Workers drilling a well in Shanghai, China a few weeks ago noticed a miraculous sight: fire dancing on the surface of the well water.
The water, bubbling up from 200 feet underground, was ignited when a worker tried to light a cigarette.
This effect is beautiful and harmless, but it's related to a more sinister phenomenon that made the news in the U.S. a few years ago. Fracking wells, used to dredge up natural gas from underground, were tainting drinking water sources in Texas and Pennsylvania with flammable methane. When you turned on a tap and sparked a lighter, the stream of water would flare up.
Unlike fracking wells, which force water and chemicals into bedrock at high pressures to release and collect the natural gas, the Shanghai well hit natural gas accidentally. According to an expert, there are only trace amounts of gas in the water, enough for a light show but not enough to put the well in danger of exploding. The water will stop burning once the gas source is exhausted, and presumably be safe to drink—if perhaps a little charred-tasting.