煤渣

yǐ xì méi zhā pū chéng de pǎo dào

以细煤渣铺成的跑道

a cinder track

yuán mù zhuǎn biàn chéng le hēi sè de méi zhā

原木转变成了黑色的煤渣。

The logs had turned into blackened cinders.