Layer upon layer of different rocks recede down into the Grand Canyon and back through time, until the strata, at the river, revealed some of the oldest exposed rocks on earth.

• 一层层各种各样的岩石叠铺着一直伸入峡谷之中直至地层，追逐着时光的变迁，在河床中显露着一些地球上最古老的岩石。