Analysis of seafloor depth anomalies arround the south Ascension Island, South Atlantic

Observed seafloor depths from 12 kHz bathymetry coupled with seafloor spreading magnetic anomalies are used to derive depth anomalies across the Mid-Atlantic ridge axis between 2oS and 18oS. Theoretical seafloor depths are based on the plate cooling model and crustal ages depicted from magnetic anomalies between the zero age to 25 Ma. The magnetic anomalies are symmetric with respect to the ridge axis in the region, but the depth anomalies are quite asymmetric. The east side of the ridge axis is shallower (~ 1,000 meters) than the west side, probably as a result of an upwelling of thermal structure of the lithosphere. This type of thermal anomaly may be caused by a mantle plume located on the African Plate, which could well represent a larger swell linked to St. Helena Island and Fernando Pó-Annobon Volcanic Lineament as well.