On the horizon he could make out the hazy outline of one of the country's extinct volcanoes.地平线上，他只能依稀看出该国一座死火山的轮廓。The volcano is extinct.这座火山是座死火山。They have found extinct undersea volcanoes.他们发现了海底死火山。Extinct volcanoes are those that have not erupted in historic times.死火山指有史以来没有喷发过的火山。