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Mid-ocean ridges around the globe are linked by plate tectonic boundaries and the trace of the ridges across the ocean floor appears similar to the seam of a baseball. The mid-ocean ridge system thus is the longest mountain range on Earth, reaching about 65,000 km (40,000 mi).
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.
The motivating force for seafloor spreading ridges is tectonic plate slab pull at subduction zones, rather than magma pressure, although there is typically significant magma activity at spreading ridges. [3] Plates that are not subducting are driven by gravity sliding off the elevated mid-ocean ridges a process called ridge push. [4]
Diagram of a mid-ocean ridge showing ridge push near the mid-ocean ridge and the lack of ridge push after 90 Ma. Ridge push is the result of gravitational forces acting on the young, raised oceanic lithosphere around mid-ocean ridges, causing it to slide down the similarly raised but weaker asthenosphere and push on lithospheric material farther from the ridges.
Plate tectonics is a scientific theory developed in the 1960s that explains major land form events, such as mountain building, volcanoes, earthquakes, and mid-ocean ridge systems. [26] The idea is that Earth's most outer layer, known as the lithosphere, that is made up of the crust and mantle is divided into extensive plates of rock.
The simple result is that the ridge height or seabed depth is proportional to the square root of its age. [4] In all models, oceanic lithosphere is continuously formed at a constant rate at the mid-ocean ridges. The source of the lithosphere has a half-plane shape (x = 0, z < 0) and a constant temperature T 1.
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]
This paradoxically results in divergence which was only incorporated in the theory of plate tectonics in 1970, but still results in net destruction when summed over major plate boundaries. [2] Divergent boundaries are areas where plates move away from each other, forming either mid-ocean ridges or rift valleys. These are also known as ...