Geophysics, which studies the physics of the Earth, has led to many significant discoveries about the Earth and its make-up. Seismologic studies of the Earth have uncovered new information about the interior of the Earth that has helped to give credence to plate tectonic theory.
Significant progress was made in the 1960s, and was prompted by a number of discoveries, most notably of the Mid-Atlantic ridge. The most significant paper was the 1962 publication by American geologist Harry Hammond Hess (Robert S. Dietz published the same idea one year earlier in Nature. However, priority belongs to Hess, since he had already distributed an unpublished manuscript of his 1962 article by 1960). Hess suggested that instead of continents moving through oceanic crust (as was suggested by continental drift) that an ocean basin and its adjoining continent moved together on the same crustal unit, or plate. In the same year, Robert R. Coats of the U.S. Geological Survey described the main features of island arc subduction in the Aleutian Islands. His paper, though little-noted (and even ridiculed) at the time, has since been called "seminal" and "prescient". In 1967, W. Jason Morgan proposed that the Earth's surface consists of 12 rigid plates that move relative to each other. Two months later, in 1968, Xavier Le Pichon published a complete model based on 6 major plates with their relative motions.
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