The Grand Canyon is one of the most spectacular landscapes in the United States. Located in northern Arizona, the canyon is over a mile deep from rim to river and up to 17 miles wide. The north rim sits 1000 feet higher than the south and at its most narrow point is only 1-mile wide.

The exact process that formed the Grand Canyon is still a bit of a mystery. It's not a simple case of the Colorado River gouging out the canyon through the eons. Many theories have been proposed over the years. Even the course and age of the Colorado River through time is debated. Is it an old river or a young one? Were other bodies of water or rivers long since gone involved in its formation? How much did volcanic activity or continental plate movement contribute? It's likely that many factors have contributed to it's formation over tens of millions of years.

And it's interesting to think the canyon we see today could look completely different in a few more million years...