(GPS) equipment. Extrapolating this data to areas on Borneo and Sumatra underlain by known coal deposits, it was estimated that more than 250,000 coal-seam fires may have been burning in Indonesia in 1998. Land clearing practices which use fire, often starting forest fires, may be the cause of coal-seam fires in Indonesia. In 1982 and 1983 one of the largest forest fires in this century raged for several months through an estimated 5 million hectares of Borneo's tropical rainforests. Goldammer and Seibert however concluded that there are indications that coal-seam fires already occurred between 13,200 and 15,000 BP. A fire season usually occurs every 3 to 5 years, when the climate in parts of Indonesia becomes exceptionally dry from June to November due to the El Niño–Southern Oscillation off the west coast of South America. Since 1982, fire has been a recurring feature on the islands of Borneo and Sumatra, burning large areas in 1987, 1991, 1994, 1997–1998, 2001 and 2004. In October 2004 smoke from land clearing again covered substantial portions of Borneo and Sumatra, disrupting air travel, increasing hospital admissions, and extending to portions of Brunei, Singapore and Malaysia. Coal outcrops are so common in Indonesia it is virtually certain these fires ignited new coal-seam fires. New Zealand Burnett's Face, West Coast Strongman Mine, West Coast Wangaloa, Otago Pike River Mine, West Coast Millerton area, Stockton Mine, West Coast, South Island, New Zealand Norway In 1944, Longyearbyen Mine #2 on Svalbard was set alight by sailors from the German battleship Tirpitz on its final sortie outside of Norwegian coastal waters. The mine continued to burn for 20 years, while some of the areas were subsequently mined from the reconstructed Mine #2b. South Africa Transvaal and Delagoa Bay Collieries near Emalahleni (formerly known as Witbank), Mpumalanga has been burning since the mine was abandoned in 1953. United States Many coalfields in the US are subject to spontaneous ignition. The federal Office of Surface Mining (OSM) maintains a database (AMLIS), which in 1999 listed 150 fire zones. In mid-2010, according to OSM, more than 100 fires were burning beneath nine states, most of them in Colorado, Kentucky, Pennsylvania, Utah and West Virginia. Some geologists say that many fires go unreported, so that the actual number of them may be nearer to 200, across 21 states. In Pennsylvania, 45 fire zones are known, the most famous being the Centralia mine fire