Thursday, January 11, 2018

The Giants of Continental Drift & Plate Tectonics

Some of milestones in the development and acceptance of the theory of plate tectonics. Note that the dates may represent a period rather than one specific year. Also, the work may have been carried out at more than the one location given.

1858. Antonio Snider-Pellegrini (American geographer living in Paris).  Constructed maps that demonstrated how the American and African continents once fit together and later separated. Based on plant fossils in both Europe and America that were identical.
1914.  Joseph Barrell (Yale).  Developed an earth model based on the presence of gravity anomalies over continental crust. He inferred that there must exist a strong, solid upper layer (the “lithosphere”) above a weaker layer which could flow (the “asthenosphere”).
1915.  Alfred Wegener (University of Hamburg). Hypothesized that the continents are slowly drifting around the Earth, based on the observation that the various large landmasses almost fit together like a jigsaw puzzle.
1919.  Arthur Holmes (University of Durham).  Proposed that the earth's mantle contained convection cells that dissipated radioactive heat and moved the crust at the surface.
1935.   Boris Choubert (French Research Institute for Development).  Published a reconstruction of the relative positions of America, Africa and Europe, based on the 1000-meter isobath which produced a better representation of the limits of the continents.
1951.  Keith Runcorn (Cambridge) & P.M.S. Blackett (Imperial College).  Compiled paleomagnetic reconstructions of the relative motions of Europe and America which revived the theory of continental drift and was a major contribution to plate tectonics.
1953.  Maurice Ewing, Marie Tharp and Bruce Heezen (Lamont-Doherty Earth Observatory of Columbia University).  Carried out detailed mapping of the Mid-Atlantic Ridge using seismic surveying, coring etc.
1962.  Harry Hess (Princeton). Proposed that the seafloor itself moves, carrying the continents with it, as it expands from a central axis.
1963.  Frederick John Vine (Cambridge).  Showed that magnetic reversals frozen into the sea floor rocks can be seen as parallel strips as you move perpendicularly away from the ridge crest.
1965.  John Tuzo Wilson (University of Toronto).  Proposed the transform fault, a major plate boundary where two plates move past each other horizontally (e.g. the San Andreas Fault).

1968.  Xavier Le Pichon (Collège de France, Paris). Developed a complete model based on six major plates with their relative motions, which marked the final acceptance by the scientific community of plate tectonics.