Oceanography in the mid-20th century was “one of the greatest periods of exploration of the earth … Every time you went to sea, you made unexpected discoveries. It was revolutionary. Nothing that we expected was true. Everything we didn’t expect was true.”
This striking declaration comes from Roger Revelle, the U.S. Navy’s chief oceanographer during World War II and the man responsible for transforming the Scripps Institution of Oceanography in La Jolla, California into a major research institution, leading major expeditions to the Mid- and South-Pacific in 1950 and 1952 (as quoted in Daniel Yergin’s “The Quest: Energy, Security and the Remaking of the Modern World“).
What oceanographers realised was that the deep-sea floor was not a flat and featureless plan but rather a dynamic landscape with vast mountain ranges, deep basins, and long trenches. Although this understanding had been developing for centuries, the real breakthroughs came after World War II.
There was the discovery of vast, underwater mountains ranges, as noted by the U.S. Geological Survey:
In the 1950s oceanic explorations greatly expanded. Data gathered by oceanographers from many countries led to the discovery of a great mountain range on the ocean floor virtually encircling the Earth.
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. Though hidden beneath the ocean surface, the global mid-ocean system is the most prominent topographic feature on the surface of the planet.
Other discoveries included unexpected heat flowing from the sea floor, as noted by Elizabeth Noble Shor in a history of Scripps during this period:
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. “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 source of heat, therefore, must be deeper within the earth, presumably beneath the Mohorovičić discontinuity.
They also discovered unexpected magnetic patterns on the sea floor, per Shor:
The chart of magnetic intensities from the Pioneer survey startled geologists. 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 survey was “the first attempt to make a detailed magnetic map of an extensive area of the oceans,” said Bullard and Mason. “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.”
From these and other breakthroughs came a radical re-understanding of plate tectonics, per USGS:
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. 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. …
[H]ow could new crust be made and continuously added along the ridges without increasing the size of the Earth? The question intrigued Harry H. Hess, a Princeton University geologist, and Robert S. Dietz, a scientist with the U.S. Coast and Geodetic Survey. Dietz and Hess coined the expression seafloor spreading. They understood the broad implications of this phenomenon. If the Earth’s crust was expanding along the oceanic ridges, it must be shrinking elsewhere. Hess suggested that the new oceanic crust continuously moves away from the ridges’ conveyor belt-like motion. Millions of years later, the oceanic crust descends into oceanic trenches. As old crust was consumed in the trenches, new magma rose and erupted along the spreading ridges to form new crust. In effect, the ocean basics were perpetually being “recycled” with the creation of new crust and the destruction of old oceanic lithosphere occurring simultaneously. According to Hess, the Atlantic was expanding and the Pacific shrinking.
The continents, which are lighter than the ocean crust, glide over the surface of the Earth in response to the expansion and contraction along oceanic ridges. They are carried along as the ocean floor spreads from the ridges.
A better understanding of the oceans, which cover 71% of Earth’s surface, as well as the tectonic processes that shape our planet would prove useful in many fields. Perhaps most importantly, it began to unlock the study of climate change and the role that humans would play by increasing the buildup of carbon dioxide in the atmosphere, what Revelle called, “a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.”
Not only were these discoveries incredibly important, but being an oceanographer in this heady climate sounds fun, too.
That much is obvious in an account by Edward S. Barr of how after his junior year of high school in San Diego he convinced Revelle to take him on the 1950 MidPac expedition as a $US75-a-month lab assistant, and how they traveled to Honolulu, the Marshall Islands, the Kwajalein Atoll, and deep into the South Pacific, with prolific discoveries and adventure all the way.
One photo included in the memoir, which shows Barr using a fathometer echo sounder on August 31, 1950, is labelled: “Discovering the MidPac Mountain Range on my watch!”
Here’s a map of the mountain range they discovered:
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