Evidence for a variety of active hydrothermal venting phenomena, including black smokers, was discovered at a site on the Mid-Atlantic Ridge by a research team of government and university scientists. The work was accomplished on a cruise of the National Oceanic and Atmospheric Administration (NOAA) ship Researcher during July 1985 as part of the NOAA Vents Program. The site of the venting phenomena is the Trans-Atlantic Geotraverse (TAG) Hydrothermal Field on the east wall of the rift valley of the Mid-Atlantic Ridge at 26°N. The TAG Hydrothermal Field was the first hydrothermal field to be found on an oceanic ridge; it was discovered 12 years ago in 1973. However, until the present cruise, only low-temperature hydrothermal activity had been documented, and the existence of higher-temperature hydrothermal activity along slow spreading oceanic ridges (half rate 2 cm/yr), such as the Mid-Atlantic Ridge, was in question.