Bathymetry of the Gibbs Hill area, Bermuda

Abstract

Precision depth recordings were made South of Gibbs Hill, Bermuda, along a number of closely spaced sounding tracks. The accuracy of transit navigation and the sounding coverage were considered sufficient to justify correcting the soundings for both sound velocity and slope. The corrected soundings show that a steep sided submarine spur extends south-south-east from the shelf break off Gibbs Hill. The spur has a topographic relief of 300 fm and is about 3 miles long and 1 2 mile wide. At the 1000 fm curve, the feature broadens into a platform that extends another 12 miles seaward to the 2000 fm curve. True slopes along the steep portion of the spur are as high as 50° and the bottom echoes appear to be from a number of highlights causing “crescent” on the record. Where a definite break in slope occurs, the apparent bottom shown on the bathygram is that of a diffraction pattern from an edge and all points on this crescent migrate to a point, which is the true position of the break in slope.