Cat tales

Our relationship with our pets has a very long history.

We know more about our connection to dogs; we've been keeping dogs (or vice versa) for at least ten thousand years, based on genetic analysis of bones found in proximity to human settlements -- and often, buried with honor.  How this relationship started is a matter of conjecture:

Wolf: I'm going to attack you, and viciously tear apart and eat your children!  You are no match for my ferocity!

Cave man: We have peanut butter, sofas, and squeaky toys.

Wolf:  ... I'm listening

Domestic cats, on the other hand, have more uncertain origins.  They were known to have been revered in ancient Egypt, and in fact the much-loved protector goddess Bastet is always depicted with a cat's head.  The ancestors of today's house cats are thought to be the Libyan wildcat (Felis lybica), a small felid which is still found in most of Africa, the Middle East, and central and southern Asia.  They were probably encouraged to live alongside humans for their use as mousers, and eventually became companion animals, just as dogs had earlier.

What's certain is that after that relationship formed, wherever humans went, their pets came along.  A very cool series of studies a while back used patterns of cat genetics -- in particular, the prevalence of the polydactyly gene and the gene that controls swirled tabby coat coloration -- to figure out the paths of migration taken by their human owners.  And just this week a fascinating paper appeared in the journal Science looking at how domestic cats first arrived in China, much more recently than you might think.

The first written reference to cats in China comes from the Tang Dynasty, and dates to the middle of the seventh century C.E.  It's a rather horrifying story.  An imperial concubine name Xiao ran afoul of a higher-ranked wife named Wu Zetian (Wu eventually was to become empress outright).  Wu had Xiao condemned to death -- by having her hands and feet chopped off, then to be drowned in a barrel of wine -- and before the sentence was carried out, Xiao said, "In my next life, may I be reborn as a cat, and Wu Zetian as a mouse.  I will then seize her by the throat to extract my revenge!"

Wu wasn't impressed, and had her rival executed anyhow.  History doesn't record any subsequent rebirths as cats and/or mice.

The earliest domestic cat bones found in China are from an archaeological site called Tongwancheng, and date to only around 1000 C.E.  There were earlier feline specimens, but they all seem to be the remains not of modern domestic cats but of the leopard cat (Prionailurus bengalensis), a small south Asian wildcat species (that recently was crossbred with the domestic cat to produce the Bengal breed), and which probably lived alongside humans but was never truly domesticated.

Bengal cat [Image licensed under the Creative Commons User:Lightburst, Paintedcats Red Star standing, CC BY-SA 4.0]

As far as domestic cats, they seem to have arrived in China via the Silk Road.  Bones found in Kazakhstan, dating to the ninth century C.E., have a mitochondrial DNA signature that links both to later Chinese cats and to cats in the Middle East -- suggesting that merchant travel between the two is how cats arrived in east Asia.

Once there, they established a place in Chinese culture as the favorite pet of the wealthy.  Like the earlier study of cat genes and human migration, this one has an odd filigree having to do with how human selection influences evolution.  In Chinese culture, white is a symbol of purity, and white animals are especially revered.  This gave Silk Road merchants an incentive to find and transport white cats -- a practice over a thousand years ago which has left its mark all these centuries later.  This selectivity of importation is probably why today a disproportionate number of modern Chinese cats are white (or have white patches).

So we move, and we take our pets with us, and that changes both them and us.  It's a very old connection, and one many of us cherish deeply.  Think of that next time you cuddle with your kitty or puppy -- you're taking part in a relationship that goes back thousands of years, and was important enough even in those rough times that it drove commerce.  So even before the existence of mail-order places like Chewy, where we can spend inordinate amounts of money pampering our furry friends, our bonds with our pets were still a deeply important part of our lives.

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Hotspot

Today's topic in Skeptophilia isn't controversial so much as it is amazing.  And shows us once again what a weird, endlessly fascinating universe we live in.

First, though, a bit of a science lesson.

A great many processes in the natural world happen because of the Second Law of Thermodynamics.  The Second Law can be framed in a variety of ways, two of which are: (1) heat always tends to flow from a hotter object to a colder one; and (2) in a closed system, entropy -- disorder -- always increases.  (Why those are two ways of representing the same underlying physical law is subtle, and beyond the scope of this post.)

In any case, the Second Law is the driver behind weather.  Just about all weather happens because of heat energy redistribution -- the Sun warms the ground, which heats the air.  Hot air tends to rise, so it does, drawing in air from the sides and creating a low pressure center (and wind).  As the warm air rises, it cools (heat flowing away from the warmer blob of air), making water vapor condense -- which is why low pressure tends to mean precipitation.  Condensation releases heat energy, which also wants to flow toward where it's cooler, cooling the blob of air further (which is also cooling because it's rising and expanding).  When the air cools enough, it sinks, forming a high pressure center -- and on and on.  (Circular air movement of this type -- what are called convection cells -- can be local or global in reach.  Honestly, a hurricane is just a giant low-pressure convector.  A heat pump, in essence.  Just a fast and powerful one.)

Okay, so that's the general idea, and to any physicists who read this, I'm sorry for the oversimplifications (but if I've made any outright errors, let me know so I can fix them; there's enough nonsense out there based in misunderstandings of the Second Law that the last thing I want is to add to it).  Any time you have uneven heating, there's going to be a flow of heat energy from one place to the other, whether through convection, conduction, or radiation.

But if you think we get some violent effects from this process here on Earth, wait till you hear about KELT-9b.

KELT-9b is an exoplanet about 670 light years from Earth.  But it has some characteristics that would put it at the top of the list of "weirdest planets ever discovered."  Here are a few:

• It's three times the mass of Jupiter, the largest planet in our Solar System.
• It's moving at a fantastic speed, orbiting its star in only a day and a half.
• It's tidally locked -- the same side of the planet is always facing the star, meaning there's a permanently light side and a permanently dark side.
• It's the hottest exoplanet yet discovered -- the light side has a mean temperature of 4,300 C, which is hotter than some stars.

So the conditions on this planet are pretty extreme.  But as I found out in a paper by Megan Mansfield of the University of Chicago et al. in Astrophysical Journal Letters, even knowing all that didn't stop it from harboring a few more surprises.

Artist's conception of KELT-9b [Image is in the Public Domain courtesy of NASA/JPL]

Tidally-locked planets are likely to have some of the most extraordinary weather in the universe, again because of effects of the Second Law.  Here on Earth, with a planet that rotates once a day, the land surface has an opportunity to heat up and cool down regularly, giving the heat redistribution effects of the Second Law less to work with.  On KELT-9b, though, the same side of the planet gets cooked constantly, so not only is it really freakin' hot, there's way more of a temperature differential between the light side and the dark side than you'd ever get in our Solar System (even Mercury doesn't have that great a difference).

So there must be a phenomenal amount of convection taking place, with the atmosphere on the light side convecting toward the dark side like no hurricane we've ever seen.  But that's where Mansfield et al. realized something was amiss.  Because to account for the temperature distribution they were seeing on KELT-9b, there would have to be wind...

... moving at 150,000 miles per hour.

That seemed physically impossible, so there had to be some other process moving heat around besides simple convection.  The researchers found out what it is -- the heat energy on the light side is sufficient to tear apart hydrogen molecules.

At Earth temperatures, hydrogen exists as a diatomic molecule (H2).  But at KELT-9b's temperatures, the energy tears the molecules into monoatomic hydrogen, storing that as potential energy that is then rereleased when the atoms come back together on the dark side.  So once again we're talking the Second Law -- heat flowing toward the cooler object -- but the carrier of that heat energy isn't just warm air or warm water, but molecules that have been physically torn to shreds.

So, fascinating as it is, KELT-9b would not be the place for Captain Picard to take his away team.  But observed from a distance, it must be spectacular -- glowing blue-white from its own heat, whirling around its host star so fast its year is one and a half of our days, one side in perpetual darkness.  All of which goes to show how prescient William Shakespeare was when he wrote, "There are more things in heaven and Earth, Horatio, than are dreamt of in your philosophy."

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Lenses and rings

"Spacetime tells matter how to move; matter tells spacetime how to curve."

This rather mind-blowing statement by groundbreaking American physicist John Archibald Wheeler summarizes, in one sentence, Einstein's General Theory of Relativity.  The presence of matter warps the fabric of spacetime, and that curvature affects how objects are able to move through it.  In a sense, gravity isn't pulling on you right now; you're simply occupying a position in space where the mass of the Earth curves space so much that you're constrained to moving with it as it rotates on its axis.  The Earth itself traces an elliptical path around the Sun because the Sun's huge mass contorts the space around it; the Earth is following the shortest possible path through a spacetime that is itself curved.

If this is hard for you to picture, you're not alone.  It's easier if you reduce the dimensions by one, and picture a two-dimensional sheet deformed into a third spatial dimension by a heavy weight, like a bowling ball resting on a trampoline.  If you roll a marble toward it, it will follow the curvature of the surface -- not because the bowling ball is somehow attracting the marble, but because the sheet itself curves.

[Image licensed under the Creative Commons OpenStax University Physics, CNX UPhysics 13 07 spacecurve, CC BY 4.0]

So what this means is that gravity can affect even something that doesn't have mass -- like light.  Light takes the shortest possible path through the space it crosses, so the common-sense assumption is that this would be a straight line, consistent with the Euclidean geometry we all learned in high school.

The thing is, space isn't Euclidean.  Oh, it's close enough, on small scales and when you're not close to ginormously massive objects; the famed Greek mathematician did pretty well, given what information he had access to.  It's just that there are objects in the universe that are so massive that spacetime curves dramatically -- and light near them no longer travels in a straight line, but follows the curvature of the space it's passing through.  The effect is called gravitational lensing, because the light bends as if it were passing through a curved glass lens.

As you might expect, this distorts your view of whatever the light is coming from.  And the results can be nothing short of bizarre -- such as the image we just got to see this week from the Euclid Space Telescope of an "Einstein ring," where two massive astronomical objects are in perfect alignment with the Earth, so that the light from the farther one is bent as it passes around the nearer, creating a ghostly halo.

The ring is light coming from a single object which is directly behind the central bright galaxy; the mass of the galaxy has warped the space the light is passing through, stretching the background image into a circle [Image is in the Public Domain courtesy of NASA]

"An Einstein ring is an example of strong gravitational lensing," said Conor O'Riordan, of the Max Planck Institute for Astrophysics, who was lead author of the paper analyzing the ring, which was published in the journal Astronomy & Astrophysics.  "All strong lenses are special, because they're so rare, and they're incredibly useful scientifically.  This one is particularly special, because it's so close to Earth and the alignment makes it very beautiful."

"Close," of course, is a relative term.  The foreground galaxy, NGC 6505, is 590 million light years away; the background galaxy -- the one whose light has been distorted into a ring -- is 4.42 billion light years away.  But still, the fact that they've lined up so precisely that the lensing effect creates the image of a ring is pretty spectacular.

The coolest thing about this, though, is that it is a visible and tangible demonstration of a principle in physics that is kind of out there by anyone's estimation.  The results of the General Theory of Relativity -- phenomena like time dilation and Lorenz contraction -- are so bizarre that it's easy to say, "Oh, come on, that can't possibly be true."  (Never mind that even a relatively lightweight object like the Earth is massive enough that our GPS satellites have to adjust for relativistic effects -- or within a couple of days, our global positioning data would become so inaccurate as to be useless.)

But in this case, the effect is also strangely beautiful, isn't it?  It's hard to look at the photographs from Euclid and JWST and Hubble and not be overawed by how magnificent the universe is.  And the more we understand it -- like finding a glittering ring that falls right in line with Einstein's predictions -- the more astonishing it becomes.

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All that glitters

If you own anything made of gold, take a look at it now.

I'm looking at my wedding ring, made of three narrow interlocked gold bands.  It's a little scratched up after twenty-two years, but still shines.

Have you ever wondered where gold comes from?  Not just "a gold mine," but before that.  If you know a little bit of physics, it's kind of weird that the periodic table doesn't end at atomic number 26.  The reason is a subtle but fascinating one, and has to do with the binding energy curve.

The vertical axis is a measure of how tightly the atom's nucleus is held together.  More specifically, it's the amount of energy (in millions of electron-volts) that it would take to completely disassemble the nucleus into its component protons and neutrons.  From hydrogen (atomic number = 1) up to iron (atomic number = 26), there is a relatively steady increase in binding energy.  So in that part of the graph, fusion is an energy-releasing process (moves upward on the graph) and fission is an energy-consuming process (moves downward on the graph).  This, in fact, is what powers the Sun; going from hydrogen to helium is a jump of seven million electron-volts per proton or neutron, and that energy release is what produces the light and heat that keeps us all alive.

After iron, though -- specifically after an isotope of iron, Fe-56, with 26 protons and 30 neutrons -- there's a slow downward slope in the graph.  So after iron, the situation is reversed; fusion consumes energy, and fission releases it.  This is why the fission of uranium-235 generates energy, which is how a nuclear power plant works.

It does generate a question, though.  If fusion in stars is energetically favorable, increasing stability and releasing energy, up to but not past iron -- how do the heavier elements form in the first place?  Going from iron to anywhere would require a consumption of energy, meaning those will not be spontaneous reactions.  They need a (powerful) energy driver.  And yet, some higher-atomic-number elements are quite common -- zinc, iodine, and lead come to mind.

Well, it turns out that there are two ways this can happen, and they both require a humongous energy source.  Like, one that makes the core of the Sun look like a wet firecracker.  Those are supernova explosions, and neutron star collisions.  In fact, a while back, two astrophysicists -- Szabolcs Marka of Columbia University and Imre Bartos of the University of Florida -- found evidence that the heavy elements on the Earth were produced in a collision between two neutron stars, on the order of a hundred million years before the Solar System formed.

This is an event of staggering magnitude.  "If you look up at the sky and you see a neutron-star merger a thousand light-years away," Marka said, "it would outshine the entire night sky."

What apparently happens is when two neutron stars -- the ridiculously dense remnants of massive stellar cores -- run into each other, it is such a high-energy event that even thermodynamically unfavorable (energy-consuming) reactions can pick up enough energy from the surroundings to occur.  Then some of the debris blasted away from the collision gets incorporated into forming stars and planets.  And here we are, still with tons of lightweight elements, but a surprisingly high amount of heavier ones, too.

But how do they know it wasn't a nearby supernova?  Those are far more common in the universe than neutron star collisions.  Well, the theoretical yield of heavy elements is known for each, and the composition of the Solar System is far more consistent with a neutron star collision than with a supernova.  And as for the timing, a chunk of the heavy isotopes produced are naturally unstable, so decaying into lighter nuclei is favored (which is why heavy elements are often radioactive; the products of decay are higher on the binding energy curve than the original element was).  Since this happens at a set rate -- most often calculated as a half-life -- radioactive isotopes act like a nuclear stopwatch, analogous to the way radioisotope decay is used to calculate the ages of artifacts, fossils, and rocks.  Backtracking that stopwatch to t = 0 gives an origin of about 4.7 billion years ago, or a hundred million years before the Solar System coalesced.

So next time you look at anything made of heavier elements -- gold or silver or platinum, or (more prosaically) the zinc plating on a galvanized steel pipe -- ponder for a moment that it was formed in a catastrophically huge collision between two neutron stars, an event that released more energy in a few seconds than the Sun will produce over its entire lifetime.  Sometimes the most ordinary things have a truly extraordinary origin -- something that never fails to fascinate me.

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The forbidden words

George Orwell, in his classic book 1984, writes characters who speak a dialect of English called "Newspeak."

The "Minitrue" (Ministry of Truth) controls the public perception of what is true, perceptions that are enforced by the "Thinkpol" (Thought Police).  The Thinkpol are responsible for stopping "thoughtcrime," including "facecrime" -- forbidden thoughts as revealed in your facial expression.  Toward that end, they "rectify" historical accounts (to conform to the government's agenda regarding what happened), eliminating anything that is "malquoted" or "misprinted."  You're trained to the point of accepting the government's views based on "bellyfeel" -- how they affect you emotionally, not whether they're true.

Intercourse between a man and a woman -- preferably without any pleasure -- is "goodsex."  Anything else is a "sexcrime."  The preference of the government is that babies are conceived by "artsem" -- artificial insemination.

Someone who breaks any of these rules -- or worse, contradicts what Big Brother wants you to do or say -- is not only killed, every trace of them is erased.  They become an "Unperson."

[Image is in the Public Domain]

Orwell was strikingly prescient.  If you doubt that we're heading down that road, consider the story that appeared in Gizmodo yesterday, that employees at the National Science Foundation and Center for Disease Control have been given a long list by the Trump administration of words they are not allowed to use in official correspondence or publications without review and authorization.

Here's a sampler -- for the complete list, check the link:

• advocacy
• bias
• climate
• cultural heritage
• disability
• discrimination
• diversity
• ethnicity
• evidence-based
• female (no, I'm not making this up)
• gender
• inequality
• LGBTQ
• political
• racial
• science-based
• socioeconomic
• transgender
• women (no, I'm still not making this up)

When I first read this, my initial reaction was, "This can't possibly be true."  The NSF being forbidden from using the words "evidence-based?"  But after some digging about, all I can say is that it appears at the time of this writing to be true.

I'm not sure what to be appalled at most about this.  That we don't want a study identified as "biased," because then we might have to address whose political interests are being served by the bias.  That because of the Trump administration's ongoing war on minorities, we mustn't speak of diversity.  That LGBTQ individuals, whose rights to fair treatment are being threatened with each new executive order, are guilty of "sexcrime;" and we have to pretend transgender people don't even exist.

And "science-based" and "evidence-based?" What the fuck is the NSF supposed to base its policy on, then?  Magic?  The Bible?  Prophecy?

Or just what its "bellyfeel" is?

I've tried not to engage in hyperbole about what this administration is doing, but every new thing I read drives me further toward the conclusion that they have only two motives: consolidating power and seeking revenge against anyone who has stood in their way.  Toward that end, shutting down resistance, eliminating free speech and the free press, rewriting the truth to conform to whatever Trump's cadre says it should be.  Everything contradictory is "oldspeak" that should be "rectified."

The result should be "doubleplusgood," don't you think?  Or maybe we should just stick with "Great Again."

My hope is the fact of this having been made public will give NSF and CDC employees the courage to defy this order.  People have to fight back, tell the 2025 version of the Thinkpol "No way in hell."  We have to spread this story far and wide, because you know the first thing the Trump administration is going to do is claim that this is all "fake news."

"Malquoted" and "misprinted."  Just like the erasure of any reference to the riots and insurrection on January 6.  Just like Trump's insistence that the recent series of horrible airplane crashes had to do with "DEI" and not with the fact that two weeks before the first one, he'd dismissed the head of the FAA and laid off hundreds of air traffic controllers.  Just like the tragic wildfires in California having nothing to do with climate change, but with "failed water policy" by the state's Democratic governor -- and that Trump came in and saved the day by releasing billions of gallons of water from reservoirs that didn't even flow toward Los Angeles, the loss of which will jeopardize agricultural irrigation for months.

Doesn't matter what's actually true.  If it strokes Trump's bloated ego, and allows him to post smug, self-congratulatory, usually misspelled messages on social media, then it's de facto the New Truth.

Of course, forbidden words are not the only hurdle academia is facing in the United States; coupled with all of the funding cuts the NSF, CDC, and NIH are undergoing, it's looking like a war that might not be winnable, at least not in the short term.  If what the administration really wants is to destroy the United States as a leader in scientific and medical research worldwide, they're going about it the right way.  What Trump and Musk and their cronies have done in the last three weeks isn't "rooting out corruption and waste;" it's placing free inquiry into an ideological straitjacket that will set American academia back decades, if it doesn't ruin it completely.

And as far as Orwell goes -- looks like got the details right.  All he missed was the year it happened.

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Executive orders, task forces, and paranoia

In further evidence that we're living in the Upside Down, a man who once publicly said "I have no reason to ask God for forgiveness when I have never made any mistakes," and who says his favorite book of the Bible is "Two Corinthians," has once again somehow convinced evangelical Christians that he is the Lord's Anointed One, despite his most striking claim to fame being embodying all Seven Deadly Sins in one individual.

The latest stunt by Donald Trump is the creation of a "task force to eliminate anti-Christian bias" from the United States.  This plays right into the evangelicals' all-time favorite hobby, which is looking around for stuff to be outraged about.  To listen to their preachers and televangelists and whatnot, you'd swear being a Christian in the United States was to risk being dragged into the Superdome, Roman-Colosseum-style, and fed to the lions.  Unsurprisingly -- to people who have at least some glancing connection to reality -- the opposite is true.  Just shy of ninety percent of the members of Congress identify as Christian; amongst Republican members, the figure rises to 98%.  In some parts of the country you couldn't be elected as Village Roadkill Collector unless you're a Christian.

For Trump, of course, this move is not because he actually believes that Christians are being persecuted, or would particularly care if they were.  As far as I've seen, Trump's beliefs can be summed up as "I'm in support of whatever gets me praise, power, and money."  This is all about cozying up to evangelical power brokers like John Hagee and Mike Huckabee, and through them, to their rabid MAGA supporters.  As far as the "anti-Christian bias" they're trying to eliminate, it's mostly regarding issues like requiring the Bible be taught as factual in public school classrooms, the Ten Commandments being in every governmental office building, and eliminating evil stuff like admitting we queer people actually exist and deserve rights.

The thing is, the clownish attempts by Trump and people like Representative Nancy Mace of South Carolina (who recently accomplished the astonishing feat of edging out both Lauren Boebert and Marjorie Taylor Greene as the stupidest person in Congress) are only a smokescreen for a far darker and more insidious push toward turning the United States into a Christofascist theocracy.  Trump may not have the first clue about actual Christian theology, but you can bet that people like Pete Hegseth, Russell Vought, and J. D. Vance do.  Those three, and others like them, are deadly serious; given free rein, and they'd look very like the American version of the Taliban.

[Image is in the Public Domain]

Fortunately for those of us who like the idea of separation of church and state, Trump has one saving grace; he has the attention span of a disordered toddler.  As Representative Alexandria Ocasio-Cortez put it, "Yes, this administration is dangerous and cruel, but they are also shockingly dim and incompetent."  As further evidence of this, Trump has now (by executive order, of course) created a "White House Faith Office" with televangelist and certifiable lunatic Paula White-Cain in charge.  White-Cain, you might recall, has been something of a frequent flyer here at Skeptophilia, most recently because of a claim that she'd had a vision wherein "God came to me last night and showed me a vision of Trump riding alongside Jesus on a horse made of gold and jewels.  This means he will play a critical role in Armageddon as the United States stands alongside Israel in the battle against Islam," and that because of this the faithful should donate their entire January salary to her and she'll make sure to pass the cash along to Jesus just as soon as she gets around it it.

In choosing White-Cain, however, Trump hasn't pleased everyone.  Illustrating the general rule that for every evangelical there's an equal and opposite evangelical, some prominent Christian leaders have objected to White-Cain's prominence, one even going so far as to call her a "heretic and known false teacher who has no regard for the Gospel of Jesus Christ."  Scott Ross, a Texas-based "Christian leadership coach," said, "Paula White, head of Trump’s White House Faith Office, is no Christian leader.  She preaches the heresies of Word of Faith & Prosperity Gospel, both utterly opposed to authentic Christianity.  Worse, she has lived a life of scandal, with multiple husbands, twisting the Gospel for profit.  Arguably, this is the worst and most dangerous thing President Trump has done—putting a false teacher at the helm of faith outreach.  Lord, have mercy on our country and this administration."

Even so, it's doubtful this will be enough to change many people's minds.  All Trump and White-Cain will have to do is to start snarling about the evil anti-religious libs and us hellbound LGBTQ+ people running around clamoring for equal rights (if you can even imagine), and the MAGA types will pull right back together into a nice, orderly herd again.

It'll take more than this minor internal squabbling to rid the Religious Right of its paranoia.

In one way, of course, the Christians are right to be freaking out.  Church attendance has been dropping steadily for twenty-five years; in 2018, for the first time ever, the number of people who state that they attend church weekly dropped below the number who say they never attend.   Estimates are that Christian church attendance has been decreasing by around twelve percent yearly for the past fifteen years, and there's no sign of that changing -- regardless of any mandates via executive order.

Funny how when religious leaders embrace hate, intolerance, and bigotry, use their religion to impose their will on others, and champion a president who is a narcissistic, vengeful, spiteful serial adulterer and compulsive liar, a lot of people decide it's time to find better things to do with their Sunday mornings.

I'll add here something I've said many times; it's not that I have anything against Christianity per se.  I have a lot of Christian friends of various denominations, and by and large, we get along fine.  My staunchly-held opinion is that we all come to an understanding of the universe and our place within it, and the big questions like the existence of God (or gods), the role of spirituality, and the meaning of life, in our own way and time.

But if you start using your religion as a weapon, either to force your own particular subset of beliefs on others or to deny rights to people you don't happen to like, I (and many of my friends, of both the believing and nonbelieving varieties) are gonna object.  Strenuously.

And if that makes you feel "persecuted" -- well, that sounds like a "you problem" to me.

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The bellringer

Between December 16, 1811 and February 7, 1812, a series of four earthquakes -- each estimated to be above magnitude 7, with the first and last perhaps at magnitude 8 -- hit what you might think is one of the most unlikely places on Earth; southeastern Missouri.

The centers of continents are ordinarily thought to be tectonically stable, as they are generally far from any of the three typical sorts of faults -- divergences, or rifts, where plates are moving apart (e.g. the East African Rift Zone); convergences, or thrust faults, where plates are moving together (e.g. the Cascadia Subduction Zone); and strike-slip faults, where plates are moving in opposite directions parallel to the fault (e.g. the San Andreas Fault).  The Midwest is located in the middle of the North American Craton, an enormous block of what should, according to the conventional wisdom, be old, stable, geologically inactive rock. 

But the 1811-1812 earthquake series happened anyhow.  If they'd occurred today, it would likely have flattened the nearby city of Memphis, Tennessee.

So much for conventional wisdom.

The fault responsible was named the New Madrid Seismic Zone for the county right in the center of it, and its capacity for huge temblors is staggering.  The biggest (and final) earthquake of the four was powerful enough that it was felt thousands of kilometers away, and rang church bells in Charleston, South Carolina.  The shift in terrain changed the course of the Mississippi River, cutting off a meander and creating horseshoe-shaped Reelfoot Lake.

So what created a seismic zone where one shouldn't be?

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

The topic comes up because I just finished reading seismologist Susan Elizabeth Hough's excellent book Earthshaking Science: What We Know (and Don't Know) About Earthquakes, which is one of the best laypersons' introductions to plate tectonics and seismicity I've come across.  She devotes a good bit of space to the New Madrid earthquakes, and -- ultimately -- admits that the answer to this particular question is, "We're still not sure."  The problem is, the fault is deeply buried under layers of sediments; current estimates are that the hypocenter (the point directly underneath the epicenter where the fault rupture occurred) is between fifteen and thirty kilometers beneath the surface.  And since the quakes in question happened before seismometers were invented, we're going off inferences from written records, and such traces that were left on the surface (such as "sand blows," where compression forces subsurface sand upward through cracks in the stratum, and it explodes through the surface).

As far as the cause, Hough has a plausible explanation; the New Madrid Seismic Zone is an example of a failed rift, where a mantle plume (or hotspot) tried to crack the continent in half, but didn't succeed.  This stretched the plate and created a weak point -- called the Reelfoot Rift -- where any subsequent stresses were likely to trigger a rupture.  Since that time, the North American Plate has been continuously pushed by convection at the Mid Atlantic Rift, which is compressing the entire plate from east to west; those stresses cause buckling at vulnerable points, and may well have been the origin of the New Madrid earthquakes.

One puzzle, though, is what happened to the hotspot since then.  This is still a matter of speculation.  Some geologists think that friction with the rigid and (relatively) cold underside of the plate damped down the mantle plume and ultimately shut down convection.  Others think that as the North American Plate moved, it simply slid off the hotspot, making the plume appear to move eastward (when in actuality, the plate itself was moving westward).  This may be why another anomalous mid-plate earthquake zone is in coastal South Carolina, and it might also be the cause of the Bermuda Rise.

That point is still being debated.

Another open question is the current risk of the fault failing again.  There's paleoseismic data suggesting major earthquake sequences from the Reelfoot Rift/New Madrid Seismic Zone in around 900 and 1400 C.E., suggesting a timing between events of about four to five hundred years.  But these are estimates themselves, and I probably don't need to tell you that earthquake prediction is still far from precise.  Faults don't fail on a schedule -- which is why it annoys me every time I see someone say that an area is "overdue for an earthquake," as if they were on some kind of calendar.

Still, I can say with at least moderate confidence that it's unlikely to generate another big earthquake soon, which is kind of a relief.

So that's our geological curiosity of the day.  I have a curious family connection to the area; my wandering ancestor Sarah (Handsberry) Overby-Biles-Rulong (she married three times, had nine children, and outlived all three husbands) lived in the town of New Madrid in 1800, after traveling there from her home near Philadelphia as a single woman in the last decade of the eighteenth century.  I've never been able to discover what impelled her to leave her home and, with a group of relative strangers, cross what was then trackless wilderness to a remote outpost, and I've often wondered if she might have been either running away from something, or perhaps might have been a prostitute.  I'm not trying to malign her memory; it bears mention that a good eighty percent of my forebears were rogues, ne'er-do-wells, miscreants, and petty criminals, so it would hardly be a surprise to add prostitution to the mix.  And whatever else you can say about my family members, they were interesting.  I've often wished I could magically get a hold of Sarah's diary.

In any case, Sarah was in Lafayette, Louisiana by 1801, so she missed the New Madrid earthquakes by ten years.  But kind of interesting that she lived for a time in the little village that was about to be the epicenter of one of the biggest earthquakes ever to hit the continental United States, one that rang bells thousands of kilometers away, and which created a geological mystery the scientists are still trying to work out.

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