image: Redwall Caverns, a large grotto in the Redwall Limestone in Marble Canyon, eastern Grand Canyon. This image relates a study by Dr. Victor Polyak and colleagues at University of New Mexico in Albuquerque, N.M., titled "Age and Evolution of Grand Canyon Revealed by U-Pb Dating of Water Table-Type Speleothems." The article appeared in the March 7, 2008, issue of the journal Science, published by AAAS. view more
Credit: Image courtesy of Victor Polyak