. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography In the technique of coring, a core barrel consisting of a tube several centimeters in diameter up to about 20 meters in length pene- trates into the sediments of the ocean bottom either by gravitational impact or mechanical vibration (fig. 8). The core barrel recovers a sample in the form of a vertical column through the ocean bottom (Shepard, 1963). Several cores can be collected in an hour on the con- tinental shelf using a power operated winch to
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography In the technique of coring, a core barrel consisting of a tube several centimeters in diameter up to about 20 meters in length pene- trates into the sediments of the ocean bottom either by gravitational impact or mechanical vibration (fig. 8). The core barrel recovers a sample in the form of a vertical column through the ocean bottom (Shepard, 1963). Several cores can be collected in an hour on the con- tinental shelf using a power operated winch to lower and retrieve the coring device on a cable. Standard coring devices are not suitable for penetrating rocks. Dredging is a technique to gather fragments of rocks exposed on the sea floor that are too hard and large to recover by coring. A chain basket or pipe suspended from the ship on a cable is dragged along the bottom in areas where echo sounding records and bottom photographs indi- cate rock ledges or loose nodules and rock fragments (fig. 9). Information from ccring and dredging may be portrayed as a map of the distribution of sediment and rock types (fig. 10). Drilling techniques are employed to recover samples of rock or of sediments beyond the penetration of conventional coring techniques. Ship mounted rotary, percussive, and vibratory drills of various sizes are capable of different penetrations. Drilling for oil is done by rotary drills mounted on floating barges or on fixed platforms capable. Figure 7. A deep-sea photograph showing about one square meter of the ocean bottom covered with manganese nodules. The individual manganese nodules are about the size of ten- nis balls (7 to 10 cm in diameter). (Photograph by R. M. Pratt and Woods Hole Oceanographic Institution). 770. 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
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