壮观的地下火世界上许多地方都有地下大火。现在美国16个州中,计有260处地下煤田正在燃烧。它们有些发生在废弃了的矿井中,有些发生在还未开采的煤层和露天煤田中。这些大火有被闪电点燃的,有由草原烈火引起的,也可能是自燃或人们抛弃的燃烬所点燃。它们也许象香烟一样慢慢地燃烧,也许象高炉一样凶猛。这些大火几十年甚至几个世纪地燃烧着。大火已威胁到人类的安全,但要扑灭地下火也许是至今为止人类所遇到的最复杂的消防难题。由于火焰在煤矿层中运动难以捉摸,仅仅发现地下火的边界就已十分困难。而且,大火在地下迁移,并能穿过地下非可燃性物质组成的广阔屏障,在远处引起新的大火。 Spectacular underground fire There are underground fires in many parts of the world. Of the 16 U.S. states now, 260 underground coal fields are burning. Some of them occur in abandoned mines and some in unexplored coal seams and open pit coal fields. These fires were ignited by lightning, caused by grassland fires, or ignited by spontaneous combustion or abandoned by people. They may burn slowly as cigarettes, perhaps as fierce as blast furnaces. These fires burn for decades or even centuries. Fire has threatened humankind, but putting out underground fires may be the most complex firefighting problem humanity has encountered so far. Due to the elusive flame movement in the coal seam, it has become very difficult to find the boundaries of underground fires. Moreover, the fire has migrated underground and can pass through the vast barrier of underground non-flammable substances, causing new fires in the distance.