There are regular volcanoes, and then there are the supervolcanoes. Massive calderas of hot magma of incomprehensible size. Bad news, these things explode randomly and catastrophically. Worse news, there are a bunch around the Earth.
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Fraser: Hi, everyone. Fraser here
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Astronomy Cast Episode 440: Supervolcanoes!
Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know but how we know what we know.
My name is Fraser Cain. I’m the publisher of Universe Today and with me is Dr. Pamela Gay, the director of Technology and Citizen Science at the Astronomical Society of the Pacific and the director of CosmoQuest.
Hey, Pamela. How are you doin’?
Pamela: I’m doing well. How are you doing, Fraser?
Fraser: I’m doing great.
So I’ve got sort of two pieces of adminis-trivia.
So, the first thing is that our good friend, Nancy Graziano – one of the sort of heads of the Weekly Space Hangout crew – is looking for work. She is a talented technical writer and one of the most skilled human beings that I know of and has sort of popped out of the woodwork and made herself instantly super-important to the whole – you know, all the projects that we work on, as a volunteer – and you really need to hire her to get her a job.
So just send her an email if you’ve got technical writing work, like a position as a technical writer somewhere in the United States: email@example.com. Let her know you’ve got work for her.
Pamela: And both of us will write her rec letters.
Fraser: Yeah, we’re –
Pamela: This is from both of us.
Fraser: Yeah. But if you are, like, in some firm – you know, Google; any one – and you want to – you’re looking for, like, a really skilled both human being and technical writer, Nancy’s your person.
The second thing is I just want to, you know, remind – this is sort of the third time I guess I’ve made this joke now – but just to remind everyone that, no matter how enthusiastic Pamela gets about the concept of supervolcanoes, she does recognize and understand that they are the cause of tremendous human suffering. So, please remember that as you hear her enthusiasm, don’t – you know, just don’t think that she’s a horrible, soulless monster.
Alright, let’s get on.
So, there are regular volcanoes and then there are supervolcanoes; massive calderas of hot magma of incomprehensible size. Bad news: These things explode randomly and catastrophically. Worse news: There’s a bunch around the Earth.
Alright, so tell us the difference between a regular, plain old volcano and a supervolcano.
Pamela: It basically comes down to “size matters” if you’re a volcano. They break volcanoes up into their Volcanic Explosivity Index; so, how much of a mess, a disaster, a world-changing event can one of these things cause.
And supervolcanoes are generally considered to be those volcanoes that have a VEI (Volcanic Explosivity Index) of 7 or 8. And I’ll back that up and put numbers on that.
Fraser: Yeah, please do.
Pamela: So a 6, which is not a supervolcano – we know what these look like because we had Krakatoa go off in 1883; we have written records of that. We had Pinatubo go off in 1991. These were category 6 – and this is a logarithmic scale. So these are things that produced 10 and 25 cubic kilometers of magma coming out of them and coating the landscape – logarithmic scale.
So, it’s the level 7s and 8s that are the supervolcanoes. So here we’re looking at things that have, like, 10 to the 15 kilograms of ejecta coming out of them.
Fraser: Yeah, they measure it in cubic kilometers, right?
Pamela: Yeah, so it’s a hundred cubic kilometers to over a thousand cubic kilometers for these things. So let’s think about that. This is how you make new mountain ranges. So, the Siberian Traps – this is where we’ve had this kind of an outlaying of magma in the past. So, yeah – just let’s change the whole landscape with lava. Why not?
Fraser: Right, right.
And so, you know, you mentioned the Siberian Traps. I don’t know why they call it the Siberian Traps but –
Pamela: The word “Traps” –
Fraser: Is it because it was like the Deccan – Deccan Traps as well, right?
Pamela: Well – and they’re both actually –
Fraser: Is that the same thing?
Pamela: Yeah. And they’re both using a Swedish word. I don’t know why it’s a Swedish word. But the word means “stairs” and when you look at them – because lava coming out in different epochs ends up forming bottom layer, next layer – they kind of look like stairs.
And so, the Siberian Traps – Siberian “stairs” – this is where we have millions of square kilometers of area covered in lava.
Fraser: Right, okay. So you’ve got, you know, like a regular volcano. Maybe they have a few cubic kilometers like the Krakatoa, like the Pinatubo – a few cubic kilometers. When you get up into the supervolcano, then you have potentially hundreds of thousands of cubic kilometers of material that gets ejected all in one go.
What does the – like the caldera – like, what does it look like geographically if you could sort of slice the Earth in half and take a look inside? When you’re looking at a supervolcano, what are you seeing?
Pamela: So different supervolcanoes – it’s, again, a descriptor of how much stuff is going to come out when this chamber of magma blows. And so, geographically, they can have multiple sources, just like volcanoes have two different sources
So, in general, when we’re looking at volcanoes, we have hot-spot volcanoes like the Hawaiian Islands that are caused by magma plumes welling up and, as the crust moves over one of these magma plumes, the magma drills through the crust of the Earth and spews out the surface, creating new islands.
Pamela: Now, Yellowstone – supervolcano, super caldera – is one of these hot spots and it’s actually, of the lists of massive eruptions known through history, it is the cause of the largest number of gigantic eruptions of all of the massive volcanoes. It has, in fact, had six magnitude 7 and 8 volcanic eruptions. This is a hot spot under the crust of the Earth with a magma plume that just keeps filling up a chamber with increased – more and more pressure – tilting lakes so that they flow across the surface of the planet.
Pamela: And when it blows –
Fraser: Right, okay.
Pamela: – it just, yeah.
Fraser: So give us a sense of the devastation, right? So, in Yellowstone, this gigantic caldera; hundreds, thousands of cubic kilometers of magma ready to explode. What kind of an impact, if such a volcano was to go off?
Pamela: So, I found this awesome diagram of “notable volcanic eruptions” and some of the ones that it shows for past Yellowstone eruptions have the impact zone for where there was serious destruction on the surface of the planet; essentially spanning from the Mississippi River, where I am at the border between Illinois and Missouri, all the way out to the coast of California.
So we’re looking at pretty much all of the Great Plains, the Rocky Mountain regions, California; it looks like it ends right around Vancouver. So, yeah – we’re talking massive amounts of destruction.
Fraser: And so, are you saying that there are lava flows from the Pacific Ocean to the Mississippi?
Pamela: It’s not just lava flows. So, what –
Fraser: Ash fall.
Fraser: Gigantic rocks coming down.
Pamela: Yes. So the area of massive carnage and destruction is essentially from –
Fraser: And don’t forget about the terrible loss of human life.
Pamela And the terrible loss of human life –
Pamela: – if people don’t evacuate. I’m all for evacuating.
Fraser: Right. Well, we’re going to talk about that in a second.
Pamela: I’m a firm believer of evacuating.
Fraser: Yep, yep.
Pamela: So, yeah – from the Mississippi to the Pacific Ocean.
Fraser: Right, okay. That is a very large – I mean, that hits you and it hits me.
Fraser: And we are thousands of kilometers apart.
How – Okay, great. So how much warning do we get?
Pamela: We don’t know.
And so, this is one of those things that we’re currently dealing with because one of the other famous, massive supervolcanoes – in this case, we’re looking at the other kind of volcano; one that’s caused by a subduction zone. This is where you have one plate of the Earth plunging under another plate of the Earth – things melt, things come up (literally).
And, in this case, there is a – and I’m going to pronounce this horribly because this is what I do on this show – it’s the Campanian Ignimbrite. It’s generally listed as the CI caldera just about everywhere that I was reading today. This is the one that’s under Naples and associated with the Phlegraean Fields, and all of these things that you read about in books – and if you’re me, you haven’t heard enough people pronounce out loud.
And it turns out that last time this particular caldera decided to give up its magma to the atmosphere; it might have been the turning point in Neanderthal civilization.
Fraser: Right, the timing is such that the Neanderthals – okay.
So let’s talk a bit about just the devastation. You’ve got this volcano going in – be it Europe, be it Yellowstone. I think the biggest one is in Asia, like maybe in – I think it’s in Indonesia.
Anyway, this thing goes off. We already talked about the size. You know, you’re looking at thousands of kilometers across, as a place where bad things happen. What kinds of bad things happen?
Pamela: So, locally, what you’re looking at is – it looks like these volcanic eruptions can occur in different phases, just like other volcanic eruptions at more normal scales do; where you have the oozing stage – where there’s a great amount of stuff coming out but it’s just hot lava sliding down the side of a mountain at “melted rock” kind of speeds.
Fraser: Right – pouring into the environment, turning what was once a lovely national park into a parking lot.
Pamela: Yes. Yes, that would be exactly true.
Fraser: Right. And you could run away from it –
Fraser: – at running speed. Yeah.
Pamela: Yeah – Jeeps, cheetahs; all these kinds of things are useful.
Fraser: Yeah, yeah.
Pamela: But then you’re also looking at things like the pyroclastic flows. So, for instance, if you have water involved, if you have ice involved, you can end up with sudden extremely-high-speed liquid magma, breccia – all of this sort of stuff – flowing at high speeds. This is the stuff you can’t outrun.
Fraser: And, like, talk about speeds because the speeds are stunning. You get this mixture of rock and water and gasses and dust, and this – the, you know – the pyroclastic – I mean, usually you can’t outrun the pyroclastic flow. That is an understatement. They are going –
Fraser: Like, how fast are we talking about here?
Pamela: So, some of these things have been clocked at like 700 kilometers per hour; that’s 450 miles per hour.
Fraser: Yeah, so you have to like – It’s like going almost the speed of sound – from the explosion. Like, there’s no getting away from this.
Pamela: No. No, this is the “you die” stage. It is simply the “you die” stage.
Pamela: So, yeah. Yeah.
Fraser: Okay, you got – So you got slow, oozing lava; no problem. I mean, at a scale you can scarcely comprehend, you’ve got pyroclastic flows that are flowing, you know, away for quite a ways. Right?
Pamela: So then, we’re looking at: How does it end its life?
We have the puffing large amounts of ash into the atmosphere that can go on. We have continued lava coming out. And exactly how these things go through their phases – we luckily haven’t seen it happen in real time – but from looking at the way material has been lain out – Well, let’s go back to that Naples caldera again.
Pamela: It was estimated that in its eruption 39,000 years ago, there was up to 2 centimeters, 5 centimeters of ash, all the way into central Russia, deposited.
Pamela: If you do that onto growing crops, they don’t do so well. So, in the area right around the volcano – so here, we’re looking at like the width of Italy – there was about half a meter of ash. And ash is harder to shovel than snow.
Pamela: There was –
Fraser: Yeah – and it doesn’t melt. Right?
Pamela: No, no.
Fraser: Yeah. We had the ash – Sorry. You know, during Mount St. Helens –
Fraser: – we got some of the ash up here on Vancouver Island and in Vancouver and it was awful. It was like this light – For us, it was this light dusting but then, for other people, it was – It just got worse and worse.
And I actually have some of the stuff here. I don’t know if people could see. Here, let me just – I’m gonna – Well, behind me – podcast listeners can’t see it but people who are viewing can see – right beside my telescope, I’ve got a little jar there and that’s filled with Mount St. Helen ash. And I’ve actually got some chunks of pumice inside.
Fraser: And they actually float, which is cool. So, we have friends that live down in the affected area and they gathered some of the stuff up because it was everywhere. And, like, you know?
Fraser: You couldn’t do anything with it. Yeah, it was a disaster – but very fertile.
Pamela: So, with the last time our CI supervolcano down in the Naples area went off, there was as much as 10 centimeters of ash basically covering the Fertile Crescent. So all –
Pamela: All of Italy south of Naples, Greece – Greece was covered – all of the Fertile Crescent, northern Africa – yeah. So a large swath of the planet – at least what was the particularly interesting part of the planet at the time – covered in ash.
Fraser: Covered in ash, so everything dies.
Fraser: And now – But fortunately, those of us, you know, around the world nowhere near the affected zone – we’re fine, right?
Sorry, I just – This is, like, this is such –
Fraser: I know.
Pamela: – cool science, I can’t help but giggle.
Fraser: I know.
Pamela: I am not a fan of death and destruction.
Fraser: I know, I know.
Pamela: I think this is so cool.
Fraser: And that’s – Don’t worry. I already disclaimed you at the beginning of this episode, that you were going to get, like, giggly –
Fraser: – about a significant geological event, unrivaled –
Fraser: – in power and destructiveness.
Fraser: And you are deeply aware of the depth of human suffering that would be caused by such a thing.
Fraser: So you can feel free to get silly about this and know that all those deaths would weigh heavy on your conscience.
So I mentioned that the CI eruption 39,000 years ago probably did really bad things to the culture of the Neanderthals. The Siberian Traps, when they last went off 252 million years ago, that was kind of about when the Permian-Triassic extinction occurred – and this was one of those extinctions that, like, killed everything. Everything.
Fraser: Yeah, it didn’t matter if you were on land, didn’t matter if you were on the water – 99 percent of all life, or 90 percent of all life, just died.
Pamela: Yes. And what we’re looking at is a whole lot of different problems. You have – Locally, you’re failing to outrun the pyroclastic. You are watching your city get buried in lava. You are then watching ash fall in hundreds, thousands of kilometers around the volcano.
Fraser: The volcanic blocks are just raining down – you know, the size of a house.
Pamela: Yeah. But let’s look at what’s happening above that volcano.
So, there’s a volcano going off today – there’s almost always volcanoes going off. There’s usually more than one volcano going off. But the one that’s being particularly interesting today is the Bogoslof volcano. And according to the Center Weather Service Unit, a pilot has estimated that this particular Alaskan volcano is shooting ash 38,000 feet into the air. This is well above the height that your typical trans-oceanic flight –
Fraser: Right, they have to fly –
Pamela: – is flying at.
Fraser: Right. They have to go above it.
Pamela: And they can’t. So, this is the kind of ash you simply go around because you can’t go over.
Fraser: And if it gets in your engines – like, forget it.
Pamela: It shreds your plane. Yeah, we’re –
Fraser: Yeah. I mean, so just imagine the Neanderthals and the terrible destruction they had on their airplane engines.
Pamela: So, beyond what it does to aircraft engines, all of this dark, light-absorbing material getting tossed up into the atmosphere at, like, 10 to the 15 kilograms-worth of this stuff – it kind of changes the climate.
Pamela: It kind of causes Ice Ages and glaciation and, well, climate change goes in a very different direction when these things happen.
Fraser: Yeah, things will get cold. Right.
Pamela: So, we’re looking at changing the planet’s climate for a significant chunk of time, which – I’m kind of a fan of getting a giant, more Pinatubo- or Krakatoa-sized eruption going off somewhere, that would hopefully not kill anyone – with sufficient warning that we evacuate whatever island is about to blow.
Fraser: What are the –
Pamela: And we oft –
Fraser: What are the “fun” volcanoes?
Pamela: What are the fun volcanoes?
Fraser: Yeah, the ones that go off at a place that nobody lives and does no long-lasting destruction to the environment and really – it’s just really great pictures and you can see all the cool lightning strikes going on in the – you know, in the clouds. That’s all you – Great.
Fraser: Sure, that’s what you would hope for.
Pamela: So, when Pinatubo went off, it did cause some measurable temperature differences.
Pamela: It caused significantly different color sunsets. Now, it – Naturally, Krakatoa and Pinatubo did kill large numbers of people but we’re getting better at evacuating islands. We really are.
Fraser: Yep. Yeah, and did a pretty good job of evacuating Mount St. Helens.
Pamela: Yes, yes. There, it was the stalwart individuals were like, “No, I won’t die. I’m going to stay here.”
Pamela: So, that’s Darwinism. What we’re talking about is – like, with a lot of the Indonesian islands – when the volcano alerts go off, they will actually, like, evacuate an entire island. Luckily, volcanoes like to rumble a lot before they burst. So, as long as we get this kind of warning and it’s one of the remote places.
Now, the issue is that, like I said, Yellowstone – if it went off the way it has in the worst cases in the past – that’s everything from the Mississippi to the ocean.
Pamela: So that’s like: Los Angeles, San Francisco, San Diego, Seattle, Portland, Denver – yeah, I’m gonna stop there.
Pamela: I don’t think we can evacuate that.
Fraser: No, no.
Pamela: Naples is actually a whole lot worse because now you’re looking at a whole lot of places where you can’t actually drive to escape, because there are all of those Greek islands and Italian islands and owned-by-other-people’s islands that – It takes a boat. And there’s only so many boats.
So, yeah – supervolcanoes tend to be nice, interesting-to-live places that tend to be rather well populated at the moment. But you did bring up Toba, which is one of the other massive supervolcanoes.
Fraser: Yeah, the one in Indonesia.
Fraser: The one that created a lake within a lake within a – Have you seen this?
Fraser: This is the lake within a –
Pamela: It’s an amazing photo.
Fraser: It’s an island within a – It’s an island on a lake in an island in a lake in an island.
Fraser: Maybe one more of those but – yeah.
Pamela: And this is one of the ones that quite often gets misidentified as being an asteroid impact kind of crater because it looks so asteroid-impacty cratery. But no, this is known for catastrophic eruption theory: Volcanic winter lasting six to ten years and a 1,000-year cooling episode.
Fraser: Entirely possible to have – I mean, for this to be the causes of Ice ages.
Pamela: Mm-hmm. This – In fact, people are doing more and more to link – as we’re understanding our planet better, as we’re going through and measuring the different radioisotopes in these different lava fields, basalts – yeah. As we’re going through and working to figure this stuff out, we’re realizing the timing alignment with a lot of these things seems to link either asteroid/comet impacts or massive volcanic eruptions – or both – to many of these extinction events.
And you and I actually did an episode on this a while back.
Fraser: So, when was the last supervolcano to go off?
Pamela: The last – here, we’re going to have massive watch-things-die-off – was the Naples one 39,000 years ago. But there’s been ones more recent, in parts of the world that are new enough they weren’t particularly populated, like New Zealand.
These are two fairly significant islands and they’re still being formed. It’s really creepy when you visit New Zealand. Around Wellington, there’s a highway along the ocean and my driver took the time to let me know that the road had only been there for 300 years. And there was, like, historical records of when that part of the land rose up out of the sea.
Pamela: So –
Fraser: Like, a road was only possible there for the last 300 years or so.
Pamela: Yeah, yeah.
Pamela: So, the most recent category 8 was 26.5 thousand years ago in New Zealand; part of making New Zealand, as you do.
Fraser: I don’t know. Every 26 thousand years – I like those odds.
Pamela: Now, the category 7 ones occur quite a good deal more recently. So, looking in Indonesia, Mount Tambora went off about 135 years ago – so now we’re starting to get at things only slightly older than the oldest humans. Again, in Indonesia about 700 years ago, there was Mount Rinjani. So this is part of the reason that Indonesia is so good at evacuating islands; they have a history.
Pamela: But these things aren’t dead. And we tend to get very lackadaisical about, “Oh, that volcano’s dormant.”
Pamela: The Three Sisters complex in Oregon – one is extinct, one is dormant and one is still probably pretty active and could blow. And we don’t talk about these things.
And what’s amusing is I just noticed the person who was driving me in New Zealand, Citizen Gold, is online right now. He’s the one that told me about the road forming 300 years ago.
Fraser: That’s awesome.
So, I guess where I want to go in the end here is like, how can we know this is happening? What will be some of the warning signs and when we’ll know that it’s time to bug out?
Pamela: So, GPS is your friend. Use it at all times to measure small motions in the surface of the planet.
So, what they do – places like Yellowstone – is they deploy sensors kind of all over the place that are measuring the expansion of the planet; changes in the tilt of the surface; changes in the altitude of the surface; changes in the north, south, east, west position of the surface. And all of these things can be used to measure how the planet is bulging.
Then there’s also just keeping constant track of: Where are there hot springs? Oh, by golly, are we getting a whole lot more of these suddenly? Is there steam starting to come out of the surface of the planet? Let’s quickly measure the gasses and make sure that it is steam and not other gasses coming out of the surface.
Pamela: One of the things that really got me is I was able to visit Delphi a few years ago. And the Oracle of Delphi was actually some poor set of women that were getting gassed by the planet, which was emitting toxic fumes – because Greece and Italy are basically very volcanically active.
Pamela: So, our planet gives off bad gas.
I fear that we may have panicked and frightened people. So, can we bring it all home here? As we mentioned, you know, the last time a major supervolcano went off, it’s 26,000 years ago in a largely uninhabited location. Your chances of this happening is very low. So –
Pamela: No. No, don’t say that. So –
Fraser: Focus on your health: Don’t smoke, eat good food and don’t drink and drive.
Pamela: So, I do want to say, that’s false statistics. All because it’s been 36,000, 24,000 –
Fraser: I know. I know, I know, I know.
Pamela: That’s – We have to look at: What is the frequency of these things occurring? And now, is one going to go off tomorrow? Probably not – but it could. And –
Fraser: Mm-hmm. Yeah, and one could go off every day for the next – until we run out of supervolcanoes, right?
Pamela: But –
Fraser: Absolutely. That’s the way statistics work. We did a whole show on this!
Pamela: But I think the lesson is: Live fully, live completely; know we could all die tomorrow – but we probably won’t.
Fraser: Right, we probably won’t. So don’t use any of this as an excuse not to brush your teeth is what I’m saying.
Fraser: Alright. Well, thanks Pamela. I have no idea if we’re going to continue this series. I’m having fun. Clearly, you had fun. We will talk to you next week.
Pamela: Sounds good. Talk to you later, Fraser.
Male Speaker: Thank you for listening to Astronomy Cast, a non-profit resource provided by Astrosphere New Media Association, Fraser Cain and Dr. Pamela Gay. You can find show notes and transcripts for every episode at astronomycast.com. You can email us at firstname.lastname@example.org. Tweet us @astronomycast. Like us on Facebook or circle us on Google Plus.
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Duration: 32 minutes