15 DANGEROUS BEAUTY

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    IN THE 1960s, while studying the volic history of Yellowstoional Park, BobChristiansen of the Uates Geological Survey became puzzled about something that,oddly, had not troubled anyone before: he couldn’t find the park’s volo. It had been knownfor a long time that Yellowstone was voli nature—that’s what ated for all itsgeysers and other steamy features—and the ohing about voloes is that they aregenerally pretty spicuous. But Christiansen couldn’t find the Yellowstone voloanywhere. In particular what he couldn’t find was a structure known as a caldera.

    Most of us, whehink of voloes, think of the classie shapes of a Fuji orKilimanjaro, which are created wheing magma accumulates in a symmetrical mound.

    These  form remarkably quickly. In 1943, at Parí in Mexico, a farmer was startled tosee smoke rising from a pat his land. In one week he was the bemused owner of a efive hundred feet high. Within two years it had topped out at almost fourteen hundred feet andwas more than half a mile across. Altogether there are some ten thousand of these intrusivelyvisible voloes oh, all but a few hundred of them extinct. But there is a sed, lesscelebrated type of volo that doesn’t involve mountain building. These are voloes soexplosive that they burst open in a single mighty rupture, leaving behind a vast subsided pit,the caldera (from a Latin word for cauldron). Yellowstone obviously was of this sed type,but Christiansen couldn’t find the caldera anywhere.

    By ce just at this time NASA decided to test some new high-altitude cameras bytaking photographs of Yellowstone, copies of whie thoughtful official passed on to thepark authorities on the assumption that they might make a nice blow-up for one of thevisitors’ ters. As soon as Christiansen saw the photos he realized why he had failed to spotthe caldera: virtually the whole park—2.2 million acres—was caldera. The explosion had lefta crater more than forty miles auch too huge to be perceived from anywhere atground level. At some time in the past Yellowstone must have blown up with a violence farbeyond the scale of anything known to humans.

    Yellowsto turns out, is a supervolo. It sits on top of an enormous hot spot, areservoir of molten rock that rises from at least 125 miles down in the Earth. The heat fromthe hot spot is owers all of Yellowstone’s vents, geysers, hot springs, and popping mudpots. Beh the surface is a magma chamber that is about forty-five miles acrhlythe same dimensions as the park—and about eight miles thick at its thickest point. Imagine apile of TNT about the size of Rhode Island and reag eight miles into the sky, to about theheight of the highest cirrus clouds, and you have some idea of what visitors to Yellowstoneare shuffling around on top of. The pressure that such a pool of magma exerts on the crustabove has lifted Yellowstone and about three hundred miles of surroundiory about1,700 feet higher than they would otherwise be. If it blew, the cataclysm is pretty well beyondimagining. Acc to Professor Bill McGuire of Uy College London, “youwouldn’t be able to get within a thousand kilometers of it” while it was erupting. Thesequehat followed would be even worse.

    Superplumes of the type on which Yellowstos are rather like martini glasses—thin onthe , but spreading out as they he surface to create vast bowls of unstable magma.

    Some of these bowls  be up to 1,200 miles across. Acc to theories, they don’talways erupt explosively but sometimes burst forth in a vast, tinuous outp—aflood—of molten rock, such as with the De Traps in India sixty-five million years ago.

    (Trap in this text es from a Swedish word for a type of lava; De is simply anarea.) These covered an area of 200,000 square miles and probably tributed to the demiseof the dinosaurs—they certainly didn’t help—with their noxious outgassings. Superplumesmay also be responsible for the rifts that cause tis to break up.

    Such plumes are not all that rare. There are about thirty active ones on the Earth at themoment, and they are responsible for many of the world’s best-known islands and islands—Id, Hawaii, the Azores, aries, and Galápagos archipelagos, little Pit inthe middle of the South Pacifid many others—but apart from Yellowstohey are alloio one has the fai idea how or why Yellowstone’s ended up beh atial plate. Only two things are certain: that the crust at Yellowstone is thin and that theworld beh it is hot. But whether the crust is thin because of the hot spot or whether the hotspot is there because the crust is thin is a matter of heated (as it were) debate. The tialnature of the crust makes a huge differeo its eruptions. Where the other supervoloestend to bubble away steadily and in a paratively benign fashion, Yellowstone blowsexplosively. It doesn’t happen often, but when it does you want to stand well back.

    Sis first knowion 16.5 million years ago, it has blown up about a huimes, but the most ret three eruptions are the ohat get written about. The last eruptionwas a thousand times greater than that of Mount St. Helens; the one before that was 280 timesbigger, and the one before was so big that nobody knows exactly how big it was. It was atleast twenty-five huimes greater than St. Helens, but perhaps eight thousand timesmore monstrous.

    We have absolutely nothing to pare it to. The biggest blast i times was that ofKrakatau in Indonesia in August 1883, which made a bang that reverberated around the worldfor nine days, and made water slosh as far away as the English el. But if you imagihe volume of ejected material from Krakatau as being about the size of a golf ball, then thebiggest of the Yellowstone blasts would be the size of a sphere you could just about hidebehind. On this scale, Mount St. Helens’s would be no more than a pea.

    The Yellowstoion of two million years ago put out enough ash to bury New YorkState to a depth of sixty-seve or California to a depth of twenty. This was the ash thatmade Mike Voorhies’s fossil beds iern Nebraska. That blast occurred in what is nowIdaho, but over millions of years, at a rate of about one inch a year, the Earth’s crust hastraveled over it, so that today it is directly under northwest Wyoming. (The hot spot itselfstays in one place, like ayleorch aimed at a ceiling.) In its wake it leaves the sort ofrich volic plains that are ideal frowing potatoes, as Idaho’s farmers long agodiscovered. In awo million years, geologists like to joke, Yellowstone will beprodug French fries for Mald’s, and the people of Billings, Montana, will be steppingaround geysers.

    The ash fall from the last Yellowstoion covered all or parts of eeernstates (plus parts of ada and Mexiearly the whole of the Uates west of theMississippi. This, bear in mind, is the breadbasket of America, ahat produces roughlyhalf the world’s cereals. And ash, it is worth remembering, is not like a big snowfall that willmelt in the spring. If you wao grow crops again, you would have to find some place toput all the ash. It took thousands of workers eight months to clear 1.8 billion tons of debrisfrom the sixteen acres of the World Trade ter site in New York. Imagine what it wouldtake to clear Kansas.

    And that’s not even to sider the climatisequehe last supervolo eruptioh was at Toba, in northern Sumatra, seventy-four thousand years ago. No one knowsquite how big it was other than that it was a whreenland ice cores show that the Tobablast was followed by at least six years of “voliter” and goodness knows horowing seasons after that. The event, it is thought, may have carried humans right to thebrink of extin, redug the global population to no more than a few thousandindividu<q>.９9lｉb.</q>als. That means that all modern humans arose from a very small population base,which would explain our lack of geic diversity. At all events, there is some evideosuggest that for the wenty thousand years the total number of people oh was nevermore than a few thousand at any time. That is, needless to say, a long time to recover from asingle volic blast.

    All this was hypothetically iing until 1973, when an odd occurrence made itsuddenly momentous: water in Yellowstone Lake, in the heart of the park, began to ruhe banks at the lake’s southern end, flooding a meadow, while at the opposite end of the lakethe water mysteriously flowed away. Geologists did a hasty survey and discovered that a largearea of the park had developed an ominous bulge. This was lifting up one end of the lake andcausing the water to run out at the other, as would happen if you lifted one side of a child’swading pool. By 1984, the whole tral region of the park—several dozen square miles—was more than three feet higher than it had been in 1924, when the park was last formallysurveyed. Then in 1985, the whole of the tral part of the park subsided by eight inches. Itnow seems to be swelling again.

    The geologists realized that only ohing could cause this—a restless magma chamber.

    Yellowstone wasn’t the site of an a supervolo; it was the site of an active o wasalso at about this time that they were able to work out that the cycle of Yellowstoions averaged one massive blow every 600,000 years. The last one, iingly enough,was 630,000 years ago. Yellowsto appears, is due.

    “It may not feel like it, but you’re standing on the largest active volo in the world,” PaulDoss, Yellowstoional Park geologist, told me soon after climbing off an enormousHarley-Davidson motorcycle and shaking hands whe at the park headquarters atMammoth Hot Springs early on a lovely m in June. A native of Indiana, Doss is anamiable, soft-spokeremely thoughtful man who looks nothing like a National ParkService employee. He has a graying beard and hair tied ba a long ponytail. A smallsapphire stud graces one ear. A slight paunch strains against his crisp Park Serviiform.

    He looks more like a blues musi than a gover employee. In fact, he is a bluesmusi (harmonica). But he sure knows and loves geology. “And I’ve got the best plathe world to do it,” he says as we set off in a bouncy, battered four-wheel-drive vehicle in thegeneral dire of Old Faithful. He has agreed to let me apany him for a day as he goesabout doing whatever it is a park geologist does. The first assigoday is to give anintroductory talk to a new crop of tuides.

    Yellowstone, I hardly need point out, is sensationally beautiful, with plump, statelymountains, bison-specked meadows, tumbling streams, a sky-blue lake, wildlife beyondting. “It really doesn’t get aer than this if you’re a geologist,” Doss says. “You’vegot rocks up at Beartooth Gap that are nearly three billion years old—three-quarters of theway back to Earth’s beginning—and then you’ve got mineral springs here”—he points at thesulfurous hot springs from which Mammoth takes its title—“where you  see rocks as theyare being born. And iween there’s everything you could possibly imagine. I’ve neverbeen any place where geology is more evident—or prettier.”

    “So you like it?” I say.

    “Oh, no, I love it,” he answers with profound siy. “I mean I really love it here. Thewinters are tough and the pay’s not too hot, but when it’s good, it’s just—”

    He interrupted himself to point out a distant gap in a range of mountains to the west, whichhad just e into view over a rise. The mountains, he told me, were known as the Gallatins.

    “That gap is sixty or maybe seventy miles across. For a long time nobody could uandwhy that gap was there, and then Bob Christiansen realized that it had to be because themountains were just blown away. When you’ve got sixty miles of mountains just obliterated,you know you’re dealing with something pretty potent. It took Christiansen six years to figureit all out.”

    I asked him what caused Yellowstoo blow when it did.

    “Don’t know. Nobody knows. Voloes are strahings. We really don’t ua all. Vesuvius, in Italy, was active for three hundred years until aion in 1944and then it just stopped. It’s been silent ever since. Some volologists think that it isrecharging in a big way, which is a little w because two million people live on oraround it. But nobody knows.”

    “And how much warning would you get if Yellowstone was going to go?”

    He shrugged. “Nobody was around the last time it blew, so nobody knows what thewarning signs are. Probably you would have swarms of earthquakes and some surface upliftand possibly some ges iterns of behavior of the geysers and steam vents, butnobody really knows.”

    “So it could just blow without warning?”

    He houghtfully. The trouble, he explained, is that nearly all the things that wouldstitute warning signs already exist in some measure at Yellowstone. “Earthquakes aregenerally a precursor of volic eruptions, but the park already has lots of earthquakes—1,260 of them last year. Most of them are too small to be felt, but they are earthquakesheless.”

    A ge itern of geyser eruptions might also be taken as a clue, he said, but thesetoo vary uably. Ohe most famous geyser in the park was Excelsieyser. Itused to erupt regularly and spectacularly to heights of three hundred feet, but in 1888 it juststopped. Then in 1985 it erupted again, though only to a height of eighty feet. SteamboatGeyser is the biggest geyser in the world when it blows, shooting water four hundred feet intothe air, but the intervals between its eruptions have ranged from as little as four days to almostfifty years. “If it blew today and agai week, that wouldn’t tell us anything at all aboutwhat it might do the following week or the week after or twenty years from now,” Doss says.

    “The whole park is so volatile that it’s essentially impossible to draw clusions from almostanything that happens.”

    Evacuating Yellowstone would never be easy. The park gets some three million visitors ayear, mostly ihree peak months of summer. The park’s roads are paratively few andthey are kept iionally narrow, partly to slow traffic, partly to preserve an air ofpicturesqueness, and partly because of topographical straints. At the height of summer, it easily take half a day to cross the park and hours to get anywhere within it. “Wheneverpeople see animals, they just stop, wherever they are,” Doss says. “We get bear jams. We getbison jams. We get wolf jams.”

    Iumn of 2000, representatives from the U.S. Geological Survey and National ParkService, along with some academics, met and formed something called the YellowstoneVolic Observatory. Four such bodies were ience already—in Hawaii, California,Alaska, and Washington—but oddly none in the largest volie in the world. The YVOis not actually a thing, but more an idea—an agreement to coordinate efforts at studying andanalyzing the park’s diverse geology. One of their first tasks, Doss told me, was to draw up ahquake and volo hazards plan”—a plan of a in the event of a crisis.

    “There isn’t one already?” I said.

    “No. Afraid not. But there will be soon.”

    “Isn’t that just a little tardy?”

    He smiled. “Well, let’s just say that it’s not any too soon.”

    O is in place, the idea is that three people—Christiansen in Menlo Park, California,Professor Robert B. Smith at the Uy of Utah, and Doss in the park—would assess thedegree of danger of any potential cataclysm and advise the park superinte. Thesuperinte would take the decisioher to evacuate the park. As for surroundingareas, there are no plans. If Yellowstone were going to blow in a really big way, you would beon your own once you left the park gates.

    Of course it may be tens of thousands of years before that day es. Doss thinks such aday may not e at all. “Just because there attern in the past doesn’t mean that it stillholds true,” he says. “There is some evideo suggest that the pattern may be a series ofcatastrophic explosions, then a long period of quiet. We may be in that now. The evidenow is that most of the magma chamber is cooling and crystallizing. It is releasing itsvolatiles; you o trap volatiles for an explosive eruption.”

    In the meahere are plenty of other dangers in and around Yellowstone, as was madedevastatingly evident on the night of August 17, 1959, at a place called Hebgen Lake justoutside the park. At twenty mio midnight on that date, Hebgen Lake suffered acatastrophic quake. It was magnitude 7.5, not vast as earthquakes go, but so abrupt andwreng that it collapsed aire mountai was the height of the summer season,though fortunately not so many people went to Yellowstone in those days as now. Eightymillion tons of rock, moving at more than one hundred miles an hour, just fell off themountain, traveling with such ford momentum that the leading edge of the landslide ranfour hundred feet up a mountain oher side of the valley. Along its path lay part of theRock Creek Campground. Twe campers were killed, een of them buried toodeep ever to be found again. The devastation was swift but heartbreakingly fickle. Threebrothers, sleeping ient, were spared. Their parents, sleeping in aent besidethem, were swept away and never seen again.

    “A big earthquake—and I mean big—will happen sometime,” Doss told me. “You t on that. This is a big fault zone for earthquakes.”

    Despite the Hebgen Lake quake and the other known risks, Yellowstone didn’t getperma seismometers until the 1970s.

    If you needed a way to appreciate the grandeur and inexorable nature of geologic processes,you could do worse than to sider the Tetons, the sumptuously jagged rahat stands justto the south of Yellowstoional Park. Nine million years ago, the Tetons did.

    The land around Ja Hole was just a high grassy plain. But then a forty-mile-long faultopened within the Earth, and sihen, about once every nine hundred years, the Tetonsexperience a really big earthquake, enough to jerk them another six feet higher. It is theserepeated jerks over eons that have raised them to their present majestic heights of seventhousa.

    That nine hundred years is an average—and a somewhat misleading one. Acc toRobert B. Smith and Lee J. Siegel in Windows into the Earth , a geological history of theregion, the last major Teton quake was somewhere between about five and seven thousandyears ago. The Tetons, in short, are about the most overdue earthquake zone on the pla.

    Hydrothermal explosions are also a signifit risk. They  happen anytime, pretty muywhere, and without any predictability. “You know, by design we funnel visitors intothermal basins,” Doss told me after we had watched Old Faithful blow. “It’s what they eto see. Did you know there are meysers and hot springs at Yellowstohan in all therest of the world bined?”

    “I didn’t know that.”

    He nodded. “Ten thousand of them, and nobody knows when a new vent might open.” Wedrove to a place called Duck Lake, a body of water a couple of hundred yards across. “It lookspletely innocuous,” he said. “It’s just a big pond. But this big hole didn’t used to be here.

    At some time in the last fifteen thousand years this blew in a really big way. You’d have hadseveral tens of millions of tons of earth and rod superheated water blowing out athypersonic speeds. You  imagine what it would be like if this happened under, say, theparking lot at Old Faithful or one of the visitors’ ters.” He made an unhappy face.

    “Would there be any warning?”

    “Probably not. The last signifit explosion in the park was at a place called Pork ></a>hopGeyser in 1989. That left a crater about five meters across—not huge by any means, but bigenough if you happeo be standing there at the time. Fortunately, nobody was around sonobody was hurt, but that happened without warning. In the very a past there have beenexplosions that have made holes a mile across. And nobody  tell you where or when thatmight happen again. You just have to hope that you’re not standing there when it does.”

    Big rockfalls are also a dahere was a big o Gardiner yon in 1999, but againfortunately no one was hurt. Late iernoon, Doss and I stopped at a place where therewas a rock  poised above a busy park road. Cracks were clearly visible. “It could goat any time,” Doss said thoughtfully.

    “You’re kidding,” I said. There wasn’t a moment when there weren’t tassih it, all filled with, in the most literal sense, happy campers.

    “Oh, it’s not likely,” he added. “I’m just saying it could. Equally it could stay like that fordecades. There’s just no telling. People have to accept that there is risk in ing here. That’sall there is to it.”

    As we walked back to his vehicle to head bamoth Hot Springs, Doss added: “Butthe thing is, most of the time bad things don’t happen. Rocks don’t fall. Earthquakes don’toccur. New vents don’t suddenly open up. For all the instability, it’s mostly remarkably andamazingly tranquil.”

    “Like Earth itself,” I remarked.

    “Precisely,” he agreed.

    The risks at Yellowstone apply to park employees as much as to visitors. Doss got ahorrifise of that in his first week on the job five years earlier. Late one night, three youngsummer employees engaged in an illicit activity known as “hot-potting”—swimming orbasking in ools. Though the park, for obvious reasons, doesn’t publicize it, not all thepools in Yellowstone are dangerously hot. Some are extremely agreeable to lie in, and it wasthe habit of some of the summer employees to have a dip late at night even though it wasagainst the rules to do so. Foolishly the threesome had failed to take a flashlight, which wasextremely dangerous because much of the soil around the ools is crusty and thin andone  easily fall through into a scaldi below. In any case, as they made their wayback to their dorm, they came across a stream that they had had to leap over earlier. Theybacked up a few paces, linked arms and, on the t of three, took a running jump. In fact, itwasn’t the stream at all. It was a boiling pool. In the dark they had lost their bearings. he three survived.

    I thought about this the  m as I made a brief call, on my way out of the park, at aplace called Emerald Pool, in the Upper Geyser Basin. Doss hadn’t had time to take me therethe day before, but I<u>９9ｌｉb?</u> thought I ought at least to have a look at it, for Emerald Pool is a historicsite.

    In 1965, a husband-and-wife team of biologists homas and Louise Brock, while ona summer study trip, had done a crazy thing. They had scooped up some of the yellowy-brown scum that rimmed the pool and exami for life. To their, aually the widerworld’s, deep surprise, it was full of living microbes. They had found the world’s firstextremophiles—anisms that could live in water that had previously been assumed to bemuch too hot or acid or choked with sulfur to bear life. Emerald Pool, remarkably, was allthese things, yet at least two types of living things, Sulpholobus acidocaldarius andThermophilus aquaticus as they became known, found it genial. It had always beensupposed that nothing could survive above temperatures of 50°C (122°F), but here wereanisms basking in rank, acidic waters nearly twice that hot.

    For almost twenty years, one of the Brocks’ two new bacteria, Thermophilus aquaticus,remained a laboratory curiosity until a stist in California named Kary B. Mullis realizedthat heat-resistant enzymes within it could be used to create a bit of chemical wizardry knownas a polymerase  rea, which allows stists to gee lots of DNA from verysmall amounts—as little as a single molecule in ideal ditions. It’s a kind of geicphotocopying, and it became the basis for all subsequeic sce, from academicstudies to police forensic work. It won Mullis the Nobel Prize iry in 1993.

    Meanwhile,  stists  were  finding even hardier microbes, now knoerthermophiles, which demand temperatures of 80°C (176°F) or more. The warmestanism found so far, acc to Frances Ashcroft in Life at the Extremes, is Pyrolobusfumarii, which dwells in the walls of o vents where the temperature  reach 113°C(235.4°F). The upper limit for life is thought to be about 120°C (248°F), though no oually knows. At all events, the Brocks’ findings pletely ged our perception of theliving world. As NASA stist Jay Bergstralh has put it: “Wherever we go oh—eveninto what’s seemed like the most hostile possible enviros for life—as long as there isliquid water and some source of chemical energy we find life.”

    Life, it turns out, is infinitely more clever and adaptable than anyone had ever supposed.

    This is a very good thing, for as we are about to see, we live in a world that doesn’t altogetherseem to want us here.

    PART V   LIFE ITSELFThe more I examihe universeand study the details of its architecture,the more evidence I find that theuniverse in some sense must haveknoere ing.

    -Freeman Dyson

百度搜索 A Short History of Nearly Everything 天涯 或 A Short History of Nearly Everything 天涯在线书库 即可找到本书最新章节.