Abstract

Digital seafloor imagery collected on 37 camera tows and Alvin dives, in which we identify 186 contacts between new and old lava, are used to create the most detailed map of a mid-ocean ridge (MOR) eruption to date. Lava flows erupted in 2005–2006 at the East Pacific Rise (EPR) covered an area of 14.6 km2 along ∼18 km of the EPR crest between 9°46′ and 9°56′N. The 2005–2006 lava is characterized by inflated lobate and sheet morphologies in the flow interiors and pillow forms at terminal flow fronts. Numerous lava channels ∼10–50 m wide and 1–5 m deep trending approximately east-west served as distributory pathways. Eruptions were sourced from fissures within the EPR axial summit trough as well as fissures located on an off-axis fissure mound ∼600 m east of the EPR axis between 9°52′ and 9°56′N. Portions of the lava flow reached as far as ∼2 km east of the axis near 9°51.2′N. Using a conservative estimate of 1.5 m for the average flow thickness implies that the 2005–2006 eruptions produced ∼22 × 106 m3 of lava, 4–5 times larger than estimated volumes of 1991–1992 EPR lava flows. Estimated lava volume for the 2005–2006 eruptions represents <15% of the magma available in the axial magma chamber.

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