. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. SECT. 2] OCEANIC ISLANDS, SEAMOUNTS, UUVOTS AND ATOLLS ;}73 The Pratt-Welker group of guyots in the Gulf of Alaska, however, has relatively concordant peaks at a depth of 700-800 m ; and the guyots among the Austral Islands are concordant at about 1500 m. Individual guyots have the sizes and shapes that would be produced by planing off existing volcanic islands. The first random crossings of the "flat" tops indicated that the center was flat and that the margins sloped gently. This has not been confirmed by surve
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. SECT. 2] OCEANIC ISLANDS, SEAMOUNTS, UUVOTS AND ATOLLS ;}73 The Pratt-Welker group of guyots in the Gulf of Alaska, however, has relatively concordant peaks at a depth of 700-800 m ; and the guyots among the Austral Islands are concordant at about 1500 m. Individual guyots have the sizes and shapes that would be produced by planing off existing volcanic islands. The first random crossings of the "flat" tops indicated that the center was flat and that the margins sloped gently. This has not been confirmed by surveys. Instead the entire top slopes gently to a point in the center or a in places few pinnacles rise from near the center. The. Fig. 4. Pratt Guyot in the North Pacific. topography, in short, is exactly the same as that of an insular shelf except that the islands have been eroded away. Islands have terraces in their submarine slopes in some j3laces, and random echogram crossings have suggested to various writers that similar terraces have been cut in the sides of guyots. Detailed surveys show that terraces that can be traced around a seamount or guyot are very rare at best. The broad sound cone of an echo-sounder normally causes a pinnacle on a steep slope to appear as a terrace. Consequently, many so-called "terraces" may be parasitic cones. In any event, any conclusions about changes in sea-level suggested by unsurveyed terraces appear Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hill, M. N. (Maurice Neville), 1919-. New York : Interscience Pub.
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