Friday, June 30, 2006

Mine fire

A Mine fire is the underground smouldering of a coal mine. They are emerging as a global threat with significant economic, social and ecological impacts, neglected before.Mine fires can burn for very long periods of time (months or years), until the seam in which they smoulder is exhausted. They propagate in a creeping fashion along mines shafts and cracks. Because they are underground, they are extremely difficult and costly to reach and put out. To date, there are virtually no reported successful attempts to extinguish a mine fire. There is a strong similarity between mine fires and peat fires.

Some fires along coal seams are natural occurrences. Some coals may self-ignite at temperatures below 100°C (212°F) in the right conditions of moisture and grain size. Wildfires (lightning caused or others) can ignite the coal closer to the surface or entrace, and the smouldering fire can spread through the seam, creating subsidence that may open further seams to oxygen. Prehistoric clinker outcrops in the American West are the result of prehistoric coal fires that left a residue that resists erosion better than the matrix, leaving buttes and mesa. "Scientists estimate that Australia's Burning Mountain, the oldest known coal fire, has burned for 6,000 years,"

Mine fires may begin as a result of an industrial accident, generally involving a gas explosion. Historically, some mine fires were started when bootleg mining was stopped by authorities, usually by blowing the mine up. Many recent mine fires have started from people burning trash in a landfill that was in proximity to abandoned coal mines .

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