Deep-subaqueous implosive volcanism at West Mata seamount, Tonga
Earth and Planetary Science Letters
Deep subaqueous volcanic eruptions (>500 m below sea level (mbsl)) remain enigmatic due to a lack of visual observations and difficulty recreating ambient conditions in the lab. Eruptive activity at West Mata seamount in May 2009 remains one of two deep subaqueous eruptions to have ever been filmed. A distinct low-intensity eruptive style, termed bubble escape activity, was observed at Hades vent (1200 mbsl) characterized by the ascent and implosion of 0.2 - 1 m diameter volatile-filled vapor bubbles (Resing et al., 2011). Video of this volcanic activity is used to constrain simple numerical models and produce the first subaqueous eruption actualistic model driven by visual observations. Bubble escape activity occurs in three stages defined by changing exsolved volatile and lava behavior. During Stage 1, vapor bubble ascent in a magma filled conduit drives either ductile or brittle deformation of the lava surface at the vent, depending on the timescale of lava cooling prior to bubble escape activity. Fragmentation of the lava during Stage 2 culminates with the vapor bubble coming into direct contact with the ambient water. At this point, Stage 3, bubbles implode through rapid condensation and contraction of the exsolved volatile phase, due to rapid heat loss from the vapor bubble to the ambient water. Numerical modeling of exsolved volatile expansion during conduit ascent to vents across the ocean depth range has identified a transition in exsolved volatile expansion characteristics at 2 - 5 MPa. This transition would produce a fundamental change in eruption processes, from which the characteristics and depth range of deep and shallow end members of bubble escape activity are defined. Bubble escape activity highlights implosive behavior driven by underpressure that develops during exsolved volatile contraction as a key, but often overlooked, component of both pyroclastic and effusive subaqueous volcanism across the entire ocean depth range. This stands in contrast to overpressure driving subaerial explosive eruptions. The fact that exsolved volatiles can expand, contract, or maintain an approximately constant volume in subaqueous volcanism also calls for the careful application of terminology (e.g. explosive) to describe subaqueous eruption processes.
National Science Foundation
implosion, NE Lau basin, remotely operated, submarine eruption, underwater vehicle, West Mata
Arran P. Murch, Ryan A. Portner, Ken H. Rubin, and David A. Clague. "Deep-subaqueous implosive volcanism at West Mata seamount, Tonga" Earth and Planetary Science Letters (2022). https://doi.org/10.1016/j.epsl.2021.117328