Carnegie Ridge bathymetry

Carnegie Ridge is a sea floor elevation lying directly west of Ecuador, but separated from the continent by a narrow trench. Its westward extention joins the platform on which the Galapagos Islands are found through a saddle at a depth between 1200 and 1300 fm. About 7200 square nautical miles of sea floor on Carnegie Ridge lie shoaler than 800 fm. The feature is of geological interest because it lies so close to the South American continent yet is so distinctly separated from it by the trench. The general features of Carnegie Ridge have been described previously by the writer, and some geological implications have been discussed (Shumway, 1954). Since this earlier report, thousands of miles of new sounding lines have been obtained on the Research Vessels Horizon and Spencer F. Baird of the Scripps Institution of Oceanography during the "Shellback" and "Eastropic" Expeditions, and on Atlantis of the Woods Hole Oceanographic Institution during Cruise 221 (Fig. 1). A more detailed bathymetric chart (Fig. 2) has been constructed on the basis of this new data together with that from the U.S. Navy Expedition "Hijump" and with spot soundings from U.S.N. Hydrographic Office Charts 0823, 1176, 1177, 1798, and 5486. Nominal echo sounder depths, based on the assumption of a sound velocity in sea water of 4800 ft/sec, have been used for this chart. Some generalized coastal geology of Ecuador is included for the sake of completeness (Lewis, Tschopp, and Marks, P1. 1 in Jenks, 1956).