This story appears in the February 2012 issue of National Geographic magazine. Carry a lawn chair and a sunshade—plenty of water too—onto the sage flats just south of Arizona's Highway 89A ...

The age of the fossil must be determined so ... it is possible to work out the relative ages of rocks. In the Grand Canyon, the layers of strata are nearly horizontal. Most sediment is either ...

Something dramatic happened about 500 million years ago called the Cambrian "explosion," during which an incredible diversity ...

To learn more about Red Rock Canyon, visit the conservation area's website. Grand Canyon West, Hoover Dam Stop and Optional Lunch and Skywalk ...