Ridge crests are roughly 700 m deeper at the equator than they are in high latitudes. The flanks of the East Pacific Rise show a similar latitude dependence. In addition, there are wavelike depth anomalies with heights of 0.7--1.0 km and wavelengths of 4000 km that extend across the Pacific and Nazca plates. They have long dimensions parallel to plate motions and except for wavelength resemble the anomalies predicted for horizontal convection cells.