GRAND CANYON NATIONAL PARK – The Grand Canyon’s beauty beckons like gravity, pulling even the timid to the chasm’s edge.

But for those committing to the challenge of a cross-canyon hike, there awaits below the rim a reward beyond the spectacular scenery: time travel.

Those horizontal stripes on the postcard panoramas trace a billion years of geological history. They are the sediment and fossils of ancient oceans. According to author Scott Thybony, who literally wrote the books on canyon trails, to hike the canyon is to go back an average of 100,000 years with each downward step. As the trail winds and sometimes plummets through layers of hermit shale, redwall limestone and Tapeats sandstone, the canyon deepens and the climate warms. The hiker sheds his outer layers, and even some layers within; when the cell signal is gone, the world is quiet and the mind centers on the simple: food, water and the next footstep.