Check out this new trail guide and geologic description of the Rio de Flag.
The Arizona Geological Survey has just released this online publication that explores the origin and geology of the Rio de Flag by Dr. Richard Holm, retired NAU professor of Geology and long time resident of Flagstaff.
It includes maps and guides to walking different reaches of the Rio, as well as a discussion on regional and local geology.
You can download this for free by going to the link below.