The Trans-Atlantic Geotraverse (TAG) Hydrothermal Field, which lies on the east wall of the Mid-Atlantic Ridge at about 26°N, has been a focus of study since low-temperature hydrothermal activity was discovered there in 1973. In July 1985, scientists making an intensive investigation of the site discovered the first black smokers on the ridge (Eos, 66, October 1, 1985, p. 682).
The smokers appeared in images from a towed deep-sea photovideo camera. Water temperature anomalies were recorded by a near-bottom thermister array mounted on the camera. A conductivity-temperaturedepth (CTD)/nephelometer package sent real-time data of plume depth, distribution, and concentration. Shipboard analysis provided total reactive Mn.