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.

Hot and Heavy – The Truth about Diamonds

Humans are brilliant animals. Over the eons, we have used our ingenuity and problem solving to craft a civilization that, as imperfect as it can be, does a pretty effective job of keeping us out of the food chain. However, clever as we may be, we have a few weaknesses. Chief among them are greed, the ability to be manipulated, and an inexplicable fondness for shiny things. The perfect symbol of these primeval flaws is the modern diamond engagement ring. 

Now, don’t get me wrong, scientifically speaking, diamonds are impressive things. They are made from the same single ingredient as coal: carbon; but we proudly put one in jewelry, while we are content to throw the other in the fire.

A common misconception about diamonds is that they form from coal as the Earth does its thing by applying heat and pressure. In fact, if coal has ever had anything to do with diamonds, it has been incidental and insignificant, and has produced some pretty lousy diamonds. If you need proof, consider that most natural diamonds on Earth are between 1 and 4 billion years old, while coal (which formed from dead plants before bacteria evolved to have the ability to digest wood) has only been around for about 500 million years.

So if coal isn’t the culprit, where do diamonds come from? It turns out there are several answers:

Deep Source Eruptions – Most diamonds form in the layer of semi-molten rock that the Earth’s crust floats around on. We call this the mantle, and it is not a place you want to find yourself in. The section of the mantle where diamonds generally form is around 150 km (90 miles) below the surface, so for starters it would be hard to get out of. Second, it is hot, around 1,050 C (2,000 F). To make matters worse, the pressure is about 725,000 pounds per square inch. 

While this would really, really suck for any human without a magical ship from a crappy sci-fi movie, it is quite a swell place for diamonds to form. Carbon dioxide, trapped in the mantle when the Earth first formed, undergoes a “redox reaction” due to the extreme conditions. The carbon oxidizes (rusts, in its own weird way) and gains electrons. When the pressure is suddenly reduced very rapidly – say, when a weak section of Earth’s crust drifts over top of it – the molten rock erupts to the surface, the carbon condenses, and forms diamonds. This process is responsible for all the commercial diamonds in the world.

Subduction – Diamonds can also form as the Earth’s tectonic plates bump and grind. As dense oceanic plates grind underneath lighter continental plates, the resulting heat and pressure can produce diamonds. This process could involve coal as a carbon course, but it is more likely that the material comes from limestone and other rocks.

Impact Sites – Being underneath an asteroid as it impacts the Earth is one of the few places you could find yourself that would be worse than the mantle, but, if you can run away in time and get back before anyone else, you could score big. The heat and pressure from the impact has the ability to metamorphosize carbon and produce diamonds. The catch is that the biggest ones you are likely to find, thanks to the keen smashing ability of objects from space, would be in the 1 mm range. That would make for a pretty insulting engagement ring.

Space – Diamonds can also form in space as objects smash into each other at high speed. The process is basically the same as it is at impact sites on Earth. Except in space, no one can hear your fiancée shriek with delight… well, maybe David Bowie.

The curious thing about diamonds is that, as much as we value them, they aren’t at all rare. Since 1870, when massive diamond deposits were discovered in Kimberley, South Africa, the world has basically had all the diamonds we could want. In fact, last week a team of chemists at John Hopkins University reported that the complex “redox reaction” that forms diamonds could be produced by water under the right conditions. Given the amount of water on Earth, there is probably a shocking amount of diamond mines just waiting to be discovered.

The only reason diamonds are expensive is because of that pesky manipulation and greed we started the article with. After the diamond rush of 1870, a company that came to be called DeBeers bought up all the diamond producing mines in existence and began to sharply limit the supply to keep prices high. They coupled that with a 20^th century ad campaign that tried to convince us all that the only way to show someone you love them enough to marry them is to put a shiny hunk of carbon on their finger.

Dropping 3 month’s salary (cue the hysterical laughing) on a ring seems a lot less special when you realize there is basically an infinite supply of replicates in some rich guy’s vault.

Sinkholes: Nature’s most awful trick

It is easy to forget that the planet we live on is in many ways itself a living thing. Part of what makes the Earth so amazing is that it is one of the few places in the universe we know about that is geologically active. Internal forces churn magma, tectonic plates shift and crash into each other, volcanoes spew rock and ash sometimes with explosive force. The thing that these forces have in common is that they generally work slowly but surely beneath our feet before revealing themselves in some cataclysmic event – an earthquake, an eruption, etc. We can live with this because science (and a little common sense) lets us know where the danger zones are so we can avoid them or at least know about the risk. However, every once in a while the Earth quite literally pulls the rug out from beneath us.

Anyone who regularly watches the news has at some point seen footage of the geologic event known as a sinkhole and it probably boggled their mind. The picture is usually the same: a busy street in the middle of an urban area punctuated by a massive, seemingly bottomless hole in the ground, the black maw swallowing any light foolish enough to fall on it. Sinkholes that form suddenly to suck up a building or car are scary things. They often occur without much warning and if you are the unlucky sap driving over top when one decides to open up, there really isn’t much you can do about it.

Sinkholes form because of the layered nature of the Earth’s crust. Ask any kid with a shovel and they will explain that as you dig down into our planet, you will encounter various layers. To keep things relatively simple let’s focus on two key ones: the top bit we all know and love comprised of sand, soil, clay and the odd rock (occasionally and unceremoniously called “overburden”) and the layer of more solid rock beneath it called bedrock.

Bedrock can be made from any number of different types of stone, some extremely hard and tough and others that are more porous and relatively weak. Weaker forms of bedrock generally include things like salt, gypsum, limestone or dolomite. While you certainly wouldn’t want to bash your head against a piece of limestone, it is pretty wimpy in the world of rocks. Limestone and its kin are easily eroded by water that is even a little acidic. As water works its way through the ground is often absorbs chemicals like carbon dioxide that increase its acidity, allowing it to eat away at bedrock.

If you’ve ever explored a cave or been to the grand canyon you’ve seen what water can do to rock given enough time. Problems occur when the overburden on top of a layer of eroded bedrock has a little rigidity to it. Sometimes. seemingly solid ground we are walking, driving or building on is really just a soft cap covering a gaping chasm of nothingness. When enough weight is place on top of such a cap, or enough water flows through it to weaken it, the whole thing can come tumbling down.

But the really unfair thing about sinkholes is that they can sometimes form in places that we know are solid. One particularly awesome example of such an event is what happened in Louisiana at a place called Lake Peigneur on November 20, 1980. The thing about Lake Peigneur is that it sits on top of a massive salt deposit that is covered by a thin layer of soil. It also has some modest oil reserves. With that in mind, in November 1980 there were two industrial operations going on beneath the water: a salt mine and an exploratory oil drilling project.

Unfortunately, the team drilling for oil made a miscalculation about where one of the channels for the salt mine was. They drilled through the soil beneath the lake and right into the chamber where people were working. The men in the mine we barely able to escape before water started rushing in through the 14 inch hole the oil rig had created. Essentially they pulled the cork on the bathtub that was Lake Peigneur.

The thing about water, as we have learned, is that is can dissolve salt. As the water filled the salt mine it ate away at the walls, expanding the cavern. Over the course of a few hours the entire lake drained into the ground, pulling the surrounding Earth down with it. The canal that ran out of the lake into the Gulf of Mexico even changed direction, following inland and creating  a 150 foot waterfall (the biggest ever in Louisiana). The pressure and displaced air even created a 400 geyser. It was a scene out of the end of the world.

The vortex of draining water sucked up barges and fishing boats until enough water had been pulled in from the Gulf to equalize things, at which point everything that was sucked down popped back to the surface. Nowadays if you go to Lake Peigneur you can see the chimneys of houses that used to sit next to the lake poking out the salty water.

Keep that in mind next time to feel like you have your feet planted on solid ground. Sometimes it’s hard to know what lies beneath.

Our Bi-Polar Planet – Magnetic Reversals and Death from Above

Special thanks to reader Mark L. for this week's polarizing topic.

If you’ve ever spent time navigating in the outdoors or sitting in an elementary school science class, you understand that the Earth is a gigantic magnet. If you’re the curious type who digs into these things a little deeper, you probably know that that is a wonderful thing. Besides being able to find your way home with a compass if you ever get lost, the magnetism of the Earth creates a protective bubble that blocks harsh solar particles from reaching the Earth and bathing us in radiation.

As agreeable as this state of affairs is, there is something you should know about the planet you are in a long-term relationship with… It’s unstable. Avid outdoorspeople are all aware of something called magnetic declination: the difference between true north and magnetic north. As it happens, your compass points to the Earth’s magnetic north pole and your map is oriented towards “true north” – the point around which the planet spins – and those are not the same thing. In fact, the magnetic pole tends to wander. On average, it moves in loops of around 80 kilometers (50 miles) per day and the annual average of those daily points moves around 41 kilometers (25 miles) per year.

That might pose a slight inconvenience for hikers and sailors who have to keep up with revised estimates of what exactly they are walking or drifting towards, but it is generally something we can deal with. The real problems happen when our planet moves from mildly unpredictable shifts to outright mood swings. When those happen, the north pole and south pole can actually switch places.

The Earth’s magnetism is caused by the movement of molten iron in the planet’s core. Way down beneath you, wherever you are reading this, is a solid iron ball at the centre of the globe. Around that is another, larger ball of liquid iron. The inner part of that outer core is hotter than the outer part and the difference in temperature causes iron to drift up and down and create currents (hot iron rises, cold iron falls). When those currents speed up, the magnetic field around the Earth gets stronger. When they slow down, the field gets weaker.

When the field gets too weak the north and south pole flip back and forth until things stabilize. In the distant past, this was a pretty rare event… but still probably more frequent than you would guess. Between 1.5 and 2.9 billion years ago a flip happened once every 5 million years or so. Since then, the outer core has cooled and the inner core has grown. The result is less stability and now the poles flip, on average, once every 200,000 years. The last switch was 780,000 ago however, so we are very much due.

So will the poles switch in our lifetime? Surprisingly, the answer is “Yeah, maybe.” These things are hard to predict with any degree of certainty but over the past 150 years the strength of the magnetic field has been weakening by about 5 per cent per decade whereas before that it weakened by about 5 per cent per century. That could mean that one day in the not too distance future, your compass will be useless.

What does that mean for life on Earth? Overall, probably not much. As I mentioned, the poles have flipped and flopped literally thousands of times in Earth’s history. We know this because the magnetic elements in very old rocks show patterns of alignment that only make sense if the poles were in different places. No big animal or plant die offs correspond with these changes, so we will probably be okay. The major risks are increased solar radiation, raising your risk of skin cancer (sunscreen up!) and communications being wiped out or messed up. It turns out our cell phones and the internet depend on the protection the Earth's magnet field provides.

The irony of the whole situation is if our communications collapse and society crumbles (rather than just reverting back to 1800’s levels), we won’t be able to use compasses to guide our wandering nomadic tribes… I guess it’s time we all buy a star atlas and start studying. See you on The Road, everybody!

Climate or Climb It? How changing weather builds mountains

It is easy to think of mountains as permanent features of a landscape. Don’t do it. That is what they want you to do. Let your guard down for one second and those craggy jerks will be on you like white on rice. Mountains change and they do it constantly. We all know about plate tectonics and how ancient sea floors are now some of the loftiest places on the planet. But did you know that climate can also shape mountains?

  

Recent research from the University of California at Berkley has revealed that California’s already substantial Sierra Nevada Mountains have risen 10 millimeters in the past 7 years. You might expect that this is due to things like earthquakes and tectonics plates crashing into each other, but that is only partly the case. The researchers have also suggested that California’s ongoing and increasingly severe drought has been causing the peaks to shoot upward.

The thing about the Earth’s crust is that it’s a lot more like a mattress than it seems. Put some weight on it and it will dent pretty easily. Take the weight off and watch it spring back up (if you have a few decades to spare). Much of North America’s crust is still rebounding upward in response to the removal of the weight of glaciers from the last ice age, a process called isostatic rebound. In California, glaciers are generally hard to come by, even during an ice age. The uplifting there is the result of water loss in the soil.

It may not seem like it it, but water is massively heavy stuff. It is even heavier than ice, which is why the "rocks" in your scotch float. A one meter by one meter by one meter cube of water weighs a ton. That means the bed of an average pickup truck could hold several thousand pounds of water. Imagine how much the rain water that falls on a mountain range in a year weighs and you can begin to understand why a long running drought might cause mountains to rise.

As water fluctuates and the Earth’s crust reacts, we can get into some pretty hairy situations. A growing body of research is providing evidence that changing rainfall and ice-melt patterns associated with climate change might even cause volcanoes to become more active (Capra, 2006; Deeming et al., 2010). Your classic stratovolcano is just a mountain with a lot of internal pressure. As the amount of ice or water on the overlying mountain changes, the magma chamber underneath can become unstable. When enough weight has been removed the effect is like taking the cap off a shaken up bottle of coke.

Even if the magma chamber doesn’t blow its top, melting ice can destabilize the soil in a slope and cause landslides. The massive landslide in Washington State on March 22, 2014 that killed 41 people came after a period of intense rain that weakened the slope which eventually failed.

Mountains are pretty uncool in that way. They can sit there for millions of years looking all rock-solid and majestic. They watch and wait as we build towns at their bases so we can enjoy the view, going about their natural processes of erosion and uplift at a pace that the human eye just can’t observe. Then one day, either because it has rained too much or not rained enough they are capable of kicking things into overdrive. The lesson in all of this? It’s okay to make friends with a mountain. You can even hang out from time to time. But don’t for a second think you can trust them. They’re more lively than they seem.

References:

Capra, L. (2006). Abrupt climatic changes as triggering mechanisms of massive volcanic collapses RID C-2371-2011. Journal of Volcanology and Geothermal Research, 155(3-4), 329-333. doi:10.1016/j.jvolgeores.2006.04.009

Deeming, K. R., McGuire, B., & Harrop, P. (2010). Climate forcing of volcano lateral collapse: Evidence from Mount Etna, Sicily. Philosophical Transactions of the Royal Society A-Mathematical Physical and Engineering Sciences, 368(1919), 2559-2577. doi:10.1098/rsta.2010.0054

Volcanoes: Flatulence of the Earth

If I had to take a guess at what really got the whole idea of “science” going, and if that motivator was some singular event, I think the safe money would be on a volcanic eruption. I imagine some early human scratching his head and looking on with an expression of dumbfounded awe as a pyroclastic flow swept past at 100 km/hour, simultaneously burying him in a heap of ash and debris and cooking him at a temperature up to 700 degrees C.

Whether they are entombing cavemen, spewing lava into the air, or simply dominating the horizon volcanoes are one of the few things that both the average person and the most devoted nerd can agree are just plain awesome.

Volcanoes come in three main varieties: spreading centre volcanoes, subduction zone volcanoes, and intraplate volcanoes. Each is the result of intense pressure deep within the Earth and the mechanics of tectonic plates.

To really understand volcanoes you need to understand plate tectonics. Since this article is meant to focus on the former, I will sum up the latter in a single sentence: The Earth’s surface is made up of enormous plates that fit together like a badly made jigsaw puzzle, moving around and smashing into each other to produce all the features of the planet’s landscapes.

When plates pull apart from one another, hot rock from beneath bubbles to the surface and you get a spreading zone volcano. 

When two plates smash into each other, one is forced beneath the other (AKA subduction) where the pressure and friction cause the rock to melt. Eventually that rock finds its way up through cracks in the surrounding material to the surface and you get a subduction zone volcano. 

When you have a plate with a weak spot and some particularly hot and motivated magma beneath it, you get an intraplate volcano.

Beyond that, volcanoes don’t like it when you try to come up with general rules about them. Spreading zone volcanoes tend to be the least explosive, but Iceland is really just a combination of these sorts of volcanoes and explosive eruptions there have halted global air traffic and cost the world economy billions of dollars. Intraplate volcanoes tend to be the most destructive, but the Hawaiian hotspot has been quietly erupting more or less constantly for at least the past thousand years.

Clearly, volcanoes are full of surprises. Unfortunately they are rarely the kind of surprises that you look forward to. In 1980, volcanologists in Washington state watched and waited while Mount Saint Helens swelled and rumbled, expecting either an impressive vertical eruption or for the volcano to slowly go back to sleep. No one predicted the lateral (sideways) explosion of ash and debris that killed 57 people and flattened 200 square miles of forest.

The most recent surprise that volcanologists have unearthed is one that they seemingly should have discovered quite a while ago. On September 6, 2013, scientists announced that they had discovered the largest volcano on Earth (so far). Tamu Massif as the peak is known rises 3.5 km from the sea floor about 1,600 kilometers east of Japan and occupies an area of 310,000 square kilometers, making it about the size of the British Isles. The volcano formed over millions of years as eruptions piled up one on top of another and collapsed outwards and upwards, although the summit still lies about 2,000 meters (6500 feet) beneath the waves.

Tamu Massif is being compared to another massive volcano called Olympus Mons which is found on Mars and still holds the title of “biggest volcano in the solar system.” Until now, mountains as big as Olympus Mons were not thought to exist on Earth. The reason is took so long to find the behemoth volcano is that the world’s oceans are one of the few things that are less well understood than volcanoes themselves. Also, scientists originally thought the formation was the result of multiple volcanoes joining together. The recent breakthrough was in establishing the existence of a single vent responsible for forming Tamu.

It’s pretty incredible to think that something like the world’s biggest volcano could exist beneath the ocean, unknown to people, until the 21^st century. It really makes you wonder what other incredible things lay hidden by water and question whether or not it’s a good idea to keep dumping radioactive waste and movie directors into the depths.

Terraforming: It’s a nice planet, but we can make it better.

Last week we looked at some of the doom and gloom associated with planets and how they change over time. Things heat up and habitable zones drift away leaving planets both balmy and dead. This week we will try to come up with an escape plan for the human race.

While it is pretty uncertain whether or not humans will exists when the issue becomes relevant, scientists agree that if we plan on surviving indefinitely as a species we will eventually have to leave Earth. So where do we go? We’ve been to the moon so we could set up shop there for a while, but since the moon is tied to the Earth it doesn’t solve much in the way of the sun roasting us to death. We could go to Venus, but moving towards the growing Sun would be equally unproductive. No, if we want a new home the most accessible options will be nearer to the edge of the solar system.

Astrobiologists have proposed three options within our own solar system. Two of them are moons. Titan is the largest of Saturn’s 53 known moons and has an atmosphere similar to what the Earth’s may have been like early in its development. Unfortunately, with a surface temperature of -178 degrees Celcius (-289 Fahrenheit), oceans of liquid methane, and a sky that rains gasoline, the comparisons end there. Europa is our other potential moon-base. It orbits Jupiter once every 3.5 days and is smaller than Titan but, like Earth, it has an Iron core and oceans made of water. The problem is that the oceans are deep enough to cover all the land and they are frozen. While Titan and Europa both have potential, there is only one object in our solar system that is even close to Earth in its current condition, and luckily it’s right next door.

Mars has long been of interest to astronomers both because of its proximity and its characteristics. It is a rocky planet (like Earth) with an atmosphere and evidence suggests that it may have once had liquid water. The problem is, that water is now frozen and as far as we can tell the planet is lifeless. It has an atmosphere that is 95% carbon dioxide and only 0.2% oxygen, but it takes more than poisonous air to squash an astrobiologist’s optimism. Enter terraforming.

Terraforming (literally “Earth Shaping”) is the process of changing a planet so that it can support human life. It sounds like science fiction, and right now is more or less is, but one day it might be just another thing that people do in space. We are already shaping our own planet through the burning of fossil fuels and the release of chemicals into the atmosphere, so why not try it someplace else?

Theorists have proposed three methods we might use to turn Mars into Earth 2.0 and they all focus on turning up the Martian thermostat. They are:

1. Orbital Mirrors
2. Pollution Factories
3. Smashing Asteroids Into It

None of those options is a joke.

Orbital Mirrors (up to 250 kilometers in diameter) would be positioned around Mars to deflect more sunlight at the surface and begin to heat things up. Pollution factories would do what they do here on Earth and pump greenhouse gases into the atmosphere, trapping more of the heat that reaches the surface. Finally, for the impatient terraformer, there is the option of strapping rockets to asteroids that have a high ammonia content, pointing them Mars, lighting the fuse, and running like hell. The impacts would heat the surface by a few degrees each, but leave the planet off limits for a few centuries due to the generally unfavourable state of chaos they produce.

The idea is to warm things up enough for liquid water to begin flowing. From there, bacteria could be introduced to do what they did in the early days of the Earth and convert the atmosphere from almost entirely carbon dioxide to a more congenial mix of oxygen, nitrogen, and greenhouse gases.

The technology and the motivation to change Mars into humanity’s next home are likely many many years away, but as the Sun heats up and Earth gets crowded the red planet may gradually become the apple of our collective eye.