The backyard volcano

Of all of the sciences, geology is the one where deep understanding of the underlying processes eluded us the longest.  Even the two other contenders -- genetics and astronomy -- were at least partially unraveled sooner.  Plate tectonics, the model that provides a framework for comprehending just about every other geological process, wasn't elucidated until Frederick Vine, Drummond Matthews, and Harry Hess came along in the early 1960s.  Until then, geology texts fell back on hand-waving explanations like synclines and anticlines, and pretty much ignored questions like why most of the world's volcanoes and major earthquakes fall along a tracery of curves that encircle the Earth like the stitching on a baseball (the most famous of which is the Pacific Ring of Fire).

Part of the reason it took us so long to figure all this out is because geological processes are, for the most part, slow, so it's easy to look around and conclude that the Earth has pretty much always looked like it does today.  Then... they discovered anomalies like marine fossils in the Himalayas, Kansas, the Rockies, and right here in my own neck of the woods in upstate New York.  It took the brilliant Scottish geologist Charles Lyell to recognize that if rates of sedimentation are fairly constant, then big sedimentary rock layers like the White Cliffs of Dover must have taken tens of millions, rather than thousands, of years to form.  The recognition of how slow most geological phenomena were meant the Earth was a great deal older than the six-thousand-year estimate by Archbishop Ussher -- setting up the first of many clashes between geologists and the church establishment.

But "usually slow" doesn't mean "always slow."  Sometimes major geological processes can occur, literally, overnight.  Take, for example, the appearance in 1943 of a new volcano, dubbed Parícutin after the nearest town, in a Mexican farmer's cornfield.

The locals did at least have a little bit of warning.  For weeks prior to the initial eruption, they had heard sounds "like thunder but with no clouds in the sky," now thought to be the rumblings of magma moving beneath the surface.  There were over twenty small earthquakes over 3.2 on the Richter Scale, and hundreds of smaller ones -- the day before the eruption, there were more than three hundred small earthquakes.

What happened next is best said in the words of Dionisio Pulido, the farmer who witnessed it first-hand:

At 4 p.m., I left my wife to set fire to a pile of branches when I noticed that a crack, which was situated on one of the knolls of my farm, had opened... and I saw that it was a kind of fissure that had a depth of only half a meter.  I set about to ignite the branches again when I felt a thunder, the trees trembled, and I turned to speak to Paula; and it was then I saw how, in the hole, the ground swelled and raised itself two or two and a half meters high, and a kind of smoke or fine dust – grey, like ashes – began to rise up in a portion of the crack that I had not previously seen...  Immediately more smoke began to rise with a hiss or whistle, loud and continuous; and there was a smell of sulfur.

By the next morning, where Pulido's cornfield had been was a scoria cone fifty meters high; a week later, it was double that.  It was continuously erupting volcanic bombs and small pyroclastic flows, and Pulido decided that his home and land were done for, so he got the hell out.  Before leaving, he put up a sign saying "This volcano is owned and operated by Dionisio Pulido" -- indicating that even in dire circumstances, you can still hang on to your sense of humor.

Parícutin in 1943 [Image is in the Public Domain]

The entire eruption cycle went on for two years, and by the end, there was a massive conical mountain, over four hundred meters tall, where before there'd only been a flat valley.  Only three people died during the eruption, and oddly, none of them were from the lava or pyroclastic surges; the three died when they were struck by lightning during an ash eruption.  (The tiny particles of volcanic ash are often electrically charged; lightning strikes in ash columns are common.)

It did, however, render much of the (former) valley uninhabitable.  Here's a photograph of the ruins of the old church of San Juan Parangaricutiro, which was destroyed by lava and ash along with the rest of the village of the same name:

[Image is in the Public Domain]

At the time of the eruption, all that was known was that it added another peak to the Trans-Mexican Volcanic Belt, which runs east-west across the entire country and includes much more famous volcanoes such as Popocatépetl.  Since then, we've learned that the whole range owes its existence to the subduction of the Rivera and Cocos Plates underneath the North American Plate at the Middle America Trench; the waterlogged rock and sediments are pulled down into the upper mantle, heated, and melt, forming the magma that eventually erupts somewhere behind the trench.

But at the time, the appearance of a volcano was a source of mystification both to the locals and the scientists.  To be sure, some geological phenomena are sudden; earthquakes, for example, often happen without much in the way of warning (and accurate earthquake prediction is still a dicey affair).  But we're used to things pretty much staying in the shapes and positions they were in before.  It takes a huge earthquake -- the 9.2-magnitude Anchorage megathrust quake comes to mind -- to radically reshape the land, in this case raising a long stretch of coastline by as much as nine meters.  And while big volcanic eruptions, such as the current one from Mount Etna, are spectacular and can be deadly, most of the time they're from volcanoes we already knew about.

Parícutin, though, kind of came out of nowhere, at least by the scientific understanding of the time.  And that's one of the benefits of science, isn't it?  It allows us to understand the processes involved, not just name them after they've happened.  While we're still not at the point where we can predict with much lead time when something like this will happen, at least now we can say with some assurance that we understand why it happened where it did.

Little consolation to Dionisio Pulido, of course.  I'm guessing that "owning and operating" a volcano was nowhere near as lucrative as his cornfield had been.  But that's life in a geologically active area.  However much we understand about the science behind such events, it's good to keep in mind there's always a human cost.

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Time to act

I know we really don't need anything else to worry about.  World events have been depressing enough, and here in the United States we've got an election on Tuesday that is making me pop Xanax as if they were Skittles.  But I ran across something in a book I'm reading that was absolutely jaw-dropping, and not in a good way, and I knew I would be seriously remiss in not writing about it here.

I mentioned a few days ago (in a post about some bizarre volcanoes in the East African Rift Zone) that I've been reading Tamsin Mather's wonderful book Adventures in Volcanoland: What Volcanoes Tell Us About the World and Ourselves.  Mather's specialty is monitoring gas production from volcanoes, and using the composition of offgassed material to gather information about magma characteristics and the likelihood of eruptions.  She's traveled all over the world collecting and analyzing samples, comparing hotspot volcanoes (like the ones in Hawaii) to rift volcanoes (like Ol Doinyo Lengai in Tanzania) to trench/subduction volcanoes (like Etna, Vesuvius, Krakatoa, Fujiyama, the Andes, and the North American Cascades).  Her research puts her in position as one of the world's foremost and most knowledgeable experts on volcanic offgassing, and what it means for our understanding of what is going on inside the Earth's mantle.

In her book, she not only references currently-active volcanoes, but prehistoric eruptions -- and one of those she discusses is the astonishingly huge Siberian Traps.  

[Image licensed under the Creative Commons OlgaChuma Ольга Чумаченко, Плато Путорана-3, CC BY-SA 3.0]

This eruption, of a type known as a large igneous province or flood basalt, happened 252 million years ago, at the end of the Permian Period.  Flood basalt eruptions occur when something rifts the crust of the Earth and deep-source, extremely hot basaltic (low silica content) lava flows out.  This lava is incredibly fluid, and fills up valleys like water fills a bowl.  In the case of Siberia, it was a quantity that beggars belief; current estimates stand at around four million cubic kilometers of lava.  The disaster this caused was amplified by the fact that prior to the eruption, the Earth had had a long period of warm, wet climates pretty much worldwide, facilitating the growth of widespread swamps and rainforests.  The age when this occurred is called the Carboniferous Period, so named because all that dead compressed plant matter locked up gigantic quantities of atmospheric carbon, forming enormous seams of coal.

When the Siberian Traps erupted, the lava ripped its way through those massive coal deposits, and the carbon they contained was suddenly returned to the atmosphere as carbon dioxide.  Mather writes:

Estimates of total carbon dioxide emissions over the million-year-scale lifetimes of these basaltic floods are in the region of tens to hundreds of trillion tonnes...  Estimates of varying emission rates over the very long lifetimes of these provinces are harder to make than the totals, but one recent study put the maximum emission rate during the Siberian Traps at around eighteen billion tonnes per year.

The result was widespread disruption of the climate, global marine anoxia, and the largest mass extinction ever -- the Permian-Triassic Extinction, which wiped out on the order of ninety percent of life on Earth.

The kicker comes in the very next paragraph, when Mather tells us that the rate of carbon dioxide production from the most massively devastating volcanic eruption on record, the rock from which covers an area of seven million square kilometers, is half the rate our current fossil fuel use is currently churning out carbon dioxide.

I don't exaggerate when I say I had to read that passage three times before I was convinced I'd understood her correctly.

I've all too frequently heard laypeople give a sneering chuckle at the climatologists, saying stuff like, "What a lot of bullshit.  One volcanic eruption emits more carbon dioxide than all the cars on Earth do."  They rarely cite a source, and when they do it's from something like the fossil-fuel-industry-funded Heartland Institute, but -- because this opinion is a great excuse for continuing to do stuff the same way we always have -- they almost never get challenged on it.

It's astonishing how easy it is to accept a false viewpoint when it gives you a comforting reason not to do anything inconvenient to your lifestyle.

But here's the straight scoop from Tamsin Mather, who (allow me to reiterate) is a volcanologist who specializes in analysis of volcanic offgassing:

Despite the wide error bars in our estimates of the global rate of volcanic carbon degassing, what we can know is that these natural emissions pale into insignificance compared to what humans produce.  In 2019, human fossil-fuel burning released over 35 billion tonnes of carbon dioxide into our atmosphere.  This is seventy times more than even our most generous current estimates of global magmatic carbon degassing.  In 2022, the aviation industry alone emitted 800 million tonnes of carbon dioxide, eclipsing estimates of that from our planet's background tectonism before even considering other sectors of human industry.  We cannot look to Earth's volcanism today to reassure ourselves that our rate of carbon emission might not be too much of a change in terms of our planet's natural cycles.  Powerful as the forces of tectonics that daily drive the slow creep of plate movement and volcanic activity across the globe are, the human race has currently surpassed them in terms of its carbon dioxide flux to the atmosphere.  It is apposite to reflect upon the level of responsibility that should appropriately come with the level of power attained by our species that, by this carbon metric, overwhelms all Earth's volcanoes.

Despite this, we have a candidate for president here in the United States -- I doubt I need to tell you which one -- who has stated he wants to discontinue investment in renewable energy and withdraw from the Paris Accords, and frequently says "Drill baby drill, and frack frack frack!" to cheering crowds.

Anyhow, I'm sorry to post alarming stuff, but perhaps now isn't such a bad time after all.  We have the chance to make a difference not only by our actions and choices, but in the voting booth.  It put me in mind of a conversation that occurs in my novel In the Midst of Lions, which seems a fitting way to end this post:

Mary Hansard's face registered near panic.  "It's not just here.  It’s everything we know.  Soon it’ll all be gone, and if we don’t find a way out, us with it.  We've got to do something, now.”

Soren glanced at Dr. Quaice.  “Okay, this is scaring the shit out of me.”

Mary tightened her grip on Soren’s sleeve.  “Good.  Good.  You should be scared.  Scared people act.” She hitched a sob.  “Complacent people die.”

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The oddest volcano on Earth

As far as we've progressed in our understanding of science, we still have a long way to go.

This is true in every scientific endeavor, but I was thinking about it apropos of geology while reading volcanologist Tamsin Mather's wonderful recent book Adventures in Volcanoland: What Volcanoes Tell Us About the World and Ourselves.  Mather's fascinating and often lyrical narrative takes us all over the world, describing her studies of volcanoes in Nicaragua, Greece, Hawaii, Iceland, Japan, Indonesia, Wyoming, Sicily, Ethiopia, and Tanzania.  It was this last-mentioned that got me pondering the gaps in our understanding, because she described seeing the bizarre Ol Doinyo Lengai volcano in the northern part of the country.

Ol Doinyo Lengai is strange by any standards.  It sits in the middle of the East African Rift Zone, which extends from Ethiopia to Mozambique, and is one of the Earth's only above-water divergent zones, places where two pieces of crust are moving apart.  The Rift being on land won't last forever, of course; ultimately a crescent-shaped chunk of East Africa will cleave off from the rest of the continent, the ocean will flood in, and afterward the rift will (like most of the others) lie at the bottom of the sea floor.  The separated piece will then creep off to the east, becoming an island -- or, depending on how you define it, a new continent.

The violent geology of the region has created a topography that in a post last year I referred to as "a beautiful hellscape."  The Dallol Depression is already 48 meters below sea level; the only thing keeping the water out is the Afar Highlands to the east acting as a barrier.  It's not only filled with bubbling mud pots and hot springs, but its position near the equator and the surrounding mountains creating a rain shadow make it blisteringly hot -- think Death Valley in midsummer -- so despite the otherworldly beauty of the brilliantly-colored rocks, it's not a place most people would ever think of going.

But even by comparison to the strange landscape that surrounds it, Ol Doinyo Lengai is peculiar.  It is the only active volcano on Earth that produces carbonatite lava, which (as you might surmise) is rich in carbonate minerals like calcite, dolomite, sodalite, apatite, and ancylite.  The magma is cool by volcanic standards, at only around 500-600 C, and yet produces some of the most fluid, low-viscosity lava flows known, moving at around five meters per second -- so about a typical human running speed.

Staying out of the way when Ol Doinyo Lengai erupts is a really good idea.

The lava comes out dark brown or black, but once it freezes and is exposed to the air for a few days, carbonate minerals crystallize on the surface and turn it a frosty white.

[Image licensed under the Creative Commons Thomas Kraft, Kufstein, Lava lengai, CC BY-SA 3.0]

So the entire cone has a snow-covered appearance, but there's no snow there -- it's all mineral deposits.

The weirdest thing is that we don't really understand where all this carbonatite magma is coming from.  My first guess was that somehow the plumbing of the volcano was moving up through a limestone or marble deposit, and picking up the carbonates as it went, but geochemical analysis of the rocks produced from it seems to have ruled that out.  Right now, it's thought to be some kind of weird fractionation -- the source magma deep underground is separating into high-carbon and low-carbon bits, and the high-carbon bits are the ones feeding this particular volcano -- but the fact is, this is a guess, and the word you see most often attached to its mineralogy and chemistry is "peculiar."

So what's happening here in northern Tanzania -- and even more apposite, why it isn't happening anywhere else on Earth -- is a mystery.  The strangeness, though, only increases its fascination, and there are geologists who are devoting a lot of time to figuring out what is going on in this odd and inhospitable place.  Strange, too, that the East African Rift Valley is where humanity got its start; Oluduvai Gorge, where some of the best-preserved hominin fossils were found, is part of the Rift complex. 

Perhaps there's a reason we're drawn to this mysterious spot.  Our roots are here -- in one of the most tectonically-active places on the planet.  That it still leaves us with unanswered questions only makes the draw stronger, bringing us back to the place our distant kin left a hundred thousand years ago, to use the tools of science to finally understand our own ancestral home.

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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.

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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!]