Because drilling near Guam was not envisioned as part of the Leg 191 plan, no maps of the drill site were on board the JOIDES Resolution. Two published small-scale maps were faxed from shore. A low-resolution map of the eastern side of Inutil Seamount had been derived from echo-sounder profiles taken in 1983 during a dredging cruise of the Thomas Washington (Dixon and Stern, 1983). At the time of writing, the date and navigation parameters of that cruise were not known. A later publication contained low-resolution bathymetric contours from U.S. Navy SASS multibeam coverage (Stern et al., 1989). The data are presumably as accurate as possible with mid-1970s navigation and multibeam echo sounding, but the details of this survey are classified. In addition, the contours are generalized and sometimes moved slightly in order to get them declassified (N.C. Smoot, pers. comm., 1990). Nevertheless, comparison of the two maps showed no apparent offset in position.
From 0230-1110 hr UTC on 3 September 2000, the JOIDES Resolution made a short survey of the western part of Inutil Seamount using the 3.5- and 12.0-kHz echo sounders and magnetometer (Fig. F1). The survey showed a crater >200 m in depth with breached walls on the western side. Slopes on the volcano's flanks are typically ~14°, and sharp-topped ridges surround the crater. Site 1180 was chosen at a depth of slightly >2100 m on the lower flanks where the slope seemed less steep (Fig. F2). Site 1181 was chosen at the top of the crater rim, where survey profiles indicated a possible graben (Fig. F3).