The pressure cooker

It will come as no surprise to regular readers of Skeptophilia that I have a peculiar fascination for things that are huge and powerful and can kill you.

I'm not entirely sure where this obsession comes from, but it's what's driven me to write here about such upbeat topics as giant predatory dinosaurs, tornadoes, hurricanes, massive earthquakes, supernovas, gamma-ray bursters, and the cheerful concept of "false vacuum decay" (which wouldn't just destroy the Earth, but the entire universe).  I'm guessing part of it is my generally anxiety-ridden attitude toward everything; after all, just because we don't think there's a Wolf-Rayet star nearby that's ready to explode and fry the Solar System doesn't mean there isn't one.  I know that worrying about all of that stuff isn't going to (1) make it any less likely that it'll happen, or (2) make a damn bit of difference to my survival if it does, but even so I don't seem to be able to just relax and focus on more positive things, such as the fact that with the sea-level rise predicted from climate change, it looks like here in upstate New York I may finally own ocean-front property.

It's also why I keep regular tabs on the known volcanoes on the Earth -- on some level, I'm always waiting for the next major eruption.  One of the potentially most dangerous volcanoes on Earth is in Italy, and I'm not talking about Vesuvius; I'm referring to the Campi Flegrei ("burning fields," from the Greek φλέγω, "to burn"), which isn't far away from the more famous mountain and seems to be powered by the same magma chamber complex that obliterated Pompeii, Herculaneum, and Stabiae in 79 C.E.  Both Vesuvius and the Campi Flegrei are highly active, and near the top of the list of "world's most dangerous volcanoes."

The problem is, the three million residents of Naples live right smack in between the two, only twenty-odd kilometers away from Vesuvius (to the east) and Campi Flegrei (to the west).  (For reference, Pompeii was nine kilometers from the summit of Vesuvius.)

The Campi Flegrei, looking west from Naples [Image licensed under the Creative Commons Baku, VedutaEremo2, CC BY-SA 4.0]

The problem is that volcanoes like these two don't erupt like the familiar fountains of lava you see from Kilauea on the Big Island of Hawaii, and the recent eruption on La Palma in the Canary Islands and the one near Grindavík in Iceland.  The most typical eruption from volcanoes like Vesuvius and Campi Flegrei are pyroclastic flows -- surely one of the most terrifying phenomena on Earth -- a superheated mass of steam and ash that rush downhill at speeds of up to a hundred kilometers an hour, flash-frying everything in its wake.  That the Campi Flegrei volcanoes are capable of such massive events is witnessed by the surrounding rock formation called the "Neapolitan Yellow Tuff."  A "welded tuff" is a layer of volcanic ash that was so hot when it stopped moving that it was still partially molten, and fused together into a solid porous rock.

A video of a pyroclastic flow from Mount Unzen in Japan in 1991

The Neapolitan Yellow Tuff isn't very recent; it came from an eruption about 39,000 years ago.  But there are signs the Campi Flegrei are heating up again, which is seriously bad news not only for Naples but for the town of Pozzuoli, which was built right inside the main caldera.  The residents of Pozzuoli have had to get used to regular rises and falls of the ground, some by as much as an alarming two meters.  In fact, between 1982 and 1984, there was so much uplift -- followed by magnitude-4 earthquakes and thousands of microquakes -- that the harbor became too shallow for most ships to dock, and the entire population of forty thousand was evacuated until things seemed to simmer down.

In fact, the reason the topic comes up is a study out of Stanford University and the University of Naples that appeared this week in the journal Science Advances, that found this terrifying swell-and-subside isn't due primarily to magmatic movement, as was feared -- it's the bubbling of superheated groundwater.  The study looked at the composition of the "caprock," the rock layer on top of the formation, and found that when mixed with hot water it forms something like a natural fibrous cement.  This then plugs up cracks and prevents groundwater from escaping.

The whole thing is like living on the lid of a giant pressure cooker.

Of course, unlike (I hope) your pressure cooker, the rock doesn't have the tensile strength to manage the pressure fluctuations, so ultimately it breaks somewhere, triggering an earthquake and steam eruptions, after which the caprock settles back down for a while until the cracks all reseal and the pressure starts to rebuild.

This is all pretty scary, but it does point scientists in a direction of how to mitigate its potential for harm.  "I call it a perfect storm of geology -- you have all the ingredients to have the storm: the burner of the system -- the molten magma, the fuel in the geothermal reservoir, and the lid," said Tiziana Vanorio, who co-authored the study.  "We can't act on the burner but we do have the power to manage the fuel.  By restoring water channels, monitoring groundwater, and managing reservoir pressure, we can shift Earth sciences toward a more proactive approach -- like preventive health care -- to detect risks early and prevent unrest before it unfolds.  That's how science serves society."

Which is all very well, but I still wouldn't want to live there.  I visited Italy last year and loved it, but the area around Naples -- that'd be a big nope for me.  When we were in Sicily, itself no stranger to seismic unrest, one of our tour guides said, "We might be taking a risk living here, I suppose.  But those people up in Naples -- they're crazy."

That anyone would build a town on top of an active volcano is explained mostly by the fact that humans have short memories.  And also, the richness of volcanic soils is generally good for agriculture.  Once Pompeii was re-discovered in the middle of the eighteenth century, along with extremely eerie casts of the bodies of people and animals who got hit by the pyroclastic flow, you'd think people would join our Sicilian tour guide in saying, "no fucking way am I living anywhere near that mountain."  But... no.  If you'll look at a world map, you might come to the conclusion that siting big cities near places prone to various natural disasters was some kind of species-wide game of chicken or something.

Not a game I want to play.  Such phenomena make me feel very, very tiny.  I'm very thankful that I live in a relatively peaceful, catastrophe-free part of the world.  Our biggest concern around here is snow, and even that's rarely a big deal; we don't get anything like the killer blizzards that bury the upper Midwest and Rocky Mountain states every year.  Given my generally neurotic outlook on life, I can't imagine what I'd be like if I did live somewhere that had serious natural disasters.

Never leave my underground bunker, is probably pretty close to the mark.

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The rain of fire

On the morning of October 24, 79 C.E., Mount Vesuvius erupted in one of the deadliest volcanic events in recorded history.

The nearby towns of Pompeii, Herculaneum, Stabiae, and Oplontis had warnings.  There was a series of earthquakes during the lead-up to the eruption, which got a few people to leave the area -- everyone remembered that there'd been a powerful earthquake in February of 62 that had destroyed a number of buildings, and the skittish thought that something similar might be about to happen again -- but by and large, the residents just shrugged their shoulders.  Pliny the Younger, who wrote the only extant eyewitness account of the eruption (he was safely in Misenum, thirty kilometers away across the Bay of Naples, when it happened), said that the earthquakes that preceded the eruption "were not particularly alarming because they are frequent in Campania," and thus the majority of people in the area ignored them and stayed home.

This turned out to be a mistake.

The morning of October 24 dawned clear and bright, but there was already a plume of steam coming from the summit of the mountain that loomed over the four cities.  This, too, was nothing unusual; it's doubtful many people even noticed.  But at around midday, there was a sudden jolt, and the entire peak exploded, sending a column of ash, rock, and superheated steam an estimated thirty kilometers high, blasting out material at a rate of 1.5 million tons per second.  Rocks and ash rained down on the cities, but worse was to come; by evening, the pressure forcing the column upward dropped suddenly and the entire column collapsed, causing a pyroclastic surge with an estimated temperature of six hundred degrees Celsius pouring downhill at about a hundred kilometers an hour.  Anything or anyone left that hadn't been killed by asphyxiation or roofs collapsing died instantly, and the ash flow blanketed the region.  The greatest quantity of ash landed in Herculaneum, which was buried under a layer twenty meters thick.

But all four cities were completely obliterated, to the point that within a hundred years, most people forgot that they'd ever existed.  References to Pompeii, Herculaneum, Stabiae, and Oplontis, four prosperous towns that had been wiped out by the wrath of the gods, were considered fanciful legends -- a little like Plato's mention of the mythical land of Atlantis sinking beneath the waves.

Then, in 1709, a farmer was plowing his field, and the plow hit the edge of a buried wall.  It turned out to be a surviving piece of masonry from Herculaneum.  Something similar happened in Pompeii in 1748.  Archaeologists were called in, and gradually, the work started that is still ongoing -- clearing away meters-thick layers of welded ash to uncover what is left of the four cities.

Today it's a strange, somber place.  Wandering around its cobblestone streets, and looking at the snaggletoothed silhouette of Vesuvius in the distance -- the mountain lost almost half of its original height in the eruption -- was chilling despite the bright warmth of the sun.  We looked at remnants of homes, shops, temples, baths, the central forum, and even a brothel (each room decorated with highly explicit paintings of what services you could expect within).

We got to see some of the casts of the people who died during the eruption, their names long forgotten, their bodies entombed in fused hot ash, then burned and decayed away to leave a cavity that archaeologists filled with plaster to reveal their ghostly forms.

Many of the 1,044 molds of human victims were found with their hands over their faces, futilely trying to shield themselves from the choking, scalding ash.

Today, around three million people live in the shadow of Vesuvius, most of them in the city of Naples and the nearby towns of Pozzuoli, Bagnoli, San Giorgio a Cremano, and Portici.  Our guide said there were two reasons for this, and for the number of people living in other volcanic areas, such as Indonesia, Japan, Costa Rica, Cameroon, and Ecuador -- (1) volcanic soil is wonderfully fertile for agriculture, and (2) people have short memories.  But now that we have a better understanding of plate tectonics and geology, you have to wonder why people are willing to accept the risk.  A man we talked to in Rome had an explanation for that, too.  "Those people down in Naples," he said, shaking his head, "they're crazy."

Today Pompeii is seemingly at peace, its ruins as quiet as the cemetery it in fact is.  Flowers grow in profusion in every grassy spot.

But not far beneath the surface, the magma is still moving.  The processes that destroyed the region in the first century C.E. are haven't stopped, and the tranquil scene up above is very much an illusion.  After seeing the city, we hiked up to the summit of Vesuvius and looked down into the crater, the hole blasted out of the center of the mountain.

The whole thing was enough to make me feel very small and very powerless.  We flatter ourselves to think we can control the forces of nature, but in reality, we're still at their mercy -- no different from the residents of Pompeii on October 23, who knew the mountain was rumbling but figured there was nothing to worry about.  The rain of fire that was to come only twenty-four hours later was unstoppable.  Although now we can predict volcanic eruptions better than the first-century Romans, we still are at the mercy of a natural world that cares little for our lives.

But there's nothing wrong with being reminded of this periodically.  A bit of humility is good for the mind.

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A dangerous beauty

The Greek island of Thera -- often known by its Italianized name of Santorini -- is the southernmost of the Cyclades, an island chain in the Aegean Sea southeast of mainland Greece.  Like much of the region, it's a stunningly beautiful place.  In fact, one of Thera's names in antiquity was Καλλίστη -- "the most beautiful one."

[Image licensed under the Creative Commons Pedro Szekely from Los Angeles, USA, Santorini, Greece (38051518795), CC BY-SA 2.0]

The steep, rugged, rocky terrain, though, didn't happen by accident.  Thera and the other Cyclades formed because they sit near the margin of the Hellenic Subduction Zone, where the northern edge of the enormous African Plate is being shoved underneath the much smaller Aegean Sea Plate.  The result is the formation of an island arc, where the material in the subducted plate is pushed downward to a depth were it melts, and the blobs of magma rise toward the surface to create a chain of volcanoes.  (Most of the islands in the Caribbean, the Aleutians, and pretty much the entirety of the nations of Japan and Indonesia were formed this way.)

This makes it a dangerous place to live.  It was the site of the Minoan-era city Akrotiri, which became prosperous because of being a central port for the copper trade out of Cyprus (the Latin word for copper, cuprum, actually means "metal from Cyprus").  It was second only to Crete as a center of civilization for the Minoan Empire, and was famed for its art, especially elaborate and beautiful frescoes, pottery, and sculpture.  Many of the houses there had running water carried by bronze pipes, and geothermal heat.

The geothermal heat might have clued its residents in that something was going on underground.  All of the high times came to an end with a colossal eruption of the volcano just offshore in around 1600 B.C.E. 

[Nota bene: this is not what inspired the myth of Atlantis, despite the claims you see all over the place on the interwebz.  Plato made it clear that the legend said Atlantis was "west of the Pillars of Hercules" (the Straits of Gibraltar), somewhere out in the Atlantic (thus the name).  But... allow me to stress this point... Atlantis never existed.  Because it's a myth.]

Anyhow, the eruption of Thera not only destroyed pretty much the entire island, but blew an estimated forty cubic kilometers of dust and ash into the air, triggering atmospheric and climatic effects that were recorded by contemporaneous scholars in Egypt and China and draw comparisons from modern geologists to the Mount Tambora eruption of 1815 that caused "The Year Without A Summer."  The eruption generated a tsunami that devastated coastal cities all over the Mediterranean, including the Minoan city of Knossos on the north shore of Crete.  (The Minoan civilization limped along for another couple of hundred years after this calamity, but was finally finished off by a massive earthquake in 1350 B.C.E. that destroyed Knossos completely.)

Here's the thing, though.

The volcano off the coast of Thera is still active.

A paper last week in Nature Communications looked not at the enormous 1600 B.C.E. eruption, but a much smaller eruption in 1650 C.E.  The leadup to this eruption, however, was about as ominous as you could get.  People noticed the water in the seas off the north coast of Thera boiling and changing color -- and dead fish rising to the surface as well, cooked in situ.  Sulfurous gases wafted over the island.  This was followed by a cinder cone emerging from the sea, which proceeded to fling around molten rocks and ash plumes.

Then... boom.

The new research suggests that what triggered the eruption was a landslide, similar to what kicked off the famous Mount Saint Helens eruption of 1980.  In this case, though, the landslide was underwater, off the northwest flank of the volcano.  This landslide did two things -- it displaced huge amounts of water, generating a twenty-meter-high tsunami, and it took the pressure off the top of the magma chamber, causing it to explode.

The combination killed seventy people and hundreds of domestic animals -- horrible, but nowhere near what the island proved itself capable of 3,600 years ago.  The study found that the magma chamber is refilling at a rate of four million cubic meters per year, meaning with regards to subsequent eruptions -- to invoke the old cliché so often used in connection to active volcanoes and tectonic faults, it's not a matter of "if," it's a matter of "when."

Unsurprisingly, the people in the region seem unaware of the time bomb they're sitting on.  "Local populations, decision-makers, and scientists are currently unprepared for the threats posed by submarine eruptions and slope failures, as has been demonstrated by the recent 2018 sector collapse of Anak Krakatau and the 2022 [Hunga Tonga] eruption," the authors write.  "Therefore, new shore-line crossing monitoring strategies... are required that are capable of being deployed as part of rapid response initiatives during volcanic unrest and which enable real-time observation of slope movement."

It remains to be seen how this could help the almost two thousand people who currently live on the slopes of the island, many of them living in houses sitting on layers of fused ash deposited there during the 1600 B.C.E. eruption.  It's something we've seen here before; people like living in tectonically active regions because (1) the terrain is often dramatic and beautiful, (2) volcanic soils are good for agriculture, and (3) people have short memories.  If the last time things went kablooie was almost three hundred years ago, it's easy for folks to say, "What, me worry?"  (Witness the millions of people living near the terrifying Cascadia Subduction Zone, about which I wrote three years ago.  As well as all the people in the aforementioned countries of Japan and Indonesia.)

Anyhow, that's our rather ominous scientific study of the day.  The Earth is a beautiful and dangerous place, and nowhere does that combination come into sharper focus than the Greek islands.  Makes me glad I live where I do -- despite the cold winters, at least I don't have to worry about the place blowing up.

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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."

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A geological champagne bottle

I've always found the idea of an unstable system fascinating, even before I knew the name to put on it.  As a kid I liked to do things like build towers of stones and see how high I could get them before they'd teeter and collapse, and got quite good at creating a multi-tiered house of cards.  (Can't do it any more -- I drink too much coffee to have the steady hands I did at age twelve.)  What I found interesting was that up to a point, such systems tend to self-stabilize; touch your tower of stones gently, and sometimes it'll jostle a bit then settle back into its original position.  But introduce too much energy into it, and it destabilizes fast.  After that, every bit of the collapse feeds more energy into the process, until all you have left is a pile of chaotic rubble.

This phenomenon of a tipping point -- the point where the system crosses the line between stable and unstable -- is a special case of a wider phenomenon called hysteresis, which is the dependence of a system's state on its history.  If something has started a trend in the past, sometimes it takes far less energy to keep it going than it did to get it started in the first place.  Think, for example, of popping the cork on a champagne bottle.  The amount of force you have to exert to push the cork up the bottle neck stays the same until... suddenly... it doesn't.  Once the frictional force between the cork and the neck is exceeded by the force exerted by the pressure in the bottle, the system changes state fast.

Bang.

Lots of systems act this way, but none quite as alarmingly powerful as a volcanic eruption.  Take, for example, what happened to Anak Krakatau, an island in the Sunda Strait in the Indonesian archipelago.  This island was the site of the stupendous 1883 eruption of Krakatau (more commonly, but less correctly, spelled Krakatoa), one of the largest in recorded history.  But volcanoes seldom stop at one eruption; the magma chamber feeding them doesn't just empty and go away.  The same processes that caused the first eruption eventually rebuild the volcano and generate subsequent outbursts.  Anak Krakatau ("Child of Krakatau" in Indonesian) emerged in 1927 from the giant caldera left by the eruption forty-four years earlier, and continued to grow and produce steam, ash bursts, and lava flows afterward.

An eruption of Anak Krakatau in 2008 [Image is in the Public Domain]

Then in 2018, the entire island collapsed.  I'm not overstating.  It lost two-thirds of its above-sea-level volume, and the summit dropped from 338 meters above sea level to 110.  This sudden cave-in generated a two-meter-high tsunami that killed over four hundred people and displaced forty thousand, mostly along the coastline of Sumatra and Java.  Geologists knew the potential of the island to generate another deadly eruption, and even that there was a potential for collapse, but no one saw it coming on the day it happened.  No warning, everything's quiet, then...

Bang.

The sudden collapse of Anak Krakatau was the subject of a paper this week in Earth and Planetary Science Letters which studied the lead-up to the event, looking at whether there were signs in the preceding months that might have tipped geologists off to what was going to occur.  And... scarily... there weren't.  Just like the cork in a champagne bottle giving you no warning when it's going to pop.  The authors write:

The lateral collapse of Anak Krakatau volcano, Indonesia, in December 2018 highlighted the potentially devastating impacts of volcanic edifice instability.  Nonetheless, the trigger for the Anak Krakatau collapse remains obscure.  The volcano had been erupting for the previous six months, and although failure was followed by intense explosive activity, it is the period immediately prior to collapse that is potentially key in providing identifiable, pre-collapse warning signals... [Our research] suggests that the collapse was a consequence of longer-term processes linked to edifice growth and instability, and that no indicative changes in the magmatic system could have signalled the potential for incipient failure.  Therefore, monitoring efforts may need to focus on integrating short- and long-term edifice growth and deformation patterns to identify increased susceptibility to lateral collapse.  The post-collapse eruptive pattern also suggests a magma pressurisation regime that is highly sensitive to surface-driven perturbations, which led to elevated magma fluxes after the collapse and rapid edifice regrowth.  Not only does rapid regrowth potentially obscure evidence of past collapses, but it also emphasises the finely balanced relationship between edifice loading and crustal magma storage.

This put me in mind of another geological phenomenon that results from a similar kind of champagne-cork effect; kimberlite eruptions, which I wrote about here last year, and which apparently have the same no-warning-then-boom behavior.  (These are the eruptions that produce diamonds -- and, once you read my post, you'll be glad to hear that they are thought to be a feature of Earth's distant past, and very unlikely to happen now.)

It's easy for us to look around and think everything we see -- not only the geology, but the climate, the global ecosystem, society itself -- is stable, and any perturbations will set up a feedback that will return everything to "normal."  The problem is, for a lot of systems, there is no "normal."  They're stable up to a point -- but if pushed beyond that point, unravel fast.  Some of these phenomena, like the caldera collapse that struck Anak Krakatau four years ago, are powerful and unpredictable, and other than evacuating people, there wouldn't have been anything we could have done to prevent it even if we had known.  But we'd damn well better not close our eyes to the analogy between this event and the bigger picture.  It's easy and convenient to believe that "everything will be fine because it's always been fine," but that kind of thinking gives people license to keep poking at things, heedlessly pushing on the superstructure and acting like it has infinite resilience.

Then, without any warning, where you had an orderly stone tower, all you have left is a pile of rocks, dust, and debris.

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Since reading the classic book by Desmond Morris, The Naked Ape, when I was a freshman in college, I've been fascinated by the idea of looking at human behavior as if we were just another animal -- anthropology, as it were, through the eyes of an alien species.  When you do that, a lot of our sense of specialness and separateness simply evaporates.

The latest in this effort to analyze our behavior from an outside perspective is Pascal Boyer's Human Cultures Through the Scientific Lens: Essays in Evolutionary Cognitive Anthropology.  Why do we engage in rituals?  Why is religion nearly universal to all human cultures -- as is sports?  Where did the concept of a taboo come from, and why is it so often attached to something that -- if you think about it -- is just plain weird?

Boyer's essays challenge us to consider ourselves dispassionately, and really think about what we do.  It's a provocative, fascinating, controversial, and challenging book, and if you're curious about the phenomenon of culture, you should put it on your reading list.

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

Hot times

In today's contribution from the Completely Useless Advice department: if you own property in southern Africa, you might want to consider selling it some time in the next ten million years or so.

The reason I say this is because of a paper published a couple of months ago in Nature Geoscience that was once again thrown my way by my pal Gil Miller, who seems to have an inordinate talent at ferreting out truly fascinating stuff I hadn't heard about.  The paper is entitled "A Tree of Indo-African Mantle Plumes Imaged by Seismic Tomography," by Maria Tsekhmistrenko, Karin Sigloch, and Kasra Hosseini (of Oxford University), and Guilhem Barruol (of the Université de Paris), and describes the structure of the mysterious "hotspots" -- upwelling of extremely hot magma from deep in the mantle -- that are responsible for such volcanically-active regions as Hawaii, Yellowstone, and Réunion Island.

These hotspots have long puzzled geologists, because they are quite distant from tectonic plate boundaries, where most of the world's seismic and volcanic activity occurs.  Hawaii is the best-studied hotspot; it was one of the most powerful pieces of evidence of plate movement, back in the 1960s when the theory of plate tectonics was first being studied.  The Big Island of Hawaii is just the easternmost point in a chain that extends way beyond what we usually think of as the Hawaiian Islands; even the westernmost island that pokes up above sea level, Kure Atoll, isn't the end of it.  It continues into the Emperor Seamount Chain, which extends underwater all the way to the Kamchatka Peninsula of Siberia. 

My long-ago geology professor described it as being like pulling a piece of fabric (the Pacific Plate) through an upside-down sewing machine (the Hawaiian Hotspot); the needle of the sewing machine punches regular holes upward through the fabric as it moves through, but the sewing machine itself stays in the same place.  The plates are moving; the hotspot isn't.  (And the angle in the chain of seamounts indicates that at some point in the past, the Pacific Plate changed direction, probably because of jostling against other plates.)

The Pacific Ocean floor, showing the Hawaiian-Emperor Seamount Chain [Image is in the Public Domain courtesy of NOAA]

What is still mysterious about hotspots is why they happen at all.  We have a pretty decent idea of why the activity along plate margins occurs -- strike-slip faults like the famous San Andreas, where two plates are moving along each other in opposite directions; trenches/subduction zones like Indonesia, where you get both powerful quakes and huge volcanoes; and mid-ocean ridges/divergent zones like the Mid-Atlantic Ridge, where plates are moving apart and new magma upwells to fill the gaps.  But why would there be a persistent chain of volcanoes out in the middle of a stable plate?

The current paper describes blobs of extremely hot magma originating from the lower parts of the mantle, which rise and then diverge into branches.  The authors write:

Mantle plumes were conceived as thin, vertical conduits in which buoyant, hot rock from the lowermost mantle rises to Earth’s surface, manifesting as hotspot-type volcanism far from plate boundaries.  Spatially correlated with hotspots are two vast provinces of slow seismic wave propagation in the lowermost mantle, probably representing the heat reservoirs that feed plumes...  Using seismic waves that sample the deepest mantle extensively, we show that mantle upwellings are arranged in a tree-like structure.  From a central, compact trunk below ~1,500 km depth, three branches tilt outwards and up towards various Indo-Austral hotspots.  We propose that each tilting branch represents an alignment of vertically rising blobs or proto-plumes, which detached in a linear staggered sequence from their underlying low-velocity corridor at the core–mantle boundary.  Once a blob reaches the viscosity discontinuity between lower and upper mantle, it spawns a ‘classical’ plume-head/plume-tail sequence.

So the Réunion Hotspot is apparently connected to the East African Rift Zone, three-thousand-odd kilometers away.  The EARZ is a developing rift that is ultimately going to shear off the "Horn of Africa," opening a new ocean and creating a new "microcontinent" made up Somalia and bits of Ethiopia, Kenya, and Tanzania.  (As an aside, it's also the site of Olduvai Gorge, where some of the earliest hominin fossils were found.)

[Image is in the Public Domain courtesy of the USGS]

"From looking at the core-mantle boundary, you can maybe predict where the oceans will open,” said study co-author Karin Sigloch.  "If the new models are accurate, a few tens of millions of years from now, you may not want to be in South Africa — or, perhaps, on planet Earth at all."

The reason Sigloch says this is that the team's analysis of the "tree" of magma that underlies both Réunion and the EARZ suggests that it's in the process of forming another branch -- another mantle plume -- that will ultimately end up underneath what is now South Africa.  "In tens of millions of years, a blob of nightmarishly gargantuan proportions will pinch off from the central cusp," Sigloch said, in an interview with Quanta magazine.  "This would produce cataclysmic eruptions.  The Deccan Traps [one of the largest volcanic eruptions ever, and which probably contributed to the extinction of the non-avian dinosaurs 66 million years ago] were caused by what we would think of as a solitary mantle plume.  This future mega-blob, though, would be capable of producing volcanism so prolific and extensive that the Deccan Traps would be a firecracker in comparison."

Pretty scary.  But like I said, if you want to visit South Africa, or if you live there, you still have a ten-million-year window to take care of business.  What's interesting from a geological perspective is that up till now, South Africa has been very stable tectonically.  The majority of the country is made of extremely old rock, what geologists call a "craton" -- a chunk of some of the oldest continents on Earth.  A massive flood basalt eruption, like the Deccan Traps, the Columbia River Flood Basalts, and the largest of them all -- the Siberian Traps, implicated in the cataclysmic Permian-Triassic Extinction -- would (literally) overturn three billion years of stable geology, with catastrophic results for the entire planet.

So yeah.  That's cheerful.  But since we have ten million years before we have anything serious to worry about, it'd be better if to turn your attention to more pressing concerns, even if you live in Johannesburg.  Like what we're doing to destroy the global ecosystem our own selves by our seeming commitment to burn every last gallon of fossil fuels out there, damn the climate, full speed ahead, and which could make the Earth pretty close to uninhabitable a great deal sooner. 

Which now that I think of it, isn't all that reassuring.

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Like graphic novels?  Like bizarre and mind-blowing ideas from subatomic physics?

Have I got a book for you.

Described as "Tintin meets Brian Cox," Mysteries of the Quantum Universe is a graphic novel about the explorations of a researcher, Bob, and his dog Rick, as they investigate some of the weirdest corners of quantum physics -- and present it at a level that is accessible (and extremely entertaining) to the layperson.  The author Thibault Damour is a theoretical physicist, so his expertise in the cutting edge of physics, coupled with delightful illustrations by artist Mathieu Burniat, make for delightful reading.  This one should be in every science aficionado's to-read stack!

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

Looking forward to cataclysm

Is it just me, or do you sometimes get the feeling that people want catastrophes to happen?

I see it every time there's a near pass of an asteroid.  Hysterical notes start showing up all over social media about how "this time it's for real" and "we better get ready" and "make your peace with God" and "how 'bout a planet-sized game of Whack-a-Mole?"  Then, when the asteroid misses by a significant margin -- amazingly enough, just as NASA predicted -- people seem somehow disappointed.

Dammit, they say.  Maybe next time will be the fiery cataclysm I've been so looking forward to.

This comes up because I'm once again seeing all sorts of buzz about the Yellowstone Supervolcano, and how the state of Wyoming is about to get blasted into the stratosphere.  Now, to be fair, Yellowstone is an active volcanic area, and previous eruptions have been pretty stupendous.  One that occurred 640,000 years ago blew a thousand cubic kilometers of rock, ash, and pyroclastic debris into the air -- for reference, this is about a thousand times larger than the amount of ash from Mount Saint Helens -- and the resulting fallout blanketed most of what is now the central United States.

I know 640,000 years seems like a long time, but it's not much geologically, and geologists consider another large caldera eruption from Yellowstone a sure thing.  Here's where the problem starts, though, because "a sure thing" doesn't mean "next Tuesday at 4:30 PM."  What it means is that there'll be an eruption some time in the next 100,000 years, give or take, and (this is the critical part) we're seeing no sign of it being any time soon in human terms.

Sapphire Pool, Grand Prismatic Spring Complex, Yellowstone National Park.  The deep blue water in the center is about 90 C and has a pH of 9.  Swimming not recommended.

The pro-cataclysm cadre got their push this time because of an announcement that the Steamboat Geyser has resumed regular eruptions after a three-year quiescent phase.  To be sure, Steamboat is pretty spectacular; its column of hot water and mud is one of the highest ever measured, jetting up to 115 meters into the air.  So having it start up again suddenly after not erupting since early 2018 is understandably going to raise some eyebrows.

What it doesn't mean, however, is that the entire caldera basin is going to go kaboom, as it did 640,000 years ago.  All it means is that underground hotspots come and go in volcanically active regions, and the plumbing system that powers geysers and hot springs shifts around sometimes.  Geologists are seeing no signs of magma movement, which would be the precursor to an actual volcanic eruption.

They're pretty curious, though, about why Steamboat has reactivated so suddenly.  One possibility is that because water in geysers and hot springs is usually laden with dissolved silica and other minerals, a slight fluctuation in temperature can cause a sudden precipitation of crystalline material (in fact, the shorelines of the Yellowstone hot springs are coated with the stuff).  This could, literally, clog the pipes and cause the pressure to release elsewhere, or to build up until it's sufficient to blast the clog to pieces.  In short, we're not sure why Steamboat is active again, but it's virtually certain it's not an imminent eruption.

Honesty compels me to use the word "virtually," and even Michael Manga of the University of California-Berkeley, who is leading the study of Steamboat Geyser, says we can't really be certain of the timing of volcanic eruptions.  After all, massive eruptions are so infrequent that we haven't had all that many opportunities to study the lead-up and see what would be the typical seismological warning signs.  "What we asked are very simple questions and it is a little bit embarrassing that we can't answer them, because it means there are fundamental processes on Earth that we don't quite understand," Manga said.  "One of the reasons we argue we need to study geysers is that if we can't understand and explain how a geyser erupts, our hope for doing the same thing for magma is much lower."

So as befits a cautious scientist, Manga is saying "we're not sure."  But from what we know of volcanoes, it doesn't look at all likely.  So the pro-cataclysm crowd will have to kick at the gravel in disappointment and look for the next opportunity for a large part of the surface area of the Earth to be covered in flaming debris.  

Better luck next time, guys.  Cheer up, maybe there's an asteroid out there heading our way.

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What are you afraid of?

It's a question that resonates with a lot of us.  I suffer from chronic anxiety, so what I am afraid of gets magnified a hundredfold in my errant brain -- such as my paralyzing fear of dentists, an unfortunate remnant of a brutal dentist in my childhood, the memories of whom can still make me feel physically ill if I dwell on them.  (Luckily, I have good teeth and rarely need serious dental care.)  We all have fears, reasonable and unreasonable, and some are bad enough to impact our lives in a major way, enough that psychologists and neuroscientists have put considerable time and effort into learning how to quell (or eradicate) the worst of them.

In her wonderful book Nerve: Adventures in the Science of Fear, journalist Eva Holland looks at the psychology of this most basic of emotions -- what we're afraid of, what is happening in our brains when we feel afraid, and the most recently-developed methods to blunt the edge of incapacitating fears.  It's a fascinating look at a part of our own psyches that many of us are reluctant to confront -- but a must-read for anyone who takes the words of the Greek philosopher Pausanias seriously: γνῶθι σεαυτόν (know yourself).

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

When the volcano blows

If you were wondering what the final act of the 2020 fever-dream theater might be, I have a possible contender.

Geologists have just discovered another supervolcano besides Yellowstone.

Supervolcanoes -- known in scientific circles as caldera eruptions -- are insanely powerful.  The famous 1883 eruption of Krakatoa, in Indonesia, was a caldera eruption, but even that was on the small end of things; it blasted 25 cubic kilometers of ash and rock fragments into the air, while the last major eruption of Yellowstone (650,000 years ago) released forty times that much, and covered most of what is now the central United States in a meter or two of ash.

And Toba, another Indonesian volcano, released almost three times more than that, 74,000 years ago -- and some anthropologists think the resulting climate impact nearly wiped out the up-and-coming human race, by some estimates reducing the entire population of humans to only about a thousand individuals.

By comparison, the eruption of Mount Saint Helens in 1980 was pretty much a wet firecracker.

So anyhow, why this all comes up is because we thought we knew where most of the potentially huge calderas were located, and geologists have given a great effort to calming everyone down, saying we have a handle on things and will have plenty of warning if any of them show signs of an imminent eruption.

Turns out, we didn't even know one of them was there.

A cluster of six islands in the Aleutian chain -- Carlisle, Cleveland, Herbert, Kagamil, Chagulak, and Uliaga -- have long been known to be stratovolcanoes, conical, explosive volcanoes of the same type as Mount Vesuvius.  What scientists didn't know until now is that apparently, the magma reservoirs of these six islands are not separate blobs, but one enormous blob underlying the entire island chain.

Just like the one under Yellowstone.

Mount Cleveland [Image is in the Public Domain]

The findings, which will be formally presented at the meeting of the American Geophysical Union on Monday, are a little alarming.  According to the press release from Science Daily:

Researchers from a variety of institutions and disciplines have been studying Mount Cleveland, the most active volcano of the group, trying to understand the nature of the Islands of the Four Mountains.  They have gathered multiple pieces of evidence showing that the islands could belong to one interconnected caldera.

Unlike stratovolcanoes, which tend to tap small- to modestly-sized reservoirs of magma, a caldera is created by tapping a huge reservoir in the Earth's crust.  When the reservoir's pressure exceeds the strength of the crust, gigantic amounts of lava and ash are released in a catastrophic episode of eruption...

If the researchers' suspicions are correct, the newfound volcanic caldera would belong to the same category of volcanoes as the Yellowstone Caldera and other volcanoes that have had super-eruptions with severe global consequences.

So yeah.  That's just marvelous.  Okay, I know, the discovery doesn't mean it's going to erupt any time soon, although it bears mention that Mount Cleveland has erupted 22 times in the past 230 years, and eight of those eruptions were in the last eleven years.  So it would totally be on-brand for 2020 if the whole thing went kablooie.

Yes, I know, I'm not supposed to be superstitious or engage in magical thinking or anything.  Given how this year's gone, I think I deserve a little slack, here.  No one will be happier than me if January 1, 2021 comes and the Aleutian Islands still exist, but at present I'm not ruling anything out. 

There we have it -- a supervolcano that we didn't even realize existed.  Just another thing to put in your Box of Anxiety.  Honestly, at the moment I'm more concerned about what Donald "Cheeto Benito" Trump and his cronies could potentially do to the United States on the way out the door.  In my experience, assholes can do more damage than ash holes.

Even the super-sized ones.

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One of the most compellingly weird objects in the universe is the black hole -- a stellar remnant so dense that it warps space into a closed surface.  Once the edge of that sphere -- the event horizon -- is passed, there's no getting out.  Even light can't escape, which is where they get their name.

Black holes have been a staple of science fiction for years, not only for their potential to destroy whatever comes near them, but because their effects on space-time result in a relativistic slowdown of time (depicted brilliantly in the movie Interstellar).  In this week's Skeptophilia book-of-the-week, The Black Hole Survival Guide, astrophysicist Janna Levin describes for us what it would be like to have a close encounter with one of these things -- using the latest knowledge from science to explain in layperson's terms the experience of an unfortunate astronaut who strayed too close.

It's a fascinating, and often mind-blowing, topic, handled deftly by Levin, where the science itself is so strange that it seems as if it must be fiction.  But no, these things are real, and common; there's a huge one at the center of our own galaxy, and an unknown number of them elsewhere in the Milky Way.  Levin's book will give you a good picture of one of the scariest naturally-occurring objects -- all from the safety of your own home.

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

When the volcano blows

A recommendation for bloggers and other commentators: if you are going to write about science, make sure you understand the damn science.  And for readers: make sure you find out about the writer's biases.

This comes up because of a link sent to me by a loyal reader of Skeptophilia called, "Why Volcanic Eruptions and Earthquakes are Increasing."  The whole thing pivots on the scary idea that the Earth is becoming more tectonically active, which certainly would have a major impact on humanity.  But let us begin with the most pressing question, which is: are volcanic eruptions and earthquakes increasing?

Mt. Nyiragongo, Democratic Republic of Congo [Image licensed under the Creative Commons MONUSCO/Neil Wetmore, An aerial view of the towering volcanic peak of Mt. Nyiragongo, CC BY-SA 2.0]

The answer appears to be "no."  According to the site Volcano World, maintained by the geology department of Oregon State University, there is no evidence that there's more seismic or volcanic activity lately.  Not even a slow overall increase over the past few thousand years.  The appearance that there's more rumbling going on, they say, is due to two things:

1. The Earth is being more intensively monitored now than any other time in its history, so we're more aware of even small events than we would have been.  This information then gets relayed all over the globe, increasing laypeople's awareness of what's going on.
2. Because of the increase in human population, the impact of these events has become much greater.  To use the example from the site, if the 2010 eruption of Eyjafjallajökull in Iceland had occurred in 1500, it's doubtful that it would have bothered -- or even been noticed by -- anyone but the Icelanders.

So we start out with a problem, which is that the central claim appears to be incorrect.  And in fact, if you're talking about violent eruptions, what we're seeing from Kilauea in the last few days is peanuts compared to the eruptions of Krakatoa, Tambora,and Toba in the Indonesian archipelago (respectively in 1883, 1815, and about 75,000 years ago) and the Lake Taupo (New Zealand) eruption in 180 C. E.  And even those pale by comparison to the events that formed the Columbia River Flood Basalts, the Deccan Traps, and the Siberian Traps, the latter of which spewed out 4 million cubic kilometers of lava, an amount that beggars belief, and which is believed to have played a role in the Permian-Triassic Extinction that wiped out 95% of the species on Earth.

But never mind all that.  The next thing the authors throw out is their explanation for this increase (which, recall, isn't occurring anyhow).  And the answer is: cosmic rays.

My first inclination was to guffaw at this, but then I decided to do some research (always a good idea, especially when there's the likelihood of rejecting an idea solely because "it seems wrong").  And I found that there is a (scientific) claim out there that the timing of volcanic eruptions is correlated with sunspot minimums, because those are correlated with a higher cosmic ray flux.  The paper in question is "Explosive Volcanic Eruptions Triggered by Cosmic Rays: Volcano as a Bubble Chamber," by Toshikazu Ebisuzaki, Hiroko Miyahara, Ryuho Kataoka, Tatsuhiko Sato, and Yasuhiro Ishimine, of the RIKEN Advanced Science Institute and the University of Tokyo, which appeared in Gondwana Research back in 2011.  What the scientists propose is that for silica-rich volcanoes, the magma can become superheated, and a cosmic ray could act to trigger nucleation -- quick, explosive liquefaction.

But here's the problem.  The Ebisuzaki et al. study only looked at eleven volcanoes, all in Japan, which already seems like a pretty small sample size.  They found that nine of the volcanoes erupted during a solar minimum, and the other two nearer to a solar maximum.  But without even trying hard I went through some eruption records back to 1700 (the cutoff for their study) and found twelve more stratovolcano eruptions (volcanoes with explosive, silica-rich magma) -- Pinatubo (1991), Mount St. Helens (1980), Novarupta (1912), Santa Maria (1902), Mount Pelée (1902), Krakatoa (1883), Tambora (1815), and La Soufrière (1718, 1812, 1902, 1971, and 1979).  Of those, eight occurred during solar maximums; only two (Novarupta and the 1971 eruption of La Soufrière) were during a clear minimum.  Two eruptions, Tambora and the 1812 eruption of La Soufrière, occurred during a local maximum in the middle of a thirty-year period of overall low sunspot activity (the "Dalton Minimum").  So let's not count those in either column.

So with my additions, that brings us up to twenty-one eruptions -- eleven during minimums, and ten during maximums.

In other words, random chance -- no connection to sunspot activity whatsoever.

Now, I'm neither a geologist nor a statistician, and if there's something wrong with my reasoning, I'm happy to correct it.  But I haven't even hit the punchline yet: the whole thing winds its way around to the claim that the Earth isn't actually warming, it's cooling.

So we're back in climate change denial la-la land, which I should have realized the moment I read them quoting Roy W. Spencer, a meteorologist who is on the advisory board of the denialist, pro-fossil-fuels Heartland Institute.  The site Skeptical Science takes Spencer's claims apart one at a time, and with far more authority than I can wield, so I suggest perusing the site.

Anyhow, the original claim looks like bullshit to me, and yet another example of someone with an ax to grind cherry-picking data that supports what they would very much like to be true.  In any case, I think we can rest assured that the cosmic rays aren't going to cause volcanoes to erupt, and that volcanic eruptions in any case have been pretty frequent occurrences throughout Earth's history.  Me, I'm more worried about the fact that we're still burning fossil fuels like mad despite a near-universal scientific consensus that what we're doing is going to jeopardize the long-term habitability of the planet.  And that seems to me more important than fretting about sunspots and cosmic rays.

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This week's book recommendation is a brilliant overview of cognitive biases and logical fallacies, Rolf Dobelli's The Art of Thinking Clearly.  If you're interested in critical thinking, it's a must-read; and even folks well-versed in the ins and outs of skepticism will learn something from Dobelli's crystal-clear prose.