Sea
a general name for the great body of salt water which covers the ocean are:
Pacific Ocean Indian Ocean Arctic Ocean 13,438 feet. 13,654 12,887 3,837 " “ “ The greatest depth hitherto recorded is 5,269 fathoms or 31,614 feet in the Pacific near the island of Guam. In the Atlantic the greatest depth is 4,561 fathoms, off Porto Rico. Ross records a sounding in the Antarctic ocean where he found no bottom at 4,000 fathoms. By far the larger portion of the sea floor lies between the depths of 1,000 and 3,000 fathoms, equal to nearly 78 per cent., while about 17½ per cent. is found in depths less than 1,000 fathoms, and about 4½ per cent. in depths greater than 3,000 fathoms. The bulk of water in the SEA whole ocean is estimated at 315,000,000 composition of 1,000 cubic centimeters of cubic miles. sea water:
SEA sea water:
Sodium chloride Magnesium sulphate Water Potassium sulphate Magnesium bromide Each base is probably in combination Water Temperature. The temperature of the surface waters of the ocean varies places the surface layers are subject to or 86° in equatorial regions. In many places the surface layers are subject to great annual changes due to the seasons and the direction of the wind. The temthe ocean over the abysmal areas ranges from 32.7° F. to 36.8° F. The great the ocean over the abysmal areas ranges mass of the ocean consists of cold water -i. e., of water below 40° or 45° F.; at a depth of little over half a mile the water in the tropics has generally a temperature below 40° F. In the open ocean the temperature usually decreases as the depth increases, the coldest water as the depth increases, ses, the coldest water being found at the bottom. In inclosed or partially inclosed seas, cut off by barriers from the great ocean basins, the temperature remains uniform from the height of the barrier down to the bottom; for instance, in the Mediterranean the temperature is about 56° from 200 fathoms down to 2,000 fathoms.
Circulation. The circulation of oceanic waters is maintained by the action of the Circulation.-The circulation of oceanic prevailing winds and by other causes.
In the oceanic areas the prevailing winds are governed by the large anticyclonic areas situated toward the centers of the north and south Atlantic and north and south Pacific. The winds blow out from instance, in the Southern Hemisphere the warm salt water of the tropical regions is driven to the S. along the E. coasts of South America, Africa, and Australia, till on reaching a latitude of between 50° and 55° S. it sinks on being cooled and spreads slowly over the floor of the ocean to the N. and S. A similar circulation takes place in the northern hemisphere, though much modified by the peculiar configuration of the land masses; for instance, the cold salt water at 30° F. which occupies the deeper parts of the Arctic basin is largely made up of the dense Gulf Stream water, which sinks to the bottom on being cooled in the Norwegian Sea. The water evaporated from the sea surface is borne to the land masses and condensed on the mountain slopes. the sea surface is borne to the land masses gions of greatest evaporation; for instance, in the Red Sea, Mediterranean, and in in the trade-wind regions of the great ocean basins. gions of greatest evaporation; for inable that every element is in solution in sea water, the great majority, however, present only in exceedingly minute traces.
If the average density of sea water be taken at 1,027, pure water being 1,000, then the following would represent the 4.0568 1,7665 1,3425 0.9193 0.8809 0.1287 989,7073 1027,0000 Each base is probably in combination with each acid, so that there are really 16 salts altogether from the mixture of the four bases and four acids. The total amount of sea salts may vary greatly in ents that the ratio of the ducted experiments that the ratio of the constituents of sea salts is nearly everybeen shown by hundreds of carefully conducted experiments constituents of sea salts is nearly everywhere constant, with one significant exception, that of lime, which is in slightly greater proportion in the water from the deeper parts of the ocean basins. Nitrogen remains at all times and places nearly tion of oxygen is much reduced in deep water, owing to the process of oxidation and respiration. Carbonic acid free or a most important rôle in the economy loosely combined is abundant, and plays and magnesia to solution in the form of ing soluble normal carbonates of lime and magnesia to solution in the form of bicarbonates. Water, as is well known, is but slightly compressible, and almost any substance that will fall to the botfall to the bottom of the deep ocean. fall to the bottom of the deep ocean.
Still the compressibility of water must not be neglected in oceanographical ques- tions. In the deeper parts of the ocean the pressure amounts to four or five tons. per square inch; hence, in an ocean with a depth of 5 miles, were the action of gravity suddenly to cease, the ocean per square inch; hence, in an ocean with gravity suddenly to cease, the ocean waters would rise 500 feet above their present level from expansion.
It has long Life. The color of pure sea water is a light shade of blue; it has, however, frequently various shades of green and brown, owing to the presence of organisms and matters in suspension. It has been definitely established that life in some of its many forms is universally distributed throughout the ocean. been known that marine plants and animals abound in the shallow waters surdisappear from the sea-bed at depths rounding continents and islands. Algæ between 100 and 200 fathoms, but a great abundance of animals have been procured in the greater depths. The term "Benthos" is now used for all the animals and thos" is now used for all the animals and over the bottom of the ocean, "Plankton" being the term for all the plants and ani- / SEA mals which live in, and are carried along by the currents of the ocean. In the great body of oceanic waters life is most abundant in the surface and sub-surface waters down to about 100 fathoms.
Pelagic algæ, such as diatoms and oscillatoria, are abundant in this region, and are the principal and original source of food for many pelagic and nearly all deep-sea animals. In the intermediate depths of the ocean life though present is less abundant.
Deposits. All marine deposits may be divided into two classes-viz., those made up principally of the débris from the solid land of the globe, laid down in greater or less proximity to the shores of continents and islands, called "terrigenous" deposits, and those in which this continental débris is nearly or quite absent, laid down in the abysmal regions of the ocean, called "pelagic" deposits.
Commencing with the former, there are first the littoral and shallow-water deposits, forming around the land masses from the shore down to a depth of about 100 fathoms, consisting of sands, gravels, and muds derived almost entirely from the disintegration of the neighboring lands. The littoral deposits, laid down between tide marks, cover about 63,000 square miles, and the shallow-water deposits, between low-water mark and 100 fathoms, about 10,000,000 square miles.
Proceeding seaward from an average depth of about 100 fathoms, the deposits gradually change in character, the proportion of land detritus decreasing, while the remains of oceanic organisms increase in abundance till at a considerable distance from land and in comparatively deep water the terrigenous deposits pass insensibly into truly pelagic deposits. The terrigenous deep-sea deposits-i. e., those formed at depths great greater th than 100 fathoms-may be briefly summarized as follows:
Blue mud, the most extensive, is grayish or bluish in color, with usually a thin reddish upper layer, and is characterized by the presence of fragments of rocks and mineral particles coming from the disintegration of the land. Blue mud is found along the coasts of continents and continental islands, and in all inclosed and partially inclosed seas.
Blue mud is estimated to cover about 14,500,000 square miles of the earth's surface-4,000,000 in the Arctic, 3,000,000 in the Pacific, 2,500,000 in the Antarctic, 2,000,000 in the Atlantic, 1,500,000 in the Indian, and 1,500,000 in the Southern ocean. Red mud covers about 100,000 square miles off the coast of Brazil.
Green mud and sand are similar to the blue muds, but are characterized by the presence of the mineral glauconite in SEA isolated grains or in small concretions; the dead shells of calcareous organisms are usually filled with the glauconite, which gives the green color to the deposits. Green mud and sand cover about 850,000 square miles-300,000 in the Atlantic, 250,000 in the Pacific, 150,000 in the Indian, 90,000 in the Southern, and 60,000 in the Antarctic.
Volcanic mud and sand are deposited around the oceanic islands of volcanic origin and the name is derived from the presence of fragments and particles of volcanic rocks and minerals, which are larger and more numerous nearer the islands, when the deposit is called a sand.
Volcanic mud and sand cover about 600,- 000 square miles-300,000 in the Pacific, 200,000 in the Atlantic, and 100,000 in the Indian ocean.
Coral mud and sand occur similarly around the oceanic coral islands and off those coasts and islands fringed by coral reefs. Coral mud and sand cover about 2,557,000 square miles-1,417,000 in the Pacific, 760,000 in the Atlantic, A and 380,- 000 in the Indian ocean.
Of pelagic deposits there are five types, four of or organic origin, receiving their designations from the distinctive presence of the remains of calcareous or siliceous organisms, the fifth and most extensive being of inorganic origin.
Globigerina ooze is so called from the presence of the dead shells of pelagic Foraminifera, those belonging to the genus Globigerina predominating, which live in the surface and sub-surface waters of the ocean, being especially abundant in tropical regions, and the shells of which after death fall to the bottom and there accumulate in moderate depths. The depth at which Globigerina ooze is found varies from less than 500 to over 2,500 fathoms, the average depth being about 2,000 fathoms. Globigerina ooze covers about 49,520,000 square miles-17,940,000 in the Atlantic, 11,300,000 in the Pacific, 10,560,000 in the Southern, and 9,720,000 in the Indian ocean.
Pteropod ooze resembles Globigerina ooze in all respects, except that there is a greater abundance of the dead shells of pelagic mollusca, such as pteropods and heteropods; it is usually found in lesser depths than the Globigerina ooze.
Pteropod ooze covers about 400,000 square miles in the Atlantic.
Diatom ooze is distinguished by the presence of numerous remains of siliceous organisms, principally Diatoms, though fragments of siliceous sponge spicules and Radiolaria and Foraminifera are rarely absent. It is found in the Antarctic and Southern oceans and also in the northwest Pacific. Diatom ooze covers about 10,880,000 square miles-10,000,000 in the Radiolarian ooze in like manner con- Southern, 840,000 in the Antarctic, and 40,000 in the Pacific.
Radiolarian ooze in like manner contains a varying proportion of siliceous remains, in this case principally Radiolaria and their fragments. Calcareous organisms and mineral particles are nearly always present in both these oozes, being usually more numerous and the mineral particles larger in the diatom ocean. latter generally occurs in greater depths than the former. Radiolarian ooze covers the deeper abysses of the ocean, occurring Red clay occupies nearly the whole of in its most characteristic form in the ocean.
Red clay occupies nearly the whole of the deeper abysses in its most characteristic form in the sses of the ocean, occurring central regions of the Pacific, far removed from continental land. It is of a reddish or chocolate color, due to the presence of the oxides of manganese and iron. Mineral particles of secondary origin, arising from the decomposition of volcanic débris, are associated with the red clay, and in some regions of the central Pacific isolated crystals and spheroidal groups of phillipsite of seconconsiderable quantity of the deposit. The considerable quantity of the deposit. The lying alongside others belonging to exist- some of them belonging to extinct species presence of the remains of vertebrates, some of them belonging to extinct species lying alongside others belonging to existing species, as well as the formation of manganese nodules and zeolitic crystals in situ, and the presence of metallic and chondritic spherules of cosmic origin, appear to indicate that the red clay accumulates at a very slow rate. Red clay pear to indicate that the red clay accucovers about 51,500,000 square miles 37,230,000 in the Pacific, 5,800,000 in the Atlantic, 4,350,000 in the Southern, and 37,230,000 in the Pacific, 5,800,000 in the covers about 51,500,000 square miles— 4,120,000 in the Indian ocean.