CONFIGURATION OF THE ALEUTIAN RIDGE RAT ISLANDS—SEMISOPOCHNOI I TO WEST OF BULDIR I

Abstract

The configuration of a 150 by 200 mile section of the Aleutian Ridge, extending from the Aleutian Trench on the south to the floor of the Bering Sea on the north, is presented by means of depth curves at 50-fathom depth intervals. Advances in electronic position indicating had enabled the U. S. Coast and Geodetic Survey to complete accurate and detailed hydrographic surveys of this entire area based on accurate horizontal control. The authors used copies of the large-scale survey sheets for adding 50-fathom depth curves. Compilation on Plate 1 accentuated the submarine topography and gave substance to many interesting configurations that were not evident on the published navigational chart. The scale of Plate 1 is designed for regional coverage. Geologists and others interested in more precise and detailed physiography may refer to the large-scale basic survey sheets of the U. S. Coast and Geodetic Survey. Submarine contours of the Aleutian Trench, a submerged central-cone depression, four sea valleys, and many transverse canyons are shown. Murray Sea valley is completely contained in the study. The Aleutian Ridge is shown to rise in inclined steps from the floors of the Trench and Bering Sea. The Aleutian Bench is a prominent step on the south slope of the Ridge. The volcanic arc is at the north edge of another prominent step on the north slope of the Ridge. Bowie Canyon is a definite submerged line of demarkation between the Aleutian Ridge and Bowers Ridge. Many implications relative to the formation of mountains, island arcs, and trenches may be seen in the configurations. Vertical and horizontal movement may take place along inclined step faults. The step faults and canyonlike transverse faults may outline irregular crustal blocks where differential movement would occur. Great distortion of the bottom occurs along the edges of the sea valleys. Most of the earthquake epicenters may be aligned along inferred step faults by allowing for probable uncertainties in their locations. Definite correlation between earthquakes and submarine topography, if possible, must wait for more accurate epicenter determinations along the Aleutian Ridge.