Some parts are 2 billion years old. It' stretched across Arizona 280 miles. It drops 2000 ft from the highest point of the Colorado River to the lowest part. It formed when the Rockies were developed to the east, and the Colordo Plateau rose 2 miles causing the vast amount of water to receed rapidly cutting into the rocks. Installation of a few dams has greatly reduced the erossion. There may be a new canyon forming to the east, and I have captured a picture of it.