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urprise： the mightiest and mostextensive mountain range on earth was—mostly—underwater。 it traced a continuous pathalong the world’s seabeds； rather like the stitching on a baseball。 if you began at iceland； youcould follow it down the center of the atlantic ocean； around the bottom of africa； and acrossthe indian and southern oceans； below australia； there it angled across the pacific as ifmaking for baja california before shooting up the west coast of the united states to alaska。
occasionally its higher peaks poked above the water as an island or archipelago—the azoresand canaries in the atlantic； hawaii in the pacific； for instance—but mostly it was buriedunder thousands of fathoms of salty sea； unknown and unsuspected。 when all its brancheswere added together； the network extended to 46；600 miles。
a very little of this had been known for some time。 people laying ocean…floor cables in thenineteenth century had realized that there was some kind of mountainous intrusion in the mid…atlantic from the way the cables ran； but the continuous nature and overall scale of the chainwas a stunning surprise。 moreover； it contained physical anomalies that couldn’t be explained。
down the middle of the mid…atlantic ridge was a canyon—a rift—up to a dozen miles widefor its entire 12；000…mile length。 this seemed to suggest that the earth was splitting apart atthe seams； like a nut bursting out of its shell。 it was an absurd and unnerving notion； but theevidence couldn’t be denied。
then in 1960 core samples showed that the ocean floor was quite young at the mid…atlanticridge but grew progressively older as you moved away from it to the east or west。 harry hessconsidered the matter and realized that this could mean only one thing： new ocean crust wasbeing formed on either side of the central rift； then being pushed away from it as new crustcame along behind。 the atlantic floor was effectively two large conveyor belts； one carryingcrust toward north america； the other carrying crust toward europe。 the process becameknown as seafloor spreading。
when the crust reached the end of its journey at the boundary with continents； it plungedback into the earth in a process known as subduction。 that explained where all the sedimentwent。 it was being returned to the bowels of the earth。 it also explained why ocean floorseverywhere were so paratively youthful。 none had ever been found to be older than about175 million years； which was a puzzle because continental rocks were often billions of yearsold。 now hess could see why。 ocean rocks lasted only as long as it took them to travel toshore。 it was a beautiful theory that explained a great deal。 hess elaborated his ideas in animportant paper； which was almost universally ignored。 sometimes the world just isn’t readyfor a good idea。
meanwhile； two researchers； working independently； were making some startling findingsby drawing on a curious fact of earth history that had been discovered several decades earlier。
in 1906； a french physicist named bernard brunhes had found that the planet’s magnetic fieldreverses itself from time to time； and that the record of these reversals is permanently fixed incertain rocks at the time of their birth。 specifically； tiny grains of iron ore within the rockspoint to wherever the magnetic poles happen to be at the time of their formation； then staypointing in that direction as the rocks cool and harden。 in effect they “remember” where themagnetic poles were at the time of their creation。 for years this was little more than acuriosity； but in the 1950s patrick blackett of the university of london and s。 k。 runcorn ofthe university of newcastle studied the ancient magnetic patterns frozen in british rocks andwere startled； to say the very least； to find them indicating that at some time in the distant pastbritain had spun on its axis and traveled some distance to the north； as if it had somehowe loose from its moorings。 moreover； they also discovered that if you placed a map ofeurope’s magnetic patterns alongside an american one from the same period； they fit togetheras neatly as two halves of a torn letter。 it was uncanny。
their findings were ignored too。
it finally fell to two men from cambridge university； a geophysicist named drummondmatthews and a graduate student of his named fred vine； to draw all the strands together。 in1963； using magnetic studies of the atlantic ocean floor； they demonstrated conclusively thatthe seafloors were spreading in precisely the manner hess had suggested and that thecontinents were in motion too。 an unlucky canadian geologist named lawrence morley cameup with the same conclusion at the same time； but couldn’t find anyone to publish his paper。
in what has bee a famous snub； the editor of the journal of geophysical research toldhim： “such speculations make interesting talk at cocktail parties； but it is not the sort of thingthat ought to be published under serious scientific aegis。” one geologist later described it as“probably the most significant paper in the earth sciences ever to be denied publication。”
at all events； mobile crust was an idea whose time had finally e。 a symposium ofmany of the most important figures in the field was convened in london under the auspices ofthe royal society in 1964； and suddenly； it seemed； everyone was a convert。 the earth； themeeting agreed； was a mosaic of interconnected segments whose various stately jostlingsaccounted for much of the planet’s surface behavior。
the name “continental drift” was 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 “crustal blocks” or sometimes “pavingstones。” not 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 geologic