Initial results of the rapid response to the 1993 CoAxial event: Relationships between hydrothermal and volcanic processes

Abstract

Between June 26 and July 10, 1993, swarms of “T‐wave” events occurred over a 40‐km portion of the CoAxial segment on the northern Juan de Fuca Ridge. A rapid response utilizing a CTD/rosette/chemical scanner and a remotely operated vehicle occurred in the month following the T‐wave swarms. The pattern of T‐wave events and water‐column anomalies (including several event plumes) are remarkably coincident. The only known eruptive area is at the northern swarm area, where a very fresh pillow lava ridge was discovered, mapped, and sampled with the remotely operated vehicle ROPOS. A vent area about 22 km south of the lava flow was emitting large quantities of bacterially generated floccular material. The temporal pattern of T‐wave events and the coincidence between the T‐wave swarms, the young lava flows, and hydrothermal plumes suggests that there is a close analogy between this activity and lateral dike injections such as have been closely monitored at Icelandic central volcanoes.