Ocean, spreading centre

Abstract

A midocean ridge, an underwater mountainous feature, extends for a length of about 65,000 km as a single continuous body in the global oceans. It is a window to the Earth’s interior, through which magma is continuously upwelling and drives the lithospheric plates on either side in order to accommodate newly accreted crust. Many of the oceanic ridges in the world oceans have been abandoned in the geologic past and led to resume the activity elsewhere either in the intra-oceanic or intracontinental plate regions. Partial melted mantle upwelled through the midocean ridge forms a layer of basaltic crust 3–6 km thick, but at a later stage the same crust moves away from the ridge crest and allows growth of mantle component. The upwelling magma rates along the mid-oceanic ridges, in general, control the internal structure. Fast spreading ridge such as East Pacific Rise has an axial magma chamber (AMC) at a shallow depth within the crust, whereas beneath an intermediate spreading ridge, the Mid-Atlantic Ridge, an axial magma chamber, is not traceable. Geophysical experiments over the global midoceanic ridges have found some explicit relationships between spreading rate, seismic structure, and ridge-axis morphology.