Marcus Gerhardt Langseth, a pioneering earth scientist at Columbia University's Lamont-Doherty Earth Observatory for 40 years, died Saturday, January 4, 1997, at his home in Palisades, N.Y. He was 64.
The cause was lung cancer, said his wife, Lillian Langseth.
In the late 1950s and early 1960s, Dr. Langseth, working at Lamont with Robert "Sam" Gerard and the observatory's founder, Maurice Ewing, developed one of the first modern instruments and techniques for measuring the flow of heat through the Earth's upper layers. On numerous cruises in the 1960s aboard Columbia's legendary research vessel, the Vema, he gathered heat-flow measurements from all the world's oceans. With these data, he and Richard Von Herzen at the Woods Hole Oceanographic Institution compiled the first global map of how and where heat flowed near the Earth's surface.
The picture they painted helped prove the emerging theory of plate tectonics and demonstrated how the ocean floor evolved. Dr. Langseth's global heat-flow explorations also ultimately led to the remarkable discovery of hydrothermal vent systems at the mid-ocean ridges, where 700-degree geysers of mineral-rich water support extraordinary biological communities.
Between 1966 and 1975, Dr. Langseth headed the Apollo Lunar Heat Flow Experiment, in which he adapted his devices to measure the deep structure and evolution of the moon. In spite of a series of mishaps, including a misstep by an astronaut, the experiment proved that Earth's satellite had dissipated much of its original internal heat and showed no signs of recent volcanic activity.
Dr. Langseth was born in Lebanon, Tenn., on Nov. 24, 1932. His parents separated three years later under Depression-era strain, and he lived with his siblings until age 12 in the Monroe Children's Home in Nashville, where his mother was subsequently employed.
In the summer of 1953, he walked into the newly-founded Lamont Observatory seeking summer employment. He was hired the same day to work with the pioneering seismologist Jack Oliver, who was recording seismic waves of explosions being set off to build the nearby Palisades Parkway. After graduating with a B.S. degree from Waynesburg College in 1954, he returned to Lamont for the summer and joined the staff full-time in 1955. After a two-year stint in the Army from 1956 to 1958, he came back to the Columbia observatory as a research staff assistant and the following year decided to pursue graduate studies under Lamont Director Ewing.
"In those days, graduate students were sent out to sea with a mission to collect as much data from as many instruments as possible from every ocean," said Walter C. Pitman III, special research scientist at Lamont, who was a shipmate of Dr. Langseth's on many of those pioneering voyages. While Dr. Pitman became an expert on magnetic data that confirmed seafloor spreading, Dr. Langseth was assigned the task of launching a research program to collect global seafloor heat-flow measurements, until then poorly known.
"The heat-flow instruments were difficult to build, operate, maintain and make sense of," Dr. Pitman said. Dr. Langseth developed an archetypal heat-flow probe that solved many of the problems and greatly improved measurements. It was called the "outrigger" design because the probes attached directly to piston corers that sampled seafloor sediments, like the spars of an outrigger canoe.
"It was a great advance in heat-flow research," Dr. Von Herzen said, and it still provides a model for today's heat-flow instruments.
The new measurements from the world's oceans showed that oceanic rocks were not much colder than continental rocks, which surprised many scientists who had assumed that continental rocks would be much hotter because they are rich in heat-generating radioactive elements. The explanation was that high heat flowed at the mid-ocean ridges, where molten rock rises from the mantle and solidifies to create new seafloor. Dr. Langseth's heat-flow evidence provided corroborating evidence of the heat engine that drives plate tectonics: As young seafloor spreads out from mid-ocean ridges, it gradually cools until it becomes dense enough to sink back into the mantle, 200 million years after its birth.
In the early 1970s, Dr. Langseth and his heat-flow research group at Lamont made the surprising discovery that ocean sediments at the very apex of mid-ocean ridges - the apparent fount of rising hot magma - were cold. Intrigued by this enigmatic finding, scientists dispatched the submersible Alvin to a ridge summit for closer investigations. They found the first hydrothermal vents, which spewed superheated water into the cold, deep ocean and allowed heat to escape. The mineral-rich vents also nourished communities of animals unseen until then that thrived without sunlight.
Even before Dr. Langseth earned his Ph.D. degree at Columbia in 1964, he was already among the world's few heat-flow experts, so he was asked to lead the lunar heat-flow experiments. For the hard lunar surface, he helped design special drill equipment to insert the heat-flow probes, which were also specially designed to operate in the moon's airless atmosphere. The instruments were first placed aboard the ill-fated Apollo 13 mission. On the Apollo 15 mission, an obstruction kept the probe at only half its intended depth. On Apollo 16, the instrument was set up and ready to go when an astronaut, walking in a bulky spacesuit and unable to see his feet, accidentally tripped and cut the cable leading to the probe. The experiment was eventually conducted on the final Apollo 17 mission and it confirmed that the moon had lost much of its internal heat long ago. Dr. Langseth was given NASA's Special Achievement Award.
Dr. Langseth continued his heat-flow studies until this year, most recently finding unusual patterns in subduction zones where plates descend into the mantle. In the 1990s, he chaired a scientific committee that organized the first unclassified scientific missions aboard Navy nuclear-powered submarines. Three missions so far to the Arctic Ocean have given scientists a wealth of new data on a region where permanent ice and frigid weather have deterred extensive exploration in the past.
In 1993, Dr. Langseth was appointed Palisades Geophysical Institute Senior Scientist at Lamont. He was also an adjunct professor of earth and environmental sciences at Columbia. Dr. Langseth married Lillian Protz in 1963 and lived in Palisades. In addition to his wife, he is survived by two sisters, Christine Benagh in Nashville and Elva Corbitt in Lewisville, Texas. A memorial service will be held at 2 P.M., Saturday, January 11, in the Palisades Presbyterian Church. In lieu of flowers, the family requests donations be made to any local hospice.
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