THE ATLANTIC is the most branching of the oceans, and is especially
distinguished by the number and great size of its inland seas. Two of
these, the Mediterranean Sea and the Gulf of Mexico, lie in the warm
regions; and two, Hudson Bay and the Baltic Sea, in colder latitudes.
The broader seas are represented by the Caribbean Sea, within the
tropics and the Gulf of St. Lawrence and the North Sea in temperate
latitudes. The Gulf of Guinea, and the Bay of Biscay, are examples of
the more shallow coast waters.
THE PACIFIC is particularly rich in vast border seas, a continuous
series of which lines the Asiatic and Australian coasts. Among these are
the Behring Sea, enclosed by the peninsula of Alaska and the Aleutian
Islands; Okhotsk Sea, enclosed by Kamchatka and the Kurile Islands; the
Sea of Japan, and the North and South China seas; and the Arafura,
Coral, and New Zealand seas, on the Australian Coast.
Only two inland seas of considerable size--the Gulf of California in
North America, and the Yellow Sea in Asia--mark this entire basin.
THE INDIAN OCEAN is characterized by gulfs, two of which form the entire
extension of the basin; namely, the Gulf of Bengal, and the Arabian Sea.
It has also two inland seas of considerable extent, the Red Sea and the
Persian Gulf, isolating the peninsula of Arabia from the adjacent
continents; but border seas are wholly wanting in the Indian Ocean.
THE ARCTIC OCEAN is a partially enclosed sea, which a comparatively
inconsiderable rise of the sea-bottom would convert into a true
Mediterranean. Three openings connect it with the Pacific and Atlantic
Oceans, namely, Behring Straight (narrow and shallow), Davis Straight,
and the broad expanse of water lying between Norway and Greenland. Of
these, the last is by far the most important, for through it the warm
waters of the Gulf Stream find access to the Polar basin, and keep the
sea free from ice throughout the year. This current is supposed to flow
feebly along the coast of Siberia, until, deflected by the land, it
becomes merged in the cold counter-currents which, passing along the
eastern coasts of Greenland and Labrador, carry immense masses of ice
into the Atlantic.
[Illustration: =PICTORIAL DIAGRAM OF THE STRUCTURE OF THE EARTH IF THE
WATERS WERE REMOVED=
Ridges, mountains, plateaus, which may represent submerged continents of
the past, and many an abyss that exceeds in depth the height of the
highest mountains, are shown above. The shallow coasts, marked by the
lightest shade, are part of the present Continental Shelf, and do not
exceed six hundred feet in depth. Beyond this shelf, as a rule, the
oceans rapidly attain great depths. Our knowledge of the ocean bed has
been obtained from the extensive soundings.]
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.