Southern EPR at 8°S Volcano — Undersea Features

A massive 15 +/- 4 km3 lava flow field covers about 220 km2 of the East Pacific Rise (EPR) axis crest at about 8°S. The high reflectivity of the lava flow indicates a very youthful age. Teleseismically recorded earthquakes in 1964, 1965, and 1969, were of an unusual magnitude. A helium megaplume of a volume consistent with the eruption of a lava flow of this volume was detected several years later at a distant location; its movement was consistent with inferred circulation patterns at mid-ocean depths. These observations led Macdonald et al. (1989) to suggest that part or all of this lava field may have been emplaced within the previous 25 years, during one or more eruptions coincident with the earthquakes and onset of the helium plume.