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74 PHYSICAL GEOGRAPHY.

belong, properly, to the continental systems of

elevations.
' 199, The Oceanic Areas. _The ocean is one
continuous body of water, but for purposes of
description and study it is generally divided into
five smaller bodies: the Pacific, Atlantic, Indian,
Aretic, and Antarctic Oceans. The last two are
separated from the preceding by the polar circles ;
. the others are separated mainly by the continents.
As the continents do not extend to the Antarctic
Circle, the meridians of Cape Horn, Cape of
Good Hope, and South Cape in Tasmania, are
taken as the ocean boundaries south of these
points. .
The following table gives the relative size of the oceanic
areas:
The Pacific occupies aed
“ Atlantic “
“ Indian “ ft

Antarctic
« Arctic sf we

200. Articulation of Land and Water—The
indentations of the oceans, or the lines of junc-
tion between the water and the land, may be
arranged under four heads:

(1.) Inland Seas, or those surrounded by a
nearly continuous or unbroken land-border; as
the Gulf of Mexico, Hudson Bay, the Baltic, and
the Mediterranean, in the Atlantic; the Red Sea
and the Persian Gulf, in the Indian; and the
Gulf of California, in the Pacific.

(2.) Border Seas, or those isolated from the
rest of the ocean by peninsulas and island chains ;
as the Caribbean Sea, the Gulf of St. Lawrence,
and the North Sea, in the Atlantic; and Bering
Sea, the Sea of Okhotsk, the Sea of Japan, and
the North and South China Seas, in the Pacific.

(3.) Gulfs and Bays, or broad expansions of
the water extending but a short distance into
the land; as the Gulf of Guinea and the Bay of
Biscay, in the Atlantic; and the Bay of Bengal
and the Arabian Sea, in the Indian.

(4.) Fiords, or deep inlets, with high, rocky
headlands, extending often from 50 to 100 miles

the entire water-area,
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into the land. One of the best instances of this

form of indentation is off the Norway coast. Ac-
cording to Dana, fiords are valleys that were ex-
cavated by vast ice-masses called glaciers, but
which have since become partially submerged by
the gradual subsidence of the land.

Fiord valleys occur on the Norway coast, on
the coasts of Greenland, Labrador, Nova Scotia,
and Maine, on the western coast of Patagonia

 

 

then) aA, wlAn MA BAR

Ges

and Chili, and on the western coast of North
America north of the Straits of Fuca. On parts
of the coast of Greenland the glaciers are now
cutting out their partially submerged valleys,
and forming what will probably become fiord
valleys.

The Atlantic Ocean is characterized by inland
seas; the Pacific, by border seas; the Indian, by
gulfs and bays; the Atlantic and the Pacific, by
fiords.

201. Depth of the Ocean The mean depth of
the ocean is about 12,000 ft.,.or nearly 23 miles.
Recent soundings give the greatest depth of the
Atlantic, in the neighborhood of the island of
St. Thomas of the West Indies, as- 27,000 feet.
The greatest depth in the Pacific, as reported by
recent careful soundings, ocems=ea
qudeis BECO These give a edi of shout

} miles, or less than the greatest elevation of the
inca It is probable, however, that some portions .
of the ocean are much deeper.

The greater depressions of the ocean are called
deeps, the shallower portions are called rises.

202. The Pacific Ocean—The shape of the
shore-line of the Pacific is that of an immense
oval, nearly closed at the Ho) but broad and
open at the south.

 

As indicated by the island chains, a number of shallow
places, or rises, extend in the direction of the north-west
trend: the summits of those on the north form the Sand-
wich Islands, and the summits of those on the south form
the Polynesian Island chain.

208. The Atlantic Ocean—The shape of the
shore-line of the Atlantic is that of a long,

-trough-like valley, with nearly parallel sides.

The Atlantic has a broad connection with both
the polar oceans, and forms the only open chan-
nel for the intermingling of the warm and cold
waters.

Shape of the Bed.—Recent soundings in the Atlantic show
the presence of a submarine plateau extending in mid-
ocean parallel to the coasts of the continents from the lati-
tude of the southern point of Africa to Iceland, thus di-
viding the basin into eastern and western valleys. The
western valley is the deeper; the average depths of the two
being respectively 18,000 and 13,000 feet. A remarkable

Feet. Level of the sea.

 

Fig. 69, The ToleeaNaib Plateau.

plateau extends across these valleys, from Newfoundland
to Ireland. Its depth ranges from 10,000 to nearly 13,000
feet. It is called the Telegraphic Plateau, and bears a
number of telegraphic cables. The eastern and western’