A whole lot of shakin'

I didn't realize how complicated it is to calculate the magnitude of an earthquake.

Most of us are probably familiar with the Richter Scale, the one most commonly used in the media.  It was developed in 1935 by seismologist Charles Francis Richter to give a standard scale to measure the power of earthquakes.  The scale is logarithmic; each increase in one on the scale represents a ten-fold increase in intensity.  The scale is based upon the displacement amplitude on a seismograph at a distance of one hundred kilometers from the epicenter, starting with a magnitude 0 earthquake causing the needle to move with an amplitude of one micron.  The scale extends up to an unspecified "greater than 9" -- because at that point, pretty much everything in the vicinity, including the seismograph, gets completely pulverized.

When you start looking more closely, though, the problems with the scale start to become obvious.  First of all, if the measurement is being made one hundred kilometers from the epicenter, the terrain in between is a significant factor.  Tremors passing through material with a high amount of shear (such as sand or mud) will lose intensity fast, as compared to ones going through a material that is rigid (such as solid rock).  Second, the origin of the earthquake usually isn't at the epicenter, which is the point on the surface nearest the source; the origin is the hypocenter, directly underneath -- but which can be at any depth from right near the surface down to hundreds of kilometers down.  (The deepest earthquake ever recorded was a minor tremor off the island of Vanuatu in 2004, which had a hypofocus 736 kilometers deep.)  Then there's the fact that earthquakes can be of different durations -- a less powerful earthquake that lasts longer can do as much damage as a more powerful, but shorter, tremor.

Another problem is that earthquakes can result in differences in the oscillation of the waves relative to the direction they're moving.  This is largely due to the fact that there are three basic sorts of faults.  There are thrust faults or convergent faults, where two tectonic plates are moving toward each other; what happens then can be one plate being pushed underneath the other (subduction), which is what causes the quakes (and the volcanoes) in Indonesia and Japan, or the two plates kind of smashing together into a jumble, which is the process that created the Himalayas.  There are extension faults or divergent faults, where the two plates are moving apart; this usually creates smaller but more frequent quakes, and lots of volcanism as magma bubbles up from the underlying mantle.  This is happening in Iceland, and is also the cause of the Great Rift Valley in Africa, which will eventually peel off the Horn of Africa (Somalia and parts of Ethiopia, Kenya, and Tanzania) and open up a new ocean.  Last, there are strike-slip faults or transform faults, where the plates are moving in opposite directions on each side of the fault, such as the famous San Andreas Fault in California.

Map of the (known) tectonic plates [Image is in the Public Domain courtesy of NASA/JPL]

The problems with the Richter Scale have led to the development of several other scales of intensity, such as the Surface-wave Magnitude Scale (which is pretty much just what it sounds like, and doesn't take into account source depth), the Moment Magnitude Scale (which is based on the amount of energy released as measured by the amount and distance of rock moved), the Duration Magnitude Scale (which figures in how long the tremor lasts), and so on.  But these all use different numerical benchmarks, and given that the Richter Scale is more widely known, a lot of people have continued to use that one despite its downsides.

The reason all this comes up is a new study from the University of Southampton that has identified evidence of what appears to be the biggest earthquake known; an almost unimaginable 9.5 on the Richter Scale quake that happened in Chile 3,800 years ago.  Trying to find the epicenter brings up yet another problem with measuring quake intensity, because the evidence is that this particular quake originated from the rupture of a part of the thrust fault between the Nazca Plate and the South American Plate off the coast of the Atacama Desert -- a rupture that was one thousand kilometers long.

The result was a tsunami that deposited marine sediments and fossils of oceanic animals several kilometers inland, and then traveled across the Pacific Ocean and slammed into New Zealand, tossing boulders the size of cars over distances of hundreds of meters.  That region of the Atacama Desert had been inhabited prior to the quake -- astonishing considering how dry and inhospitable the place is -- but it was (understandably) abandoned by the survivors for a long while afterward.

"The local population there were left with nothing," said geologist James Goff, who co-authored the study.  "Our archaeological work found that a huge social upheaval followed as communities moved inland beyond the reach of tsunamis.  It was over a thousand years before people returned to live at the coast again, which is an amazing length of time given that they relied on the sea for food.  It is likely that traditions handed down from generation to generation bolstered this resilient behavior, although we will never know for sure.  This is the oldest example we have found in the Southern Hemisphere where an earthquake and tsunami had such a catastrophic impact on people’s lives.  There is much to learn from this."

The obvious next question is, "Could this happen again?"  The answer is not just that it could, but it will.  Probably not in the same spot, but somewhere along the many tectonic boundaries in the world.  Nor do we know when.  Earthquake prediction is very far from an exact science.  We have instruments like strain gauges to estimate the tension rock is experiencing, but that doesn't tell you what's going on deeper in the ground, nor when the rock will fracture and release that energy as an earthquake.  Predicting volcanic eruptions is much easier; vulcanologists have gotten pretty good at detecting magma movement underground, and recognizing when a volcano is likely to blow.  (This is why the ongoing hoopla about the Yellowstone Supervolcano is all hype; sure, it'll probably erupt again, but some time in the next hundred thousand years or so, and it's showing no signs of an imminent eruption.)

The Earth is a dynamic planet, and the plates on the surface are in constant motion, jostling, coming together, moving apart, a bit like ice sheets on a river when they begin to break up in the spring.  You can't help but be fascinated by the amount of power it's capable of -- a catastrophic release of energy so large that the scales we've developed to measure such things are all but incapable of expressing.

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The lenses of language

When we think of the word "endangered," usually what comes to mind isn't "languages," but there are a staggering number of languages for which the last native speakers will be gone in the next few decades.  Of the seven-thousand-odd languages currently spoken in the world, ten of them -- a little over a tenth of a percent of the total -- are the main language of 4.9 billion people, about sixty percent of the Earth's population.

It's easy to see why biological diversity is critical to an ecosystem; species can evolve such narrow niches that if they become extinct, that niche vanishes, along with everything that depended on it.  It's a little harder to put a finger on why linguistic diversity is critical.  If some obscure language spoken in the Australian Outback disappears, who (other than linguists) should care?

I choose Australia deliberately.  Since the first major contact between indigenous Australians and Europeans, in 1788 when the "First Fleet" of convicts from England and Wales landed in what is now Sydney Harbor, over half of the 250 or so indigenous languages have vanished completely.  About 110 are still in use, primarily by the older generation, and only twenty are in common usage and still being learned by children as their first language.

Language is such an integral part of cultural identity that this is nothing short of tragic.  But the loss goes even deeper than that.  The language(s) we speak change the way we see the world.  Take, for example, the Guugu Yimithirr language, spoken in one small village in the far north of Queensland, which has 775 native speakers left.  This language has the odd characteristic -- shared, so far as I know, only with a handful of languages in Siberia -- of not having words for left, right, in front of, and behind.  The position of an object is always described in terms of the four cardinal directions.  Right now, for example, my laptop wouldn't be "in front of me;" it would be "southeast of me."

When the Guugu Yimithirr people first came into contact with English speakers, they at first were completely baffled by what left and right even meant.  When it finally sunk in what the English speakers were trying to explain, the Guugu Yimithirr thought it was hilarious.  "Everything in the world depends on the position of your body?" they said.  "And when you turn your body, the entire world changes shape?  What an arrogant people you must be."

Every language lost robs us of a unique lens through which to see the universe.

The reason this rather elegiac topic comes up is because of another place that is a hotspot for endangered languages -- South America.  Last week it was announced that Cristina Calderón, of Puerto Williams in southern Chile, died at the age of 93.  Calderón, known to locals as Abuela Cristina, was the last native speaker of Yaghan, an indigenous language in Tierra del Fuego.  Not only was Yaghan down to a single native speaker, the language itself is a linguistic isolate -- a language that shows no relationship to any other language known.

So this isn't like losing a single species; it's like losing an entire family of species.

The government of Chile, in a well-meant but too-little-too-late effort, is funding the development of an educational curriculum in Yaghan, as well as a complete (or complete as it can be) Yaghan-Spanish dictionary.  The problem is -- as anyone who has learned a second language can attest -- there's a world of difference between second-language acquisition and learning your native language.  As Calderón put it, "I'm the last speaker of Yaghan.  Others can understand it but don't speak it or know it like I do."

As far as Yaghan's fascinating characteristics, the one that jumps out at me is the presence of rich sound symbolism.  This isn't onomatopoeia (like the words bang and boom in English), but is when a phonemic feature tends to show up in words with similar meanings.  Sound symbolism of some sort seems to be pretty universal.  The most famous example is the "kiki-bouba effect," discovered in 1929 by linguist Wolfgang Köhler.  Köhler made two simple drawings:

He then asked people of various linguistic and cultural backgrounds one question: a newly-discovered language has names for these two shapes.  One of them is called kiki and the other is called bouba.  Which is which?

Across the board, people identified the left-hand one as kiki and the right-hand one as bouba.  Something about the /k/ and /i/ phonemes in kiki was associated with sharpness and angularity (and negative or harsh concepts), and the /b/ and /u/ phonemes in bouba with softness and roundness (and positive or pleasant concepts).  It shows up in English in words like screech and scream and creep, and bubble and bless and billow -- but it's an effect that has shown up in just about every language where it's been tested.

In Yaghan, the sound symbolism is much richer.  It's usually connected with the beginnings or ends of the words -- words ending in /m/ often connote something rounded or soft (think of lump and bump in English), while /x/ at the end often connects with something dry or brittle.  An initial /tʃ/ (pronounced like the first sound in the word chip) is frequently associated with objects with spines or thorns or sharp edges.  And so on.

How does this shape how a native Yaghan speaker sees, understands, and classifies the world?

I know that language extinction isn't really preventable, at least not in the larger sense; languages have been splitting and evolving and going extinct for as long as our ancestors have had the capacity for speech.  But I can't help but feel that the primacy a handful of languages have achieved over the thousands of other ways to communicate is robbing us of some of the depth of the human experience.  Especially when you consider that a significant component of that primacy has been the determination by colonizers to eradicate the culture of indigenous groups and replace it with their own.

So in the grand scheme of things, it may not mean all that much that the last native speaker of Yaghan is gone.  But I still feel sad about it.  It's only by looking at the world through a new lens that we find out how limited our own view is -- and how much that view can expand by observing our knowledge through a different one.

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In the long tradition of taking something that works and changing it so it doesn't work anymore, Amazon has seen fit to seriously complicate how content creators (i.e. people like me) incorporate affiliate links in their online content.  I'm trying to see if I can figure out how to get it to work, but until that happens, I am unfortunately going to suspend my Skeptophilia book-of-the-week feature.  If I can get it up and running again with the new system, I'll resume.  I'll keep you updated.

A new kind of thagomizer

When I was an undergraduate, I think one of the most startling things I learned was how few prehistoric animals we actually know about.

Like many kids, I grew up with books on dinosaurs and other prehistoric animals, and I was captivated by the panoramic artistic recreations of the Cretaceous landscape, with lumbering triceratops and T. rexes, and pterodactyloids gliding overhead (and always, for some reason, with a smoldering volcano in the background).  It was my evolutionary biology professor who blew all this away.

Fossilization, he said, is ridiculously rare.  It takes a significant series of very unlikely events to result in a fossil at all, much less one that could last 66-plus million years.  The deceased organism has to land in, or be covered by, sediments; it can't be eaten up or otherwise destroyed by animals.  The sediments it's encased in have to be undisturbed long enough to harden into rock, then that rock has to avoid erosion and the other geological processes that eventually degrade most of the rocks the Earth produces.

Then, that surviving fossil-bearing rock has to be found by scientists.

So we're basing our picture of prehistoric landscapes upon a random sampling of a very small number of species.  It is, my professor said, like someone tried to put together a picture of the modern landscape using only the remains of a mouse, a maple tree, a deer, a sparrow, a bullfrog, and a great white shark.

The situation may not be quite that bleak, but it's not far off.  For every one pre-Cretaceous-extinction organism we know about, there are likely to be ninety-nine we have no record of.  Which is why even after a couple of hundred years of serious fossil-chasing, we still have surprises awaiting.

Take, for example, the discovery of a fossil in Chile that was so weird that for a while, paleontologists had reconstructed it as an entirely different animal.  It was a tail that had sharp plates on either side -- clearly some kind of defensive weapon.  The plates put the researchers in mind of the stegosaurus:

[Image licensed under the Creative Commons DataBase Center for Life Science (DBCLS), 202009 Stegosaurus stenops, CC BY 4.0]

The spiky tail of the stegosaurus is called the thagomizer -- which came, I kid you not, from Gary Larson's iconic The Far Side, specifically the one with some cave men looking at a diagram of a stegosaurus.  One of them is pointing to the tail, and says, "And this is called the thagomizer, after the late Thag Simmons."  The name stuck, and the thagomizer it's been ever since.

Well, when the paleontologists looked at the new fossil, they realized that the thagomizer on this puppy was in a class by itself.  This thing could have chopped a T. rex off at the knees.  But further analysis of the rest of the skeleton showed that it wasn't a stegosaurus relative at all; it was a type of ankylosaur, a group of tank-like dinosaurs, most of which had tails ending in clubs (formidable enough weapons in and of themselves).

"It's a really unusual weapon," said Alex Vargas, of the University of Chile, who co-authored the paper on the find this week in Nature.  "Books on prehistoric animals for kids need to update and put this weird tail in there. ... It just looks crazy."

The new species was christened Stegouros elengassen.  Here's an artist's reconstruction:

[Illustration by Luis Perez Lopez]

The fossil has been dated to about seventy-five million years ago, so less than ten million years before the Chicxulub Meteorite collision ended the non-avian dinosaurs' hegemony.  And the weirdest thing about it is that it's nowhere near any of the ankylosaurs we know about; most of that group were from western North America, which at the time was separated from what is now South America by a large swath of ocean.  There's some speculation that this might be a species that had relatives in Antarctica, which was much closer, but that continent is so poorly explored no one can be certain.  In any case, it once again highlights how little we actually know about prehistoric flora and fauna.

It gets me thinking about what surprises we'd have in store if we were to go back in time to see what the Cretaceous landscape really looked like.  Not only would we be shocked at the colors and body coverings (hair, fur, feathers, etc.), which rarely ever fossilize, but there would be a stunning diversity of plants and animals that we had no idea about.  And not to end on an elegiac note, but consider what that says about our current biodiversity -- what's lost is truly lost forever, most of it lost so completely our distant descendants a million years hence (assuming there are any) would never have an inkling that it had ever existed.

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As I've mentioned before, I love a good mystery, which is why I'm drawn to periods of history where the records are skimpy and our certainty about what actually happened is tentative at best.  Of course, the most obvious example of this is our prehistory; prior to the spread of written language, something like five thousand years ago, most of what we have to go by is fossils and the remnants of human settlements.

Still, we can make some fascinating inferences about our distant ancestors.  In Lost Civilizations of the Stone Age, by Richard Rudgely, we find out about some of the more controversial ones -- that there are still traces in modern languages of the original language spoken by the earliest humans (Rudgely calls it "proto-Nostratic"), that the advent of farming and domestication of livestock actually had the effect of shortening our average healthy life span, and that the Stone Age civilizations were far more advanced than our image of "Cave Men" suggests, and had a sophisticated ability to make art, understand science, and treat illness.

None of this relies on any wild imaginings of the sort that are the specialty of Erich von Däniken, Zecharia Sitchin, and Giorgio Tsoukalos; and Rudgely is up front with what is speculative at this point, and what is still flat-out unknown.  His writing is based in archaeological hard evidence, and his conclusions about Paleolithic society are downright fascinating.

If you're curious about what it was like in our distant past, check out Lost Civilizations of the Stone Age!

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The rain of glass

A couple of weeks ago I looked at the rather unsettling fact that the seeming benevolence of our home planet is something of an illusion.  As I write this, I'm sitting in a warm house with the calm, clear sunshine sparkling on frost-covered grass, hardly a cloud in the sky, and it's difficult to imagine it ever being any different.  While I don't believe a thoroughly pessimistic outlook helps anything or anyone, it does bear keeping in mind how fragile it all is -- if for no other reason, so that we value what we have.

I started thinking about how quickly and unpredictably a place can go from tranquility to devastation when I ran across a paper that appeared in the journal Geology two weeks ago.  In it, I learned about something I'd never heard about -- a seventy-five-kilometer-wide patch of the Atacama Desert in northern Chile that is covered with shards of black and green glass.

The Atacama Desert is a strange place in and of itself.  Other than the dry valleys of Antarctica, it is far and away the most arid place on Earth; the average rainfall is around fifteen millimeters per year, and there are parts of it that are down in the nearly-unmeasurable range of one to three millimeters.  The few plants and animals that live there have dry-climate adaptations that beggar belief; they get most of the water they need using condensation from fog.  The reason for the peculiar climate is a combination of a more-or-less permanent temperature inversion produced by the South Pacific Anticyclone and the cold, northward-flowing Humboldt Current, combined with a two-sided rain shadow caused by the parallel Andes Mountains and Chilean Coast Range.  It's so dry and barren that it was used by NASA as one of the places to test the Mars Lander's ability to detect the presence of microscopic life.

The aridity is what allowed for the discovery that was the subject of the November 2 paper.  Geologists Peter Schultz (Brown University), R. Scott Harris (Fernbank Science Center), Sebastián Perroud (Universidad Santo Tomás), and Nicolas Blanco and Andrew Tomlinson (Servicio Nacional de Geología y Minería de Chile) analyzed the peculiar shards that cover the patch on the northern end of the desert, and found out that they were all formed in one event -- the mid-air explosion of a comet about twelve thousand years ago.

The authors write:

Twisted and folded silicate glasses (up to 50 cm across) concentrated in certain areas across the Atacama Desert near Pica (northern Chile) indicate nearly simultaneous (seconds to minutes) intense airbursts close to Earth’s surface near the end of the Pleistocene.  The evidence includes mineral decompositions that require ultrahigh temperatures, dynamic modes of emplacement for the glasses, and entrained meteoritic dust.  Thousands of identical meteoritic grains trapped in these glasses show compositions and assemblages that resemble those found exclusively in comets and CI group primitive chondrites.  Combined with the broad distribution of the glasses, the Pica glasses provide the first clear evidence for a cometary body (or bodies) exploding at a low altitude.  This occurred soon after the arrival of proto-Archaic hunter-gatherers and around the time of rapid climate change in the Southern Hemisphere.

The dry climate is why we even know about this event.  Cometary collisions almost never leave a crater; given that comets are mostly made of various kinds of ice, the heat of friction from the atmosphere causes them to evaporate and finally explode, creating an airburst but no solid-object impact.  The airburst can be devastating enough, of course.  The 1908 Tunguska Event, the largest such occurrence in recorded history, flattened eighty thousand trees in over two thousand square kilometers of Siberian forest, and registered on seismographs all the way around the world in Washington, D.C.  If Tunguska had happened over a major city, there wouldn't have been a person left alive or a building left standing in the blast zone.

Like Tunguska, at the time and place of the Atacama airburst, there weren't many people in the danger zone.  There was, however, a lot of sand, and the heat from the collision melted it into glass -- indicating temperatures in excess of 1,700 C.  In a climate with ordinary amounts of rainfall, the glass would have been degraded and eroded, but here, it rained out of the sky and then has just kind of sat there for the intervening twelve thousand years.

"It was clear the glass had been thrown around and rolled," study lead author Peter Schultz said, in an interview with Science News.  "It was basically kneaded like bread dough."

The glass shards (the dark bits) in the northern Atacama Desert [photograph by Peter Schultz]

It would have been quite a spectacular thing to witness (from a safe distance), and you have to wonder how the survivors explained it.  "It would have seemed like the entire horizon was on fire," Schultz said. "If you weren’t religious before, you would be after."

So that's our disquieting scientific research for the day.  The reassuring news is that we've gotten pretty skilled at mapping the asteroids, meteors, and comets out there in the Solar System, and none of them seem to be headed our way, at least not for a good long while.  Which is a bit of a relief.  As often as I complain about how dull it is to live in a part of the world where the biggest excitement of the day is when the farmer across the road lets his cows out into the field, this isn't the kind of change of pace I'm really looking for.

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

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

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

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

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