Title: Collected reprints / Atlantic Oceanographic and Meteorological Laboratories (and) Pacific Oceanographic Laboratories
Identifier: collectedreprin00atla (find matches)
Year: 1968 (1960s)
Authors: Atlantic Oceanographic and Meteorological Laboratories; Pacific Oceanographic Laboratories; United States. Environmental Science Services Administration. Research Laboratories; Environmental Research Laboratories (U. S. )
Subjects: Oceanography Periodicals.
Publisher: Washington, D. C. : U. S. Dept. of Commerce, Environmental Science Services Administration, Research Laboratories : For sale by Supt. of Docs. U. S. G. P. O.
Contributing Library: Penn State University
Digitizing Sponsor: LYRASIS Members and Sloan Foundation

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Li geu(/ Volcanic Arc Sedimentary Arc I Primary -« Trench Cap Rfltige TrdtJscuiTcnt Fault Zone or Fractured Aic Fig. 2. Distribution of island arcs in the northwest Pacific Ocean (from J. T. Wilson, 1954). (By permission of The University of Chicago Press.) 1951; Hobbs. 1925). Double island arcs are not as numerous as the single island arc systems, but an excellent example is found in the northeast Indian Ocean. Here the Andaman and Nicobar Islands form an outer arc of sedimentary islands and there is an inner volcanic trend which manifests itself in two isolated volcanic islands and a chain of sub- marine volcanoes (see Andaman Sea. Vol. I). Less obvious examples are Kodiak Island, part of a sedi- mentary arc, and the volcanic trend on the Alaska Peninsula. In this latter case, the clear arcuate trends of the single arc systems are less well defined, since a portion of this double arc system is part of the con- tinent itself. Certain single and double island arcs exhibit large transcurrenl (or strike-slip) fault zones which suppress the ideal arcuate pattern. These island arcs are called /ractiircJ island arcs. Typical exam- ples of these are the Melanesian arcs from the Philippines to New Zealand. Morphologic Associations There are several fundamental morphologic relationships between the island arcs themselves and the sea floor from which thev rise. In case of the relatively simple single island arcs, the chain of volcanic islands is characteristically associated with a deep-sea trench on its convex side. Whereas the island arc-deep sea trench system may be several thousand kilometers in length, the width of the system is generally only a few hundred kilo- meters. Many of the volcanoes on the islands have elevations of 1-2 km above sea level, and the adjacent deep-sea trench may reach depths exceed- ing 10km. The greatest depth surveyed in the Mariana Trench is approximately II km. Thus, together with the cordilleran-trench combinations (e.g. Andes-Peru Trench) with relief in excess of 15 km. the island arc-deep sea trench systems represent the maximum relief features found on the earth's surface. Moving toward a single island arc from the open ocean, the deeper ocean basin, which may have an average depth of 4- 5 km. becomes shallower at first (by approximately I km), then dips with in- creasing steepness into the deepest portions of the trench (Fig. ."<). The ocean floor rises somewhat more sharply on the inner wall of the trench, up to the island platform itself. The shallower part of the deep-sea floor seaward of the trench is called the Si5

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