. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 260 HEEZEN AND MENARD [chap. 12 Tn the North Atlantic, the Bermuda Rise is the best known example (Figs. 3 and 22). Tn contrast to the mid-oceanic ridges, oceanic rises are non-seismic; their relief is more subdued and they are asymmetrical in cross- section. The western and central parts of the Bermuda Rise are characterized by gentle, rolling relief. The average depth gradually decreases to^^•ard the east. In the eastern third, the rise is cut by a series of 500-1000-fm-high scarps which drop the sea floor to the level o
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 260 HEEZEN AND MENARD [chap. 12 Tn the North Atlantic, the Bermuda Rise is the best known example (Figs. 3 and 22). Tn contrast to the mid-oceanic ridges, oceanic rises are non-seismic; their relief is more subdued and they are asymmetrical in cross- section. The western and central parts of the Bermuda Rise are characterized by gentle, rolling relief. The average depth gradually decreases to^^•ard the east. In the eastern third, the rise is cut by a series of 500-1000-fm-high scarps which drop the sea floor to the level of the abyssal plain on the east. The series of eastward-facing scarps suggest block faulting. Situated approximately in the center of the Bermuda Rise is the volcanic pedestal of Bermuda. A small archipelagic apron surrounds the pedestal. The turbidity-current origin of the smooth surface of the apron is supported by cores containing shallow-water carbonate clastic sediments in depths of 2300 fm. g. Fracture zones Fracture zones are long, thin bands that are conspicuously more mountainous than the sea floor in general and ordinarily separate regions with diff"erent depths. The first wholly submarine fracture zones were discovered only a few 120' 100* 80° — MAJOR LINE«ION •~~ MINOR LINEATION -• LINE OF SEAMOUNTS. lec Mcr Fig. 23. Major and minor lineations in the northeastern Pacific. (After Menard, ) years ago in the northeastern Pacific basin. Now scores are known in the Pacific and Atlantic. They form a pattern of east-west parallel lines, relatively evenly spaced down the whole eastern Pacific (Fig. 23). Three follow great circles and all are remarkably straight. Each is about 100 km wide and more than 2000 km long. Within the zones are asymmetrical ridges and narrow troughs parallel to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrat
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