The dynamic Earth

The highlight of my trip to Iceland this past August was seeing the newly-erupting volcano of Fagradalsfjall, southwest of the capital city of Reykjavík.

Fagradalsfjall is Icelandic for "mountain of the beautiful valley."  I'm not sure I'd use the word "beautiful," which to me carries connotations of "benevolent."  When we were there, you could feel the eruption before you heard or saw it; the entire floor of the valley was vibrating, a subsonic rumble that I felt in my gut.  Then you hear the roar, a guttural, low-pitched thunderous booming.  Then you smell it -- the characteristic sulfurous, rotten-egg smell of an active volcano.  Then you crest the top of a low hill, and see it for the first time.

We were close enough that we could feel the warmth radiated from the lava.  Much closer, and the combination of the heat and the sulfur gases would have been overwhelming.  Orange-hot plumes of molten rock exploded out of the fissure and splattered onto the sides of the cinder cone, almost instantly turning to shattered, jagged chunks of black basalt as it cooled and hardened.

It was one of the most spectacular things I've ever witnessed.  In the presence of this kind of power, you truly feel tiny and very, very fragile. 

We were really extraordinarily lucky to see what we did; we were there on the 15th of August, and -- for reasons unknown -- the eruption abruptly ceased on the 21st.  Fagradalsfjall is still very much an active volcano, though.  Just last week it started up again, and this cycle looks like it may actually be even more dramatic.

What brings all this up is a paper last week in Nature about some research out of the University of California - Santa Barbara that analyzed the lava from Fagradalsfjall and found that it ran counter to the conventional model of how volcanoes erupt.  The previous understanding was that magma chambers fill gradually, and undergo mixing from convection and the physical shaking from earthquakes; then, when the eruption happens, the chamber drains.  This would result in a relatively uniform chemistry of the rock produced from the beginning of the eruption to the end.

That's not what geologists saw with Fagradalsfjall.

"This is what we see at Mount Kilauea, in Hawaii," said Matthew Jackson, who co-authored the study.  "You'll have eruptions that go on for years, and there will be minor changes over time.  But in Iceland, there was more than a factor of 1,000 higher rates of change for key chemical indicators.  In a month, the Fagradalsfjall eruption showed more compositional variability than the Kilauea eruptions showed in decades.  The total range of chemical compositions that were sampled at this eruption over the course of the first month span the entire range that has ever erupted in southwest Iceland in the last 10,000 years."

Why this happened is uncertain.  It could be that Fagradalsfjall is being fed by blobs of liquid magma rising from much deeper in the mantle, where the chemistry is different; those much hotter blobs then rose to the surface without a lot of mixing, resulting in a dramatic alteration of the rock being produced over the course of the eruption.  This adds a significant complication to interpreting records of past eruptions, not only in Iceland, but with other volcanoes.

"So when I go out to sample an old lava flow, or when I read or write papers in the future," Jackson said, "it'll always be on my mind: This might not be the complete story of the eruption."

It's fascinating that as far as science has come, we still have a lot to work out -- not only out in the far depths of space (as yesterday's post about MoND described) but right beneath our feet on our own home world.  As eminent astrophysicist Neil de Grasse Tyson put it, "You can’t be a scientist if you’re uncomfortable with ignorance, because scientists live at the boundary between what is known and unknown in the cosmos.  This is very different from the way journalists portray us.  So many articles begin, "Scientists now have to go back to the drawing board."  It’s as though we’re sitting in our offices, feet up on our desks—masters of the universe—and suddenly say, "Oops, somebody discovered something!"  No.  We’re always at the drawing board.  If you’re not at the drawing board, you’re not making discoveries."

****************************************

Prelude to a detonation

Even though in general I don't think synchronicity Means Anything, there's no doubt that it can be pretty peculiar.

For example, it seems like in the last few days the universe has tried to get me to think about volcanoes.  First, Scientific American recently featured in their "New Books" column Robin George Andrews's Super Volcanoes, and given my fascination with volcanoes in general I had to get it (and it impressed me enough that it's this week's book-of-the-week).  Andrews's book goes a long way toward dispelling a lot of the hype around places like Yellowstone (no, it's not on the verge of an eruption), and has a lot of cool interviews with volcanologists, much in the style of the wonderful essayist John McPhee.  Only a couple of days after I started reading it, a friend sent me a link to the Naked Science YouTube video "Supervolcanoes," which seemed to be the anti-Andrews; if I can sum it up, it would be "WE'RE ALL FUCKED RUN FOR YOUR LIFE."  It isn't terrible, and does include some actual science, but the most striking thing about it is a CGI rendition of Yellowstone blowing sky-high which they use over and over and over and over in the fifty-minute-long video, as if they'd paid somebody a hefty sum to do the rendering, and by god, they were gonna get their money's worth out of it.

Then, just yesterday, a (different) friend sent me a link to a paper in Proceedings of the National Academy of Sciences that kind of splits the difference between Naked Science's screaming alarmism and Andrews's breeziness; it looks at the scarily huge Mount Toba volcano in Indonesia, and comes to the unsettling conclusions that (1) it definitely will erupt again, and (2) we probably won't have much warning when it does.

The last significant eruption of Toba was about 74,000 years ago, and was a VEI8 -- the highest ranking on the Volcanic Explosivity Index -- releasing an estimated three thousand cubic kilometers of ash and lava, and causing a worldwide (if temporary) drop in average temperature by about three degrees Celsius.  (For comparison, this is over seven hundred times the volume ejected by the May 1980 eruption of Mount St. Helens.)  The eruption blew the entire top of the mountain clean off, and the evacuation of the magma chamber beneath it caused the caldera to collapse.  It filled with water, and is now a beautiful -- and seemingly peaceful -- crater lake, Lake Toba.

[Image licensed under the Creative Commons Visions of Domino, Indonesia - Lake Toba (26224127503), CC BY 2.0]

The operative word here is "seemingly."  The processes that caused the original eruption, mostly the subduction of the Indian and Australian Tectonic Plates beneath the Sunda Plate, continue to cause massive earthquakes including the colossal (9.2 on the Richter Scale) Sumatra-Andaman Earthquake of December 2004, which killed over 225,000 people.  In the case of Toba, the magma chamber has been steadily refilling, and now contains an estimated 50,000 cubic kilometers of magma -- four times the volume of Lake Superior.  This refilling has pushed the entire caldera upward, lifting Samosir Island and the Uluan Peninsula an estimated 450 meters.

It's hard to talk about this without lapsing into superlatives.  The scariest thing about it, though, is that the recent study indicates that such volcanoes can seem quiescent until -- well, until they aren't any more.  "[W]ith few super-eruptions in the last two million years, it is not possible for us to obtain statistically significant values for the frequency of these catastrophic events at a global scale," said study co-author Ping-Ping Liu of Peking University, in a press release from the Université de Genève.  "Our study also shows that no extreme events occur before a super-eruption.  This suggests that signs of an impending super-eruption, such as a significant increase in earthquakes or rapid ground uplift, might not be as obvious as pictured in disaster movies by the film industry.  At Toba volcano, everything is happening silently underground."

The reassuring part is "not as obvious" doesn't mean "without any warning;" the entire Indonesian archipelago is an area of intense study by volcanologists and seismologists, and it's likely there'd be enough anomalous activity to give us at least a hint that an eruption was impending.  Whether we'd do much about it in the form of evacuations is another matter.  Sumatra (where the volcano is located) and the nearby island of Bali are densely populated, and the idea of getting all those people out (to where?) makes the phrase "mammoth undertaking" a significant understatement.  And for those of you who like certainty, the current study doesn't give us any clear idea of exactly when the next big eruption will occur, just that (1) it's inevitable, (2) when it does, it'll be bad, (3) the filling of the magma chamber is still happening, and (4) there are signs that the volcanic activity at Toba and the surrounding regions is speeding up.

"[There's been a] progressive increase of the temperature of the continental crust in which Toba’s magma reservoir is assembled," Liu said.  "The input of magma has gradually heated the surrounding continental crust, which makes the magma cool slower.  This is a ‘vicious circle’ of eruptions: the more the magma heats the crust, the slower the magma cools and the faster the rate of magma accumulation becomes.  The result is that super-eruptions can become more frequent in time."

So there's your cheerful news of the day.  As far as the synchronicity aspect of this, I'm not gonna make much of it.  The fact that two different friends know enough of my obsession with volcanoes and earthquakes to send me the link to the YouTube video and paper is hardly to be wondered at.  As far as the book review, it's no wonder I noticed it given that the tile of the book is Super Volcanoes.  I don't think this is some kind of cosmic warning that we're about to get blown to smithereens.

So if you were looking for an excuse to stay home from work this week, you'll probably have to come up with a different one.

*********************************************

If Monday's post, about the apparent unpredictability of the eruption of the Earth's volcanoes, freaked you out, you should read Robin George Andrews's wonderful new book Super Volcanoes: What They Reveal About the Earth and the Worlds Beyond.

Andrews, a science journalist and trained volcanologist, went all over the world interviewing researchers on the cutting edge of the science of volcanoes -- including those that occur not only here on Earth, but on the Moon, Mars, Venus, and elsewhere.  The book is fascinating enough just from the human aspect of the personalities involved in doing primary research, but looks at a topic it's hard to imagine anyone not being curious about; the restless nature of geology that has generated such catastrophic events as the Yellowstone Supereruptions.

Andrews does a great job not only demystifying what's going on inside volcanoes and faults, but informing us how little we know (especially in the sections on the Moon and Mars, which have extinct volcanoes scientists have yet to completely explain).  Along the way we get the message, "Will all you people just calm down a little?", particularly aimed at the purveyors of hype who have for years made wild claims about the likelihood of an eruption at Yellowstone occurring soon (turns out it's very low) and the chances of a supereruption somewhere causing massive climate change and wiping out humanity (not coincidentally, also very low).

Volcanoes, Andrews says, are awesome, powerful, and fascinating, but if you have a modicum of good sense, nothing to fret about.  And his book is a brilliant look at the natural process that created a great deal of the geology of the Earth and our neighbor planets -- plate tectonics.  If you are interested in geology or just like a wonderful and engrossing book, you should put Super Volcanoes on your to-read list.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

I felt the earth move under my feet

Some of you probably recall the highly scientific 1990 nature documentary Tremors, wherein Kevin Bacon has to battle gigantic worms that can tunnel through rock, and which have evolved such sophisticated sensory organs that they can feel your footsteps and follow you until an opportune moment to pop up and eat you for lunch, yet are still stupid enough to die from running into the wall of an aqueduct or launching themselves out of a cliff face in the fashion of Wile E. Coyote being shot from the barrel of an Acme E-Z Cannon.

The reason this comes up is because of a piece of research in the journal Geology, which I can confidently assert would have reminded no one else in the entire world of Tremors, but I'm not responsible for how my brain works, and I figure if on some level you didn't enjoy free association, you wouldn't be here.  Anyhow, the paper is titled "Eruption Risks from Covert Silicic Magma Bodies," which as you can tell from the title has zero to do with giant carnivorous worms, but does have to do with the fact that there seem to be dangerous and undetected pockets of magma underground that can be located by their seismic traces.

(See the connection?  See?  The tagline for Tremors is "They say there's nothing new under the sun, but under the ground...".  I rest my case.)

What spurred the four geologists who wrote the paper -- Shane M. Rooyakkers, John Stix, and Kim Berlo (of McGill University), Maurizio Petrelli (of Università degli Studi di Perugia), and Freysteinn Sigmundsson (of the University of Iceland - Reykjavík) -- were three instances of what they euphemistically call "Unintentional encounters with silicic magma at ~2-2.5 km. in depth," which is science-speak for some people at a drill site looking into the hole and then yelling, "FUCKING HELL WE JUST HIT A MAGMA CHAMBER."  The three sites were on Krafla (in Iceland), Menengai (in Kenya), and Kilauea (in Hawaii), and in each case was a shock because the areas had been studied extensively and the magma chambers they hit hadn't previously been detected.

Magma chambers are usually found by their seismic properties; the sound waves from explosions, and the pressure waves from earthquakes, travel at a different speed in solids than they do in liquids, so by comparing how long it took for those waves to arrive at detectors in different locations, you can infer how much of the intervening material is liquid and how much is solid.  (That's a vast oversimplification, but the gist of it, anyhow.)  Given how good this technique is, geologists thought they had all of the near-surface magma chambers pinpointed, so it was a significant shock to find out that there were some out there that we didn't know about.

Another piece of this that raised red flags for me was that word "silicic" in the title.  Magma usually comes in two flavors, mafic and felsic (or silicic).  Mafic magma is high in magnesium and iron, hardens into dark-colored rocks like basalt, and when it's molten it's highly fluid, like the rivers of lava you probably think of when you picture a volcano.  Felsic magma is high in silica and feldspar, hardens into light-colored rocks like granite and rhyolite, and is very viscous and thick when it's molten -- so volcanoes powered by a felsic magma chamber often build up so much pressure beneath that blob of sticky glop that when they erupt, it's explosive.  (Examples are Vesuvius, Mount Saint Helens, and La Soufrière -- currently erupting on the island of Saint Vincent.)

So an undetected near-surface magma chamber filled with felsic/silicic magma is not good news.  People are walking around without realizing it on top of what amounts to a giant superheated bomb.

The 1980 eruption of Mount Saint Helens [Image is in the Public Domain courtesy of NASA]

"In traditional approaches to volcano monitoring, a lot of emphasis is placed on knowing where magma is and which magma bodies are active," said study lead author Shane Rooyakkers, in an interview with Science Daily.  "Krafla is one of the most intensely-monitored and instrumented volcanoes in the world.  They've thrown everything but the kitchen sink at it in terms of geophysics.  And yet we still didn't know there was this rhyolitic magma body sitting at just two kilometers' depth that's capable of producing a hazardous eruption...  So the concern in this case would be that you have a shallow rhyolitic magma that you don't know about, so it hasn't been considered in hazards planning.  If it's hit by new magma moving up, you might have a much more explosive eruption than you were anticipating."

Which is a lot worse than a bunch of giant carnivorous earthworms.

Anyhow, that's our unsettling piece of scientific research for today.  The good news is that it's not like these magma chambers are scattered about everywhere; they still seem to occur only near active volcanoes.  So it's not like an eruption is likely to take place in the middle of Newark, or anything, which is kind of a shame, because an erupting volcano in Newark would probably be considered urban renewal.  But you never know.  Even Kevin Bacon got taken off guard by what's underground.

************************************

This week's Skeptophilia book recommendation is pure fun: Arik Kershenbaum's The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal About Aliens and Ourselves.  Kershenbaum tackles a question that has fascinated me for quite some time; is evolution constrained?  By which I mean, are the patterns you see in most animals on Earth -- aerobic cellular respiration, bilateral symmetry, a central information processing system/brain, sensory organs sensitive to light, sound, and chemicals, and sexual reproduction -- such strong evolutionary drivers that they are likely to be found in alien organisms?

Kershenbaum, who is a zoologist at the University of Cambridge, looks at how our environment (and the changes thereof over geological history) shaped our physiology, and which of those features would likely appear in species on different alien worlds.  In this fantastically entertaining book, he considers what we know about animals on Earth -- including some extremely odd ones -- and uses that to speculate about what we might find when we finally do make contact (or, at the very least, detect signs of life on an exoplanet using our earthbound telescopes).

It's a wonderfully fun read, and if you're fascinated with the idea that we might not be alone in the universe but still think of aliens as the Star Trek-style humans with body paint, rubber noses, and funny accents, this book is for you.  You'll never look at the night sky the same way again.

[Note: if you purchase this book from the image/link below, part of the proceeds goes to support Skeptophilia!]