Walter Pitman: Discovered a Key to Plate Tectonics
Walter Pitman, a seagoing geophysicist who spotted a crucial piece of a huge puzzle that revolutionized the earth sciences, died Oct. 1 at the age of 87. The cause was complications of pneumonia, said his family; he passed away at the Hebrew Home in Riverdale, N.Y. At the time of his death, he was a special research scientist at Columbia University’s Lamont-Doherty Earth Observatory, in Palisades, N.Y., where he had spent his entire scientific career.
In the 1960s, Pitman and his colleagues showed that the magnetic polarity of the seabed changes with time and space—a signal that the crust on the ocean floor is moving, as new sections are created and old ones destroyed, over years to hundreds of thousands of years. It clinched the idea that earth’s surface is divided into mobile chunks that create continents and oceans, earthquakes and volcanoes—the theory of plate tectonics, on which all modern earth science rests. Among other things, Pitman also did groundbreaking work on changes in past sea levels. He also presented the still widely discussed hypothesis that the Biblical flood was a real event, which took place in what is now the Black Sea.
Walter Clarkson Pitman III was born Oct. 21, 1931, in Newark, N.J., and grew up on a small farm outside Morristown, N.J. His father, Walter Pitman Jr., was an administrative engineer at Bell Labs, home of many scientists who worked on key 20th-century technologies including lasers and transistors. His mother, the former Esther Sherman, was a homemaker.
Pitman’s father frequently took him to work and introduced him to researchers who patiently explained what they were doing—an experience he later credited with inspiring him to become a scientist. His grandfather owned several sports-fishing boats that sailed from the New Jersey shore, and Pitman spent a lot of time on these. “Once I got over being seasick, the ocean became an old friend,” he said in a 2016 interview. “Sometimes a violent friend, but a friend.”
Pitman graduated in 1956 from Pennsylvania’s Lehigh University with a degree in electrical engineering, and took a job as a project manager at the Hazeltine Corporation, a major designer of components for radios and other consumer products. By his own account, his four years there bored him. The exception: a project he worked on to develop navigation instruments for U.S. Navy submarines. After discovering that scientists at Lamont-Doherty were at that time collecting vast amounts of deep-sea data and developing instruments themselves, he applied for a job there.
Lacking credentials in either geology or oceanography, Pitman signed on initially as an electronics technician. In 1961, he shipped off on Lamont’s schooner, the Vema, on a nine-month voyage spanning the eastern Atlantic, south Pacific and the Southern Ocean, down to the edge of the polar ice pack. Among other things, he was expected to keep a magnetometer and other instruments going; help pull cores of sediment from the seabed; and toss sticks of dynamite overboard to create echoes used to chart the bottom. The apprenticeship gained him admittance as a graduate student, and he took up the study of seafloor magnetism.
By the mid-1960s, a growing number of scientists were developing evidence for plate tectonics, or continental drift, as it was called then. One line of investigation was the recently mapped system of mid-ocean ridges—undersea volcano chains that gird the globe like stitching on a baseball. Proponents asserted that lava oozing from these ridges was continually creating new sections of seafloor; at the same time, the outer edges of ocean basins dove back under the continents, creating the volcanoes and earthquakes that so clearly cluster along coasts. Many elder scientists, including virtually all of Lamont’s leaders, thought this was nonsense.
On a 1965 cruise to the Pacific and Antarctic, Pitman helped collect magnetic data around one such newly mapped feature, the Pacific-Antarctic Ridge. Pitman, then still a student, was only vaguely aware of plate-tectonic theory until he read a paper about it upon his return. But he did know that other researchers had recently shown that earth’s magnetic field periodically reverses polarity, and that each reversal could be read in the orientation of minerals within volcanic lavas that hardened at that time the reversal took place. Scientists including the young British geophysicist Fred Vine had spotted regular patterns of polarity reversals around some ridges, and argued that they proved the ridges were spreading. But the evidence was inconclusive.
In succeeding months, Pitman and another Lamont student, Ellen Herron, processed the data from their cruise and two others to the same region. After compressing it all, late one evening Pitman tacked up a simple penciled chart on a colleague’s door. It showed that the ridge was flanked on each side with a mirror-image series of stripes, each one indicating a new reversal of magnetic polarity. Combined with pre-existing data gathered by others, it neatly showed a series of reversals spanning 3.4 million years. The finding allowed him to calculate that the ridge was spreading by about 4.5 centimeters (1.75 inches) a year. “It was like being struck by lightning—we had this magic key,” Pitman later remembered. “Symmetry is just something you see—it doesn’t come over you gradually. I’m sure every science has their moments when things click and you say, ‘My gosh, that’s how it works!’ ”
In December 1966, Pitman and his advisor, James Heirtzler (up to then himself a continental drift opponent), published the findings in the leading journal Science. Vine wrote a complementary synthesis of support for the new theory. Nearly overnight, opposition dissolved. Soon afterward, Pitman and colleagues documented similar magnetic patterns around the world.
In 1974, based on collected observations, Pitman coordinated the assembly of a global map showing the ages of all the ocean basins and the trajectories of the continents over eons. “I didn’t imagine ever being involved in something so astonishing and so very, very important at such a young stage,” he said. “A whole bunch of us were working on it together, and together we accomplished a lot in just a few years.”
In the late 1970s, Pitman produced another series of influential papers showing how plate tectonics influences rates of sea-level change. Later, he investigated how sea levels influence the building of mountains on land.
Reaching these conclusions required looking at mountains of data, and Pitman was part of the computing revolution that allowed scientists to do this. He helped write some of the first software that allowed ocean researchers to put seafloor observations into digital format, then sort through it. However, he eschewed computers himself; colleagues often saw him sitting alone for hours at a drafting table, manipulating numbers on a hand-cranked calculator, trying to figure something out.
Pitman spent many months at sea. In an essay for the history book Plate Tectonics, he described the profound silence when a vessel cut its engines in the Antarctic. “The heavy layer of ice damped the waves, but they still rolled slowly, lifting the ice ever so gently a few inches and down again, perpetually groaning, as if the ice itself were alive,” he wrote. Conditions could be dangerous. A few years prior to Pitman’s first voyage, three crew members were swept off the Vema by heavy seas; only two were rescued. Pitman himself was once nearly washed off the ship by a giant wave, and survived only by clinging to a brace. While Pitman was on a cruise off Chile in 1961, the vessel’s chief scientist, John Hennion, was killed when a half-stick of dynamite he was preparing to throw overboard blew up on him. With a tangle of other explosives set afire by the blast, Pitman and a comrade turned a firehose on them, washing them across the deck and off the fantail, probably saving other crew members and preventing severe damage to the ship.
Colleagues described Pitman as a humble, friendly man, more at home telling yarns or helping out colleagues than discussing complex science. John LaBrecque, one of Pitman’s many students, said Pitman once calmed him down after a rival beat LaBrecque out of funding for a major project. Pitman took LaBrecque to a nearby driving range, and encouraged him to transfer his rage to the golf balls. Then Pitman found workaround financing to get the project done. Even for many years after Pitman formally retired in 1994, his Upper West Side New York apartment continued serving as a free hotel for many former students passing through town. One former student observed that before going for his daily walk from the apartment, Pitman would load his pockets with dollar bills to pass out to the homeless people lining Broadway.
At one point, Pitman became interested in the question of whether some current inland seas might once have been dry land. One candidate for this was the Black Sea, which connects to the much larger Mediterranean via Turkey’s narrow Bosporus Strait. In the 1970s, he and Lamont geologist William Ryan speculated that the Black Sea might have formed after the last Ice Age, when ocean levels rose, causing the Mediterranean to top a narrow neck of land blocking the Bosporus. They even speculated whether the story of the Biblical flood in the book of Genesis—Noah’s 40 days and 40 nights of rain—could have been inspired by such an event. They had a chance to circle back to this in 1993, when a Bulgarian oceanographer wrote to them with his own evidence that the Black Sea was once dry. Through personal connections, they wangled themselves onto a Russian research vessel investigating the Black Sea bottom.
Deep underwater, they spotted apparent remains of ancient beaches, and sediments showing a sudden switch from freshwater mollusks to saltwater ones, which they estimated took place around 5600 BC. Jumbled deposits near the Bosporus suggested a violent inrush of water at one time. Their conclusion: the rising Mediterranean flowed over the Bosporus neck first as a trickle, then with a force of 200 Niagara Falls. Rising water would have driven out humans and animals within weeks or months from the entire region that became the Black Sea—possibly the origin for the story of Noah and related Greek and Mesopotamian tales. Based on this, Pitman and Ryan produced several papers, and the popular 1998 book Noah’s Flood, which delved into geology, archaeology, linguistics and myth. It brought them a deluge of publicity. Opposing camps of scientists have since researched and debated the question, but never reached a consensus. Pitman and Ryan appeared as recently as 2015 in a British TV documentary about the flood.
Pitman received many honors, including the Vetlesen Prize in earth sciences, the American Geophysical Union’s Maurice Ewing Medal, and the National Academy of Sciences’ Alexander Agassiz Medal. In the 1990s, colleagues named a zigzagging seafloor fracture off Antarctica that Pitman discovered the Pitman Fracture Zone. Visitors to his office, which he kept well after his formal retirement, noted that instead of hanging the prizes on a wall, he kept them stacked unobtrusively on a windowsill.
Pitman’s marriage to the former Virginia Piser ended in divorce; he never remarried. He is survived by his brother Donald Pitman; two daughters, Amanda Pitman and Cordelia Pitman; and two grandchildren.