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!]

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!]