万物简史英文版_比尔·布莱森-第35章
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ace behavior。
the name 鈥渃ontinental drift鈥潯as fairly swiftly discarded when it was realized that thewhole crust was in motion and not just the continents； but it took a while to settle on a namefor the individual segments。 at first people called them 鈥渃rustal blocks鈥潯r sometimes 鈥減avingstones。鈥潯ot until late 1968； with the publication of an article by three americanseismologists in the journal of geophysical research ； did the segments receive the name bywhich they have since been known： plates。 the same article called the new science platetectonics。
old ideas die hard； and not everyone rushed to embrace the exciting new theory。 well intothe 1970s； one of the most popular and influential geological textbooks； the earth by thevenerable harold jeffreys； strenuously insisted that plate tectonics was a physicalimpossibility； just as it had in the first edition way back in 1924。 it was equally dismissive ofconvection and seafloor spreading。 and in basin and range； published in 1980； john mcpheenoted that even then one american geologist in eight still didn鈥檛 believe in plate tectonics。
today we know that earth鈥檚 surface is made up of eight to twelve big plates （depending onhow you define big） and twenty or so smaller ones； and they all move in different directionsand at different speeds。 some plates are large and paratively inactive； others small butenergetic。 they bear only an incidental relationship to the landmasses that sit upon them。 thenorth american plate； for instance； is much larger than the continent with which it isassociated。 it roughly traces the outline of the continent鈥檚 western coast （which is why thatarea is so seismically active； because of the bump and crush of the plate boundary）； butignores the eastern seaboard altogether and instead extends halfway across the atlantic to themid…ocean ridge。 iceland is split down the middle； which makes it tectonically half americanand half european。 new zealand； meanwhile； is part of the immense indian ocean plate eventhough it is nowhere near the indian ocean。 and so it goes for most plates。
the connections between modern landmasses and those of the past were found to beinfinitely more plex than anyone had imagined。 kazakhstan； it turns out； was onceattached to norway and new england。 one corner of staten island； but only a corner； iseuropean。 so is part of newfoundland。 pick up a pebble from a massachusetts beach； and itsnearest kin will now be in africa。 the scottish highlands and much of scandinavia aresubstantially american。 some of the shackleton range of antarctica； it is thought； may oncehave belonged to the appalachians of the eastern u。s。 rocks； in short； get around。
the constant turmoil keeps the plates from fusing into a single immobile plate。 assumingthings continue much as at present； the atlantic ocean will expand until eventually it is muchbigger than the pacific。 much of california will float off and bee a kind of madagascar ofthe pacific。 africa will push northward into europe； squeezing the mediterranean out ofexistence and thrusting up a chain of mountains of himalayan majesty running from paris tocalcutta。 australia will colonize the islands to its north and connect by some isthmianumbilicus to asia。 these are future outes； but not future events。 the events are happeningnow。 as we sit here； continents are adrift； like leaves on a pond。 thanks to global positioningsystems we can see that europe and north america are parting at about the speed a fingernailgrows鈥攔oughly two yards in a human lifetime。 if you were prepared to wait long enough；you could ride from los angeles all the way up to san francisco。 it is only the brevity oflifetimes that keeps us from appreciating the changes。 look at a globe and what you areseeing really is a snapshot of the continents as they have been for just one…tenth of 1 percentof the earth鈥檚 history。
earth is alone among the rocky planets in having tectonics； and why this should be is a bitof a mystery。 it is not simply a matter of size or density鈥攙enus is nearly a twin of earth inthese respects and yet has no tectonic activity。 it is thought鈥攖hough it is really nothing morethan a thought鈥攖hat tectonics is an important part of the planet鈥檚 organic well…being。 as thephysicist and writer james trefil has put it； 鈥渋t would be hard to believe that the continuousmovement of tectonic plates has no effect on the development of life on earth。鈥潯e suggeststhat the challenges induced by tectonics鈥攃hanges in climate； for instance鈥攚ere animportant spur to the development of intelligence。 others believe the driftings of thecontinents may have produced at least some of the earth鈥檚 various extinction events。 innovember of 2002； tony dickson of cambridge university in england produced a report；published in the journal science； strongly suggesting that there may well be a relationshipbetween the history of rocks and the history of life。 what dickson established was that thechemical position of the world鈥檚 oceans has altered abruptly and vigorously throughoutthe past half billion years and that these changes often correlate with important events inbiological history鈥攖he huge outburst of tiny organisms that created the chalk cliffs ofengland鈥檚 south coast； the sudden fashion for shells among marine organisms during the cambrian period； and so on。 no one can say what causes the oceans鈥櫋hemistry to change sodramatically from time to time； but the opening and shutting of ocean ridges would be anobvious possible culprit。
at all events； plate tectonics not only explained the surface dynamics of the earth鈥攈ow anancient hipparion got from france to florida； for example鈥攂ut also many of its internalactions。 earthquakes； the formation of island chains； the carbon cycle； the locations ofmountains； the ing of ice ages； the origins of life itself鈥攖here was hardly a matter thatwasn鈥檛 directly influenced by this remarkable new theory。 geologists； as mcphee has noted；found themselves in the giddying position that 鈥渢he whole earth suddenly made sense。鈥�
but only up to a point。 the distribution of continents in former times is much less neatlyresolved than most people outside geophysics think。 although textbooks give confident…looking representations of ancient landmasses with names like laurasia； gondwana； rodinia；and pangaea； these are sometimes based on conclusions that don鈥檛 altogether hold up。 asgeorge gaylord simpson observes in fossils and the history of life； species of plants andanimals from the ancient world have a habit of appearing inconveniently where they shouldn鈥檛and failing to be where they ought。
the outline of gondwana； a once…mighty continent connecting australia； africa；antarctica； and south america； was based in large part on the distribution of a genus ofancient tongue fern called glossopteris； which was found in all the right places。 however；much later glossopteris was also discovered in parts of the world that had no knownconnection to gondwana。 this troubling discrepancy was鈥攁nd continues to be鈥攎ostlyignored。 similarly a triassic reptile called lystrosaurus has been found from antarctica allthe way to asia； supporting the idea of a former connection between those continents； but ithas never turned up in south america or australia； which are believed to have been part ofthe same continent at the same time。
there are also many surface features that tectonics can鈥檛 explain。 take denver。 it is； aseveryone knows； a mile high； but that rise is paratively recent。 when dinosaurs roamedthe earth； denver was part of an ocean bottom； many thousands of feet lower。 yet the rockson which denver sits are not fractured or deformed in the way they would be if denver hadbeen pushed up by colliding plates； and anyway denver was too far from the plate edges to besusceptible to their actions。 it would be as if you pushed against the edge of a rug hoping toraise a ruck at the opposite end。 mysteriously and over millions of years； it appears thatdenver has been rising； like baking bread。 so； too； has much of southern africa； a portion ofit a thousand miles across has risen nearly a mile in 100 million years without any knownassociated tectonic activity。 australia； meanwhile； has been tilting and sinking。 over the past100 million years as it has drifted north toward asia； its leading edge has sunk by some sixhundred feet。 it appears that indonesia is very slowly drowning； and dragging australia downwith it。 nothing in the theories of tectonics can explain any of this。
alfred wegener never lived to see his ideas vindicated。 on an expedition to greenland in1930； he set out alone； on his fiftieth birthday； to check out a supply drop。 he never returned。
he was found a few days later； frozen to death on the ice。 he was buried on the spot and liesthere yet； but about a yard closer to north america than on the day he died。
einstein also failed to live long enough to see that he had backed the wrong horse。 in fact；he died at princeton； new jersey； in 1955 before charles hapgood鈥檚 rubbishing of continentaldrift theories was even published。
the other principal player in the emergence of tectonics theory； harry hess； was also atprinceton at the time； and would spend the rest of his career there。 one of his students was abright young fellow named walter alvarez； who would eventually change the world ofscience in a quite different way。
as for geology itself； its cataclysms had only just begun； and it was young alvarez whohelped to start the process。
part iv dangerous planetthe history of any one part of theearth； like the life of a soldier； consistsof long periods of boredom andshort periods of terror。
…british geologist derek v。 ager
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people knew for a long time that there was something odd about the earth beneathmanson； iowa。 in 1912； a man drilling a well for the town water supply reported bringing up alot of strangely deformed rock鈥斺�渃rystalline clast breccia with a melt matrix鈥潯nd 鈥渙verturnedejecta flap；鈥潯s it was later described in an official report。 the water was odd too。 it wasalmost as soft as rainwater。 naturally occurring soft water had never been found in iowabefore。
though manson鈥檚 strange rocks and silken waters were matters of curiosity； forty…oneyears would pass before a team from the university of iowa got around to making a trip to themunity； then as now a town of about two thousand people in the northwest part of thestate。 in 1953； after sinking a series of experimental bores； university geologists agreed thatthe site was indeed anomalous and attributed the deformed rocks to some ancient； unspecifiedvolcanic action。 this was in keeping with the wisdom of the day； but it was also about aswrong as a geological conclusion can get。
the trauma to manson鈥檚 geology had e not from within the earth； but from at least 100million miles beyond。 sometime in the very ancient past； when manson stood on the edge of ashallow sea； a rock about a mile and a half across； weighing ten billion tons and traveling atperhaps two hundred times the speed of sound ripped through the atmosphere and punchedinto the earth with a violence and suddenness that we can scarce
