kind of mind-blowing. So you're able to detect changes to the strength of gravity that the volcano causes because there's more matter inside it from magma. Even though the team has access to such incredibly advanced technology, the changes they're looking for are often tiny and subtle. Sometimes they have plenty of warning. Other times it only becomes clear that a volcano is going to erupt mere hours before disaster, as happened at Tull in 2020. The work of places like FIVOLCS is to study regular volcanic eruptions. But what about super eruptions? the world-altering megadisasters that listener Crystal wanted to know about?

24:13Well, that requires a different approach, because we haven't had a supereruption for a very long time. To study them, you have to look back into the deep geological past, as George, the supervolcano expert we heard from earlier, explains. Yeah, so the last supervolcanic eruption was 25 ,000 years ago, and that was the Oronui eruption from Taupo Volcanic Zone in New Zealand. Myself and colleagues have looked at super eruptions over the last 2.6 million years and there's been 13 known events in that time. So how is it possible for geologists, volcanologists like yourself to piece together the timeline of these super volcanic eruptions that happened millions of years ago?

25:00The first stage is always to go into the field and study the deposits which we see. So these are either the fall deposit, that's the ash which comes out of the volcano and falls down to the ground, and the pyroclastic flows. These deposits always contain minerals and rocks within them, and my job is to then look at those minerals, or the different crystals contained within them. Each different crystal can tell us something different about that volcano. So to date these events, we typically use the mineral zircon, which is contained within them, and we use the decay of uranium to lead that we know the half-life of, and we can date that volcanic eruption using the uranium-led concentrations contained within this crystal zircon.

25:46Using these techniques, can looking back at the history of supereruptions give us any clues that we could use to predict the next one? Predicting the next supereruption is incredibly difficult. So if we look back over time, there's no real pattern in the period of time between these large supervolcanic events. They're very sporadic. Each of these supervolcanic events has its own character. They're unique. They're not necessarily going to show us the same signals. And they also erupt from various different locations. so we would find it difficult to predict even where the next super volcanic eruption will occur as well as when the next super volcanic eruption will occur.

26:30So if one happened today how big of an effect would it have on the world? It would be globally devastating in the fact that in the near vicinity you would have these large pyroclastic flows which would wipe out populations and cities. So an example would be an eruption I studied in New Zealand where there was a pyroclastic flow that was still 7 metres thick, 150 kilometres from its source. So these things travel a huge distance and they contain hot ash, gas and rocks which would really be hugely devastating. and then further afield we would have the amount of ash produced from these things would potentially would travel the globe and it would plummet us into the never-ending winter or the dark years where we would have it would block out the light it would change global temperatures by several degrees so it would yeah it would have long-lasting devastating effect on on human population and I would imagine that would continue for many years if not decades after the event.

27:44So I mean George does the prospect of a supervolcano eruption keep you up at night? Well when we look at super eruptions in the last 2.6 million years we only have the record of 13 of them so these are extremely rare events. The systems which we are currently studying that are in the public consciousness are systems like Yellowstone. And it's really the public perception that Yellowstone will erupt another super eruption. It's even been said that it's overdue. Now, this is completely not a good term to use because the far bigger likelihood is that if an eruption does occur from Yellowstone, that will be of relatively normal size in scale.

28:32So what's really important is we just continue to understand more about these events to improve the public perception of them in order that they might help against mitigation strategies and societal impacts of future events. So, Crystal, to answer your question, a supervolcanic eruption, one that has the power to create permanent twilight, chill the planet by a few degrees, and destroy crop harvests around the world, could happen, in theory, in the near future. And predicting when or even where is surprisingly difficult. Which sounds scary, but volcanic events on that scale are incredibly rare in Earth's history.

29:15And if a supereruption did occur, although it would be truly catastrophic, there's very little we could do to stop it. So maybe not worth worrying about? But the thing is, even supervolcanoes like Yellowstone are much more likely to erupt on a smaller scale. And that's something we can monitor and prepare for, in all the ways we've heard about. Back at the top of Tal Volcano, round-the-clock monitoring continues for people like Paolo, who actually lives at the observatory during his shifts, hours away from his family. But for him, the sacrifice is worth it. And is your job, Paolo, personally for you?