Lake Hazen, the largest lake in the world entirely north of the Arctic Circle (66ø30'N), is situated at the northern end of Ellesmere Island, the largest and most northerly of the Queen Elizabeth Islands . The lake was first discovered by the Inuit. In modern times it was first discovered in 1882 by Adolphus Greely during his exploration of the region. In an earlier period the region had been occupied by Inuit of the Dorset culture, but the area was abandoned following the climatic deterioration that began about this time coincident with the spread of the more recent Thule culture. Lake Hazen is situated on the Palaeozoic rocks of the Hazen Plateau of the Eureka Uplands. North of the lake the Hazen Fault Zone forms the boundary of the Grant Land Mountains. Most of the information on Lake Hazen is derived from the results of a further IGY expedition in 1957-58. In addition to geophysical and meteorological observations, investigations on the surrounding vegetation and its susceptibility to disturbance , the lake fauna and the limnology were carried out. The region around Lake Hazen functions as a "thermal oasis" in a true polar desert, the Lake Hazen Fault Zone functioning as a gigantic solar receiver while Lake Hazen itself augments this effect. The only fish species present, the anadromous arctic charr Salvelinus alpinus, maintains a sizeable population recognizable as distinct anadromous (migratory) and non-anadromous forms. These are the most northerly stock of charr in North America, possibly in the whole world. In recent years a small sport-fishing camp has been operating on the lake, serviced out of Resolute Bay. In 1983 the region was given the protective status of a National Park.