Wednesday, 12 October 2016

Sensory Deprivation: Not as boring as it sounds

Living in the 21st century can often feel like being constantly poked with a thousand blunt sticks. The minor (and major) stresses we face every day – noisey neighbours, traffic congestion, the constant stream of pings and vibrations from the small rectangular ball-and-chains we carry around in our pockets – can really where a person down. You may be familiar with the sensation of coming home exhausted at the end of the day in spite of the fact that, physically, all you have done is sit in a chair and stare at a screen. That is because the thousands of little prods your brain gets actually where down its ability to function. Worse, the instinctive stress response our bodies produce when we, for example, get a new project with a tight timeline handed down to us by a manager can lead to high blood pressure, impaired cognitive function and a host of other physical effects that are generally bad news.

It is no wonder then, that new-agey trends like yoga and meditation have surged in popularity over the past decade. We are driven to find ways to escape the sensory overload that is just a normal part of life for so many of us. However, few interventions embody the crystal-healing, aura-cleansing, cringe-inducing pursuit of stress-escapism in the way that the practice of sensory deprivation does.

Any hardcore Simpsons fan ia familiar with the basic concept of sensory deprivation. You lay in a dark, soundproof space, tucked away from any distraction, and experience the novel sensation of nothingness. However, since Homer took his wild ride in a whale egg back in 1999, the practice – and business – has expanded dramatically in North America.


The kind of sensory deprivation you can pay to experience in between lattes takes two main forms: chamber therapy – where the participant lays on a soft, comfortable, dry platform in a dark soundproof room; and floatation therapy – where the participant lays in a space filled with salt-infused, skin-temperature water. The latter is the far more popular variant, and the one we will focus on here.


So what can laying in a tank of water with a thousand pounds of salt dissolved into it for an hour do for you? The benefits listed on the website of the float house in my own neighbourhood range from the plausible: relaxation, meditation, stress relief; to the intriguing: enhanced healing and pain management; to the dubious and downright perplexing: increased immune function, “super-learning” and deautomization (?).


The trouble with vetting these supposed benefits is that the science around the idea at the heart of floatation – restricted environmental stimulation therapy (REST)* – is sparse. Most studies rely on small sample sizes and limited timeframes. However there are a few generally agreed upon benefits including relaxation, meditation, restoration, and consolidation of new information or physical skills. Much like sleeping, float sessions have been linked to improved retention of new information (if you do your floating after your studying) and better performance on tasks requiring practice and coordination (like basketball and jazz saxophone).


In a world where tension is the norm, these benefits – along with the opportunity and implicit permission to relax for an hour – seem reason enough to be open to a dip in brine. However, researchers are quick to point out that these benefits don’t go far beyond those you would experience from relaxing in a dark room and listening to soothing music. That approach may save you the $50 - $100 bucks most float houses charge, but would rob you of an interesting “what I did this weekend” story.

Researchers also caution that a person’s experience in sensory deprivation is highly depended on their expectations. In overwhelmingly negative contexts (ex. prison and war) isolation can be used as a form of torture. The positive effects of floatation, therefore, may be as much a product of walking into a spa with friendly employees and being told you’ll soon experience the soothing sensation of deautomization as it is an actual outcome of the therapy.


The cool aspects of sensory deprivation are the wacky responses your brain produces when deprived of input. We often forget that our brains are basically machines that use stimuli to produce perspective and an image of the world. When you remove light and sound from the equation, hallucinations become very common. They range from seeing points of light and vague shapes to hearing music.

Ultimately, the best approach to take in the face of relaxation options like floatation therapy is best summarized by psychologist Neal Miller and restated by one of the most prominent researchers in the field of REST, Dr. Peter Suedfeld: Be courageous in what we try, cautious in what we claim.


*Fun Fact: REST as a field of study was pioneered in the 50’s by John C. Lilly, a neurophysiologist who would later lead a study in which a woman lived with a dolphin for 10 weeks to see if it could be taught to speak English.

Wednesday, 10 August 2016

Altitude Sickness: How mountains tell you they don’t want to be climbed

Mountains are a wonderful thing. In fact, they are the preferred geological formation of the Sketchy Science team. That is why we have spent the past several weeks on and recovering from a research expedition to some of the highest peaks North America has to offer: the 14,000 foot peaks of Colorado’s Rocky Mountains. While peaks in Alaska, B.C., and the Yukon attain higher elevations, none can rival Colorado for sheer accessibility.

Accessibility is what you need if you want to study and report on altitude sickness. With this in mind, our writer (me) and illustrator loaded up our respective vehicles and drove, with our romantic partners and two canine companions, from our elevations of residence (0 feet/m and 1,000 feet/300 m respectively) to the highest city in the continental United States: Leadville, CO (10,200 feet, 3,108 m).

Altitude impacts the human (and canine) body in a number of important ways, but they all stem from the fact that the air at altitude is less dense. At low elevations air is compressed by the weight of all the air above it. As you move towards the stratosphere, the column of air you exist in becomes shorter (there is less air above you), and so the weight is lessened and particles have more freedom to stretch out from one another. It isn’t that there is less oxygen in the air (the rate is a pretty constant 21% regardless of altitude), but in the mountains there is more space between oxygen molecules.

Aside from the relatively straightforward problem of your body not being able to get enough oxygen, the air at altitude is also drier. This causes your tissues to lose water rapidly to the air. Your body responds by constricting blood vessels and holding on to water and sodium in areas like the kidneys. The end result is higher blood pressure, a more rapid heartbeat, and an imbalance of moisture and salts.


At altitudes as low as 5,000 feet/1,524 m, this can lead to disturbed sleep as your body struggles to balance oxygen and carbon dioxide by interrupting your breathing during the night. The upshot is you are unrested as you head out exploring the mountains and you make your other symptoms (if you have any) worse. During the day, your body compensates for thin air by breathing more rapidly, leading to headaches, nausea, and dehydration.


At extreme altitudes (above 18,000 feet/5,486 m), the effects on your body can be life-threatening. The two most dangerous conditions are High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE). Both are the result of fluid leaking from your constricted blood vessels and collecting in your tissues. With HAPE, the fluid gathers in your lungs. You struggle to breath and can effectively drown without ever touching water. Unbelievably, HACE is worse as the fluid gathers in your brain. The increased pressure in your skull leads to confusion, lack of coordination, and sometimes coma and death.
Curiously, altitude doesn’t hit everyone the same way and it is tough to predict who will struggle and who will thrive where the air is thin. Marathon runners are no better off than habitual couch potatoes. If the symptoms are mild (headache, nausea, fatigue), then they generally fade with more time spent at altitude – this is called acclimatization. With rest and plenty of water you will start to feel better in as little as 12 hours. The US Army reports that the respiratory element of acclimatization is 70-80% complete within 7 to 10 days. Between 14 and 30 days you are 80 to 90% acclimatized. Total acclimatization can take months or years, though.

If, like us, you are not in immediate danger and have more ambition than common sense, you can find help from over the counter drugs like ibuprofen or by eating foods that are high in carbohydrates like pasta and bread. You can also prevent altitude sickness by spending a night at lower elevation before going higher and by ascending in stages with rest days to let your body get used to the new environment more gradually.


In the end, the hardest part about exploring the high-country is balancing respect for your health and the power of nature (storms, avalanches, and stuff) with the urge to be a hero. Pain is temporary and glory is forever, but death is even more forever. So be safe and be responsible, but enjoy the mountains and the freedom they bring.


Wednesday, 22 June 2016

Getting Biblical on CO2: How to turn your enemies to stone

Wouldn’t it be nice to have the power to turn your enemies into stone? It sounds like something out of the Old Testament or Greek myth, but it’s pretty darn effective. Unless they are careening down a hillside, at whose base you happen to be sitting, stones are relatively inert and harmless. Sadly, despite what religious texts or Tolkien books tell us, this probably isn’t a realistic strategy in the face of conflict.
Happily, no one told that to a group of scientists working in Iceland, who last week published the results of their 4-year research on turning one of humanities greatest foes into a ready supply of paperweights.


You’d be hard pressed to find a more fitting place for an epic showdown than Iceland. Desolate volcanic landscapes mix with moody weather to make it seem like the end of the world is always close at hand. Unfortunately, the gravitas of the setting is somewhat undone by the enemy we are talking about: a colourless, odorless, tasteless gas that every animal of Earth exhales but humans have found a special proclivity for pumping into the air. You know it as carbon dioxide (CO2).

Oddly enough, Iceland is one of the last places you would expect to find people working on a solution to carbon emissions. This isolated outpost of humanity in the North Atlantic gets virtually all of its power from geothermal sources. That is, the island is one big volcano, and so, they use its heat to keep the lights burning. This approach eliminates something like 95% of CO2 emissions associated with electricity production, but apparently that isn’t good enough for Icelandic scientists.


Wanting to inch a little closer to that zero-carbon goal, researchers at Hellisheidi power plant, near Reykjavik, decided to take some of their geothermal power plant’s paltry CO2 emissions and test an approach to neutralizing them; many people thought that was ridiculously impractical - ”that” being to pump the CO2 emissions deep into the ground and wait for them to turn to stone.


As you can imagine, this is a desirable way to fight climate change. The biggest challenge with carbon emissions is that gases are masterful escape artists. Put them into any container with even the slightest breach and they will soon be out mixing in the atmosphere like debutants at a cocktail party. Stone, by contrast, just tends to sit there and not do anything, like an awkward college freshman at their first frat party.

The science behind this idea is actually fairly straightforward. We have long known that when a type of rock called basalt is exposed to CO2 and a little water, the carbon will precipitate (solidify). The problem, like all things in geology, is a matter of time. In the type of uncontrolled field setting the Icelandic team was dealing with, ambitious estimates assume you would need eight years before a significant amount of the carbon was locked up.


So imagine the surprise (and presumed embarrassment) on the face of naysayers when the team from Hellisheidi reported that the process began in just a few months and that, after 2 years, 95 to 98% of the carbon injected into the rocks has turned into chalky, lifeless carbonate minerals. The process so far has been relatively small scale, pumping about 5,000 tonnes of CO2 underground per year – equal to about 15 Americans annual CO2 emissions – but it is promising.


For one thing, basalt as a resource isn’t exactly rare. Places like the Pacific Northwest, South America, and other volcanically endowed landscapes are ripe with it. Better yet, most of the Earth’s crust, beneath the oceans, is basalt. The only thing safer than turning your enemy to stone, is then placing that stone a mile or so underwater.

The major challenge at this point is cost, which sits around $17 per tonne of CO2. This compares favourably with other methods of capturing carbon emissions (usually between $23 and $95 per tonne), but is still expensive when you want to deploy it on the roughly 40 billion tonnes of CO2 that humans put into the air every year.


Clearly, we have some work to do to figure out how to scale up this technology, and in the mean time, we all need to take a hint from Iceland and switch our energy systems to renewable sources like wind, solar, and geothermal power. But, even once we stop treating the atmosphere like a garbage dump, we’re going to need technology to clean up the mess we’ve already made. The Hellisheidi technology gets us one step closer.


Wednesday, 15 June 2016

Blinded by the Sea: How eye glasses (and eyes) work

The ability to see is something we often take for granted. Every day, those of us with sight experience a range of shapes, sizes, colours, and movements that we only really appreciate when we are asked to – when watching Olympic gymnasts or when we’re confronted by something atypical, like a sunset or a mountain range. Most of us only really begin to appreciate the little things our eyes take in when they can no longer do so in a seamless way. For the average person, this happens as we age and our eyes naturally lose their ability to focus. For the not-so-average person, it can happen very suddenly.

Such an ‘unaverage’ (not a real word) experience befell our illustrator, here at Sketchy Science, just last week. While on a trip to a conference on the southeast coast of the United States, after a night of partaking in the local libations, our sketchist (also not a real word) found himself standing in the Atlantic ocean, when a rogue wave of epic (likely very small) proportions tossed him asunder, claiming his glasses to the surf. I don’t actually know if this is how it happened, but it is how I prefer to imagine it. It is much funnier than him simply dropping his glasses in the water.


Regardless of how it happened, the result was a fumbling Mr. Magoo-esque adventure through the airport, onto a plane, and back home to Canada. It’s amazing how two pieces of glass (or plastic) can play such a major role in a person’s life.


But how do glasses work and why do some of us need them? The answer lies in the three most common problems with respect to how our eyeballs function. The four parts of your eye that impact your ability to see are, from front to back - the cornea, which is the clear window on the front of your eye that lets light in; the pupil (the black part), which widens or narrows to let in more or less light; the lens, which bends and focuses the light; and the retina, which is the back wall of your eyeball onto which images are focused before sending impulses down the optic nerve into your brain for processing.


Most problems occur at the beginning of this whole operation, with the cornea. The tricky thing about eyeballs is that they are spheres, meaning that as light moves through their rounded surfaces, it bends. If your eye is not shaped just right, the light coming in can focus at a point that isn’t exactly on your retina.


If your cornea is exceptionally curvy, the light will bend too much and focus in front of the retina, leading to nearsightedness and trouble seeing distance objects; this is called Myopia.


If your cornea isn’t curvy enough, you have the opposite problem with light focusing behind the retina leading to farsightedness and trouble reading the newspaper; this is called Hyperopia.


If your cornea has a bump, ripple, or scratch on it, the light gets distorted in other ways, and this is called Astigmatism.

Glasses – or “corrective lenses”, if we want to be more accurate and inclusive of people with contact lenses – can correct these problems by bending the light in a way that compensates for misshapen corneas. The physics of light dictates that as light moves through a medium, such as glass, it bends or “refracts” towards the thickest part of that medium. Lenses are described as either “plus” or “minus” lenses depending on whether they are thicker in the middle or towards the edges.

Plus lenses are thick in the middle and so bend light inwards, leading to a focal point behind the lens itself. Pushing the focal point backward corrects for Myopia. Minus lenses refract light towards their edges, leading to a focal point that is actually in front of the lens itself. Moving the focus forward corrects for Hyperopia. To make things even more fun, plus and minus lenses can be combined to correct for more complicated vision problems.


That is really all there is to it. This impressive but simple technology has allowed people to see more clearly since the first pair of spectacles adorned some nobleman’s nose between 1268 and 1289 in Italy, after being invented by someone whose name has been lost to history. So, the person who thought up the way we still correct vision today will forever go as unappreciated as the clear vision he sought to bestow upon the masses, to only be admired when a rogue wave leaves one of us blinded.


Wednesday, 8 June 2016

Does your Dog Like Hugs? Truly Sketchy Science and the Value of Critical Thinking

As we all learned a few weeks ago, courtesy of John Oliver, sometimes the media misrepresents scientific findings. Things get blown out of proportion and the result can be total confidence in ideas that are totally wrong or frustration leading to mistrust of science in general. Fortunately, humans are equipped with an ability that few other animals demonstrate that allows us to sift through the nonsense. In school you may have learned about it as “critical thinking”, but in practice it is more like a bullshit-o-meter.

The ability to stop and ask ourselves “Wait, does that result actually make sense?” is incredibly powerful. It actually lies at the heart of science itself through the concept of peer-review, whereby other researchers get the opportunity to tear a study apart before it ever sees the light of day. Occasionally though, something slips through the cracks and it is up to the eye of the reader to spot something fishy. Such a case popped up on social media feeds around the world a last month with a study claiming, intentionally evocatively, that dogs don’t like hugs.

As a dog owner, I have my own biases that would lead me to question this research in the first place. I’ve hugged every dog I’ve ever owned and feel like my best friends would have hugged back had they possessed the appropriate shoulder joints and bipedal orientation to do so. But, that alone isn’t enough to discount the conclusions. Part of critical thinking is having an open mind and accepting the idea that I may have been wrong all these years… but I am within my rights to doubt it. That is where the critical part comes in.

The first fact worth pointing out is that, despite what the various click-bait style articles claimed, the research findings were not reported in a respected, peer-reviewed science journal. They were part of a blog post by UBC psychologist Stanley Coren, who was reporting on some data he collected from looking at pictures on the internet. The idea for the research came from Dr. Coren bringing his dog to school one day as part of a “Doggy De-stress Day” for overworked undergrads. The well-meaning doctor observed that his dog was not enjoying the hugs it was receiving and felt like he was on to something.


Now, looking at the anecdote and the research objectively, there are a couple of red flags right off the bat. A major one is that “Doggy De-Stress Day” would be better named “Doggy Distress Day” as any animal – dog, human, turtle, gibbon – that suddenly finds itself being attacked by strangers who seem hell-bent on using their arms as restraints is likely to get a little freaked out. As for the data that Dr. Coren collected by analyzing internet photos of dogs being hugged (he found that a whopping 81.6% of the dogs in the photos showed signs of stress), it also presents a couple of problems. Chief among them is that the researcher has no knowledge or control over the context in which the photos were taken. Are these purely candid moments or are the dogs being forced to pose for an overly excited person pointing a weird, flashing plastic thing (camera) at them?


A good way to evaluate the scientific merit of a conclusion is to think about how you would go about researching it under ideal conditions. If we want to test the hypothesis that dogs don’t like hugs, there are simple ways to get closer to an answer than by looking at random pictures online. First, you would want the dogs in an environment that doesn’t stress them out, preferably at home. That would allow us to rule out the surroundings as a source of stress and focus purely on the hugs. Second, you would want to control for the person doing the hugging. In this case, the findings are seeking to scold dog owners for forcing human affection onto dogs, so the dogs should only be hugged by people they know and trust. Finally, we would control the situation. Are the hugs happening out of the blue or is the dog relaxing with its owner on the couch after a long day of hiking? These are things that matter.


The point I’m trying to make is one that compliments John Oliver’s message about media misleading people about science: sometimes the research itself deserves to be questioned. You don’t need to misrepresent flawed research to reach the wrong conclusion; the data will take you there on its own. All the more reason to go back to the primary source of a new and shocking idea and ask yourself a few basic questions about how the findings were reached – well-meaning or not.


Until someone conducts a more controlled study, hug your dog. It makes you feel good and that’s all your dog wants for you anyway.


Wednesday, 11 May 2016

Fort McMurray and the Roots of Human Kindness

Humans are full of surprises. If you watch the news, it’s easy to fall into the trap of thinking that humans are the worst animals on two legs. We can be petty, selfish, mean, and violent. We wage wars, pollute the environment, and oppress one another for financial gain. But every so often something happens that allows us to glimpse the real nature of what it means to be human, and the results are among the most beautiful things on the planet.

Last week, in Canada, a wildfire ripped through the Northern end of the province of Alberta. Wildfires are a common occurrence in the boreal forest, but this one was unique for a few reasons. First, it was early; the temperatures under which the fire ignited were dry and incredibly warm (32 C compared to the average daily high for early May of about 16 C). Second, wind and very low humidity caused the fire to grow and move very quickly. Sometime on Tuesday, the flames arrived at the city of Fort McMurray, home to over 80,000 people. The fire ripped through neighbourhoods, destroying buildings and possessions along the way. By Wednesday morning, over 1,600 buildings had burned and some neighbourhoods lost 90% of houses. Shockingly, one thing that wasn’t lost was a single human life.


The evacuation of Fort McMurray was nearly as shocking as the fire that necessitated it. Nearly 100,000 people fled the city peacefully and relatively safely. Even still, cars and trucks clogged the only route out of the city as fire engulfed the forest all around. What made this possible was a human trait that has puzzled scientists for years: co-operation.


When the chips are down, as they were and continue to be for the people of Fort McMurray, few animals come together as comprehensively and effectively as humans do. As people ran out of gas on the highway, others shared jerry-cans they had with them. As fire victims made their way to shelters in Edmonton, Syrian refugees, who had only landed in the country months earlier with no possessions, gave anything they had to help. Even the beer company Labatt’s shut down their brewery to can drinking water for victims. Across Canada, tens of millions of dollars in aid have been collected. How can a species with such a mean streak in one context, be so generous in another?

There are many theories about human altruism but they all boil down to the idea of selection. Most people are familiar with Charles Darwin’s idea of natural selection, but on the face of it, helping someone out seems to be counter-productive. If there are more people around to compete for resources, logic suggests it would be harder for each individual to survive. But, selection also acts on groups, and those who work together stand a better chance of survival in the long run, compared to groups made up of people who can’t stand each other.


Some anthropologists believe that the human tendency to help out strangers, whom we see as being part of our larger social group, is what led to the development of our cultures and languages. As we worked together, it became more and more useful to have ways to connect and communicate with people we had never met before, for the good of the group.

Humans aren’t entirely alone on the altruism front, however. New research comparing us to other primates has shown that some species of monkey are also willing to lend a hand to those in need. Researchers at the University of Zurich in Switzerland compared several species of primate with respect to their willingness to give food to other members of their same species. They looked at 15 species in total, including marmosets and tamarins, lemurs, spider monkeys, capuchin monkeys, macaques, chimps, and human children ranging from 5 to 7 years old. What they found was that the species who were most likely to give food to someone else were also the ones who engage in something called cooperative breeding.


Cooperative breeding is the idea that when a baby is born, many adult members of the social group help to care for it, not just its parents. Animals that evolve the tendency to offer free childcare tend to live in rough situations. When resources become scarce, birds have been known to be cooperative breeders and the same is thought to have happened to our human ancestors as they came out of the trees in Africa and began life on the Savannah, where lions and their ilk made life way more dangerous. The upshot of cooperative breeding is that adults don’t have to wait until their babies are fully independent before having their next brood, resulting in better reproductive success for everyone in the group.


The plains of Africa are a long way from the boreal forest of Canada, but human cooperation appears to be geographically transferable. The people of Fort McMurray have a long way to go to get back on their feet, but at least they can know that their neighbours and millions of years of social evolution have got their backs.


Anyone wishing to help the relief efforts can donate to the Canadian Red Cross. Our hearts are with the people of Fort McMurray during this difficult time.


Wednesday, 27 April 2016

Death from Below: Supervolcanoes and What Makes Them Tick

A couple weeks ago we learned about how rocks from space can destroy cabins, cities, and even civilizations with little to no warning. Very few things in nature hold as much destructive potential as a wayward hunk of solar system leftovers on an unlucky path, but there is one other event that comes close and you don’t need to look far to find it. Approximately 30 km (18 miles) beneath you right now is a hot, churning mass of semi-liquid rock we call the Earth’s mantle and in a few select places around the planet, it has found a way to say hello in the most terrifying of ways.


Mantle plumes are columns of magma that rise up from deep within the Earth and form reservoirs of molten rock relatively close to the surface. The reservoirs contain the full range of materials that make up the inner-Earth, including solid rock and dissolved gases. The trouble with these reservoirs is that as more material flows into them, pressure builds. Sometimes, it builds to the point where the Earth’s crust cannot contain it and it explodes upward with startling force. This process is similar to what happens with the Earth’s many volcanoes, except it tends to be much, much bigger, and for that reason, we call these reservoirs supervolanoes.


The name is a little misleading because the processes behind (or more accurately, beneath) supervolcanoes occur on such a scale that they only vaguely resemble their smaller cousins. When these babies go off, there isn’t much you can do except head for your doomsday bunker. The generally accepted lower-bound size limit for a supervolcano is a reservoir with the potential to erupt 1000 km2 of material. By comparison, the 1991 eruption of the regular volcano Mount Pinatubo  released 5 km2 of material; just enough to circle the Earth a couple times and reduce average temperatures in the Northern Hemisphere by half a degree C for a year or two afterwards.

Supervolcanoes erupt fairly frequently in geologic time and when they do, the effect goes a little beyond needing a sweater for a few extra days a year. Supervolcanoes release enough ash to block out the sun and usher in the ice ages. The most recent eruption from one of these beasts was 26,000 years ago in New Zealand. Another event at Lake Toba in Sumatra occurred 74,000 years ago and nearly wiped out the human race – geneticists have pointed at the Toba eruption as an explanation for the lack of diversity in the human genome. Apparently, our species was reduced to a few thousand people in the wake of the blast and the subsequent volcanic winter. The biggest eruption we know of took place 28 million years ago in Colorado and left behind over 5,000 km2 of deposits, roughly the size of the island of Trinidad.


So where will the next world-shaking eruption happen? Basically, we have no idea. Despite being enormous and built into the planet we live on, supervolcanoes are hard to study. Actually, they are pretty hard to even find. The problem is that the destruction occurs on such an unimaginable scale that we tend to overlook it. The most telltale sign of a sleeping supervolcano is often a gigantic lake (flooded crater) or an absence of mountains where you would expect some to be. The latter is what allowed scientists to identify the caldera (aka magma reservoir) below Yellowstone National Park in the American west. Yellowstone’s last eruption blew up 50 km of mountains and left a caldera 50 by 70 km (30 by 50 miles) in size.


If you really want to figure out the odds of a supervolcano erupting, Yellowstone is the example to look at. On average, the hotspot beneath the park has produced an eruption once every 730,000 years. That puts the odds at around 0.00014% for any given year. The last eruption at Yellowstone was around 640,000 years ago, so you’ve probably got at least a few more years to go see Old Faithful and herds of bison. That could change though; scientists continually monitor Yellowstone for disturbances. The park experiences between 1,000 and 3,000 earthquakes per year as the caldera churns beneath it, so an increase in activity could mean an increased risk of eruption … or, it could mean pressure is being released and everything is safe.

Much like with death from the sky, supervolcanoes are unnerving in their ability to surprise.