FY 2000

In situ observations of the onset of hydrothermal discharge during the 1998 submarine eruption of Axial Volcano, Juan de Fuca Ridge

Baker, E.T., C.G. Fox, and J.P. Cowen

Geophys. Res. Lett., 26(23), 3445–3448, doi: 10.1029/1999GL002331 (1999)

A volcanic eruption at the summit of Axial Volcano on January 25, 1998, instantaneously created extensive and vigorous hydrothermal discharge. Moorings 2 km apart along the eruption fissure recorded temperature increases of ~0.6°C up to 115 m above bottom within hours of initial seismic activity. Water temperatures at the mooring sites remained high for about 5 days, then declined steadily over the next 2 weeks. A response cruise 18 days after the eruption found hydrothermal temperature anomalies of ~0.1°C over the eruption site, and a more intense and much thicker plume 20 km downstream of the eruption. We estimate the steady-state heat flux required to produce this distal plume, evidence of discharge conditions perhaps 1-13 days after the eruption, as 60-230 GW. The Axial eruption thus produced the largest vent field heat flux yet measured, but these high levels lasted less than 3 weeks.