The three main mid-ocean ridges aligned NS are separated by about 90° along equator. The division line of upper mantle directly above lower mantle division is according to analysis a downwelling one, so ocean ridges do not tend to appear exactly there. A good example is the Reykjanes Ridge, following the path 1.5° to the west of the main division of lower mantle. Therefore, the three ridges are as close to being 90° apart along equator as the system allows.
This is of course the theoretic distribution. The Mid-Atlantic Ridge is magnificent. But it is under the ocean like the other ridges.
Published by Steingrimur Thorbjarnarson
I am a geologist, graduated from the University of Iceland, and taught geology for a few years. I have gained some knowledge about Earth's inner structure, so I provide this website as my contribution to answer one of the greatest questions remaining within the realm of geoscience. Experiments show that the mantle should form convection rolls when close to the melting point. I took this literally, and calculated the dimensions and shape of these mantle convection rolls. Then I compare that model with the surface. This makes it possible to provide many interesting examples about geology found on my blog.
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