Tuvalu, Nukulaelae, Bathymetry chart, 1 to 25 000 #1

Nukulaelae atoll is located at 179 degrees 50'E and 9 degrees 23'S, with dimensions of 10.8 km along the NW-SE axis and 4.7 km along the narrow SW-NE axis. The atoll is characterised by a large central lagoon with some 20 vegetated islands predominantly on the eastern side of the atoll.
The resultant data from the SOPAC marine survey carried out for Tuvalu in 2004 was used to produce nine bathymetry charts, at scales ranging from 1:20 000 to 1:50 000 and the Nukulaelae Chart is available here for download under Distribution Info.
This work was initiated by the SOPAC/EU Reducing Vulnerability of Pacific ACP States Project (Task no.: TV 1.1.1).To provide a descriptive picture of the ocean bottom terrain, vividly revealing the size, shape and distribution of underwater features, and serve as the basic tool for scientific, engineering, marine geophysical and environmental studies, as well as marine and coastal resource management.The water depth within the survey area around Nukulaelae ranges from 9.0 to 1878.0m. The minimum water depths occur in the nearshore area on the outer reef slope, while the seabed deepens to the maximum at an average gradient of 27degrees near the seaward limits of the survey area. Locally, the seabed is expected to be quite irregular with gradients expected to behighly variable, ranging from 0 to 76 degrees. The island is encircled by a steep cliff that exceeds slope angles of 60 degrees, locatedapproximately 200–600 m seaward of the reef crest with a water depth to the top of the scarpand scarp height of 100 m and 100–240 m, respectively. Further offshore, the seabed ispredominantly featureless, sloping in a seaward direction at the average angle 27degrees.Exceptions to this are the areas to the southeast and northwest. The southeast flank isdominated by a 5-km long lateral submarine failure originating in water depths ranging from580 m in the north to 700 m at the southern extent. The scarp terminates at 1000 m belowsea level, and scarp height therefore ranges from 420 to 300 m, north to south. This submarine landslide is shown in 3D perspective view in Figure 27 of report, which also shows abathymetric high thought to comprise the mass flow deposit out at a run out distance of approximately 1.5 km. Alternatively, it represents a remnant block of volcanic origin that has resisted erosion. The north and northwest flank shows several scarps associated with downslope massmovement. The steepest of these is at the northwest margin of the surveyed area, with a scarp height of 420 m, with upslope and downslope break in slope margins in water depthsof 300 and 720 m, respectively.