The Atlantic Continental Margin

Turbidity currents, surface, and subsurface currents carry detritus from the land across the continental shelf to the adjacent continental slope where slumps and turbidity currents transport the sediment downslope for hundreds of miles to greater depths, and deep geostrophic contour currents transport it thousands of miles down-current in a direction parallel to the bathymetric contours. The combined effect of these processes has been to create a wide, thick, geosynclinal apron of sediment at the base of the continental slope. Subsidence of the continental shelf has continued since mid-Mesozoic, carrying down Lower Cretaceous reefal limestones to depths of 5,000 meters off Florida. The subsidence of the Atlantic continental margin and the basement of the continental rise geosyncline apparently commenced in mid-Mesozoic time with the creation of abyssal depths in the steadily expanding Atlantic

Alaskan Submarine Cables: A Struggle with a Harsh Environment

Reviews the laying, repair and maintenance of telegraph and cable systems, at one time 86 submarine cables, between Puget Sound and Alaska 1901-60. Failures due to entanglement by whales, bruising and mauling by anchors and fishing trawls and various destructive effects of geologic agents on the sea floor are noted. In straits on the continental shelf and upper continental slope, cable failures are attributed primarily to chafe by bottom currents and, off the mouths of major streams, to turbidity currents and gravitational slides. Cable repair data for 1903-58 are tabulated, showing reported causes. Some cables at depths of 1000-1500 fathoms on the continental margin cross at least 40 major canyons, but have never failed because of turbidity currents; this indicates a lapse of 2000, possibly 5000 yr since such currents occurred in this region.Les câbles sous-marins en Alaska, une lutte contre un milieu difficile. A un moment donné, le système de communications de l'Alaska comprenait 86 câbles télégraphiques sous-marins, s'étendant du Puget Sound vers le nord à travers l'Alaska côtier, puis vers l'ouest jusqu'à l'arc des Aléoutiennes. Les pannes de ces câbles sont révélatrices des forces dynamiques naturelles qui affectent le fond des mers. Dans les détroits du plateau continental et de la partie supérieure du talus continental, les bris s'expliquent par le frottement dû aux courants profonds : à l'embouchure des grands cours d'eau, ils sont provoqués par les courants de turbidité et les glissements sous-marins

Digital Deep-Sea Sounding Library — Description and Index List

Automated access to a worldwide coverage of over 1 000 000 deep sea soundings is provided by a new digital data library. The deep sea soundings recorded on available master plotting sheets of the major maritime nations have been incorporated in this new facility. The methods used in evaluating, digitizing, and processing the data are described in detail. The data are maintained in full both on magnetic tape and on over 60 000 frames of microfilm. The four master library lists are described and sample pages reproduced. The locations of all recorded sound profiles are presented in 708 computer generated index maps. The data in the library will now be put to use in the solution of numerical problems o f both global and regional character. Some of the applications in which this library will be employed include the determination of an average ocean depth model for numerical computations of global geophysical character (such as needed, for example, in the study of ocean tides, the propagation of tsunamis, in geodesy in general, and in the spherical harmonic analysis of earth topography), quantitative textural analysis of topography (slopes, wave lengths, amplitudes), and detailed hypsometric studies

Whales entangled in deep sea cables

Fourteen instances of whales entangled in submarine cables are reported. Ten entanglements occured off the Pacific coast of Central and South America. Six cases occured in about 500 fathoms, with 620 fathoms the maximum depth reported. Five entanglements occured in the period, Februray-March-April. All whales positively identified were sperm whales. The submarine cable was generally wrapped around jaw and often around the flukes and fins. The cable was rarely broken but always badly mauled. The entanglements often occured near former repairs where there is a chance for extra slack cable on the bottom. Two photographs of a sperm whale entangled in a cable and one photograph of a whale-jaw entangled in a cable are presented. It is concluded that sperm whales often swim alog the sea floor in depths as grat as 620 fathoms. It is suggested that the whales become entangled while swimming along with their jaw plowing through the sediment in search of food. It is possible that the whales attack tangled masses of slack cable mistaking them for items of food

Bathymetric map of the northeast Equatorial Pacific Ocean [cartographic material] /

Depths shown by gradient tints, soundings, and contours.; "The soundings on this map were principally assembled from compilations made since 1949 by the following organizations. ... ".; "Contours based on echo soundings given in total travel time (surface, to seabed, to surface) and expressed in tau (t) units".; Includes text, tau to meters conversion table, col. cross section, and index to 1:1,000,000 scale I-series maps used as sources of bathymetry in preparation of this map.; Includes bibliographical references.; Also available online http://nla.gov.au/nla.map-vn6073636