Norske, a Norwegian coal mining company, owns 4%, Arktikugol, a Russian coal mining company, owns 0.4%, while other private owners hold 0.4%. As Svalbard is north of the Arctic Circle, it experiences midnight sun in summer and polar night in winter. At 74° north, the midnight sun lasts 99 days and polar night 84 days, while the respective figures at 81° north are 141 and 128 days. In Longyearbyen, midnight sun lasts from 20 April until 23 August, and polar night lasts from 26 October to 15 February. In winter, the combination of full moon and reflective snow can give additional light. Due to the Earth's tilt and the high latitude, Svalbard has extensive twilights. Longyearbyen sees the first and last day of polar night having seven and a half hours of twilight, whereas the perpetual light lasts for two weeks longer than the midnight sun. On the summer solstice, the sun bottoms out at 12° sun angle in the middle of the night, being much higher during night than in mainland Norway's polar light areas. However, the daytime strength of the sun remains as low as 35°. Glacial ice covers or 60% of Svalbard; 30% is barren rock while 10% is vegetated. The largest glacier is Austfonna () on Nordaustlandet, followed by Olav V Land and Vestfonna. During summer, it is possible to ski from Sørkapp in the south to the north of Spitsbergen, with only a short distance not being covered by snow or glacier. Kvitøya is 99.3% covered by glacier. The landforms of Svalbard were created through repeated ice ages, when glaciers cut the former plateau into fjords, valleys, and mountains. The tallest peak is Newtontoppen (), followed by Perriertoppen (), Ceresfjellet (), Chadwickryggen (), and Galileotoppen (). The longest fjord is Wijdefjorden (), followed by Isfjorden (), Van Mijenfjorden (), Woodfjorden (), and Wahlenbergfjorden (). Svalbard is part of the High Arctic Large Igneous Province, and experienced Norway's strongest earthquake on 6 March 2009 at magnitude 6.5. History Dutch discovery, exploration, and mapping of a terra nullius The Dutchman Willem Barentsz made the first discovery of the archipelago in 1596, when he sighted the coast of the island of Spitsbergen while searching for the Northern Sea Route. The first recorded landing on the islands of Svalbard dates to 1604, when an English ship landed at Bjørnøya, or Bear Island, and started hunting walrus. Annual expeditions soon