Some Unusual Submarine Features in the North Pacific Ocean

Abstract

HE rim of the Pacific, including both the shores and the adjacent waters, is one of the most interesting parts of the earth from many viewpoints but especially in that it is the part of the earth where the processes of change to which all the rest of the earth has been subject at one time or another are in most active progress. To describe all the features of interest would require a volume. This paper is intended to bring out some of the less-known features, chiefly submarine. It was known that along the coast of Mexico and Central America there existed a deep submarine trough, the Acapulcograben of the German charts; but not till the cruise of the Coast and Geodetic Survey Steamer Guide in 1923 were the extent and maximum depth of the trough known. This vessel, using the sonic depth finder, was able to make a survey in a short time which, though far from exhaustive, outlined a series of troughs extending from Costa Rica to the Gulf of California with an average width of 40 miles, a total length of 900 miles, and a greatest depth of nearly 3600 fathoms (Fig. I). While there are much greater deeps, it is noteworthy that on both sides of this trough the depth is very much less than that of the trough, in some cases not more than half. The earthquake epicenters from the Summary of the British Association for the Advancement of Science I899 to I917, from the International Seismological Summary 1918 to 1922, and from records of the Coast and Geodetic Survey after that date were plotted and are shown in Figure I. Fifteen epicenters are in or near the trough, and half a dozen more may easily have been near it but are located with uncertainty. There is another series which lines up with a series of oceanic islands and reefs, including Guadalupe Island, the Alijos Rocks, and the eastern Revillagigedo Islands. The absence of a deep trough off the California coast and the practical absence of earthquakes except in the seaward continuation of the San Andreas fault are significant. Passing to southeastern Alaska we note in Figure 3 the outline of what is presumably a volcanic crater, for it is difficult to explain a