European Union of Geosciences

Alfred Wegener Medal

Xavier Le Pichon For his central role in establishing Wegener's ideas.

Xavier Le Pichon is one of the founders of the modern theory of Plate Tectonics. In 1968 he combined the kinematic ideas of W.J. Morgan, D. McKenzie and R.L. Parker with the large data sets collected by Lamont, and especially with the magnetic profiles, to show that Plate Tectonics could accurately describe the evolution of the major ocean basins. He showed that Wegener's ideas were correct, and that they could account for many puzzling features of the ocean basins. He carried out this work at Lamont shortly before returning to France, where he founded the first modern school of Marine Geology and Geophysics in France. With two younger colleagues he also wrote what was for many years the standard reference book on Plate Tectonics, which is still one of the best books on the subject.

Xavier Le Pichon later became a leading figure in the exploration of the deep sea with submersibles. In 1973 he led the French American Midocean Ridge Study (FAMOUS), together with Jim Heirtzler and Bob Ballard. This marked the beginning of a new type of high resolution study of the mid ocean ridges and their hydrothermal systems. From 1979 to 1981 he extended this method of exploration to the deep-sea trenches in the eastern Mediterranean, and in 1984 to the Pacific trenches of the coast off Japan. He showed that the role of fluids in these environments is not only important for earthquakes, but also affects the geochemistry of the oceans and supports the strange biological communities that are associated with the deep sea vents. He is now using Space Geodesy to study the elastic deformation that precedes earthquakes.