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Evidence for volcanic eruption on the southern Juan de Fuca ridge between 1981 and 1987

William W. Chadwick, Jr.

OSU/CIMRS, Hatfield Marine Science Center, Newport, Oregon 97365, USA

Robert W. Embley and Christopher G. Fox

PMEL/NOAA, Hatfield Marine Science Center, Newport, Oregon 97365, USA

Nature, 350, 416-418 (1991)
Copyright ©1991 Macmillan Publishers Ltd.  Further electronic distribution not allowed.

Gallery of Figures

Fig. 1. Sea Beam bathymetric map of overlap region between Cleft and Vance segments, southern Juan de Fuca ridge (50-m contours); CS is northern end of Cleft segment, VS is southern end of Vance segment. Solid black areas show locations of new pillow lava mounds. Numbers to right of each mound are for identification in text. Box around mound 1 shows outline of Fig. 2. On inset map, GR is Gorda ridge, BFZ is Blanco Fracture Zone, and JdFR is Juan de Fuca ridge.

Fig. 2. Sea Beam bathymetric maps (5-m contours) of area including southern-most new lava mound (mound 1 in Fig. 1). a, Pre-eruption bathymetry from survey in 1981. b, Post-eruption bathymetry from survey in 1990. Mound 1 is a new feature near centre of map. c, Map of the significant depth differences between 1981 and 1990 Sea Beam surveys (see text for discussion), showing outline and shape of mound 1. This corresponds exactly with the location of a mound of fresh, glassy pillow lavas based on camera tows, Alvin dives and sidescan sonar data (Fig. 3)

Fig. 3. Detailed map (outline shown in Fig. 2c) of mound 1 based on SeaMARC I sidescan sonar data, and the locations of flow contacts as surveyed by camera tows and Alvin dive 2262 (thin dashed lines). Note close correspondence with outline of mound 1 in Fig. 2c, derived independently fom Sea Beam data.


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