National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 1996

Processes and fluxes on a superfast spreading ridge: The southern East Pacific Rise

Mottl, M.J., E.T. Baker, K. Macdonald, J. Sinton, and G. Wheat (convenors)

In RIDGE Workshop Report, 12–14 January 1996, 36 pp (1996)


From its inception, the RIDGE Program has included among its primary goals the identification of relationships among magmatic, tectonic, and hydrothermal processes along the global mid-ocean ridge system. As one of the fastest spreading ridges on earth, the southern East Pacific Rise promises to yield important insights into these processes and their accompanying fluxes. Associated with the superfast spreading rate are high rates of crustal formation and hydrothermal heat loss. These high rates imply high frequencies of key events, including earthquakes, rifting and faulting, magma intrusion, diking, volcanic eruptions, and hydrothermal perturbations, all of which can be expected to influence the vent biological communities. The southern East Pacific Rise also possesses unique tectonic characteristics that are probably related to spreading rate. It has long, straight segments that exhibit a wide variation in tectonic, magmatic, and hydrothermal characteristics, including clear evidence for plate reorganization. It displays highly asymmetric spreading and subsidence, and it has abundant off-axis volcanism. It also is the site of the RIDGE Mantle ELectromagnetic and Tomographic (MELT) experiment, designed to elucidate the structure and melt distribution in the upper mantle beneath a spreading axis. The RIDGE Workshop on Processes and Fluxes on a Superfast Spreading Ridge: The Southern East Pacific Rise was convened to exchange information about current and planned fieldwork on the southern East Pacific Rise, to identify the major outstanding problems regarding mid-ocean ridge processes and fluxes that can be solved along superfast spreading ridges, and to develop ideas and long-range plans for solving them. It brought together 50 geologists, geophysicists, petrologists, geochemists, and biologists. This report summarizes their discussions, including the present state of knowledge about the southern East Pacific Rise, the outstanding scientific problems, and recommended future research to address these problems.

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