Hydrothermal vents on an axis seamount of the Juan de Fuca ridge

Abstract

The Juan de Fuca Ridge, a 500-km section of the mid-ocean ridge system, is bounded by the Sovanco and Blanco fracture zones^1,2. Although the ridge spreads at a medium rate (29 mm yr⁻¹ halfrate)³, a significant portion of its crest has a morphology typical of faster spreading ridges; the axial valley is 1–2 km wide within a central horst structure⁴. The ridge crest shoals to 1,500 m at the intersection with the Cobb–Eickelberg Seamount chain forming a broad edifice called ‘Axial Seamount’ (Fig. 1). Previous studies both north and south of Axial Seamount demonstrated hydrothermal activity associated with the shallowest portions of each of the ridge segments along the Juan de Fuca^5–9, a similar coincidence to that noted for the East Pacific Rise¹⁰. We report here the results of the first manned submersible expedition to the Juan de Fuca Ridge, which found hydrothermal activity and at least 14 new vent animals in the caldera of Axial Seamount.