Observations from 145 submersible dives are used to create a database of mid-ocean ridge scarp topography and lithology. Seafloor types are classified into extrusives, basaltic talus, dykes, gabbros and serpentinites, and the dive locations are broadly classified according to whether they are close to transform valleys and according to ridge spreading rate. The database is used to determine whether there is any difference in the maximum slope for each rock type, which might relate to differences in rock jointing, cohesion or friction properties. We find a tendency for gabbro and dykes to form steeper slopes than serpentinite. The 90th percentile of each lithology slope distribution, used as a measure of limiting slope, is 43, 39 and 32 degrees for gabbro, dykes and serpentinite, respectively. Lithologic control on slope is weak, however, compared to overall slope variability in these mid-ocean ridge settings so seafloor relief is likely to be a poor guide to underlying geology. We speculate on the structure of eroding fault scarps, with implications for attempts to infer active faults from talus ramp activity, and discuss more generally factors affecting the geomorphology of mid-ocean ridge slopes.
N. C. Mitchell, M. A. Tivey and P. Gente,
Seafloor slopes at mid-ocean ridges from submersible observations and implic
ations for interpreting geology from seafloor topography
Earth Planet. Sci. Lett., 183, 543-555, 2000.