Reading the Magnetic Record: Eight Scientists Who Made the Moving Earth Measurable

Begin with a physicist rather than a geologist. Patrick Blackett won the 1948 Nobel Prize in Physics for cloud chamber work, then turned in the 1950s to building sensitive magnetometers that could measure the residual magnetism held in sedimentary rocks. His paleomagnetic research gave new evidence for Wegener's continental drift when the idea was still widely doubted.

Stanley Keith Runcorn helped found paleomagnetism, the study of fossil magnetism in ancient rocks. His analyses of the apparent wander of Earth's magnetic pole, recorded in European rocks, supplied key early evidence for continental drift. He worked with Blackett and led the physics department at King's College, Newcastle upon Tyne.

Edward Bullard is regarded, with Maurice Ewing, as a founder of marine geophysics. In 1954 he announced that heat flow measured through the ocean floor was no different from that through continental crust, an unexpected result that pushed research toward plate tectonics. He also proposed that a dynamo in the convecting liquid iron of the outer core generates Earth's magnetic field.

Fred Vine, with Drummond Matthews, read the ocean floor as a tape recording. Their hypothesis, later joined by Morley's name, held that spreading from mid-ocean ridges freezes a symmetrical pattern of magnetic reversals into basalt on either side of a ridge, so parallel strips record Earth's past magnetic field as one moves away from the crest.

Allan Cox, working at the United States Geological Survey with Richard Doell and Brent Dalrymple, helped build the first accurate geomagnetic polarity time scale. The scale dated reversals of Earth's magnetic field recorded in volcanic rocks, and it became a major piece of supporting evidence for plate tectonics. He later became dean of Stanford's School of Earth Sciences.

Brent Dalrymple supplied the dating side of that work. His research covered the history of Earth's magnetic field and the development of radiometric dating methods, and he wrote The Age of the Earth and Ancient Earth, Ancient Skies. He served as president of the American Geophysical Union from 1990 to 1992 and received the National Medal of Science in 2003.

With Robert Parker, Dan McKenzie published a founding paper of plate tectonics in 1967, working out the mathematical principles for how rigid plates move on the surface of a sphere. His later work on mantle convection shaped understanding of how the layered mantle drives plate motion, and he has extended these ideas to Venus and Mars.

Finish with the first complete quantitative model. In a landmark 1968 paper, Xavier Le Pichon combined the kinematic ideas of W. Jason Morgan and Dan McKenzie with extensive magnetic survey data, worked out the geometry of plate motion on a sphere, and identified six major plates. He later led the French American Mid-Ocean Undersea Study of the Mid-Atlantic Ridge in 1973.