Harold Jeffreys

Harold Jeffreys (1891–1989) was a British geophysicist and mathematician whose calculations challenged continental drift and whose work helped establish modern statistical methods.

Alfred Wegener: German meteorologist who proposed that continents move across Earth’s surface. Wegener proposed continental drift; Jeffreys rejected its proposed physical mechanisms.
Continental drift: The hypothesis that continents move over geological time relative to one another. Jeffreys argued that proposed forces could not move continents through the strong oceanic crust.
Seismology: The study of earthquakes and the waves they generate. Jeffreys used seismic-wave travel times to investigate Earth’s internal structure.
Continental drift controversy: The early twentieth-century scientific debate over whether continents move across Earth’s surface. Jeffreys became one of drift’s most prominent critics, grounding opposition in physical calculations.
Arthur Holmes: British geologist who proposed mantle convection as a mechanism for continental drift. Holmes offered the mantle-convection mechanism that Jeffreys considered physically inadequate.
Mantle convection: Slow circulation of Earth’s solid mantle driven by internal heat. Convection became Holmes’s proposed engine for continental motion, but Jeffreys disputed its ability to drive drift.
Earth's core: Earth’s central region, consisting of a liquid outer core and solid inner core. Jeffreys helped establish the seismic evidence that the outer core is liquid.
Seismic tomography: A method that reconstructs images of Earth’s interior from seismic-wave measurements. Jeffreys’s seismic work helped lay quantitative foundations for imaging Earth’s interior.
George Gamow: Ukrainian-born theoretical physicist known for work in nuclear physics and cosmology. Gamow publicly disputed Jeffreys’s resistance to continental drift in a 1940s scientific exchange.
Earth's mantle: The thick layer of silicate rock between Earth’s crust and core. Jeffreys’s mechanical objections concerned the strength and flow of mantle and crustal materials.

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