Tuvalu, Niulakita, Bathymetry Chart, 1 : 1 :25 000 #2

This record holds the bathymetry chart of the offshore areas of Niulakita in Tuvalu. Chart is the result of multibeam survey conducted by SPC-SOPAC in 2004. Niulakita is the southern-most as well as the smallest and most isolated island, located in the southern part of the EEZ of Tuvalu. The surveyed area extends to a maximum of approximately 10.5 km offshore from the coastline at the southwest margin. The Niulakita Chart available here for download under the Distribution Info section of this record.
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.
StatusThe low reef island is located at 10 degrees 47’Sand 179 degrees 28’E, with its long axis running E-W, measuring 1.2 km, and a N-S axis of 520 m. The surveyed area extends to a maximum of approximately 10.5 km offshore from the coastline at the southwest margin.The water depth within the survey area around Nanumea ranges from 7.2 m on the shallow banks surrounding the island, to 2149 m in the northwest offshore margin of the surveyed area. Maximum and minimum observed slopes were 73 and 23 degrees , respectively. Niulakita lies on the southwestern edge of the Kosciusko and MarthaBank (IFREMER 1994, and Kroenke 1995), which has been suggested as a possible reef reserve (Dahl 1980). These banks are not very well delineated on official marine charts, withKosciusko and Martha Banks marked as obstructions with minimum water depths of 18 m. However the banks are clearly shown on the derived bathymetry shown in Figure 16. The submerged banks belong to the Melanesian Border Plateau, lying on the Pacific crust, north of the Vitias Trench paleo-lineament, which is part of the North Fiji Basin. The Vitias trench EU-SOPAC Project Report 50 – Krüger20 - Tuvalu – Bathymetric survey, EU EDF-SOPAC Reducing Vulnerability of Pacific ACP States lineament is considered to delineate the former subduction of the Pacific Plate below theAustralia Plate (Augustin et al. 1996). The South Tuvalu Banks area was surveyed in detail at a scale of 1:250 000, using multibeam bathymetry, sidescan sonar imagery, high-resolution sub-bottom profiler, six - channel seismic reflection, gravity and magnetic data (IFREMER 1994).The margins of the submerged reef platform (Martha Bank)were partly mapped to a distance of approximately 5 km east of Niulakita. The depth of the margin is presumed to be on average 20–30 m below sea level. More detailed mapping ofthese banks were limited due to time (reduced coverage of MBES in shallow water), and the shallow nature, and thus hazard to navigation of this feature. An arcuate scarp featureimmediately south (1600 m from shoreline) of Niulakita is situated in 100 m of water, with a scarp height of 100 m. The survey data also shows a ridge extending to the southwest ofNiulakita shoaling to 500 m, and with numerous erosional scarps on its southern flank.