southern end of the Earth's axis, lying in Antarctica, about 300 miles (480 km) south of the Ross Ice Shelf. This geographic South Pole does not coincide with the magnetic South Pole, from which magnetic compasses point and which lies on the Adélie Coast (at about 66°00′ S, 139°06′ E; the magnetic pole moves about 8 miles 【13 km】 to the northwest each year). Nor does it coincide with the geomagnetic South Pole, the southern end of the Earth's geomagnetic field (this pole also moves; during the early 1990s it was located about 79°13′ S, 108°44′ E). The geographic pole, at an elevation of some 9,300 feet (2,830 m; the elevation also changes constantly) above sea level, has six months of complete daylight and six months of total darkness each year. Ice thickness is 8,850 feet (2,700 m). First reached by the Norwegian explorer Roald Amundsen (Amundsen, Roald) on Dec. 14, 1911, the pole was reached the following year by the British explorer Robert F. Scott and in 1929 by the American explorer Richard E. Byrd. The South Pole is the site of a U.S. station and landing strip (Amundsen-Scott); owing to the movement of the polar ice cap, a new location of the exact rotational pole is marked periodically by station personnel.