Off Axis Volcanic Fields in an Ultraslow Spreading Ridge


DOEI Funded Project: 2008

We seek to document the evidence for extensive explosive volcanic fields in the  northern rift mountains of the ultraslow spreading SW Indian Ridge (SWIR) 9° to 16°E. Explosive volcanism is only now being recognized as a potentially widespread and important expression of magmatic activity along the global mid-ocean ridge system, and many aspects of how such processes occur remain unknown. We will examine the geochemical characteristics of dredged pyroclastic and volcaniclastic rocks from the area in order to verify that they were erupted locally, rather than being glacial erratics originating at the South Sandwich Islands, as was previously supposed. We will also characterize the petrologic and microtextural characteristics of the rocks to provide insight into the nature of the explosive volcanic processes. In concert with rock analyses, we will process and analyze sea-surface collected multibeam bathymetry and backscatter data to characterize the morphology of the explosive volcanic terrain and make comparisons to the adjacent rift valley and conjugate seafloor south of the axis that show no evidence for explosive volcanism. These data would then be used to write a preliminary paper documenting this entirely unique form of volcanism previously thought to be restricted to terrestrial sub aerial environments, and set the stage and provide the justification for a proposal to investigate this region in detail with deep submergence vehicles and a more extensive rock dredging program that we plan to submit to NSF-OCE upon the completion of this work (August 15, 2008 or Jan 15 2009).