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steve2470

(37,457 posts)
Tue Jul 29, 2014, 07:27 AM Jul 2014

The first map of the (Ocean) depths



http://www.moreintelligentlife.com/content/places/simon-willis/cartophilia

From INTELLIGENT LIFE magazine, July/August 2014

This map marks both a scientific and an imaginative revolution. When it was published in 1977 by Marie Tharp and Bruce Heezen, two oceanographers at Columbia University, there had never before been a map of the entire ocean floor. Here, for the first time, was our planet’s hidden majority. It was as if the plug had been pulled and the water drained out, transforming the blank seascape into a complex landscape of plains and peaks, escarpments and bluffs. Here was the full extent of the Mid-Ocean Ridge, the mightiest mountain range on Earth, its 40,000-mile length making molehills out of more familiar mountains. You can see its serpentine curl through the Atlantic, round the Cape of Good Hope to the Horn of Africa and on through the Southern Ocean, up to 1,000 miles wide and two miles high.

Tharp and Heezen began mapping the individual ocean floors in 1952, but found obstacles in their way. The big one was invisibility: when it comes to mapping the ocean floor, the sea gets in the way of seeing. The second obstacle was limited data. Tharp, who drew the maps, started with the North Atlantic, working from information gleaned on sounding expeditions. Ships travelling across the Atlantic with sonar would fire sound through the sea, working out its depth from the time it took for the echo to be detected. But Tharp had only six complete tracks across the ocean from which to figure out the topography of the whole thing—“six ribbons of light”, as she described them.

As she began analysing the data she noticed something strange, a discovery that would change our understanding of our planet. There was a crack running along the top of the Mid-Atlantic Ridge. Nobody had ever spotted it, but it appeared to be huge—in places wider than the Grand Canyon. Heezen, at first disbelieving, became convinced when it turned out the crack coincided with a string of earthquakes. Tharp’s discovery helped turn a theory then regarded as nonsense into a fundamental fact: continental drift. The sea floor was being pushed up and apart.

“It was a giant paradigm shift,” says Robin Bell, a professor of geophysics at Columbia today. “These mountains now had a reason for being there. That’s the magic place where you in London and I in upstate New York are getting farther apart every day at the rate our fingernails grow. That’s the place where new Earth crust is being made.” It was a leap towards explaining why the Atlantic coasts of South America and Africa fit so snugly together, and why Bermuda is older than the Azores. “It wasn't just random down there,” Bell says. “There was a story.”
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The first map of the (Ocean) depths (Original Post) steve2470 Jul 2014 OP
I remember that. hunter Jul 2014 #1
great post ! steve2470 Jul 2014 #2
Yeah, really, man. Thanks for that. Well done. byronius Jul 2014 #4
I guess the dark blue lines are subduction zones. And this mountain ridge spreading going AnotherDreamWeaver Jul 2014 #3
Didn't "National Geographic" have it as a big fold out map one month? CrispyQ Jul 2014 #5

hunter

(38,264 posts)
1. I remember that.
Tue Jul 29, 2014, 12:02 PM
Jul 2014

It was one of the things that distracted me from my obsession with computers, electronics, and engineering.

Eventually I changed my major in college to biology, with a heavy emphasis on paleontology. These new pictures of a very dynamic earth and the interactions of biological and geological forces fascinated me. I put down my soldering iron, got away from the workbenches and computer labs, and ventured out into the field.

I've removed ticks from every part of my body, and more amazingly, ticks from women! In those days there were very few women engineering majors, and most of them were not the sort who would strip off their clothes and jump in a river as a break from dirty and often tedious field work.

Another part of the marine geology puzzle was put into place by the Vine–Matthews–Morley hypothesis that explained the magnetic striping of the sea floor.



This striping had been detected by sensitive magnetometers which had largely been developed for submarine detection.

Wide acceptance of plate tectonics theory was delayed for the usual scientific stodginess described by Thomas Kuhn's "paradigm shifts," and by overt military secrecy. In the environment of World War II and the Cold War, even open scientific research was sometimes suppressed.

Here's a nice modern map from NASA in a projection that doesn't shrink Africa so absurdly:



http://en.wikipedia.org/wiki/File%3APlate_tectonics_map%2Egif

AnotherDreamWeaver

(2,846 posts)
3. I guess the dark blue lines are subduction zones. And this mountain ridge spreading going
Tue Jul 29, 2014, 12:15 PM
Jul 2014

up the Gulf of California.... Such a complex footing we live upon... I wonder if there are maps now of the directions the pieces are moving. Pieces of the Pacific Plate are going North along the Western US, but there seems to be subduction along Mexico. I guess that it moves at the rate a fingernail grows is somewhat comforting???

CrispyQ

(36,226 posts)
5. Didn't "National Geographic" have it as a big fold out map one month?
Tue Jul 29, 2014, 03:58 PM
Jul 2014

It looks familiar & I know I spend hours looking at the NatGeo map.

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