Depth anomalies in the Pacific: Active, fossil and precursor

Previously unreported depth anomalies in the central and eastern Pacific are described. Some of these depth anomalies exist over hot spots and propagating spreading ridges; they are not limited to the area of active volcanism but extend beyond it, into the areas toward which the volcanism is propagating. These areas may be “precursor” topographic features, showing up areas of impending or potential mid-plate volcanism or spreading. A distinction can be made between active depth anomalies and fossil ones. Gravity anomalies and high heat flow values can be correlated with active depth anomalies in one area, supporting the arguments favoring a thinning of the lithosphere as their underlying cause.