ONR seafloor natural laboratories on slow- and fast-spreading mid-ocean ridges

Abstract

Long-term Natural Laboratories for in-depth studies of the seafloor at both a slowspreading (<30 mm/yr) and a fast-spreading (>60 mm/yr) mid-ocean ridge are being established by the Office of Naval Research. The two Natural Laboratories were selected for their representativeness of global mid-ocean ridge environments, and for their logistic accessibility. The Natural Laboratory region for the slow-spreading regime is on the Mid-Atlantic Ridge from Kane Fracture Zone north to about 27°30″N (Figure 1), and the fast-spreading counterpart is on the East Pacific Rise at about 8°–10°30″N, from Siqueiros to Clipperton Fracture Zone (Figure 2). Together, the two Natural Laboratories include most significant geologic variables that are thought to control both the shape and structure of the igneous crust and the scatter of acoustic wavefields from the bottom/subbottom (BSB) at low angles of incidence.