Approximately 224 km north of Sydney, just off the New England Highway, in New South Wales, Australia, is a hill that has been burning for the last 6,000 years. The fire burns underground, at a depth of about 30 meters, fueled by a coal seam that runs through the sandstone. The aborigines called the mountain Wingen, which means ‘fire’, and used its heat for warmth in the winter months, for cooking and for the manufacture of tools. They believed that the mountain was set on fire by a tribesman to warn others when the Devil carried him off deep into the earth. European explorers and early settlers knew of the Burning Mountain but they thought the smoke coming out of the ground was volcanic in origin. It was not until 1829 that a geologist identified it as a coal seam fire.
Photo credit: NSW National Parks and Wildlife Service
Coal seam fire, as it happens, are incredibly common, and thousands of them are burning underground across the world. In the US state of Pennsylvania alone, as many as 45 fires are burning, the most famous being the Centralia mine fire which has been burning since 1962. In India, more than seventy individual fires are burning beneath a region of the Jharia coalfield in Jharkhand. The fires, which started in 1916, are rapidly destroying the only source of prime coking coal in the country. The problem is more acute in coal-rich nations such as China, where underground fires are consuming at least 10 million tons of coal annually—with some estimate putting the figure to twenty times more. Beside losses from burned and inaccessible coal, these fires contribute significantly to air pollution and increased levels of greenhouse gases in the atmosphere. A geologist from the University of Alaska at Fairbanks calls them “a worldwide catastrophe with no geographic territory, and if we don’t take care of them they’re going to take a toll on us.”
Underground coal-seam fires are the most persistent fires on Earth and can burn for thousands of years. There is geological evidence that coal seam fires existed as early as the Pleistocene era, although modern-day coal fires are usually the result of human undoing, such as mining accidents or open coal seams unintentionally coming in contact with oxygen. Some coals ignite spontaneously at temperatures as low as 40 °C. Once fire gets hold, temperatures climb rapidly. The permeability of the coal allows oxygen to reach the fire but poor ventilation traps the heat inside. Some coal fires exceed temperatures of 500 °C.
Coal fires are very difficult to extinguish. It’s like a frustrating, expensive version of whack-a-mole, writes Dan Cray for Time. “You put one down, then 300 feet later another one picks up,” says Mark Engle, a geologist with the U.S. Geological Survey. Many governments have completely given up on the effort.
One of the most visible changes coal seam fires make is upon the landscape and on the environment. For example, near a coal fire in Germany, elevated ground temperatures allowed many insects and spiders to survive the cold winter. In Australia’s Burning Mountain, the heat has killed off all vegetationexcept those in the periphery of the burning seam, which actually thrives from run-off from the brunt soil. Large areas of the land has collapsed as a result of the burnt-out coal seam, and smoke vent from many cracks on the ground. The heat has turned the soil red.
Unlike Pennsylvania’s Centralia, Burning Mountain is actually pretty safe for tourists. There is a 4 km-long walking trail through the region with information panels along the track unpacking the story of Burning Mountain and the fascinating Aboriginal heritage. A viewing platform at the climax of Burning Mountain walk provides a safe vantage point to view the exhaust vents and rocks transformed by extreme temperatures.
Source….. Kaushik in http://www.amusing planet.com