This project will use gravity and bathymetry data from a large number of detailed surveys of ridge axes with spreading rates that vary by an order of magnitude to examine the spreading rate dependence of mantle bouguer anomalies at mid-ocean ridges crests. The spreading rate dependence of the along-axis segmentation of the ridge axis will be examined and the transition between patterns observed at slow-spreading ridges and fast-spreading ridges will be determined. The spreading rate dependence of isostasy and the support of ridge axis topography will also be examined.