It’s the stuff of big-budget disaster movies - a cataclysmic explosion beneath the earth’s surface, flying rock, rivers of lava, the skies coloured black with ash. Supervolcanoes, however, are not just the product of screenwriters’ imaginations. They’re very real. These kinds of eruptions have taken place in the past, and will do so again.

But before you build an underground shelter, know that there’s no evidence a super-eruption is likely to happen in our lifetimes, according to geologists. Then again, these same geologists aren’t entirely sure how these destructive natural phenomena occur, which is slightly less comforting.

What scientists do agree on is that supervolcano is a moniker attached to volcanoes that produce highly infrequent and intensely explosive blasts registering a magnitude 8, at the upper end of the Volcanic Explosivity Index (VEI). They are formed when a huge volume of super-heated magma rises from deep underground and can’t escape the Earth’s crust. This creates a high-pressure pool several miles beneath the surface. As this pressure rises, this enormous pool of magma grows and grows until boom: a super-eruption takes place.

Obviously, no one wants to be close by if an event of this scale ever does occur. The truth is, however, you’re likely to be affected even if you lived on the other side of the planet. The effect of supervolcanoes on the global climate is so devastating that they’re thought to have contributed to the extinction of the dinosaurs, scientists told Time.

On that cheery note, here are a few facts about supervolcanoes you may not, or want, to know, plus some epic pics of less super, yet still incredibly mesmerising, volcanos around the world.

25 25. What Scientist Don’t Know About Supervolcanoes Could Fill A Super-sized Crater

Supervolcanoes are more than simply super-sized volcanoes. They are a natural phenomenon all of their own and appear not to follow the mechanics of a conventional volcano, according to Phys Org.

The scale of the processes that cause them, the depth of these mechanics, so deep underground, extending hundreds of miles across, mean that researchers still don’t fully understand how they happen. Combine this with the fact that they only happen once every 50,000 years or so - thankfully - and the lack of data concerning the types and quantities of gases they produce, and it’s very difficult for scientists to make predictions on just what the fallout would be, especially in terms of the global climate.

24 24. A Supervolcanic Eruption Occurs Approximately Every 50,000 Years...Or 5,000 Years (Scientists Aren't Quite Sure)

Prior to 2017, geologists estimated the frequency of super-eruptions to be every 45,000 to 714,000 years, which is a comfortably wide interval. However, in 2017 researchers from Bristol University examined 100,000 years of geological evidence to estimate the frequency of super-eruptions may be almost ten times as often as previously believed.

Their analysis revised this estimate to every 5,200 to 48,000 years, with the “best guess” value at 17,000 years, according to Newsweek. Great.

23 23. The Oruanui Eruption Of New Zealand's Taupo Volcano Was The World's Most Recent Super-Eruption

Lake Taupo, in the centre of New Zealand's North Island, is the caldera (a form of volcano crater) of the Taupo Volcano, which is - you guessed it - a supervolcano. The Oruanui eruption of the Taupo Volcano produced history's most recent super-eruption, some 26,500 years ago.

According to Te Ara, The Encyclopedia of New Zealand, about 1,200 cubic km of ash and rock was quickly ejected into the atmosphere, leaving deposits up to 200 metres deep over much of the central North Island, spreading ash over all the North Island and much of the South Island.

To put this in context, the Mount St. Helens eruption of 1980 only produced about one cubic kilometre, according to Science Alert.

22 22. A Super-Eruption At Yellowstone Could Cover The Whole United States In Ash

The first super-eruption at Yellowstone, 2.1 million years ago, is estimated to have ejected 2,500 times more volcanic material than the Mount St Helens eruption of 1980, which is thought of as the most violent eruption in US history.

In the 2014 published paper Geochemistry, Geophysics, Geosystems, scientists explored what a Yellowstone super-eruption might actually look like. Spoiler alert: it’s not pretty.

Among other things, they found a super-eruption could bury the northern Rockies in three feet of harmful volcanic ash, and would be capable of burying nearby states like Wyoming, Montana, Idaho, and Colorado. The Midwest would get a few inches of ash covering, while both coasts would see smaller amounts, depending on the time of year and weather patterns.

A super-eruption at Yellowstone would also eject over 2,000 million tonnes of sulphuric acid into the stratosphere, which doesn’t sound good.

21 21. The Super-Eruption At Toba In Sumatra Left Behind The Biggest Crater Lake On The Planet

One of the biggest super-eruptions we know about happened around 74,000 years ago at the Toba Volcano in Sumatra, Indonesia. In addition to leaving behind the biggest volcanic crater on the planet, about 100km across, the eruption at Toba spewed so much sulphurous gas and ash into the atmosphere that it triggered a decade-long volcano winter, which caused near global harvest failure and the end of many species.

According to Smithsonian Magazine, some scientists believe the event was so extreme that it reduced the human population to a few thousand survivors, and this hypothesis is called the “Toba catastrophe theory.” However, another study published in 2018 in the Journal of Human Evolution, that may be true, and that humans survived relatively okay. So there's hope for us yet.

20 20. If A Supervolcano Caused Mass Famine, Food Reserves Would Only Last 74 Days

In the event of a supervolcano eruption - let’s say Yellowstone, for example - the ash from the event would clog the atmosphere enough to block out the sun, which would disrupt the global climate enough to devastate crops across the world. This would cause catastrophic food shortages and the scary thing is, the world only has enough food reserves to last 74 days, according to a 2012 United Nations report, according to the BBC.

It’s facts like these that make us want to start stockpiling as soon as possible.

19 19. A Supervolcanic Eruption Would Have Catastrophic Effects On The Global Climate

Volcanoes emit sulphur aerosols that reflect sunlight back into the atmosphere and cool the climate. When Pinatubo in the Philippines erupted in 1991, it cooled the planet by about 1°C for some 15 months afterwards. The Tambora eruption in 1815, in Indonesia, cooled the planet enough to damage crops around the world. The scary thing is, these were relatively tiny eruptions compared to what a supervolcano is capable of, in theory.

A super-eruption at Yellowstone has the ability to send 1,000 cubic kilometres of ash and rock into the air, according to Forbes. This could trigger a volcanic winter around the globe, with a temperature drop by up to 12 degrees in the Northern Hemisphere and up to 16 degrees in the Southern Hemisphere. The consequence of this could be crop failure on an epic scale and mass starvation.

18 18. Researchers Don’t Believe Yellowstone Will Blow In Our Lifetime (Phew)

The Yellowstone volcano has had three “super-eruptions,” in the last 2 million years, according to the National Park Service. One occurred 2.1 million years ago, another 1.2 million years ago and a third around 630,000 years ago.

Data suggests that Yellowstone erupts every 600,000 to 700,000 years, which would kind of suggest that it’s due to blow soon, but some scientists don’t agree, thankfully. In a 2014 interview with the National Science Foundation, geologist Ilya Bindeman from the University of Oregon claimed that the past three major eruptions actually exhausted the volcano, which would mean that Yellowstone is actually in the middle of a quiet period, so the risk of eruption is small. Let's hope she's right.

17 17. There Are Ancient Supervolcanoes In Britain

Volcanoes in Britain? Yep, that’s right. Thankfully, there are no longer any active volcanoes in the United Kingdom, to the relief of its residents, and it’s been about 60 million years since there has been. However, the country is home to some ancient supervolcanoes, including Glencoe in Scotland.

This sleeping giant is located just north of Argyll, on the border with Lochaber, and it last erupted 420 million years ago. Other dead supervolcanoes can be found in Snowdonia and the Lake District.

16 16. NASA Has A Plan To Diffuse A Supervolcano (Sort Of)

A potential supervolcano poses one of the greatest natural threats to human civilisation - it’s up there with asteroids or comment strikes. It’s no surprise, then, that scientists at NASA have given the scenario some thought.

They’ve come up with a theoretical solution for calming down a super volcano on the verge of eruption, according to the BBC. The most viable solution would be to extract heat from the site, by drilling some 10km down and pumping water down at high pressure. The money and infrastructure required in such a project, however, would be epic, so it remains an idea rather than a reality.

15 15. The Campi Flegrei Supervolcano Is In A Critical State

Under the city of Naples, Italy, lies one of the world’s most dangerous supervolcanoes. And it’s showing signs of waking up.

According to scientists, Campi Flegrei may be nearing a critical pressure point necessary to cause an eruption - the first in 500 years. Since 2005, the volcano has been accumulating magma under its surface of a volcano, which is alarming for the three million people who live in its radius.

Italian authorities have responded by raising the threat level from green to yellow, which requires the supervolcano to be actively monitored.

14 14. There Are 40 Known Supervolcanoes Around The World (And 7 Are Thought To Be Active)

The good news is that most of the world’s known supervolcanoes are extinct. The bad news is that a handful are sleeping and are capable of reawakening, though it’s unlikely to happen in our lifetime. The most famous of these is the Yellowstone Caldera in Wyoming, US. There’s also Lake Toba in Indonesia, Taupo in New Zealand, Campi Flegrei in Italy, California’s Long Valley Caldera, the Valles Caldera in New Mexico and Aira caldera, Japan.

13 13. Global Warming Is More Likely To Wipe Out The Planet Before A Supervolcano Does

Climate-change sceptics have long argued that human-caused carbon emissions are minimal compared to greenhouse gases generated by volcanoes. The problem with this theory is that the science doesn’t support it, according to Scientific American.

According to the U.S. Geological Survey, the world’s volcanoes generate about 200 million tons of carbon dioxide a year. The pollution from cars and industrial activities, however, causes some 24 billion tons of emissions every year. So if the supervolcanoes don’t wipe us out first, we’ll probably do it ourselves, which is a cheery thought.

12 12. Oahu Volcano Flyby, Hawaii

Hawaii is famous for its volcanoes, which form some of the US state’s most jaw-dropping landscapes. They’re a part of Hawaiian culture and history and it’s one of the few places in the world where you can get up close to an active volcano like Oahu.

There are a variety of available packages and tours, but for one of the best views, check out one of these natural wonders from above on a helicopter tour.

11 11. Mount Fuji, Japan

At 3,776 metres, Mount Fuji is Japan’s tallest volcano. It stands on the border between Yamanashi and Shizuoka Prefectures and can even be seen from Tokyo on a clear day.

It last erupted in 1707 and remains an active volcano, and one that is revered throughout the country, according to Smithsonian Magazine. According to different religions, Fuji is a holy ground for pilgrimage, a home to deities and ancestors, a stairway to heaven, and even a portal to another world.

10 10. Eyjafjallajökull Volcano, Iceland

It’s nearly impossible to pronounce for anyone who doesn’t read or speak Icelandic, but Eyjafjallajökull is one of the most famous volcanoes in the world today, thanks to its relatively recent eruption in 2010.

In March that year, after being dormant for 180 years, Eyjafjallajokull began spewing molten lava and, after a brief intermission, the volcano resumed erupting, causing massive flooding and sending volcanic ash several kilometres up in the atmosphere. This led to air travel disruption in north-west Europe, lasting six days. It happened again in May, which resulted in the closure of airspace over many parts of Europe, leaving thousands of travellers stranded.

9 9. You Can Not Stop A Lava Flow

If a volcano starts spewing lava, like in this photo of Mount Etna, it can obviously be cause for concern. Often, the flow cools down quickly, which doesn’t make it a threat to anyone living below the volcano.

This isn’t always the case, however, as residents near Hawaii’s Kilauea volcano realised in May 2018, when a slow-moving river of lava covered more than 100 acres destroying dozens of building, prompting evacuations.

Despite what you might have seen in the movies, lava flows are incredibly difficult to stop and their path is very unpredictable. In the past, attempts to impede the flow have included bombing it, building concrete barriers, and using water, which have had limited success, according to the BBC.

8 Volcanic Lightning Is Awesome

Volcanic lightning is an awesome sight and although scientists have a basic understanding of how it occurs, there are still so many details they’re desperate to fill in.

In order for this phenomenon to occur, there needs to be a large charge separation between two masses. If this charge separation becomes big enough it is then able to create a path of ionised air and conduct electricity in the form of lightning.

Different studies put forward different reasons for lightning above erupting volcanoes. One points to static electricity from particles rubbing together in dense ash clouds. Another argues that the source is high above the Earth's surface, where colliding ice crystals unleash powerful jolts.

According to Forbes, there are still unsolved questions, like why it sometimes occurs in the absence of ash clouds, or why some volcanoes don’t appear to have it at all.

7 7. You Can Camp Next To An Active Volcano

Thanks to its location on the Mid-Atlantic Ridge, Iceland is a land full of volcanoes and has 30 active volcanic systems running through it. If you’re after a close-up encounter, this country offers lots of holiday opportunities to do just that.

Earn serious bragging rights and camp in the shadow of an active volcano. Eyjafjallajökull and Askja and two of the most popular with visitors, and in addition to hiking facilities, guided walks and 4X4 tours, they both offer campsites and huts. Bárðarbunga and Snæfellsjökull volcanoes are also good choices for camping.

6 6. Volcanic Clouds Can Be Just As Deadly As Lava

As natural phenomenon go, volcanoes are pretty flashy, what with the explosions and oozing hot lava flows. Volcano gases might not be as showy, but they can be one of the most deadly effects. Water vapour accounts for most of the gas released by an eruption, which is perfectly safe, but the other gases produced can be downright hazardous.

Carbon dioxide is not poisonous, but it displaces normal oxygen-bearing air and, because it is heavier than air, it collects in pockets, causing suffocation. When large quantities are dissolved in water, it can be fatal for nearby vegetation, livestock and people.

Sulphur dioxide and hydrogen sulphide can combine with water vapour in the air to form sulphuric acid, which is extremely corrosive and poisonous. Then there’s fluorine gas, which is also very unpleasant.

After the 1783 eruption of Laki in Iceland, fluorine poisoning and famine killed half of the country's livestock and almost a quarter of its population.