Our national parks journey this week takes us to the western state of Colorado. There, you will find a 77-kilometer-long canyon. Its exposed rocks are among the oldest you will find on Earth.
The canyon is so narrow and so deep that sunlight shines only briefly at the bottom at midday. That frequent darkness is what has given this canyon its name.
Welcome to Black Canyon of the Gunnison National Park!
Black Canyon seems impossibly steep and narrow. The fast moving Gunnison River formed the canyon over millions of years. As the river flows through the canyon, it drops an average of 18 meters per kilometer. The Gunnison River loses more elevation in its 77 kilometer canyon stretch than the Mississippi River does in 2,400 kilometers from Minnesota to the Gulf of Mexico.
This loss in elevation causes the river to gain speed and force. Over time, that force has carved and cut the hard rock, and created the wild and jagged rock formations found at Black Canyon. That process is known as erosion.