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 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. ¿ American Geophysical Union 1995