Science: Some 17 million years ago, the Grand Canyon started to form according to geologists at the University of New Mexico, led by Victor Polyak, who used a used an improved uranium-lead dating technique, which yields ages of mineral back tens to hundreds of million years.

By dating mineral deposits inside caves up and down the canyon walls, the geologists said they determined the water levels over time, as erosion carved out the mile-deep canyon as it is known today. They concluded that the canyon started from the west, then another formed from the east, and the two broke through and met as a single majestic rent in the earth some six million years ago.

Previous theories had posited six million years as the earliest age for the beginning of the entire Grand Canyon of the Colorado River.