Dr. Andrew Wozinak, associate professor of chemical oceanography at the University of Delaware’s School of Marine Science and Policy will be speaking about “Direct observations of a mid-ocean ridge seafloor volcanic eruption at 9°50’N, East Pacific Rise.”
Abstract:
Progress toward understanding submarine volcanic eruptions and their consequences for submarine geological landforms, hydrothermal vent biological communities, and deep ocean chemistry has been hindered by their remoteness, short duration, and episodic timing. In particular, few mid-ocean ridge eruptions have been detected, and none had been directly observed until 29th April, 2025, when we witnessed an active eruption at the Tica hydrothermal vent site in the HOV Alvin during an expedition to study the hydrothermal alteration of organic carbon into refractory aromatic forms at the East Pacific Rise 9° 50’N (EPR 9N) hydrothermal vent field. A 13-15 kHz acoustic signal, consistent with lava-water interaction, suggests the eruption began ~3 h before Alvin arrived on location. Video footage from the Alvin recorded hazy, high particulate matter conditions, glowing lava, and vent communities paved over by new lava flows. A towed camera system affixed to a multicorer frame deployed 3 days following the eruption revealed ~1 m thick, glassy basalt in frequently collapsed lobate, sheet, and basalt pillows over a 1.4 km transect along the EPR 9N ridge axis as well as dense, white microbial mats at sites of active diffuse flow and patches of dead Riftia tubeworms < 36 h post-eruption near historically active vent sites. Multibeam water column data imaged a continuous cloud of near-bottom particulate matter extending along the axis over the entire observed region. Further, a combination of ship-deployed sensors and chemical measurements detected large post-eruption temperature, salinity, pH, turbidity, dissolved Fe, and H2S anomalies over the EPR 9° 50’N vent region, identifying an event megaplume that extended upwards > 700 m above the seafloor. In sum, the serendipitous discovery of and response to the volcanic eruption provided the first quantitative data documenting the extent of lava flows, destruction of vent biological communities, and initial formation of a large megaplume along the EPR 9N ridge axis, yielding critical insights into this initial phase of volcanic eruption.