FY 1995

Hydrothermal event plumes from the CoAxial seafloor eruption site, Juan de Fuca Ridge

Baker, E.T., G.J. Massoth, R.A. Feely, R.W. Embley, R.E. Thomson, and B.J. Burd

Geophys. Res. Lett., 22(2), 147–150 (1995)

The episodic magmatic intrusions that accompany seafloor spreading can profoundly affect the discharge of hydrothermal heat and fluid. A rapid field response to the acoustic detection of seismic activity on the CoAxial segment of the Juan de Fuca Ridge, June/July 1993, provided the opportunity to conduct a unique series of observations of hydrothermal event plumes. Between July 3 and 26 we detected at least three event plumes ranging in plume volume from 1.3 to 4 × 10 m, and in excess heat from 2.2 to 12.4 × 10 J. Two were discovered directly above a new lava extrusion. One of these was first sampled within days of its release, as evidenced by its asymmetric shape, complex structure, and a steadily increasing light attenuation anomaly apparently generated by ongoing precipitation of hydrothermal Fe. We hypothesize that event plumes were produced intermittently in response to successive volcano-tectonic events that produced pulses in seismic activity between June 28 and July 14.