I mean, water carved this cathedral out of nothing. DR DAVE THAYER: Yep. MICHIO KAKU: And how long has this erosion been taking place? DR DAVE THAYER: Well at least 5.5 million years is what they say.

Water is everywhere around us ... as he follows the course of the Amazon River as it travels downstream. The erosion of the Grand Canyon. videoThe erosion of the Grand Canyon Liz Bonnin introduces ...