Inverse square-root dependence of mid-ocean-ridge flank roughness on spreading rate

Abstract

THE topographic roughness of mid-ocean-ridge flanks is known to increase with decreasing spreading rate1–4, but the exact form of this relationship has not been established. As the topographic features that make up ridge flank roughness (abyssal hills) are created near the axes of mid-ocean ridges by faulting and volcan-ism5–7, the relationship between roughness and spreading rate may shed light on the process of crustal accretion at spreading centres. Here I present measurements of ridge flank roughness on profiles crossing the world mid-ocean-ridge system, which show that roughness is proportional to the inverse square-root of the spreading rate. This result is consistent with some very simple inferences of how the topographic roughness of mid-ocean-ridge flanks scales with the lithospheric thickness near ridge axes, as determined by thermal models.