Ranger Minute - How Old? (mov)
Ranger Minutes are short audiocasts or videocasts in which a park ranger shares interesting stories and information about Grand Canyon National Park.
Some of the photos in Ranger David's presentation are from the United States Geological Survey's Grand Canyon Website. Click here to see more USGS photography of Grand Canyon National Park. This includes views along and within the canyon and a collection of historic images along the Colorado River taken by the Powell Expedition of 1872. Website images include both standard photograph and 3D views (as anaglyphs - requiring red-and-cyan 3D viewing glasses).
The Grand Age of Rocks: The Numeric Ages for Rocks Exposed within Grand Canyon