Interpenetration of land and sea.
Since it is from the land, as the inhabited portion of the earth's surface, that all maritime movements emanate, and to the land that all oversea migrations are directed, the reciprocal relations between land and sea are largely determined by the degree of accessibility existing between the two. This depends primarily upon the articulation of a land-mass, whether it presents an unbroken contour like Africa and India, or whether, like Europe and Norway, it drops a fringe of peninsulas and a shower of islands into the bordering ocean. Mere distance from the sea bars a country from its vivifying contact; every protrusion of an ocean artery into the heart of a continent makes that heart feel the pulse of life on far-off, unseen shores. The Baltic inlet which makes a seaport of St. Petersburg 800 miles (1,300 kilometers) back from the western rim of Europe, brings Atlantic civilization to this half-Asiatic side of the continent. The solid front presented by the Iberian Peninsula and Africa to the Atlantic has a narrow crack at Gibraltar, whence the Mediterranean penetrates inland 2,300 miles (3,700 kilometers), and converts the western foot of the Caucasus and the roots of the Lebanon Mountains into a seaboard. By means of the Arabian Sea, the Indian Ocean runs northward 1,300 miles (2,200 kilometers) from Cape Comorin to meet the Indus delta; and then turns westward 700 miles farther through the Oman and Persian gulfs to receive the boats from the Tigris and Euphrates. Such marine inlets create islands and peninsulas; which are characterized by proximity to the sea on all or many sides; and in the interior of the continents they produce every degree of nearness, shading off into inaccessible remoteness from the watery highway of the deep.
The success with which such indentations open up the interior of the continents depends upon the length of the inlets and the size of the land-mass in question. Africa's huge area and unbroken contour combine to hold the sea at arm's length, Europe's deep-running inlets open that small continent so effectively that Kazan, Russia's most eastern city of considerable size, is only 750 miles (1,200 kilometers) distant from the nearest White Sea, Baltic, and Azof ports. Asia, the largest of all the continents, despite a succession of big indentations that invade its periphery from Sinai peninsula to East Cape, has a vast inland area hopelessly far from the surrounding oceans.
Ratio of shoreline to area.
In order to determine the coast articulation of any country or continent, Carl Ritter and his followers divided area by shoreline, the latter a purely mathematical line representing the total contour length. By this method Europe's ratio is one linear mile of coast to 174 square miles of area, Australia's 1:224, Asia's 1:490, and Africa's 1:700. This means that Europe's proportion of coast is three times that of Asia and four times that of Africa; that a country like Norway, with a shoreline of 12,000 miles traced in and out along the fiords and around the larger islands,[440] has only 10 square miles of area for every mile of seaboard, while Germany, with every detail of its littoral included in the measurement, has only 1,515 miles of shoreline and a ratio of one mile of coast to every 159 square miles of area.
The criticism has been made against this method that it compares two unlike measures, square and linear, which moreover increase or decrease in markedly different degrees, according as larger or smaller units are used. But for the purposes of anthropo-geography the method is valid, inasmuch as it shows the amount of area dependent for its marine outline upon each mile of littoral. A coast, like every other boundary, performs the important function of intermediary in the intercourse of a land with its neighbors; hence the length of this sea boundary materially affects this function. Area and coastline are not dead mathematical quantities, but like organs of one body stand in close reciprocal activity, and can be understood only in the light of their persistent mutual relations. The division of the area of a land by the length of its coastline yields a quotient which to the anthropo-geographer is not a dry figure, but an index to the possible relations between seaboard and interior. A comparison of some of these ratios will illustrate this fact.
Germany's shoreline, traced in contour without including details, measures 787 miles; this is just one-fifth that of Italy and two-fifths that of France, so that it is short. But since Germany's area is nearly twice Italy's and a little larger than that of France, it has 267 square miles of territory for every mile of coast, while Italy has only 28 square miles, and France 106. Germany has towns that are 434 miles from the nearest seaboard, but in Italy the most inland point is only 148 miles from the Mediterranean.[441] If we turn now to the United States and adopt Mendenhall's estimate of its general or contour coastline as 5,705 miles, we find that our country has 530 square miles of area dependent for its outlet upon each mile of seaboard. This means that our coast has a heavy task imposed upon it, and that its commercial and political importance is correspondingly enhanced; that the extension of our Gulf of Mexico littoral by the purchase of Florida and the annexation of Texas were measures of self-preservation, and that the unbroken contour and mountain-walled face of our Pacific littoral is a serious national handicap.