Severe disruptions in air travel across the Atlantic and within Europe, caused by a volcanic (火山的;名詞為volcano) eruption (爆發) in Iceland (冰島), could continue for days, U.S. government aviation (航空) officials say. Authorities in Britain closed five major airports, including London's Heathrow, and the governments of Ireland, France, Denmark, Sweden, Finland, and Norway reportedly were taking similar precautions (預防措施). Safety officials are concerned about the threat of mechanical breakdowns posed by a huge cloud of ash (灰) generated from the eruption of a volcano (火山) under Iceland's Eyjafjallajokull Glacier (冰河). Experts say that because the superheated lava (熔岩) and vapor (蒸氣) from the volcano have to pass through hundreds of feet of ice before reaching the atmosphere (大氣層), the resulting ash cloud contains particles of glass. The bits of glass are particularly hazardous to jet engines and could cause them to shut down in midair, according to aviation experts.