1、听说训练(6)Part A模仿朗读听录音,模仿朗读短文,注意画线单词的发音。短文读两遍。How the Grand Canyon was created remains one of the geologys greatest mysteries.Some evidence suggests that the process was a gradual one in which the Colorado River slowly cut deeper and deeper into the ground over millions of years.But volcanic rock samp
2、les taken from the canyon now suggest that the canyon was down-cut instead.Down-cutting is when a flood of water rushes over a landscape with enough force to cut deeply into the ground and leaves behind a canyon.Such a flood is usually released when a natural or man-made dam bursts.How the Grand Canyon was created remains one of the
