Shuangyashan is a coal mining prefecture-level city located in the eastern part Heilongjiang province, People's Republic of China, bordering Russia's Khabarovsk and Primorsky krais to the east. Since China is known to have underground coal fires it is not unreasonable to posture that the fires seen on this satellite image might be from coal seam fires. The number of coal fires burning under the Earth's surface at any given time is not known, but it is reasonable to assume that anywhere that coal is present, fire may be as well. These fires can arise spontaneously, or be ignited by lightning strikes, forest fires, or human activity. The problem with coal seam fires is that once fire takes hold, it can burn for tens or even hundreds of years because of the seemingly unending amount of fuel at disposal to continue the fire's growth. Not only does this waste the underground coal, but the smoke arising from these fires causes serious air pollution. Sulfur dioxide, nitrogen oxide, carbon dioxide, mercury, arsenic, fluorine and selenium can all be released from coal seam fires. The compounds contribute to air pollution, acid rain and global warming, and cause respiratory and other illnesses, as well as neurological and developmental problems in animals (including humans). NASA's Terra satellite collected this natural-color image with the Moderate Resolution Imaging Spectroradiometer, MODIS, instrument on October 17, 2013. Actively burning areas, detected by MODIS's thermal bands, are outlined in red.