one of the South Shetland Islands, in the Drake Passage, off the Antarctic Peninsula. It is a sunken volcano, the crater of which, about 10 miles (16 km) in diameter, forms one of the best anchorages in the Antarctic. The harbour, known as Port Foster, has been the central port of entry for British claims in the Antarctic since 1910. The island has also served as a whaling and seal-hunting station from 1906 to 1931 and, during World War II, as a British military base. Argentina, Chile, and the United Kingdom, each of which claims the island, all have operated stations there. Volcanic eruptions and earthquakes disturbed the island in 1967 and thereafter.