The lake of bones

In Guy Gavriel Kay's brilliant, atmospheric novel Under Heaven, the character of Shen Tai has undertaken a strange vocation.

Under Heaven is set in a world that is a thinly-disguised Tang Dynasty China, and Shen Tai has distanced himself from the backstabbing intrigue of court life to live in a small house beside a lake in the far west of the country.  The lake shore was the site of an ancient battle that left thousands dead.  All his life, Shen Tai has heard the voices of the slain warriors, so once he became an adult he made the decision to spend his days unearthing their skeletons and giving them proper burials, honoring their deaths with the appropriate rituals so their spirits can finally find rest.

I was immediately reminded of Shen Tai's long and arduous task when I stumbled upon an account of the strange (real) place called Roopkund, a glacial lake in Uttarakhand State, India.  It's high up in the Himalayas, at an altitude of a bit over five thousand meters:

[Image licensed under the Creative Commons Schwiki, Roopkund Lake, CC BY-SA 4.0]

Not, to my eye, the most scenic place in the world, but nevertheless Roopkund is a popular trekking destination for a very peculiar reason; like the lake near Shen Tai's little house, Roopkund's rocky soil contains hundreds -- possibly thousands -- of human skeletons.  Some are at the surface, but more erode out of the talus after every spring snow melt.  A few are visible beneath the water's surface, bringing to mind another creepy literary allusion -- Tolkien's Dead Marshes:

The legend is that the skeletons are the remains of people killed by a freak violent hailstorm in the ninth century C. E.  Some versions of the story are even more specific -- that the victims were a local king, Raja Jasdhaval, his wife Rani Balampa, and their retinue, who were on their way to visit the nearby Nanda Devi Shrine when they perished in a storm.  And indeed, many of the skeletons show unhealed injuries of the kind you'd expect from a blow to the top of the head by a rounded object like a large hailstone.

The story, though, gets even weirder.  Recent radiocarbon and DNA analysis of the remains found that they didn't all die in a single event.  Some of them died in around 800 C. E.; all of those showed typical South Asian genetic signatures.  But another group, that died in around 1800, had highly varied DNA signatures -- not only South Asian, but Vietnamese, Malay, and... Greek!

Nothing from local histories seems to account for how a large group of Greeks and Southeast Asians ended up high up in the Himalayas over two centuries ago.  But apparently, as odd as it seems, there were two separate hailstorms that wiped out not only a bunch of locals, but a large group of foreigners a thousand years later.

I'm not superstitious, but myself, I'm thinking visiting this lake might not be such a great idea.

Be that as it may, it's become a popular destination for aficionados of "dark tourism," the hobby of visiting places with grim or sinister histories.  In fact, the government of Uttarakhand is taking measures to protect the site as a national monument, spurred by how many tourists were going there -- and bringing pieces of the skeletons home with them.

Just a wee bit disrespectful, that.  I'm doubtful anyone is going to start hearing the disembodied voices of ghosts, like Shen Tai did, but fer cryin' in the sink, these are the remains of actual human beings who died painful and gruesome deaths.  Go take a look, if it floats your boat, but then -- just let them rest in peace, okay?  You really don't need a human skull collecting dust on your mantelpiece.

Maybe just read Kay's Under Heaven and learn a few lessons there.

Anyhow, that's our weird story for the day.  A lake full of bones up in the Himalayas, the full story of which is yet to be fleshed out.

So to speak.

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A fracture beneath Tibet

If there's one thing I've learned from my forty-plus years of dabbling in science, it's that the universe is a weird and complex place.

It's why I frequently heard the complaint from my students that "in every science class, the first thing the teacher tells us is that everything we learned in the previous science class is wrong."  This, of course, is inaccurate and not particularly fair; it's not that the earlier tier of information was untrue so much as it was incomplete.  After all, you need a basic grasp of the underlying principles before you can understand the twists, complications, and exceptions.

Take, for example, the paper that appeared last week in Science about a strange phenomenon involving the plate tectonics under the Himalayas.

The simple model of plate tectonics is that there are three types of boundaries between plates: (1) a divergent zone or rift, where two plates are moving apart; (2) a convergent zone or thrust fault, where two plates are coming together, and one plunges beneath the other; and (3) a strike-slip fault or transform boundary, where two plates move in opposite directions alongside each other.  This broad-brush depiction can have an additional layer of complication added right away, when you consider the relative directions of motion (two colliding plates aren't necessarily, or even usually, going to be moving at right angles to the boundary, for example), and whether the plates in question are thin, dense, brittle oceanic plates or thick, lightweight, rigid continental plates.

To narrow in on the location in question, the junction between the Indian Plate and the Eurasian Plate is a convergent zone between two chunks of continental crust.  When this happens, the conventional wisdom is that the two big blocks of rock are too cold and thick to subduct, so they basically just ram into each other and crumple, forming a mountain range.  (Besides the Himalayas, another place this is happening is the Alps.)

[Image is in the Public Domain courtesy of the United States Geological Survey]

But it turns out that this picture of what's happening under Tibet is neither complete nor all that accurate.

A study out of Utrecht University looked at the seismic waves produced by earthquakes in the region, and found that they were consistent with a bizarre scenario; as it crashed into Eurasia, beginning about sixty million years ago, India has delaminated.  The bottom slice of the Indian Plate has peeled apart from the top, and that lower, denser piece is subducting, while the rest has simply smashed against the larger mass of the Eurasian Plate, creating two focal points for earthquakes, one shallow and one deep.

The real tipoff came when the researchers analyzed the gas bubbles in hot springs in the region.  Helium comes in two isotopes -- a light isotope, helium-3, and a heavier one, helium-4.  Helium-3, being less dense, tends to offgas more quickly in surface rocks, soils, and water, so a high He-3/He-4 ratio indicates a source lower in the mantle.  And springs in the southern parts of the Himalayas are depleted in helium-3, whereas northern parts have a higher than expected amount of the lighter isotope -- indicating that the bubbles coming from southern parts of the fault zone have a shallower source, but when you cross into the northern parts, suddenly the bubbles are originating from much deeper mantle material that has flowed in over the split section of the fractured plate.

A cross-section of the Himalayas, from south (left) to north (right)

So once again, we have a situation way more complex than the model you were taught in high school.  But that's the way it goes, you know?  Every time we think we have things figured out, the universe turns around and astonishes us.

And those of us who love science wouldn't have it any other way.

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