USGS scientist Carol Reiss holding a hydrothermal vent sample. The poster in the background is a scientific rendering by Véronique Robigou (then at University of Washington) of a hydrothermal vent deposit with the submersible Alvin drawn to scale. This structure stood 45 meters above the seafloor when it was discovered by University of Washington researchers using Alvin in July 1991. It formed on the volcanically active Juan de Fuca (spreading) Ridge off the coast of the Pacific Northwest at a depth of 2,100 meters. Sulfide and silicate minerals precipitating from 330°C water circulating through the edifice and seafloor created the deposit.