Further electronic distribution is not allowed. An investigation of this area using sidescan sonar, a towed-camera, continued water column surveys, and submersible dives followed over the next several field seasons. The purpose of the surveys was to define the volcanic, tectonic, and hydrothermal characteristics of the ridge crest from which the megaplumes originated in order to constrain the possible source mechanisms. Simplified Sea Beam map of portion of area of Plate 1 showing features discussed in text. 20 m. Temperature anomaly contours of megaplumes are from Baker et al .
Stars show location of high-temperature vents.
SCR is Split Cone Ridge. Index map at lower right shows location of mapped area. Inset at upper left shows locations of NOAA towed camera tracks made between 1987 and 1991. Location shown in Figure 1. Dashed line shows gradient of portion of north rift zone of the Krafla central volcano, Iceland.