Borders of the continents

The boundaries between the continents of Earth are generally a matter of geographical convention. Several slightly different conventions are in use. The number of continents is most commonly considered six or seven but may range as low as four when the Americas and Afro-Eurasia are each considered a single continent. According to the definition of a continent in the strict sense, an island cannot be part of any continent, but by convention and in practice most major islands are associated with a continent.

There are three overland boundaries subject to definition:

While the isthmus between Asia and Africa and that between the two Americas are today navigable, via the Suez and Panama canals respectively, man-made diversions and canals are generally not accepted on their own accord as continent-defining boundaries; the Suez Canal happens to traverse the isthmus between the Mediterranean Sea and Red Sea, dividing Asia and Africa. The remaining boundaries concern the association of islands and archipelagos with specific continents, notably:

The European and African mainlands are non-contiguous, and the delineation between these continents is thus merely a question of which islands are to be associated with which continent. At its nearest point, Spain and Morocco are separated by only 13 kilometres (8.1 miles).

The Portuguese Atlantic island possession of the Azores is 1,368 km (850 mi) from Europe, 1,507 km (936 mi) from Africa, and is usually grouped with Europe if grouped with any continent. By contrast, the Canary and Madeira islands off the Atlantic coast of Morocco are much closer to and usually grouped with Africa (Madeira is 860 km (530 mi) from Europe and 660 km (410 mi) from Africa).

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