Satellite free air gravity anomalies over the Indian ocean region 79°E–86°E, 2°S–8°S were obtained from the website http://topex.ucsd.edu and a contour map was compiled. Five profiles of the anomaly have been interpreted in terms of two-dimensional structures in the ocean. Thickness of sediments lying on the oceanic crust determined from the interpretation of gravity profiles were used to compile an isopach map of the region 79°E–86°E, 2°S–8°S. This map in combination with one of the isopach maps compiled by previous workers, provides information regarding the thickness of sediments up to 6° S. According to this map sediment thickness varies from ∼600 m over the middle part of the region to ∼800 m further south, indicating that thinning of sediments in the middle part of the region is only localized. Information provided by this gravity study may be useful in planning detailed seismological studies to delimit the outer edge of the continental margin of Sri Lanka, defined according to the United Nations Convention of the Law of the Sea (UNCLOS).
Foot of the continental slope of Sri Lanka has been determined using satellite bathymetry information downloaded from NOAA database (http://topex.ucsd.edu/) employing the second derivative method. Foot of the continental slope of Sri Lanka is situated at an average distance of about 47 km. Its maximum and minimum distances from the zero height contour are 127 km. and 16 km. Almost 70% of the foot of continental slope occurs in the depth range of 2600 -3800 m.