ridges such as the MAR and the Mid-Indian Ocean Ridge follow the orientation of
the bordering continental masses.
Other differences between slow and fast spreading ridges are due to the depth
and degree of partial melting of their mantle source (Fig. 7.1). Mantle temperature
variations have an important effect on the extent of melting beneath oceanic ridges.
As mantle rises adiabatically, decompression melting will take place beneath
oceanic ridges, but this melting will be affected by plate separation rates. Fast plate
separation at the EPR is responsible for a large extent of melting ([22 %).
Ridge Segmentations
Ridge segmentations are the result of tectonic and magmatic processes that are
responsible for forming discontinuities along the strike of the oceanic ridges. The
existence of these ridge segmentations was inferred from bathymetric contour-line
variations and from subsurface structural and compositional changes observed
Fig. 7.1 Near-axial structural profiles across accreting ridge systems with different spreading
rates showing the variable sizes of their axial rift valleys (Choukroune et al. 1984)
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7 Oceanic Spreading Ridges and Sea Floor Creation