The Antarctic Ocean is situated about or within the antarctic circle. The great Southern Ocean is that part of the ocean which surrounds the world between the latitude of 40 degrees south and the antarctic circle. The northern portions of this band are often called the South Atlantic, South Indian and South Pacific, while the southern portions are usually called the Antarctic Ocean. The average depth of the continuous ocean which surrounds south polar land is about two miles; it gradually shoals toward antarctic land, which in some places is met with a short distance within the antarctic circle. Life is abundant in the surface waters, and at the bottom of the ocean.
HOW THE FLOOR OF THE
OCEAN APPEARS
As a rule the sea is shallowest near the land, though in a few cases there is a sudden descent to a great depth at a very short distance from the coast. Lowlands have usually shallow seas near the coast, and highlands deep water.
Along the American shores, in the latitude of New York, the depth, for a distance of more than 100 miles, is less than 600 feet; then suddenly the bed descends, by a steep slope, to the depth of 6,000 or 9,000 feet. After a comparatively narrow interval, a second terrace descends to the main basin, from 15,000 to 18,000 feet deep.
The bottom of the trough of the ocean, in general, is equally varied with that of the land surface of the globe, forming mountains, hills, valleys, tablelands, etc. In many parts these marine mountains reach above the surface and form islands. On the table land extending across the Atlantic between Newfoundland and Ireland is laid the submarine-telegraph cable which connects the two hemispheres.
The Depth of the Oceans. The average depth of the Pacific Ocean has been estimated at between 15,000 and 18,000 feet, which is slightly greater than that of the Atlantic. The deeper portions may be learned on reference to the [map]. The western portion of the North Pacific in particular shows some very deep depressions. To the east of Japan lies a long deep trough which in one part has furnished the sounding of nearly five and one-half miles. This abyss is often called the Tuscarora Deep. South of the Ladrone Islands, in the Caroline Archipelago, there is also a deep abyss where an English ship, the Challenger, obtained a sounding of nearly 27,000 feet. In the Pacific soundings of over 30,000 feet have been made.
The Indian Ocean has an average depth of about 12,000 feet, and the deepest soundings have been taken on the eastern side. It is interesting to observe that the deepest sounding, about five and three-quarter miles, in the South Pacific somewhat exceeds the height of the highest mountain. Mount Everest has a height of 29,000 feet above the sea level. And it must also be noted that the mean height of the land, 1,000 feet, is only about one-twelfth the mean depth of the whole ocean, 12,000 feet. (See [colored map] showing comparative surfaces of land areas and ocean depths.)
Inland and Border Waters. These enclosed basins belong to the structure of the continents, rather than to the oceans. All are shallow in comparison with the great basins with which they are connected, as is apparent from the depths given below.
The Gulf of Mexico is from 5,000 to 7,000 feet in depth. The deepest part of the Caribbean Sea, on a line connecting Porto Rico and Costa Rica, averages 7,000 feet, and near the latter it reaches a depth of 14,000; but the ocean, immediately outside of the Lesser Antilles, is more than 18,000 feet deep.
The Mediterranean is divided into two basins, by a rocky isthmus, from 50 to 500 feet below the surface, lying between Sicily and Cape Bon, in Africa. The western basin is over 9,000 feet in depth, and comparatively uniform; while the eastern is more irregular, varying from 6,000 near the center, to 13,000 feet, south of the Ionian Islands. The Red Sea has an irregular bottom, with an average depth of 3,000 feet, but in some places it reaches 6,000.