Born in Quinhon (Quy Nhơn) on June 18, 1937, died on March 22, 2025. Xavier Le Pichon was a pioneer in research into the expansion of the ocean floor and continental drift, from the understanding of our planet's global functioning to the study of its local expressions such as earthquakes. He held the Geodynamics Chair at the Collège de France from 1986 to 2008.
Xavier le Pichon defended his thesis on the structure of the Mid-Atlantic Ridge in Strasbourg in 1966. He joined Maurice Ewing's team at the Lamont-Doherty Observatory (USA) in the late 1960s, at a time when systematic observation of the ocean floor was uncovering mid-ocean ridges, trenches and what would soon be known as transform faults, and when continental drift and expansion of the ocean floor had been proven by paleomagnetists, he followed in the footsteps of Harry Hess, Fred Vine, Drummond Matthews, Tuzo Wilson, Dan McKenzie and Jason Morgan to propose the first global quantitative model describing the relative displacements of the main tectonic plates and reconstructing the evolution of the Atlantic since the Cretaceous, in a seminal article in the Journal of Geophysical Research in 1968. The book he subsequently published with Jean Bonnin and Jean Francheteau, entitled "Plate Tectonics", in 1973, remains an indisputable record of this major scientific revolution, which created the geodynamic framework within which we have all been working ever since.
Back in France, he continued to study the displacements and deformations of the lithosphere, with major advances in the mechanisms of rifting, subduction and collision, seismic coupling in subduction zones, and the realization of the importance of space geodesy in understanding active continental deformation. He played a major role in the restructuring of French oceanography, which soon became one of the best in the world. Starting with the creation of the forerunner of IFREMER, in Brest, and then as a professor at the Pierre et Marie Curie University and the Ecole Normale Supérieure, he organized a large number of campaigns at sea to further explore the ocean floor, all of which produced significant results. To mention just three of these projects organized within the framework of international cooperation, we should mention the FAMOUS campaign, a Franco-American program, the first diving exploration of the Mid-Atlantic Ridge using the CYANA and ALVIN submersibles, and the HEAT campaign to explore the Hellenic Trenches, the first diving campaign in a subduction trench, and the Franco-Japanese Kaiko and Kaiko-Tokai campaigns to explore the trenches around Japan, combining surface geophysics and diving using a new submarine, the Nautile, descending to -6000m. His unwavering commitment to the study of the oceans made him one of the great explorers of the 20th century. France's eminent place among nations in the fields of tectonics and oceanography owes much to him.
A member of the Académie des Sciences, Xavier Le Pichon ended his career as a professor at the Collège de France, where his lectures on geodynamics over the years are still remembered. Long before this consecration, he was a renowned professor who enthused many students at UPMC (now Sorbonne University) about the dynamics of the lithosphere and the study of its physical processes. He was also a brilliant and demanding boss, always encouraging his students and collaborators to pursue their intuitions, and providing them with the means to work and make their mark in the highly competitive world of research.
His scientific work was rewarded with numerous national and international prizes and medals, including the Wollaston Medal of the Geological Society of London, the Japan Prize and the Balzan Prize. He recounted his experiences at sea in several books, including "3000 m sous l'Atlantique" (Albin Michel) about the FAMOUS expedition, "Voyage aux extrémités de la mer" about the Kaiko program, and more philosophical works on death, "Aux racines de l'homme : de la mort à l'amour" (Presses de la Renaissance) and "La mort" with Tang Yi Jie (Desclée de Brouwer).
He had a major impact on French earth sciences. His students perpetuate his approach to oceanic domains, and many other teams benefit from the exploration tools he helped create.
Source: CNRS-INSU, 2025
