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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.
This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin. The production of new seafloor and oceanic lithosphere results from mantle upwelling in response to plate separation.
The Vine–Matthews–Morley hypothesis, also known as the Morley–Vine–Matthews hypothesis, was the first key scientific test of the seafloor spreading theory of continental drift and plate tectonics. Its key impact was that it allowed the rates of plate motions at mid-ocean ridges to be computed.
With a seafloor spreading rate of about 20–40 km/million years, this represents a sediment accumulation rate of approximately 100–200 m every 25–50 million years. [1] The diagram at the start of this article ↑ shows the distribution of the major types of sediment on the ocean floor. Cosmogenous sediments could potentially end up in any ...
The East Pacific Rise near Easter Island is the fastest spreading mid-ocean ridge, with a spreading rate of over 15 cm/yr. [2] The Pacific plate moves generally towards the northwest at between 7 and 11 cm/yr while the Juan De Fuca plate has an east-northeasterly movement of some 4 cm/yr. [3]
A propagating rift is a seafloor feature associated with spreading centers at mid-ocean ridges and back-arc basins. [1] They are more commonly observed on faster rate spreading centers (50 mm/year or more). [2] These features are formed by the lengthening of one spreading segment at the expense of an offset neighboring spreading segment. [3]
Spreading in the SWIR is slow, but the plate boundary is intersected by the much slower but more diffuse Nubian–Somalian boundary. [5] The variation in spreading rates indicate the SWIR is not a spreading centre between two rigid plates, but that the previously assumed single African plate north of the SWIR is in fact divided into three plates: the Nubian, Lwandle, and Somalian plates.
The west section has 2 spreading segments running north to south with spreading rates that approximately range from 120 to 140 millimetres (4.7 to 5.5 in)/yr. These segments are connected by sinistrally slipping transform faults around 14°15' S. [ 5 ] A relay basin runs north to south along the southernmost segment as a result of past counter ...