Hydrothermal activity on the Gorda Ridge

Abstract

Near‐bottom plumes of materials indicative of discharge of metal‐rich hot springs were discovered at sites on the Gorda Ridge by a research team of government and university scientists on a cruise of the National Oceanic and Atmospheric Administration (NOAA) ship Surveyor during May 1985 as part of the NOAA Vents Program. The Gorda Ridge, off northern California and Oregon, is the only seafloor spreading center within the proclaimed 200‐mile U.S. Exclusive Economic Zone (370 km wide) of the conterminous United States and is one of the last oceanic ridges to be explored for metal‐rich hot springs. One reason for this neglect is that the Gorda Ridge is slow spreading, with half‐rates ranging from 1.1 cm/yr in the southern portion to 2.2 cm/yr in the northern portion. Slow spreading centers have not been fully evaluated with regard to hydrothermal activity by many members of the research community, who have concentrated their attention on the faster spreading East Pacific Rise to the south and the Juan de Fuca Ridge to the north of the Gorda Ridge.