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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.
The discovery of mid-ocean ridges and the process of seafloor spreading allowed for Wegener's theory to be expanded so that it included the movement of oceanic crust as well as the continents. [49] Plate tectonics was a suitable explanation for seafloor spreading, and the acceptance of plate tectonics by the majority of geologists resulted in a ...
Why this theory is so significant is the interaction between the tectonic plates explains many geological formations. [8] In regards to marine geology, the movement of the plates explains seafloor spreading and mid-ocean ridge systems, subduction zones and trenches, volcanism and hydrothermal vents, and more.
Oceanic crust is formed at sea-floor spreading centers. Continental crust is formed through arc volcanism and accretion of terranes through plate tectonic processes. Oceanic crust is denser than continental crust because it has less silicon and more of the heavier elements than continental crust.
The Wilson cycle theory is based upon the idea of an ongoing cycle of ocean closure, continental collision, and a formation of new ocean on the former suture zone.The Wilson Cycle can be described in six phases of tectonic plate motion: the separation of a continent (continental rift), formation of a young ocean at the seafloor, formation of ocean basins during continental drift, initiation of ...
The depth of the seafloor on the flanks of a mid-ocean ridge is determined mainly by the age of the oceanic lithosphere; older seafloor is deeper. During seafloor spreading, lithosphere and mantle cooling, contraction, and isostatic adjustment with age cause seafloor deepening. This relationship has come to be better understood since around ...
At spreading boundaries where plates move apart, the asthenosphere decompresses and melts to form new oceanic crust. At subduction zones, slabs of oceanic crust sink into the mantle, dehydrate, and release volatiles which lower the melting temperature and give rise to volcanic arcs and back-arc extensions. Several volcanic provinces, however ...