英語時差：奇怪的熔巖（下）

Over eons, flowing water carved new valleys to the sides of the hardened lava. The hard lava didn’t erode as much as the surrounding rock, eventually giving the landscape the appearance it has today. Think about pouring hot candle wax down a channel in a hill of sand, then blowing away some of the sand after the wax has hardened. Unfortunately, no. For that theory to work, the lava flows would have to be much older than they are. Dating of the hardened lava reveals that it might even be as young as the most recent ice age. Can you solve the mystery of the mountain-climbing lava? Tune in to our next program for the solution!