Fingerprint of a catastrophe

Ever heard of the Bruneau-Jarbridge event?

If not, it's unsurprising; neither had I.  Plus, it happened twelve million years ago, during the mid-Miocene Epoch.  It's a supervolcano eruption of the Yellowstone Hotspot, which was at the time under what is now southwestern Idaho.  Between then and now, the hotspot has stayed pretty much where it was, but the North American Plate has moved, resulting in its current location underneath northwestern Wyoming,

The Bruneau-Jarbridge event was enormous.  It created monstrous pyroclastic flows that traveled 150 kilometers from the caldera, incinerating everything in their path.  The winds at the time of the eruption were from the west; we know this because the ash produced by the eruption traveled at least 1,600 kilometers to the east, creating meters-thick layers including the ones at the amazing Ashfall Fossil Beds in northeastern Nebraska.

In fact, it's the Ashfall Fossil Beds -- now an official National Natural Landmark and State Historical Park -- that's why the topic comes up.  A friend and frequent contributor of topics for Skeptophilia sent me a photograph of the site, and asked me if I'd heard of it:

[Image licensed under the Creative Commons Carl Malamud, Ashfall fossil beds - Baby rhino "T. L.", CC BY 2.0]

I hadn't, so naturally I had to look into it.

The whole thing is staggering, if grim.  Ashfall contains the skeletons of thousands of animals killed, more or less simultaneously, by the Bruneau-Jarbridge ash cloud.  The remains of the rhinoceros species Teloceras are so common there that one part of the fossil bed has been nicknamed "the Rhino Barn."  But there are lots of other species represented as well; five different kinds of prehistoric horses, including both three-toed and one-toed; three species of camels; two canids, the fox-sized Leptocyon and the wolf-sized Cynarctus; a saber-toothed (!) deer species, Longirostromeryx; three species of turtles; and three species of birds -- a crane, a hawk, and a vulture.

Despite the size of the eruption and resulting ash cloud, everything in the area didn't die during the ashfall.  Some of the bones show signs of scavenging, and some have breaks and tooth marks consistent with the dentition of the hyena-like canid Aelurodon.  So even a horrific catastrophe like Bruneau-Jarbridge didn't extinguish life completely; there were still scavengers around to chow down on the victims.

When looking at this sort of event, the question inevitably comes up of whether it could happen again.  The facile answer is: of course it could.  The Earth is still very much tectonically active, and more specifically, the Yellowstone Hotspot is a live volcano, as the frequent earthquakes and boiling-hot geysers and lakes should indicate.  It's likely to erupt again -- whether a monumental cataclysm like Bruneau-Jarbridge, or something smaller, isn't certain.

But despite the prevalence of clickbait-y YouTube videos about how "Yellowstone is about to erupt!" and "Scientists fear the Earth will crack wide open!" (both direct quotes from video titles), there is no imminent danger from the Yellowstone Hotspot.  What the geologists are actually saying is that a major eruption is likely some time in the next hundred thousand years, which puts it well outside the realm of what most of us should be worried about.

However, there's no doubt the the Ashfall Fossil Beds are a sobering reminder of what the Earth is capable of.  They're the fingerprint of a twelve-million-year-old catastrophe that makes any recent eruption look like a wet firecracker.  But as horrible as it was for the Miocene animals in the path of the ash cloud, it's provided us with a snapshot of what life was like back then, when Nebraska had a climate more like modern Kenya -- and the Great Plains was home to rhinos, camels, horses, and wild dogs.

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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!]