SOUTH GEORGIA and the South Sandwich Islands are 2 island formations at the southern extremities of the Atlantic Ocean, not far from the Antarctic Peninsula that juts out from Antarctica, 1,000 mile (1,600 kilometer) to the south. Mostly consisting of steep mountains and ice, they have never had an indigenous population, but are instead known for 1 of the most numerous and diverse bird populations on earth. The British have administered the islands since 1908, first as dependencies of the Falkland Islands about 800 mile (1,300 kilometer) to the northwest, then as a separate territory dating from 1985. Argentina continues to claim the islands, but has formally renounced intentions to regain the islands militarily. South Georgia and the South Sandwich Islands are volcanic in origin, formed on the boundaries of 2 small tectonic plates, the Scotia and South Sandwich plates, as they rub against or are subducted beneath the much larger South American Plate. South Georgia consists of 1 main island, with smaller islands offshore (Willis, Bird, and Cooper), plus the more distant Shag Rocks, Black Rock, and Clerke Rocks. The South Sandwich Islands are a chain of 11 main islands (from north to south): Traversay, Protector Shoal, Zavodovski, Leskov, Visokoi, Candlemas, Vindication, Saunders, Montagu, Bristol, and the Thule Islands . These islands form an arc, stretching about 240 mile (400 kilometer), following the curve of the South Sandwich Trench, a deep trough in the Atlantic sea floor. The South Sandwich Islands are highly volcanic and geologically recent in origin: roughly 5 million years. Most of the islands consist of basalt and lava flow, with glaciers covering about 80 percent of each island. Together, South Georgia and the South Sandwich Islands form part of the Scotia Arc, which extends from the tip of to Antarctica (and also includes the South Shetland and South Orkney Islands, though these are not part of the British dependency). The island of South Georgia is 105 mile (170 kilometer) long, and about 25 mile (40 kilometer) wide. Two mountain ranges form its spine, with 11 peaks exceeding 6,600 foot (2,000 meter). The coastline of South Georgia is generally rough and mountainous, with plentiful large bays and inlets, mostly on the north coast, well suited for deepwater anchorages and whaling stations. Moraine on the floor of many of the bays, deposited by over 160 glaciers, creates a serious hazard for ships and has caused numerous wrecks. The interior is rugged and mostly covered in permanent ice and snow, with little vegetation. The South Sandwich Islands are difficult to approach by ship because of these extreme weather conditions.