69. Thulium: Out Of The Way

We’ll go to the land of the ice and snow… and figure out exactly where that is, too.

Featured above: The inhabitants of Thule — one version of it, anyway.

Show Notes

Show notes are a little bare at the moment, I’m afraid. Turns out buying a house takes a lot of time and energy! But as promised, Thule Air Base’s modern strategic importance is on the rise. Why? The answer is climate change. As the Arctic ice sheets melt, new passages across the seas open up. What had previously been impassable ice is becoming open ocean, and that’s especially of interest to global superpowers. What does this mean? It’s hard to say, but it will probably be interesting.

While “interesting” is good for podcasts, I’m afraid it’s rarely good for social, political, and economic stability. I suppose we shall find out!

Episode Script

If you see the periodic table as an eclectic collection of eccentric characters, today’s element is one of its most modest members. It’s qualities of color, malleability, conductivity, magnetism, and so on all place it squarely in the middle of the road. Thulium’s most notable trait is that it’s the rare member of the rare earths that’s actually rare. One must stuff through 500 tons of dirt just to gather a few kilos of the stuff.

Even so, it’s not the rarest of the lanthanides. You might remember that promethium, element 61, is quite radioactive. Since it’s so unstable, only a few hundred grams are ever present on earth before they decay into (daughter product).

Even thulium’s location on the periodic table, swept off into the lower-right corner, suggests that this element just isn’t terribly important. The most you can say, really, is that thulium stays out of the way.

Viewed in this light, the element’s name is quite fitting. Upon discovering this atom in (year), Per Teodor Cleve named it after Thule, a mythical land so far beyond the edge of any map that no one had ever reached its shores.1

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we turn north toward thulium.

A note before we proceed: t-h-u-l-e is what’s written on the map, and it’s pronounced “t(h)oo-lee.” Despite that, the element is pronounced “thoo-lee-um.” There’s no great explanation for this except that, apparently, your average chemist is unlikely to be familiar with proper pronunciation of words derived from ancient Greek.

The Greek explorer Pytheas was the first to mention Thule, all the way back in the fourth century BCE. He claimed that it was six days north of Britain by sail, although even other writers in antiquity were skeptical of these claims. Around 30 CE, Strabo wrote that Pytheas “has been found, upon scrutiny, to be an arch falsifier.” Apparently, Pytheas also described Thule as a place where “there was no longer any proper land nor sea nor air, but a sort of mixture of all three of the consistency of a jelly-fish in which one can neither walk nor sail, holding everything together, so to speak. He says he himself saw this jellyfish-like substance but the rest he derives from hearsay.”2

Yet that didn’t stop people from trying to find this strange land Pytheas spoke of. Theories ranged from Shetland to Scotland to Greenland, and more. But for most cartographers, Thule’s value was not so much as a place to visit, but as an idea. It became a poetic way to refer to the mysterious, unknown lands north of here — wherever “here” happened to be.

Eventually, this idea was heightened to Ultima Thule. Loosely translated, that means “The farthest reaches of the frozen north,” and on ancient maps it was roughly synonymous with “Here Be Dragons.”

But by the twentieth century, Thule was no longer just a name for some place ever beyond the northern horizon. Greenland-born Knud Rasmussen was an anthropologist and explorer who, in 1910, established the northernmost trading post in the world. Part of Greenland’s northwest coast, over 1,200 kilometers above the Arctic Circle, it seems only natural that he named it Thule.

For several decades, it remained little more than a curiosity. But during World War II, even the farthest-flung corners of the Earth gained strategic importance. At the time, as now, Greenland was a territory belonging to Denmark, and the Danes were having a bit of a rough go of it. In case you’ve forgotten your junior high geography course, Denmark is a small country that exists on the Jutland (s peninsula — surrounded by water on three sides, and by Germany to the south. Perhaps sensing the obvious awkwardness of the situation, Denmark declared themselves neutral at the dawn of the war.

That didn’t amount to much in the eyes of der Fuhrer, and in the spring of 1940, Denmark fell under German occupation. Thousands of Danes died over the next five years while the monarchy acted as a puppet government under the direction of Nazi Germany.

Henrik Kauffmann, the Danish Ambassador to the United States, asked the US government for help on the exact same day that Germany assumed control over Denmark. Exactly one year later, Kauffmann signed The Agreement Relating To The Defense Of Greenland, which granted the US military permission to operate in Greenland as long as both sides agreed there was a threat to North America. (As another geography refresher, Greenland is technically part of North America, even though everyone kind of acts like it’s part of Europe.)3

This agreement was denounced by the protectorate government of Denmark, and Kauffmann earned a charge of high treason. Not much came of that, though. He laid low for a while, and when Denmark was liberated in 1945, one of the very first acts of Parliament was to exonerate Kauffmann. The agreement with the US was made formal a short time later, and Thule has been the site of the United States’ northernmost Air Force Base ever since.

Considering how remote Thule Air Base is, it’s considered to have high strategic value. It just so happens to lie halfway between Washington, D.C., and Moscow. It provides a useful place from which the US government can defend against incoming airplanes and missiles… or possibly launch such an attack of their own.

This gives it something in common with dozens of other locations around the globe, but Thule drew considerable attention to itself in 1968. A fire broke out onboard a B-52 bomber while on a routine flight over Greenland. A heating vent was inadvertently covered with seat cushions, which caught fire, filled the cabin with smoke, and resulted in a loss of power onboard the plane. Six of the seven crew members ejected safely, but the seventh did not have an ejector seat and died attempting to bail out. The plane came crashing down about 8 miles west of Thule Air Base… along with its payload: four B-28 hydrogen bombs. Each of these weapons had a yield of 1.1 megatons — about 65 times more powerful than the bombs detonated above HIroshima and Nagasaki.4

While the detonators of these weapons did explode, those consist of conventional explosives. Thankfully, the nuclear part of these weapons did not blow up, but radioactive fallout was spread for miles across the icy landscape. The worst possible outcome was averted, but this was nonetheless an awkward moment for the American government: The Danish government wasn’t aware that the Americans had been transporting nuclear weapons in and out of the air base. A good-faith cleanup effort helped keep the relationship intact, and the affair became one of about three dozen incidents classified by the US Air Force as a Broken Arrow: An accident involving nuclear weapons that does not carry a significant risk of widespread harm.

Not long after Knudsen founded his northern trading post that would one day stand against the Third Reich, there was a group of citizens within German borders that was similarly enamored with ancient European legends. Beginning in the 1910s, The Study Group for German Antiquity brought together Germans of all stripes — so long as they were anticommunist white men who hated Jews. This small group of disaffected Germans was a sort of proto-Nazi party, and it slowly gained influence over key members of German society and politics. One of the ways they did this was by purchasing a newspaper, the Munich Observer, and increasing its appeal by changing its name to the Munich Observer and Sports Paper.

The Thule Society also indulged in various mystical and occult practices, accounting for some of the more bizarre beliefs found among the Nazi party.

NASA learned this history lesson the hard way in 2018, when its New Horizons spacecraft was set to fly by an object designated 2014 MU69. Because it was the most distant object to ever be visited by spacecraft, it had earned the nickname Ultima Thule. An astronomer associated with New Horizons explained, “‘Beyond the limits of the known world’ — that’s such a beautiful metaphor for what we’re doing this year.”5

It is indeed a lovely sentiment, but any kind of association with the Nazi party tends to leave an unpleasant taste in people’s mouths. After enough people brought this to NASA’s attention, 2014 MU69 was given the official name Arrokoth, from the Powhatan word meaning “sky” or “cloud.”

For his part, Cleve didn’t intend to endow his newly discovered element with so much baggage: he wrote that Thule was merely an ancient name for Scandinavia. He was unaware of the full context, which is something of a disappointment. Apparently, he thought that he was simply christening one more element after one small region of the globe, placing it among the likes of scandium, hafnium, holmium, and of course yttrium, ytterbium, erbium, and terbium.

As mentioned earlier, thulium is considerably less abundant than all of those elements. In fact, it’s so rare that isolating a pure sample helped Theodore William Richards become the first American to win the Nobel Prize in Chemistry, “in recognition of his exact determinations of the atomic weights of a large number of the chemical elements.” In practice, that meant carrying out over 15,000 crystallizations of thulium bromate, truly embodying the spirit of Carl Gustaf Mosander.

Thulium doesn’t see no use. Literally, I mean, thulium sees a non-zero amount of use — but not by much. It’s sometimes used in portable x-ray devices, but unless you happen to have one of those handy, you’re most likely to find it within mineral samples, like monazite.

You probably could’ve guessed that large quantities of monazite can be found in Ytterby. But good news, element hunters: Monazite sand can also be found on the beaches of the southeastern United States, from North Carolina all the way down to Florida.6 That means, if you so choose, you can add thulium to your collection while lounging in the warm sun, and allow the frozen wastes to remain the domain of myths and legends.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn why Thule Air Base is becoming even more strategically important, visit episodic table dot com slash T m.

Next time, we’ll visit that Swedish mining village for the fourth and final time with ytterbium.

Until then, this is T. R. Appleton, reminding you not to place anything in front of heating vents.


  1. Elementymology And Elements Multidict, Thulium. Peter van der Krogt.
  2. The Histories Of Polybius, Fragments Of Book XXXIV.
  3. Airforce Technology, Thule Air Base: Inside The US’s Northernmost Military Base In Greenland. Talal Husseini, January 23, 2020.
  4. EarthSky, 50 Years Ago: Thule Incident. Timothy J. Jorgensen, January 21, 2018.
  5. Newsweek, NASA Named Its Next New Horizons Target Ultima Thule, A Mythical Land With A Nazi Connection. Meghan Bartels, March 14, 2018.
  6. Geology.com, Monazite. Hobart M. King.

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