Oceanic ridges, magma filled cracks, and mantle plumes

Abstract

The author's model of the spreading of an oceanic ridge by injection of magma filled cracks into an oceanic plate is modified. Whereas in the original model the entire oceanic plate was considered to be cold and elastic now only the upper portion is assumed to have these properties. The lower part of the plate is taken to be hot and plastic, deformable by high temperature creep. Magma filled cracks freeze in place only in the cold upper part of theplate. If the spreading rate of a ridge is relatively fast a second magma chamber is likely to form under an oceanic ridge at the boundary between the elastic and the plastic portion of the oceanic plates.