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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