Diving on Hydrothermal Vents at The East Pacific Rise These hydrothermal vents lie at depths comparable to those on the Juan de Fuca Ridge in the North Pacific Ocean, about 250 km west of the state of Washington. The Field Museum has a considerable collection of animals from these northern vents that I have collected using the manned submersible ALVIN or the unmanned Remotely Operated Vehicles, ROPOS and JASON, over the last seven years. This cruise represents my first opportunity to go to EPR vents to make comparable collections. Vents on this tropical mid-ocean spreading center are known to support about four times as many species as do those on the Juan de Fuca Ridge. In addition to collecting specimens of EPR species for comparison with those from the Juan de Fuca vents, this cruise will allow me to gain a personal perspective on why these vents have such different species diversities.