. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 766 HEEZEN [chap. 27 seamount photographed to date (Menard, 1952; Heezen, Tharp and Ewing, 1959). Ripple marks have been observed on the crest of the Mid-Atlantic Ridge down to 2000 fm (Elmendorf and Heezen, 1957). They have also been observed on the continental slopes to similar depths. The deepest photographs of the North Atlantic abyssal floor had indicated probable scour marks in 3200 fm depth (Dietz, 1952; Elmendorf and Heezen, 1957). The deepest Atlantic photographs recently taken revealed rock bottom at 4000 fm in t
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 766 HEEZEN [chap. 27 seamount photographed to date (Menard, 1952; Heezen, Tharp and Ewing, 1959). Ripple marks have been observed on the crest of the Mid-Atlantic Ridge down to 2000 fm (Elmendorf and Heezen, 1957). They have also been observed on the continental slopes to similar depths. The deepest photographs of the North Atlantic abyssal floor had indicated probable scour marks in 3200 fm depth (Dietz, 1952; Elmendorf and Heezen, 1957). The deepest Atlantic photographs recently taken revealed rock bottom at 4000 fm in the Romanche. Fig. 19. Photograph from western rift mountains of the Mid-Atlantic Ridge in 1410 fm depth (48° 38'N, 28° 48'W). Note the patches of recent sediment lying in the de- pressions between outcropping rocks. Trench Fracture Zone (Equatorial Atlantic) (Coiisteau, 1958). These sharper topographic features are being scoured by ocean currents which remove the finer sediment and produce the ripple marks. The direction of these currents has not been determined, although a collection of oriented photographs might go far to solving the problem. It must be supposed that the sediment eroded from these peaks by the currents is deposited in their lee. A study of these deposits may produce evidence of the direction of the deep currents and the nature of their variations in late Tertiary, Pleistocene and Recent times (Figs. 20 and 21).. 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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