Archive for March, 2013

The Floors of the Oceans

Friday, March 22nd, 2013

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“When we began in 1952,” Heezen told me a decade later, “only a few such profiles had ever been drawn across the Atlantic.” He and Marie Tharp produced scores, then hundreds, finally thousands of them. In 1959 they published, with Maurice Ewing, The Floors of the Oceans: I. The North At­lantic. It accompanied the first of a series of maps that would encompass the globe.

 

Later their diagrams would be rendered by an Austrian mountain artist, Heinrich C. Berann, into more generalized, full-color map paintings. These were issued, one by one, by NATIONAL GEOGRAPHIC. To Hee­zen’s great satisfaction (he was sometimes criticized by colleagues for extrapolating and drawing “poetic truths”), the maps blos­somed on walls of schools and colleges—and in his colleagues’ offices—the world over.

BEFORE THE FIRST appeared,however, Marie Tharp had made a historic discovery of her own. She noticed that on profile after profile of the Mid-Atlantic Ridge, a deep V shaped valley appeared to run along the very crest, or centerline. When she first ven­tured that this rift might extend the entire length of the range, Heezen didn’t pay much attention. The idea seemed too vague, too farfetched.

 

About the same time Ewing and Press and other geologists at Lamont were restudying world earthquake records. Heezen began plotting the centers of the quakes on the detailed charts Marie Tharp was drawing.

The earthquakes followed the ridge crest—the path which Marie said held a rift valley. “It was as if a light suddenly went on,” Bruce Heezen said to me long after­ward. “The rift indeed was there. The earth­quakes were taking place along it.”

Belts of earthquakes had been charted down the Mid-Atlantic Ridge and along In­dian Ocean and Pacific ridges—indeed, around the whole earth. Heezen realized that the quakes traced a far more extensive feature of the planet’s hard surface than had ever been suspected: a massive scar 40,000 miles long, curving around the globe like the seam of a baseball. The Mid-Ocean Ridge, as Heezen named the system, now is known to cover as much of the earth’s surface as all the continents put together.

It is volcanic and shaken by earthquakes. The fiery upthrusts of Iceland, the Azores, Tristan da Cunha, Reunion, the Galapagos are simply places where active volcanoes of the ridge system rise above water.

 

ASMORE and more ocean expeditions proved that the central rift was really there, other facts emerged. Great east-west displacements cut across it; the Canadian geologist J. Tuzo Wilson named them transform faults. Many of the ridge quakes came from them. Not only was there high heat flow from within the earth along the ridge; most rocks dredged from its slopes were of fresh lava. Something was going on, something mas­sive and basic.

 

Almost no sediments were found on the central slopes of the ridge. Indeed, and more mystifying, nowhere in the oceans was there as much or as old sediment as there should be if the oceans were as old as the earth itself. Where had the mud and ooze gone?

“I am reasonably certain,” oceanogra­pher Roger Revelle was to say long after, “that Maurice Ewing went to his grave be­lieving that somewhere in the deep sea there was a place where  sediments of all geologic ages, back to one or two billion years, had been deposited one on top of the other.”

Yet nothing from the ocean floors, neither sediments nor bedrock, has yet been found older than about 200 million years. Were the New World of the Ocean continents in fact drifting, bulldozing off the sediments as they went? Read more interesting information on http://www.compozt.com/

About 1910 both a U. S. geologist, Frank B. Taylor, and a German meteorologist, Al­fred Wegener, had proposed continental drift as a serious possibility. The idea was still being laughed at by many geologists in 1960. But at the same time, in 1959 and 1960, a few bold theorists were beginning to put forward a wholly new idea: Was the sea-floor itself moving, carrying the continents with it? Were the oceans growing wider?