ISLAND (O.E. ieg =isle, +land 1 ), in physical geography, a term generally definable as a piece of land surrounded by water. Islands may be divided into two main classes, continental and oceanic. The former are such as would result from the submergence of a coastal range, or a coastal highland, until the mountain bases were cut off from the mainland while their summits remained above water. The island may have been formed by the sea cutting through the landward end of a peninsula, or by the eating back of a bay or estuary until a portion of the mainland is detached and becomes surrounded by water. In all cases where the continental islands occur, they are connected with the mainland by a continental shelf, and their structure is essentially that of the mainland. The islands off the west coast of Scotland and the Isles of Man and Wight have this relation to Britain, while Britain and Ireland have a similar relation to the continent of Europe. The north-east coast of Australia furnishes similar examples, but in addition to these in that locality there are true oceanic islands near the mainland, formed by the growth of the Great Barrier coral reef. Oceanic islands are due to various causes. It is a question whether the numberless islands of the Malay Archipelago should be regarded as continental or oceanic, but there is no doubt that the South Sea islands scattered over a portion of the Pacific belong to the oceanic group. The ocean floor is by no means a level plain, but rises and falls in mounds, eminences and basins towards the surface. When this configuration is emphasized in any particular oceanic area, so that a peak rises above the surface, an oceanic island is produced. Submarine volcanic activity may also raise material above sea-level, or the buckling of the ocean-bed by earth movements may have a similar result. Coral islands (see ATOLL) are oceanic islands, and are frequently clustered upon plateaux where the sea is of no great depth, or appear singly as the crown of some isolated peak that rises from deep water.

Island life contains many features of peculiar interest. The sea forms a barrier to some forms of life but acts as a carrier to other colonizing forms that frequently develop new features in their isolated surroundings where the struggle for existence is greater or less than before. When a sea barrier has existed for a very long time there is a marked difference between the fauna and flora even of adjacent islands. In Bali and Borneo, for example, the flora and fauna are Asiatic, while in Lombok and Celebes they are Australian, though the Bali Straits are very narrow. In Java and Sumatra, though belonging to the same group, there are marked developments of bird life, the peacock being found in Java and the Argus pheasant in Sumatra, having become too specialized to migrate. The Cocos, Keeling Islands and Christmas Island in the Indian Ocean have been colonized by few animal forms, chiefly sea-birds and insects, while they are clothed with abundant vegetation, the seeds of which have been carried by currents and by other means, but the variety of plants is by no means so great as on the mainland. Island life, therefore, is a sure indication of the origin of the island, which may be one of the remnants of a shattered or dissected continent, or may have arisen independently from the sea and become afterwards colonized by drift.

The word ". island " is sometimes used for a piece of land cut off by the tide or surrounded by marsh (e.g. Hayling Island).

1 The O.E. ieg, ig, still appearing in local names, e.g. Anglesey, Battersea, is cognate with Norw. oy, Icel. ey, and the first part of Ger. Eiland, etc.; it is referred to the original Teut. ahwia, a place in water, ahwa, water, cf. Lat. aqua; the same word is seen in English " eyot," " ait," an islet in a river. The spelling " island," accepted before 1700, is due to a false connexion with " isle," Fr. He, Lat. insula.

xiv. 28 a ISLAY, the southernmost island of the Inner Hebrides, Argyllshire, Scotland, 16 m. W. of Kintyre and f m. S.W. of Jura, from which it is separated by the Sound of Islay. Pop. (1901) 6857; area, 150,400 acres; maximum breadth 19 m. and maximum length 25 m. The sea-lochs Gruinart and Indaal cut into it so deeply as almost to convert the western portion into a separate island. It is rich and productive, and has been called the " Queen of the Hebrides." The surface generally is regular, the highest summits being Ben Bheigeir (1609 ft.) and Sgorr nam Faoileann (1407 ft.). There are several freshwater lakes and streams, which provide good fishing. Islay was the ancient seat of the " lord of the Isles," the first to adopt that title being John Macdonald of Isle of Islay, who died about 1386; but the Macdonalds were ultimately ousted by their rivals, the Campbells, about 1616. Islay House, the ancient seat of the Campbells of Islay, stands at the head of Loch Indaal. The island was formerly occupied by small crofters and tacksmen, but since 1831 it has been gradually developed into large sheep and arable farms and considerable business is done in stock-raising. Dairy-farming is largely followed, and oats, barley and various green crops are raised. The chief difficulty in the way of reclamation is the great area of peat (60 sq. m.), which,at its present rate of consumption, is calculated to last 1500 years. The island contains several whisky distilleries, producing about 400,000 gallons annually. Slate and marble are quarried, and there is a little mining of iron, lead and silver. At Bowmore, the chief town, there is a considerable shipping trade. Port Ellen, the principal village, has a quay with lighthouse, a fishery and a golf-course. Port Askaig is the ferry station for Faolin on Jura. Regular communication with the Clyde is maintained by steamers, and a cable was laid between Lagavulin and Kintyre in 1871.

Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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