National Geographic : 1945 Jan
Our Global Ocean-Last and Vast.Frontier Small, delicate creatures swim and crawl without discomfort on the bottom under these great pressures because the pressure of fluids within their bodies balances that on the out side. But when deep-sea fish are brought up to the surface in warm regions, the increased heat causes expansion of the gases in their body liquids, and this may bulge their entrails out through their mouths and even explode their bodies. Sediments and oozes gradually have been spread over the ocean bottom, deposited through uncounted eons of time. Near shore, off the mouths of large rivers, they accumulate at the rate of several yards per year, while out in the open ocean less than half an inch is de posited in 1,000 years. Red clay and globigerina ooze cover the largest proportion of the ocean floor, the lat ter named for the tiny sea animal of whose limy shells it is chiefly composed. Diatom ooze, composed of the flinty-hard silica shells of microscopic ocean plants, each smaller than a grain of sand, forms great belts around the Antarctic and across the North Pacific. Radium Dates Deep Ocean History Hidden in the sediments, especially in the deeper parts of the sea, are large amounts of radium and other radioactive substances. Radium continuously gives off heat, and so represents an enormous store of energy, which may have influenced the earth's past history. Radium also disintegrates at a regular rate of speed (it diminishes by half every 1,600 years), a fact which accurately measures the age of the stratum in which it is found. Knowing how much material remains from the disintegration of the radium, and how long it took to accumulate, you can tell how long ago the process of disintegration began. That is the time when the sediment was deposited. It's like an hourglass, through which sand runs at the rate of one ounce per minute. If there are 20 ounces of sand in the bottom, you know it began to run through 20 minutes ago. Seeking to learn more about ocean sedi ments, one scientist invented a deep-sea "can non" which is lowered to the sea bottom on a cable and fires a hollow metal tube down into the ooze. Others have driven tubes down into the ooze with heavy weights. Hauled to the surface, the tubes bring up "cores" of bot tom material ten or more feet long. Such cores represent cross sections of the bottom covering thousands of years of slow accumulation of sediments. Ten feet of sedi ment from the deeper parts of the ocean may tell as much about the earth's past as 10,000 feet of deposits on land. In the cores, at various levels, were found particles of magnetized minerals. Like tiny compass needles frozen in place while pointing in the direction of the earth's magnetic force as it was at that place and time, they show how the earth's magnetic field has varied through past ages. Layers of volcanic ash, and of sand and pebbles carried out to sea by floating ice, found in cores from the bottom of the North Atlantic, tell of ancient volcanic eruptions and ice ages. In the cores, too, at various levels, are fossil remains of small sea animals, exactly like some which live today in warmer waters and others in colder seas. They reveal how the climate must have fluctuated in that region, and that surface water in that part of the Atlantic once was warmer than now. In the dim past, too, on the ocean bottom, began the process that formed much of the oil that lubricates our modern machine world. Materials that may produce future oil supplies are forming under the sea today, off California, Chile, Peru, and in the Gulf of Guinea, though experts disagree as to whether the process is fast enough to keep up with our huge con sumption of petroleum (page 114). Study of the process may help us find new oil fields. Where Petroleum Production Begins The process that eventually produces petro leum begins in depressions in the ocean bot tom, where there is little circulation of water. There the countless dead bodies of the plankton-small sea plants and animals-col lect, and are preserved in sediments. Grad ually then, by a means still not fully under stood, they turn into petroleum in anywhere from 100,000 to 10,000,000 years. Flashing continuously all through the dark depths of the sea are countless lights, produced by the luminescent, or phosphorescent organs of sea animals. What is luminescence? (Scientists prefer this word to phosphorescence, for there's no phosphorus in the process.) It is cold light, produced with almost no heat, like that of fireflies. A chemical reaction takes place in the creature's body, in which proteins unite with oxygen and form light. Nature in some cases even provides filters of different colors, red, yellow, green, and blue. Luminous fish use their lights to attract prey or the opposite sex, to frighten enemies, and to see while hunting food.* There are even luminous fish diseases. * See, in the NATIONAL GEOGRAPHIC MAGAZINE, articles on deep-sea fish by William Beebe, in the issues for June, 1931, January and December, 1932, and December, 1934.