Abstract
A recent study of abyssal hills in the North Pacific has shown that some hills can be formed by local tectonism and volcanism in the crustal plate at some distance from the ridge crest. Hills formed under these circumstances are larger than those formed at the ridge crest, and show lineations parallel to or oblique to the fracture zones bounding the crustal segments. Strike-slip motion along the fracture zones due to differential spreading rates is apparently responsible for the development of the hills. An application of structural analyses to the hills may help to define periods of more active spreading.