In effect, the ocean basics were perpetually being 'recycled' with the creation of new crust and the destruction of old oceanic lithosphere occurring simultaneously. As old crust was consumed in the trenches, new magma rose and erupted along the spreading ridges to form new crust. Millions of years later, the oceanic crust descends into oceanic trenches. Hess suggested that the new oceanic crust continuously moves away from the ridges' conveyor belt-like motion. If the Earth's crust was expanding along the oceanic ridges, it must be shrinking elsewhere. They understood the broad implications of this phenomenon. Dietz and Hess coined the expression seafloor spreading. Hess, a Princeton University geologist, and Robert S. Ow could new crust be made and continuously added along the ridges without increasing the size of the Earth? The question intrigued Harry H. New magma from deep with the Earth rises easily through these weak zones and eventually erupts along the crest of the ridges to create new oceanic crust. In 1961, scientists began to theorize that mid-ocean ridges mark structurally weak zones where the ocean floor was being ripped in two lengthwise along the ridge crest. 'The results are of exceptional interest in that they reveal major structural trends of which there is little or no indication in the topography, and they provide evidence for unsuspected horizontal displacements along some of the faults of the north-east Pacific greater than any that have so far been observed over the continents.'įrom these and other breakthroughs came a radical re-understanding of plate tectonics, per USGS: The survey was 'the first attempt to make a detailed magnetic map of an extensive area of the oceans,' said Bullard and Mason. Before them lay evidence of great north-south lineations and a single right-lateral offset of 155 kilometers along the Murray fracture zone off southern California. The chart of magnetic intensities from the Pioneer survey startled geologists. Morita, Scripps Institution of Oceanography Archives, UC San Diego Library.

They also discovered unexpected magnetic patterns on the sea floor, per Shor:Ĭourtesy of Richard Y. The source of heat, therefore, must be deeper within the earth, presumably beneath the Mohorovičić discontinuity. 'The only adequate source of heat that has been suggested is radioactivity within the earth,' noted Bullard, and oceanic basalts are considerably less radioactive than continental rocks. The results from the first measurements of heat flow through the sea floor were among several surprises gathered on the first major Scripps expedition, Midpac, in 1950: the temperature gradient was very similar to that measured on lean, whereas it had been expected to be considerably less.

Other discoveries included unexpected heat flowing from the sea floor, as noted by Elizabeth Noble Shor in a history of Scripps during this period: Though hidden beneath the ocean surface, the global mid-ocean system is the most prominent topographic feature on the surface of the planet. Known as the global mid-ocean ridge, this immense submarine mountain chain more than 50,000 kilometers long and in places more that 800 kilometers across zigzags between the continents winding its way around the globe like a seam on a baseball.

Who mapped out the ocean floor in 1952