ABYSSAL HILLS FORMED BY STRETCHING OCEANIC LITHOSPHERE

Tectonic plates are formed and move apart at mid-ocean ridges. Some po rtion of this plate-separation process can occur by stretching of the crust, resulting in a complex pattern of extensional faults. Abyssal h ills, the most ubiquitous topographic features on Earth(1), are though t to be a product of this faulting(2,3). Here we report the results of a self-consistent numerical model of Lithospheric formation and stret ching that includes spontaneous fault creation, In this model, an axia l valley develops where the fault activity is most concentrated, The ' frozen' fault-generated topography, rafted out of the axial valley, is visually and statistically similar to observed abyssal hills formed a t many slower-spreading ridges. Faults appear to be replaced by new fa ults because their offset changes the local stress field, We according ly need no temporal variation in magmatism, as required by some previo us models(4-6), to control the spacing or offset of faults. Our model results suggest instead that the irregularity of abyssal hill relief m ay result from a self-organized critical stress state at spreading cen tres.