The Cambrian-age Tonto Group is a set of rocks famous for holding clues to the burst of new life that reshaped Earth 500 ...

Spectacular blooms of wildflowers are carpeting the Merced River Canyon and you'll first spot the bursts of color —poppies, lupine, red bud and more — in Mariposa on your way to the Arch Rock ...

During the summer of 1954 I also collected from the Grand Canyon of the Colorado River for the purpose of making studies of remanent magnetism on these rocks. I wish here to compare my results ...