History of submarines few years before the US, and paralleled subsequent US development in this area. In the 1950s, nuclear power partially replaced diesel-electric propulsion. The sailing of the first nuclear-powered submarine, the USN ""Nautilus"" in 1955 was soon followed by similar British, French and Russian boats. Equipment was also developed to extract oxygen from sea water. These two innovations, together with inertial navigation systems, gave submarines the ability to remain submerged for weeks or months, and enabled previously impossible voyages such as the crossing of the North Pole beneath the Arctic ice cap by the USS "Nautilus" in 1958. Most of the
Hans Tausen Ice Cap Hans Tausen Ice Cap Hans Tausen Ice Cap () is an ice cap in northern Greenland. Ice cores show it is around 3500–4000 years old. It formed since the Holocene climatic optimum of 6000-8000 BP. The ice cap is about 100 km from north to south and 80 km from east to west and sits on a 1300 m high plateau. The Hans Tausen Ice Cap is the source of many glaciers, including Ymer Glacier, Lur Glacier and the Tjalfe Glacier. It is a well studied ice cap, and is important to understanding the last Climatic Optimum. (Holocene climatic optimum)