Galapagos Rift at 86°W

About Galapagos Rift at 86°W

The Galápagos Rift is an oceanic spreading ridge between the Cocos plate to the north and the Nazca plate to the south. A large area of hydrothermal vents along the crest of the ridge ENE of the Galápagos Islands was discovered in 1977. The location listed here is the position of Clambake vent, which was surrounded by very youthful sediment-free flows of basaltic sheet lava. This position is at the northern limit of the location error circle for a 1972 earthquake swarm and only a few kilometers south of a concurrent fish kill (Macdonald and Mudie, 1974) that may have been associated with extrusion of lava flows. Very fresh, glassy, sediment-free sheet-flow lavas observed during dives near this site in February and March 1977 (Corliss et al., 1979); the morphology of the flows suggested that they were less than 5 years old (Chadwick and Embley, 1994). The rift at this point consists of a small rift valley 3-4 km wide with walls 200-250 m high. A low axial ridge formed by the youngest sediment-free lava flows rises about 20 m above the valley floor, flanked by older marginal ridges. A 2002 expedition discovered evidence for new lava flows covering markers emplaced in 1990.