Everything evaporates

In the episode of Star Trek: The Original Series called "Metamorphosis," the crew of the Enterprise encounters a man who has been kept alive and healthy for centuries by an entity he calls "the Companion."  I don't honestly remember it all that well -- it was kind of the usual Star Trek fare, as I recall -- but one line has stuck in my head all these years since I saw it: "Immortality consists largely of boredom."

I remember thinking as a kid what a bizarre statement that was.  Given the choice, who wouldn't want to live forever?  And, on the bigger scale, who wouldn't want the universe to exist for eternity?

When I was in high school, though, I started to run into some disquieting scientific ideas that made me realize what a pipe dream this was.  The Second Law of Thermodynamics -- that over time, all closed systems devolve toward chaos.  The fact that even the stars have births, lives... and deaths.  The three possibilities of the ultimate fate of the universe -- a collapse back into a singularity, a "flat universe" that slows its expansion but never quite gets to zero, and an accelerating universe that eventually speeds up until spacetime itself gets pulled apart.

None of which would be survivable by any life as we know it.

It all seemed so... bleak.  I remember rooting for the collapse ("Big Crunch") model, because some scientists thought this might result in an oscillating universe, one where death was followed by rebirth, a new Big Bang that would reset everything and start over.  It somehow seemed preferable to the clock simply winding down and eventually stopping.  But even that hope was dashed by the cosmologists; from the data we have, it appears either the universe is flat (the middle scenario) or hyperbolic (the third scenario).  

So it looks like the cosmos has a finite lifespan.  (If you've got a half-hour to have your mind blown, watch the wonderful YouTube video "The Timeline of the Universe" -- which takes us from now to the end, at least as far as current cosmology understands things.)

And a new piece of research has found that even the objects in that expanding, cooling universe aren't immortal.  Working at the Radboud University of Nijmegen, theoretical physicists have found that the phenomenon of Hawking radiation doesn't just apply to black holes -- it applies to everything.

In other words, everything eventually will evaporate.

[Image is in the Public Domain courtesy of NASA]

You probably know that empty space isn't really empty; it's filled with a seething foam of virtual particles that pop into existence in pairs (one matter particle and one antimatter particle) and, almost always, immediately mutually annihilate.  The overall result is nothing that generally impacts us on the macroscopic scale, since the lifetimes of these virtual pairs is measured in nanoseconds.  (It does contribute to the overall mass-energy density of empty space, however, something called the Casimir effect, which has been experimentally measured and agrees with the theoretical prediction perfectly -- so as bizarre as they sound, virtual particles are a real phenomenon.)

But there's more to it than this, and the key is the word "almost" in "almost always immediately mutually annihilate."  When the virtual pair is produced near the event horizon of a black hole, sometimes one of the particles gets trapped inside the event horizon, and the other escapes, radiating away into space.  This mass and energy is lost to the black hole, so it shrinks a bit -- and over large amounts of time, the black hole itself will evaporate away.

That's the Hawking radiation.  But what the current research showed is that this evaporation happens to everything -- not just black holes.

"[This research] means that objects without an event horizon, such as the remnants of dead stars and other large objects in the universe, also have this sort of radiation," said Heino Falcke, who co-authored the paper.  "And, after a very long period, that would lead to everything in the universe eventually evaporating, just like black holes.  This changes not only our understanding of Hawking radiation but also our view of the universe and its future."

So I guess the band Kansas might want to reconsider their lyric, "Nothing lasts forever but the Earth and sky."

The whole thing bothers me less now than it would have when I was younger.  It's not that I'm fond of the idea of death, mind you; I'm not ready to check out any time soon.  It's more that I've accepted its inevitability.  It's why the wonderful television series The Good Place was so incredibly poignant.  The main characters finally come to understand that maybe an eternity in the Good Place (heaven) isn't all it's cracked up to be, and that our appreciation of the beauty of the universe and what life has to offer comes from the fact that it is finite.  

But it should definitely focus our minds and hearts on appreciating what we have now.  I'll end with a quote from a different Star Trek episode, which (in my opinion) is the best one in the entire franchise: the Star Trek: The Next Generation episode "The Inner Light."

"Seize the time, Maribol.  Live now.  Make now always the most precious time.  Now will never come again."

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The Lazarus flower

The way things are, sometimes it's nice to find a bit of good news to focus on.  Today's good news comes to us by way of my dear writer friend Vivienne Tuffnell, whose books are brilliant and whose lovely blog Zen and the Art of Tightrope Walking should be on your "subscribe" list.

The article Vivienne posted was about an amazing accomplishment -- the "de-extinction" of a plant, the York groundsel (Senecio eboracensis).

[Photograph credit: Andrew Shaw/The Rare British Plants Nursery]

The plant has an interesting history.  It's an example of a curious phenomenon where a new species has resulted from hybridization -- in this case, between the exotic Sicilian ragwort (Senecio squalidus) and the native common groundsel (Senecio vulgaris).  Some time in the last three hundred years -- when Sicilian ragwort was unintentionally introduced to England -- the two cross-pollinated.  Such hybrids are usually infertile because of having sets of non-homologous (unpaired) chromosomes, but the hybrid then backcrossed to S. vulgaris, resulting in an allopolyploid, a plant that had a combination of chromosomes from two different parent species but was self-fertile.  It was also genetically distinct enough from both parent species that it couldn't backcross again, and thus was reproductively isolated -- i.e., a new species.

(Interestingly, another example of allopolyploidy is wheat, a hybrid of two grass species that have actually been identified in the wild.)

The problem was, the new species was only found in the city of York, and an extensive cleanup campaign in 1991 involved the overzealous application of weedkiller.  The only colonies of York groundsel known were destroyed.  Researchers had three small pots of the plant on a windowsill in the University of York, but the plant is an annual or short-lived perennial, and they didn't last long.  Fortunately, before dying, they produced a pinch of tiny seeds -- which were sent to the Millennium Seed Bank at the fabulous Kew Gardens.

Andrew Shaw, of The Rare British Plants Nursery, wanted to see if the York groundsel could be brought back.  There was a small amount of seeds in private ownership, but those germinated poorly.  So he approached Kew to see if the remaining seeds might be used to try to save the species from extinction.

It worked.  Of the hundred seeds planted by Shaw, all but two of them germinated.  Over the next two years, Shaw oversaw the production of over a thousand seedlings, which were planted out in specially-chosen plots of land in the city.  The reintroduced plants are now flowering in the wild for the first time in over thirty years.

"It’s a smiley, happy-looking yellow daisy and it’s a species that we’ve got international responsibility for," said Alex Prendergast, senior vascular plant specialist at Natural England, who worked on the project.  "It only lives in York, and it only ever lived in York.  It’s a good tool to talk to people about the importance of urban biodiversity and I hope it will capture people’s imagination.  It’s also got an important value as a pollinator and nectar plant in the area because it flowers almost every month of the year."

So there's your cheerful news of the day.  While humans do their fair share of damage, it's nice to know that sometimes, people who care will actually work toward fixing something.  In this case, bringing back a rare plant from the brink of extinction -- and introducing a bit of color into the landscape of a city.

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Splitting the Moon

Gervase of Canterbury was a twelfth-century English monk who lived from about 1141 to 1210.  He is best known as a historical chronicler, and wrote accounts of both the secular and ecclesiastical history of Britain, as well as producing quantities of maps showing the landholdings and bishoprics at the time.  Both of these have been of considerable value to scholars, and his writings are lucid, fact-based, and clear-eyed.

Which makes the other event he wrote about even more curious.

In June of the year 1178, Gervase says, some of the monks of the abbey were out on the lawn at twilight, enjoying a bit of leisure time in the pleasant warmth of early evening.  That was when they saw something astonishing:

[On the evening of June 18, 1178] after sunset when the Moon had first become visible, a marvelous phenomenon was witnessed by some five or more men...  Now there was a bright new Moon... its horns were tilted toward the east; and suddenly the upper horn split in two.  From the midpoint of the division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals, and sparks.  Meanwhile the body of the Moon which was below writhed, as it were, in anxiety and to put it in the words of those who reported it to me and saw it with their own eyes, the Moon throbbed like a wounded snake.  Afterwards it resumed its proper state.  This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal.  Then after these transformations the Moon from horn to horn, that is along its whole length, took on a blackish appearance.  The present writer was given this report by men who saw it with their own eyes, and are prepared to stake their honor on an oath that they have made no addition or falsification in the above narrative.

I first heard about this peculiar account almost exactly eight hundred years after it happened, on the episode of Carl Sagan's Cosmos called "Heaven and Hell."  Sagan's take on the story is that what Gervase wrote is substantially true; that despite the superstition of the time, he transcribed an unembellished record of what the other monks had seen.  Further, Sagan said, the survey work done on the Moon since that time found what may account for the odd event -- a 22-kilometer-wide recent crater just barely over the edge of the near-Earth side on the northeastern quadrant, named Giordano Bruno after the martyred sixteenth century astronomer.  What the monks witnessed was the meteorite impact that produced the crater, first creating a plume of molten rock and then scattering dark ash across the Moon's surface.  Interestingly, Giordano Bruno has rays of debris surrounding it, suggesting its recent origins:

[Image is in the Public Domain courtesy of NASA/JPL]

Further evidence supporting this conjecture is that laser rangefinding data shows that the Moon is oscillating slightly -- in Sagan's words, "ringing like a bell" -- at a frequency consistent with a meteor impact eight hundred years earlier.

Not everyone agrees with this interpretation, however.  Paul Withers, of the University of Arizona's Lunar and Planetary Laboratory, points out that such an impact would have accelerated much of the debris to escape velocity, and a significant quantity of it would have been pulled in by the Earth's more powerful gravitational field, triggering "blizzard-like meteor storms" with as many as fifty thousand meteors per hour for several days, perhaps up to a week.  No one recorded any such event.  Surely the meticulous Chinese and Korean astronomers of the time would have seen and written about such an unprecedented phenomenon.  In fact, nobody else on Earth we know of who was keeping records at the time even recorded witnessing the initial impact -- if impact it was.

Withers suggests a much more local, and prosaic, solution; what the monks of Canterbury saw was a bolide, a meteor that explodes in midair.  The most famous bolide is the Chelyabinsk meteor of February 2013, when an estimated eighteen meter long, nine thousand metric tonne chunk of rock exploded over the Russian town of Chelyabinsk, creating a tremendous fireball and shattering windows throughout the region.  The Canterbury event, Withers said, was a bolide over southeastern England that just happened to create its fireworks in front of the crescent Moon, which would explain why it wasn't seen elsewhere.

I'm not entirely happy with this explanation, either.  As Chelyabinsk illustrates, bolides are loud.  There is nothing in Gervase's account indicating that the Canterbury event made any sound at all.  Plus -- if you'll look at videos of the Chelyabinsk meteor (you can see a short clip at the page linked above) -- they move fast, leaving behind a bright streak.  Surely the monks of Canterbury had seen "shooting stars" many times before, and would have reported this not as a phenomenon on the Moon, but simply a humongous shooting star that exploded.

And finally, if it was a bolide, how could this account for the monks' statement that the paroxysms on the Moon were "repeated a dozen times or more"?

I'm still leaning toward the lunar impact explanation, myself, but I'm aware that it leaves plenty of unanswered questions.  It's a curious account, however you look at it.  We may never know for certain what happened, but even so, we're lucky that someone as clear-headed as Gervase of Canterbury was around during those dark and superstitious times to record an event that surely must have scared the absolute hell out of everyone who witnessed it.

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The mysteries of the deep

I've heard it said that we know more about the surface of the Moon than we do about the deep oceans on the Earth.

I've never seriously attempted to find out how accurate this is (and honestly, don't know how you'd compare the two), but I suspect it's substantially correct.  About seventy percent of the Earth's surface is covered by water, and given the difficulty of seeing what's down there -- even by remote telemetry -- it's no wonder we're still finding things in the ocean we never knew existed.

Take, for example, the study that appeared in Current Biology last week about the Clarion-Clipperton Zone.  The CCZ is the region between the Clarion Fracture Zone and the Clipperton Fracture Zone in the central Pacific, with an area of about six million square kilometers.  It contains several (apparently dormant or extinct) volcanoes, a number of submarine troughs of uncertain seismic activity, and a rough, mountainous topography.

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

The prevailing wisdom has been that most of the open ocean has relatively low biodiversity.  To put it more simply, that there just ain't much out there.  If you're in the middle of the ocean, any given cubic meter of water is unlikely to have many living things in it beyond single-celled plankton.  And -- supposedly -- the floor of the deep ocean, with crushing pressures, no light, and constant temperatures just above the freezing point of water, is often pictured as being pretty much devoid of life except for the bizarre hydrothermal vent communities.

That concept of the deep oceans needs some serious re-evaluation.  Last week's paper featured a survey of the abyssal life in the Clarion-Clipperton Zone, and found nearly six thousand species of animals...

...of which 92% were unknown to science.

The coolness factor of this research is tempered a little by the reason it was conducted.  The CCZ is being studied because of its potential for deep-sea mining.  The seafloor there has a rich concentration of manganese nodules, concretions of metal oxides and hydroxides (predominantly manganese and iron, with lower concentrations of other heavy metals), which are of immense value to industry.  Add to that the fact that the CCZ is in international waters -- so, basically, there for whoever gets there first -- and you have a situation that is ripe for exploitation.

What makes this even more complex is that the metals in the nodules are used, amongst other things, for high-efficiency electronics, including renewable energy systems.  The cost, though, might be the destruction of an ecosystem that we've only begun to study.

"There are some just remarkable species down there," said Muriel Rabone, of the Natural History Museum of London, who co-authored the study.  "Some of the sponges look like classic bath sponges, and some look like vases.  They’re just beautiful.  One of my favorites is the glass sponges. They have these little spines, and under the microscope, they look like tiny chandeliers or little sculptures.  There are so many wonderful species in the CCZ, and with the possibility of mining looming, it’s doubly important that we know more about these really understudied habitats."

So much of what humans have done seems to be blundering around blindly and only afterward seeing what the consequences are.  Perhaps we should investigate the ocean's mysteries before we attempt to use it for profit.

It seems fitting to end with a quote from H. P. Lovecraft, whose fascination with the ocean returns time and time again in his fiction: "But more wonderful than the lore of old men and the lore of books is the secret lore of ocean.  Blue, green, grey, white, or black; smooth, ruffled, or mountainous; that ocean is not silent.  All my days have I watched it and listened to it, and I know it well.  At first it told to me only the plain little tales of calm beaches and near ports, but with the years it grew more friendly and spoke of other things; of things more strange and more distant in space and in time.  Sometimes at twilight the grey vapours of the horizon have parted to grant me glimpses of the ways beyond; and sometimes at night the deep waters of the sea have grown clear and phosphorescent, to grant me glimpses of the ways beneath.  And these glimpses have been as often of the ways that were and the ways that might be, as of the ways that are; for ocean is more ancient than the mountains, and freighted with the memories and the dreams of Time."

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A linguistic resurrection

Earlier this month, I wrote a piece here at Skeptophilia on the reconstruction of an extinct language -- Timucuan, an indigenous language from northern Florida.  As I pointed out in the earlier piece, these sorts of efforts aren't just entertaining linguistic puzzles.  Each language encodes in its structure information about the culture, beliefs, and worldview of the people who spoke it, information which all too often is lost forever because of the effects of war, colonialism, and the simple but unfortunate effects of time on the written records.

As a linguist, I find this terribly sad.  When a language goes extinct, it's as if an entire culture's collective memory is wiped clean.  But astonishingly, sometimes artifacts will surface that allow us to reassemble an ancient language, bringing that long-extinguished knowledge back from the grave.

My eagle-eyed writer friend Gil Miller, always on the lookout for topics for Skeptophilia, sent me an article about such a miraculous resurrection this week.  It has to do with the Amorite language, spoken by a people who lived in southern Mesopotamia on the order of four thousand years ago.  While there's no doubt the people themselves were real enough -- they're mentioned in a number of records from the time, including the Bible -- the language is so poorly attested that some linguists questioned whether it even existed as a distinct language, suggesting that the Amorite people might have spoken a dialect of Akkadian.

The discovery of a remarkable artifact in Iraq has put that to rest.  It's a pair of clay tablets covered in cuneiform writing, describing everyday customs and religious practices in Akkadian, which is well understood by linguists -- with parallel text in Amorite.

One of he Akkadian/Amorite tablets [Image credit: David I. Owen]

The comparison to the Rosetta Stone is obvious.  With the Rosetta Stone, however, the reason for having the inscription in three scripts (Greek, Egyptian hieroglyphic, and Demotic) was clear.  It was an official decree from King Ptolemy V Epiphanes, so as an official document, it was important that it be readable to anyone in the region who was literate, regardless what script they knew.  Here, though, the text is about such mundane matters that it's an open question why anyone wanted it written in two different languages.  "The two tablets increase our knowledge of Amorite substantially, since they contain not only new words but also complete sentences, and so exhibit much new vocabulary and grammar," said Yoram Cohen, of Tel Aviv University, who co-authored the study.  "The writing on the tablets may have been done by an Akkadian-speaking Babylonian scribe or scribal apprentice, as an impromptu exercise born of intellectual curiosity...  Or it may be a sort of 'tourist guidebook' for Akkadian speakers who needed to learn Amorite."

Whatever its purpose, the tablets confirm that Amorite was a distinct language from the Western Semitic branch of the linguistic family tree (a branch it shares with Aramaic and modern Hebrew).  More than just increasing our knowledge of a single long-dead language, however, it provides an impetus to keep looking for traces of ancient cultures.  This amazing linguistic resurrection shows that lost doesn't necessarily mean forever -- and that with luck, perseverance, skill, and knowledge, we might still be able to gain a lens into what we thought was a long-gone culture.

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Analysis of a partnership

You probably recall from biology class the word symbiosis -- when two organisms share living space.  This sort of relationship can result in a fused life form where even so, the two participants retain a discernible separateness.  (Remember the Trill from Star Trek?)  The melding can go deeper, though; lichens, commonly seen growing on rocks and tree trunks in damp areas, are an example of such a composite, in this case between one or more types of fungus and photosynthetic cyanobacteria.  Deeper still are mitochondria -- the organelles in all eukaryotic cells that conduct cellular respiration and provide the majority of the energy required by the organism -- which are the descendants of single-celled aerobic bacteria that billions of years ago formed a partnership with their host cells so mutually beneficial that now, neither can live without the other.

Symbiosis is usually broken down into three broad classes.  The distinction is how the participating organisms fare.  That one of them benefits in some way is a given; if both were harmed, the relationship would be strongly selected against and probably wouldn't persist very long.  It's what happens to the other that determines what kind of symbiosis it is:

• parasitism -- one organism benefits, the other is harmed (an example is disease-causing bacteria)
• commensalism  -- one organism benefits, the other breaks even (such as the bacteria passively riding on our skin)
• mutualism -- both organisms benefit (such as a good many of the bacteria in our gut, which have increasingly been found to be absolutely essential for health)

The trouble is, nothing in biology is clear-cut.  Our commensal skin bacteria occupy niches that, if they were eradicated, might be taken over by pathogenic species.  (Thus the adjuration by doctors not to overuse topical antibiotics and hand sanitizers.)  So are they actually mutualistic?  Then there are the species that help in some ways and harm in others -- or, perhaps, help one species and harm another.

This, in fact, is why the whole topic comes up today.  Scientists in New Zealand have been working to preserve endangered species on the islands.  There are quite a few, owing to the country's geological (and thus biological) isolation -- it's developed a singular group of endemic species that are uniquely vulnerable to loss of habitat from agriculture and from the introduction of exotic species like cats, pigs, and the ubiquitous sheep.  One such species is the rare Cooper's black orchid (Gastrodia cooperae), which is nearly invisible for most of the year -- the only above-ground part is a long, creeping stem -- and puts on a flower stalk once during the growing season.

[Image licensed under the Creative Commons Kathy Warburton/INaturalist (CC BY 4.0)]

Orchids are notorious for being difficult to grow from seed.  The seeds are minute, and most orchid species are extreme specialists, able to survive only in a very narrow range of conditions.  The result is that conservation efforts are fraught with difficulty.  Trying to germinate the seeds in the lab requires knowing exactly what that particular species needs, which can mean a lot of trial-and-error, and the potential loss of batches of seeds when the efforts fail.

The Cooper's black orchid is no exception.  It's so rare it was only identified in 2016, and is known to live in only three sites in New Zealand.  Fortunately for this species, there is a related orchid species, Gastrodia sesamoides, that is quite common and appears to need many of the same conditions that the Cooper's black does, so scientists have been trying to identify what those conditions are so they can be replicated in the lab.

And it turns out that one of the conditions is the presence of a symbiotic fungus -- Resinicium bicolor.  The fungus infiltrates the roots of the orchid, creating a greater surface area for nutrient and water uptake, much like the mycorrhizae familiar to organic gardeners that can increase crop yields without the addition of inorganic fertilizers.

Where it gets interesting is that Resinicium bicolor was already known to botanists -- as a plant pathogen.  It's a deadly parasite on Douglas firs, an introduced tree in New Zealand that is much used for lumber, causing "white-rot disease."

So is Resinicium a mutualist or a parasite?  The question is, "with respect to what?"  It's lethal to Douglas firs, but essential to the Cooper's black orchid (and, presumably, other native orchid species).

Biology, as I mentioned before, isn't simple.

That, of course, is why it's so endlessly fascinating.  The more we look into the complexity of the natural world, the more it brings home the truth of the quote from Albert Einstein: "Life is a great tapestry.  The individual is only an insignificant thread in an immense and miraculous pattern."

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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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