Identifying Characteristic and Anomalous Mantle From the Complex Relationship Between Abyssal Hill Roughness and Spreading Rates

Abstract

AbstractThe dependence of abyssal hill roughness on mid‐ocean ridge (MOR) spreading rate is an important indicator for faulting and volcanism. I reanalyze this relationship using a global gravity‐based prediction of root‐mean‐square (RMS) heights, enabling dense sampling of RMS/spreading rate space and thus a far more detailed examination than possible with bathymetric data. RMS histograms are multimodal, indicating previously unrecognized complexity in roughness versus spreading rate that cannot be characterized by a single trend. Modal peaks are used to define four different types of abyssal hills, three of which can be associated with axial valley, transitional, and axial high MOR morphology. The most abundant type at any one spreading rate bin is used to define a “characteristic” trend that transitions abruptly from axial valley to axial high types across half rates of ~20 to 30 mm/yr. Abyssal hills outside this trend are associated geographically with anomalously “hot” and “cold” mantle regions.