Astrum Space - The Supervolcanoes Scientists Say We Should Be Paying Attention To | Astrum Earth

Episode Date: May 1, 2025

Welcome to the formidable world of Supervolcanoes - colossal volcanic systems capable of eruptions more powerful than anything in recorded history. From Yellowstone to Toba, discover how these geological giants form, what makes them so dangerous, and the chilling signs scientists are watching for. Could another super-eruption happen in our lifetime? And if it did… what would it mean for humanity?From Alex McColgan and the Astrum team comes an illuminating new adventure that turns our gaze homeward. Astrum Earth invites you to rediscover the most extraordinary planet in our universe - our very own Earth.Journey with us as we explore Earth's most captivating mysteries and marvels, from the global dance of El Niño to the intricate rhythms that have sustained life for billions of years. With the same meticulous research and breathtaking visuals that define Astrum, we'll reveal our planet's stories in unprecedented detail.Narrated by James Stewart, Astrum Earth promises to transform how you see the world beneath your feet and the skies above. Because to truly understand the cosmos, we must first understand home.Discover our new Astrum Earth YouTube channel: hhttps://www.youtube.com/@AstrumEarth

Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank. Volcanoes are nature's ticking time bombs. In full flow, one of humanity's most fearsome sights, mythical, almost otherworldly. Nothing and no one on the planet can alter their course. force once they decide to remain silent no more. But that really is just the beginning. Because dotted around the globe, supervolcanoes are ready and waiting to awaken, with

the power to wipe out entire continents. Some are hidden beneath our feet. Others hide in plain sight. But when they make themselves know, there's nowhere to hide. The most violent eruption to occur this century was fairly recently. In January of 2022, the eruption of a submarine volcano near the main island of Tonga, about 2,000 kilometres northeast of New Zealand. The eruption of Hunga Tongaunga-Hawapi, to give the volcano its full name, constituted an explosion far larger than that produced by any nuclear bomb. It could be heard in Alaska, nearly 10,000 kilometres away. And it generally generated a tsunami that was two meters high even after crossing the Pacific Ocean to Peru.

The 2022 Tonga event was undoubtedly a big one. But how does it compare to other volcanic eruptions? I'm James Stewart and you're watching Astrum Earth. In this video we'll look at the volcanic rating scale, ancient clues of super volcanic eruptions and potentially dangerous regions across the world. Just how worried should we be about the possibility of future eruptions that are bigger, much, much bigger than the Tonga event? Let's find out.

Geologists quantify the violence of a volcanic eruption using a scale called the Volcanic Explosivity Index, or VEI. Although a given eruption can be assigned a single score on this scale, exactly what score is awarded depends on a combination of factors, such as the volume of rock ejected by the eruption. the height reached by the volcano's ash cloud or plume, as well as some more qualitative descriptors. The VEI scale is open-ended in principle, but all known events are graded between zero and eight. Event scoring zero are represented by eruptions of low viscosity, or runny, lava at volcanoes

such as Kilauea or Manalahu on Hawaii. Although these eruptions can involve large volumes of material and are dangerous in their own right. They are what geologists term effusive in nature. This means that the lava flows rather than explodes from the volcanoes bent. Go up the scale to a VEI of 2 and you reach the sort of eruption represented by the ongoing activity at Mount Etna in Sicily. Keep going and at a VEI of 3 you get to something like the eruption of Soufriere Hills which covered much of the Caribbean island of Montserrat with ash in 1996 and 1997. At a VEI of 4, you reach the 2010 eruption of the Icelandic volcano, its Icelandic name on the screen here for you, whose ash clouds spread over Europe and the

Atlantic Ocean, disrupting air travel for several weeks. Because many of an eruption's attributes can't be determined with certainty, there's sometimes disagreement about what score should be assigned to a given eruption. The 2020 Tonga, event with an erupted rock volume of about 1.9 cubic kilometres and a plume that reached a height of 58 kilometres earns a 5 on the VEI scale by most estimates, although some volkologists push it up to a 6. This is roughly on a par with the famous 1980 eruption of Mount St Helens in Washington State in the US. And in case you're wondering what 1.9 cubic meters looks like, it's roughly the volume of a large open pit mine, such as the Mur

Diamond Mine in Russia, or the Bingham Canyon Copper Mine in the US. Even more violent eruptions than Tonga, those firmly within category 6, include the 1991 eruption of Mount Pinatubo in the Philippines, which calls a small but measurable cooling of the globe due to the aerosols it injected into the stratosphere. And the 1883 eruption, of Krakatawa in Indonesia, whose ash might have been responsible for the lurid red sky depicted by Edvard Munch in his painting The Scream. A VEI of 7 is reserved for the greatest eruptions in recorded history. These come with the accompanying descriptor super colossal compared to the merely cataclysmic eruptions like Tonga in the VEI

5 bracket. The most recent eruption rating 7 on the VEI scale was the 1815, eruption of Tambora in Indonesia, which caused tens of thousands of deaths locally and tens of thousands more worldwide due to the volcano's effects on the climate. Because of the ash that Tambora injected into the atmosphere, the following year 1816, is known as the year without a summer. The average global temperature that year lowered by around half a degree Celsius, causing harvest failures and food shortages. VEI7 eruptions like Tambora are few and far between. For another eruption of comparable scale, you have to go all the way back to 1257, and the eruption

of a volcano called Samalas, also in Indonesia. But if the largest eruptions in recorded history only reach a VEI of seven, what sort of events could warrant the top rank on the scale? E.I.8 eruptions given the adjective mega colossal by volcanologists are those produced by so-called supervolcanoes. Supervolcanoes eruptions involve the ejection of more than a thousand cubic kilometres of material, more than 20 times the volume erupted by Tambora in 1815, and about 500 times the volume erupted by Tonga in 2022. The huge quantities of material blasted out by these top category eruptions, form volcanic plumes, that punch high up into the atmosphere, injecting ash and other aerosols that can disrupt the climate for years.

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And the super volcanoes that produce them are also uncommon, with only about 20 of them known worldwide. This is because super volcanic eruptions can only occur under very particular geological conditions, where thick, viscous magma that can contain gases under explosive pressures accumulates under the surface in huge volumes. This rareness means that not only have scientists never observed a super volcanic eruption themselves, but they don't even have any historical records to go on. Instead, like detectives trying to solve a crime with no witnesses to question, they have to work out the processes behind super eruptions

by piecing together clues deposited thousands of years ago. So let's run through a few of these geological cold cases. The most recent super volcanic eruption that scientists know of occurred around 26,000 years ago in New Zealand's North Island. Supervolcanoes don't have the classic cone shape that you might associate with more run-of-the-mill volcanoes. The bodies of magma that feed them are so vast that when the volcano erupts and the magma chamber empties. A huge area of land simply collapses to form a giant crater called a caldera. The caldera created by the most recent super eruption in New Zealand is now occupied by Lake Topor,

186 metres deep and 46 kilometres across at its widest. The next most recent super eruption is probably one of the most famous. About 74,000 years ago, the Toba Supervolcano on the Indonesian island of Sumatra, produced one of the most violent volcanic explosions in Earth's history. Like Topor, the crater left by the Toba super eruption is now occupied by a large lake. But whereas the New Zealand event 26,000 years ago ejected a little over a thousand cubic kilometres of material, the tober super eruption 50,000 years earlier, involved at least twice the amounts and perhaps many times more.

And in case you're having trouble imagining what a thousand cubic kilometres looks like, try to picture a cube of rock and ash as tall as Mount Everest and you still won't quite be there, Everest is a little under nine kilometres tall, but you're in the ballpark. And it wasn't just rock ash that was ejected from Toba in that gargantuan eruption. All magma has various gases dissolved in it, such as hydrogen sulfide, sulfur dioxide, carbon dioxide and water vapour. In fact, it's the behaviour of these gases that determines how explosive an eruption is. As the magma moves up through the volcano's plumbing system to be erupted as lava,

the pressure decreases and the gases come out of solution. If the magma is runny, like that which feeds the volcanoes on Hawaii, the gases can bubble up and escape. But when the magma is thick and viscous, as is the case at Tober and other supervolcanoes, it's much harder for the gases to get out. Now when the pressure drops, the gases explode suddenly, like a shaken bottle of lemonade when the lid is removed. This blast the lava into pieces as fine as ash and as large as boulders. So these gases are responsible for pulverising some of the erupted material into particles, small enough to linger in the atmosphere for years, shading the planet and lowering temperatures.

But sulphur dioxide makes the problem even worse. When it reaches the atmosphere, this gas reacts with oxygen and water to form tiny droplets of sulfuric acid and other aerosols. These aerosols can remain in the stratosphere for as long as a decade, reflecting sunlight back into space and plunging the earth into a so-called volcanic winter. The super eruption of tober 74,000 years ago, released huge quantities of sulfur dioxide. Although it's difficult to distinguish volcanic effects from background climate cycles, scientists have found evidence that the eruption was followed by a century-long period of cooling. It has also been proposed, based on archaeological and genetic data, that the climatic effect of the tober super eruption caused our species to pass through a genetic bottleneck.

The global population might have dwindled to just a few thousand. This so-called tober catastrophe hypothesis is contested. Some scientists doubt that the climactic effect of the toba eruption was large enough to induce a global multi-year volcanic winter, and some question the severity of the population crash that supposedly coincided with it. But whether or not the toba supervolcano really did cause the population of humans worldwide to shrink to a number that would fit into a large concert hall, if a similar eruption were to happen to, today, the effects on global agriculture would be truly catastrophic. So how worried should we be?

Well, we know that these events are rare. Topor and Tober are the only super eruptions known to have occurred in the last 100,000 years. If you travel back in time from the Tober event, the next one you would come to is another super eruption of Topor, around 340,000 years ago. But let's not get complacence. At both tober and topor, smaller eruptions have occurred since their most recent super eruptions, and there's no reason to think that their supervolcano is now extinct. Both locations are on the so-called Pacific Ring of Fire, a region of extreme volcanic hazards surrounding the Pacific Ocean, where volcanism is triggered by oceanic cross being forced down into the underlying mantle. Presumably, one day, even if that's in thousands of years, one of these supervolcanoes will

erupt catastrophically again. And in the meantime, there are other supervolcanoes to consider. Apart from Topor and Tober, the supervolcanoes known to have hosted eruptions rating 8 on the VEI scale are clustered in the Andes of Chile, Bolivia and Argentina, and in the western half of North America. Volcanoes associated with the Andean volcanic complex show signs of unrest. Swelling ground suggests a filling magma chamber, for example. But not on a scale that makes geologists think that a super eruption is imminent. The eruptions in North America all originated in a volcanically active region known as the Yellowstone hotspot,

which is one of the most intensively monitored volcanic sites on Earth. The geology of the region is complex, and geologists. Geologists don't know whether the source of the magma is a plume originating deep in the earth, or a piece of the ocean cross that's been forced under the North American continent. Whatever the origin of the magma, the Yellowstone hotspot is thought to have hosted six VEI8 eruptions in the last 10 million years. The last one being approximately 640,000 years ago. These eruptions formed the Yellowstone Caldera, now at the centre of the river. Yellowstone National Park. If the supervolcano were to erupt similarly today, it would

devastate the states of Wyoming, Idaho and Montana with red-hot clouds of rock, ash and gas moving at hundreds of kilometers per hour. Further from the site, ash would be deposited in a thick blanket, disrupting travel and collapsing the roofs of buildings. And the climactic effect of airborne ash and sulfates would likely be pronounced cooling of the thought to have occurred after the tober eruption 74,000 years ago, which might have lowered temperatures by several degrees Celsius across much of the world. Because of this threat and because of the region's long history of activity, scientists continually observed the Yellowstone volcano for signs of ground deformation, earthquakes and volcanic gases, which could indicate

magma on the move. The problem is the Yellowstone region is so active that such occurrences are almost constant. And because nobody has ever actually witnessed the build-up to a super volcanic eruption, we can't be absolutely sure what we should expect to see before it blows. Based on the average times between the last few eruptions of the Yellowstone volcano, the charts of an eruption occurring there in any given year has been estimated at 1 in 730,000. But that's not really how volcanoes work. they don't hold to schedules like that, so it would be inaccurate to say whether an eruption is due or not.

Still, geologists monitoring the Yellowstone Supervolcano are confident that there are currently no signs that magma is accumulating in a large enough quantity to feed such an eruption at any time soon. But there are many more sites where huge eruptions have created large calderas and where a VEI-8 event could plausibly occur. And even if an eruption doesn't quite reach the magnitude necessary to qualify for the top category, it could still be locally catastrophic. One such site is the Flagrian Fields near Naples in Italy. This large complex of Calderas lies just across the Gulf of Naples from Mount Vesuvius, the volcano that famously buried the Roman town of Pompeii in 79 AD. Well, that event might seem bad enough, it scored 5 on the VEI scale, incidentally.

an eruption of the Flagrian fields could be hundreds of times larger. It has been suggested that the climate effect on an eruption about 39,000 years ago, helped to see off the Neanderthals who disappeared from Europe around this time. Although like the Toba catastrophe hypothesis, this claim is disputed. In the last few years, activity at the Flagorean field seems to be intensifying, with increasing earthquakes and ground deformation causing alarm among volcanoes. Although the probability of a large eruption is still considered very low, the situation is serious enough for authorities to devise an evacuation plan for more than a million residents of the area. There is a potential cause for alarm elsewhere in Europe too.

The Greek island of Santorini nowadays is shaped like a crescent. Wind view from above with its neighbouring islands, it's easy to imagine Santorini as making up one part of a volcanic caldera, many kilometres across. cross. No surprise then, that's exactly what it is. The eruption that caused it was not strictly a super eruption, given its eruptive volume of less than 100 cubic kilometres and its VEI of 7. Nevertheless, this eruption occurring around 1600 BC, devastated the eastern Mediterranean, generating a tsunami that was tens of meters high when it reached the nearby island of Crete. This explosion could have even called contributed to the downfall of the Minoan civilization that was based on Crete,

and might have inspired the myth of Atlantis. Volcanic activity has continued at Santorini since then, although no eruption has come close to the violence of that Bronze Age cataclysm. Scientists continue to monitor the region for signs of unrest, and although the question is when rather than if the volcano will erupt, again, there are no indications that a big one is imminent. So how worry should we be about such an eruption in our lifetimes? Well, one day, Santorini, or the Flagrion Fields, or Yellowstone or Topor, or one of the other supervolcano candidates, will blow and blow big.

That's a certainty. But it's one of those high-impact, low-probability hazards, like a large asteroid striking the Earth. Although the chances of it happening are low in any given year, it will happen, and when it does, the consequences will be severe. In the case of Santorini, the alarm bells are already ringing after the picturesque island was evacuated in February 2025. According to officials, on Wednesday the 5th of February 2025, more than 11,000 people left Santorini, with around 7,000 departing by ferry, and 4,000 people leaving by air after hundreds of earthquakes rocked the island, the strongest of which was a magnitude 5 tremor. The incident has led to a rapid scientific response,

with scientists now investigating for the first time how dangerous the next big one could be. As recently as April 2025, British Royal Research Ship the Discovery, Led by Professor Isabel Yeo and her team of 22 scientists are on a mission to understand what type of seismic unrest could indicate a volcanic eruption is imminent. At the time of recording this video, the team are still on board the vessel, undertaking research in 12-hour shifts as part of their month-long assignment. Hidden amongst the idyllic Greek aisles, some 300 metres below the design,

discovery, are bubbling hot vents. These cracks in the earth turn the sea floor into a bright orange world of protruding rocks and gas clouds, hydrothermal vents where hot water pours out from the cracks. Off the side of the research boat, a robot descends to the seabed to collect fluids, gases and snap off chunks of rock in order to try and map the hydrothermal system. They identify how fluid moves through rocks by pulsing an electromagnetic field into the earth. This creates a 3D map that shows how the hydrothermal system is connected to the volcano's magma chamber, where an eruption would come from. This information will create datasets and geohazer maps for Greece's Civil Protection Agency,

a member of the government emergency group that met daily during the earthquake. crisis. The idea is this research would help inform local people how active the volcanoes are, and it will help map the area that will be forbidden to access during an eruption. Which begs the question, how much notice are we likely to have if it happens on the time scale of our civilization? Will we recognise the warning signs? The worry is that scientists lack of direct experience of these events might mean they misinterpret what data they have available. Our current knowledge of volcanic explosions has been gathered largely from observing eruptions of volcanoes fed by comparatively small magma bodies, and even then an eruption cannot be

predicted with certainty. The 2022 eruption of Tonga, for example, was preceded by about a month of smaller eruptions, and 15 minutes before the big one, an earthquake. But those smaller eruptions were not taken as sure fire indications of the imminent VEI-5 event, and it was only after the eruption that researchers realised the significance of the earthquake. After all, the largest volcanoes occur almost by definition in the most volcanically active regions, where the Earth shows near constant signs of being unsettled in one way or another. The processes occurring under large calderas could be quite different from those that go on inside the more common volcanoes, making prediction even more difficult.

And assuming a super volcanic eruption could be forecast with confidence a month in advance, as we might argue that the Tonga eruption could have been given our perfect hindsight. That might be long enough to evacuate people from the areas of high impact, but we've seen that such an event would likely have much wider scale, longer-term consequences for the climate and agriculture. And to mitigate those effects, even a month is no time at all. Scientists will continue to monitor existing supervolcanoes and to study super eruptions that occurred in the past. If you live in an area like the Flagrion fields

where the risk of experiencing a violent, if not super volcanic eruption, is elevated, then you should be prepared to evacuate. All the rest of us can do is hope that the odds of not witnessing one of these cataclysms are in our favour.