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8°20’N Seamounts, East Pacific Rise

In the fall of 2016, we used the DSV Alvin Submersible to explore the 8°20’N seamount chain in the Pacific Ocean.  This chain extends ~200 km westward from the East PacificRise near the intersection of the ridge and the Siqueiros transform fault.  During this research cruise, we completed a geophysical survey (multi beam, gravity and magnetics) of these volcanic constructions to directly test hypotheses for 3D melt generation and transport in the mantle off-axis. We will utilize petrologic and geochemical analyses of rock samples collected by Alvin and through a series of dredges in conjunction with morphological and geophysical data to develop models for melt generation and magma evolution off-axis at a fast-spreading mid-ocean ridge.

graph showing seamount data
New bathymetric data of the 8°20′ N seamounts.


In total, we collected 374 basalts during 15 Alvin dives and 19 dredges.  In the coming years, we will measure the major content of all lavas and trace element and radiogenic isotope ratios on a subset of lavas. Compositional data will be compared to maps and photographs to better understand the petrogenesis of the seamounts.