Discontinuities in sea-floor spreading

Abstract

Time variations in the rate and direction of sea-floor spreading, though relatively slight, have occurred simultaneously along much of the Mid Oceanic Ridge at intervals of 10–30 million years. Various criteria by which such discontinuities might be recognized are examined. The recent discovery that transform faults, at least those of small offset, may be created and destroyed repeatedly during the life of an ocean basin suggests several physical models for the creation and destruction of such faults. The shape of the Mid-Oceanic Ridge may represent a minimum-work configuration for a particular spreading rate and direction. When these quantities change the ridge shape adjusts itself to a new configuration if the energy barrier is not too great. The rotation of a ridge segment with respect to the spreading direction may require several million years and depends on spreading rate, ridge orientation, and fracture spacing. Observed rotation rates are about one third or one half the theoretical maximum.