When I first saw the Grand Canyon many years ago, I asked myself the question that every visitor asks. How did this great big, amazingly beautiful hole in the ground get here?

The answer is a story that defies intuition. The Colorado River snakes through the region and lies now at the bottom of the immense canyon. Like all rivers, it carries small bits of stone that chip away at the riversides and river bottom, one tiny spec at a time. Keep that up for a few centuries, and the river slowly deepens its channel.