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； itcan 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。”
in the autumn of 2000； representatives from the u。s。 geological survey and national parkservice； along with some academics； met and formed something called the yellowstonevolcanic observatory。 four such bodies were in existence already—in hawaii； california；alaska； and washington—but oddly none in the largest volcanic zone 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 an“earthquake and volcano hazards plan”—a plan of action 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。”
once it is in place； the idea is that three people—christiansen in menlo park； california；professor robert b。 smith at the university of utah； and doss in the park—would assess thedegree of danger of any potential cataclysm and advise the park superintendent。 thesuperintendent would take the decision whether 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 was a pattern in the past doesn’t mean that it stillholds true；” he says。 “there is some evidence to suggest that the pattern may be a series ofcatastrophic explosions； then a long period of quiet。 we may be in that now。 the evidencenow is that most of the magma chamber is cooling and crystallizing。 it is releasing itsvolatiles； you need to trap volatiles for an explosive eruption。”
in the meantime there 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 minutes to midnight on that date； hebgen lake suffered acatastrophic quake。 it was magnitude 7。5； not vast as earthquakes go； but so abrupt andwrenching that it collapsed an entire mountainside。 it was the height of the summer season；though fortunately not so many people went to yellowstone in those days as now。 eighty million tons of rock； moving at more than one hundred miles an hour； just fell off themountain； traveling with such force and momentum that the leading edge of the landslide ranfour hundred feet up a mountain on the other side of the valley。 along its path lay part of therock creek campground。 twenty…eight campers were killed； nineteen of them buried toodeep ever to be found again。 the devastation was swift but heartbreakingly fickle。 threebrothers； sleeping in one tent； were spared。 their parents； sleeping in another tent besidethem； were swept away and never seen again。
“a big earthquake—and i mean big—will happen sometime；” doss told me。 “you cancount on that。 this is a big fault zone for earthquakes。”
despite the hebgen lake quake and the other known risks； yellowstone didn’t getpermanent 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 consider the tetons； the sumptuously jagged range that stands justto the south of yellowstone national park。 nine million years ago； the tetons didn’t exist。
the land around jackson hole was just a high grassy plain。 but then a forty…mile…long faultopened within the earth； and since then； 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 seventhousand feet。
that nine hundred years is an average—and a somewhat misleading one。 according 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 planet。
hydrothermal explosions are also a significant risk。 they can happen anytime； pretty muchanywhere； 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 more geysers and hot springs at yellowstone than 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 rock and superheated water blowing out athypersonic speeds。 you can imagine what it would be like if this happened under； say； theparking lot at old faithful or one of the visitors’ centers。” he made an unhappy face。
“would there be any warning？”
“probably not。 the last significant explosion in the park was at a place called pork chopgeyser in 1989。 that left a crater about five meters across—not huge by any means； but bigenough if you happened to be standing there at the time。 fortunately； nobody was around so nobody was hurt； but that happened without warning。 in the very ancient past there have beenexplosions that have made holes a mile across。 and nobody can 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 danger。 there was a big one at gardiner canyon in 1999； but againfortunately no one was hurt。 late in the afternoon； doss and i stopped at a place where therewas a rock overhang 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 two cars passingbeneath 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 back to mammoth 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 ahorrific sense of that in his first w