Gravity Anomalies over Ocean Ridges

Abstract

The presence of positive free‐air gravity anomalies over ocean ridges is supported by both the global solutions derived essentially from satellite observations and by surface measurements. The anomalies over the ridges observed by the satellite solutions are described by the harmonics of degree 8 or 9 and higher and they can be supported statically if maximum shear stresses in the lithosphere of about 1200 or 1500 bars are possible. This is not entirely ruled out by the limited information available. Thus in interpreting the global gravity field, the role of the lithosphere as a layer of finite strength cannot be ignored. A decrease in the amplitude of the anomalies over the ocean ridges with increasing spreading rate is tentatively suggested although further analyses, particularly of surface data, are required. The surface measurements indicate anomalies over the ridges that are of shorter wavelength than those observed in the satellite solutions. These anomalies can be explained by the thermal expansion of the lithosphere at the ridges, suggesting that gravity measurements can be used as constraints on the lithospheric models in the same was as heat flow and topography measurements. Copyright © 1972, Wiley Blackwell. All rights reserved