VIRGIN ISLANDS [Virgin Islands] group of about 100 small islands, West Indies, E of Puerto Rico. The islands are divided politically between the United States and Great Britain. Although constituting the westernmost part of the Lesser Antilles, the Virgin Islands form a geological unit with Puerto Rico and the Greater Antilles; they are of volcanic origin overlaid with limestone. The islands are subject to sometimes severe hurricanes between August and October and suffer from light earthquakes. The water supply is almost completely dependent on rainfall and is preserved in cisterns; some water also comes from desalinization plants. The tropical climate, with its cooling northeast trade winds, and the picturesque quality of the islands, enhanced by their Old World architecture, have encouraged a large tourist trade, but the population, predominantly of African descent, remains poor. The islands were first visited by Europeans when Columbus landed on St. Croix in 1493.