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Harry Hess proposed the seafloor spreading hypothesis in 1960 (published in 1962 [1]); the term "spreading of the seafloor" was introduced by geophysicist Robert S. Dietz in 1961. [2] According to Hess, seafloor was created at mid-oceanic ridges by the convection of the Earth's mantle, pushing and spreading the older crust away from the ridge. [3]
Spreading rate is the rate at which an ocean basin widens due to seafloor spreading. (The rate at which new oceanic lithosphere is added to each tectonic plate on either side of a mid-ocean ridge is the spreading half-rate and is equal to half of the spreading rate). Spreading rates determine if the ridge is fast, intermediate, or slow.
Robert Sinclair Dietz (September 14, 1914 – May 19, 1995) was an American scientist with the United States Coast and Geodetic Survey.Dietz, born in Westfield, New Jersey, [1] was a marine geologist, geophysicist and oceanographer who conducted pioneering research along with Harry Hammond Hess concerning seafloor spreading, published as early as 1960–1961.
Beginning in 1947 research provided new evidence about the ocean floor, and in 1960 Bruce C. Heezen published the concept of mid-ocean ridges. Soon after this, Robert S. Dietz and Harry H. Hess proposed that the oceanic crust forms as the seafloor spreads apart along mid-ocean ridges in seafloor spreading. [38]
The samples gave further evidence to support the plate tectonics theory, which at the time attempted to explain the formation of mountain ranges, earthquakes, and oceanic trenches. [6] Another discovery was how youthful the ocean floor is in comparison to Earth's geologic history.
1963: In a major advance in the development of plate tectonics theory, the Vine–Matthews–Morley hypothesis was independently proposed by Lawrence Morley, and by Fred Vine and Drummond Matthews, linking seafloor spreading and the symmetric "zebra pattern" of magnetic reversals in the basalt rocks on either side of mid-ocean ridges. [101]
Evidence from paleomagnetism led to the revival of the continental drift hypothesis and its transformation into the modern theory of plate tectonics. Apparent polar wander paths provided the first clear geophysical evidence for continental drift, while marine magnetic anomalies did the same for seafloor spreading .
Evidence of seafloor spreading has been seen in cores of the basin floor. The thickness of sediment that collected in the basin decreased toward the center of the basin, indicating a younger surface. The idea that thickness and age of sediment on the sea floor is related to the age of the oceanic crust was proposed by Harry Hess. [5]