image: View of the thick sequence of limestones that contain numerous caves in the Grand Canyon. This image relates to an article that appeared in the March 7, 2008, issue of the journal Science, published by AAAS. The study, by Dr. Victor Polyak and colleagues at University of New Mexico in Albuquerque, N.M., was titled "Age and Evolution of Grand Canyon Revealed by U-Pb Dating of Water Table-Type Speleothems." view more
Credit: Image courtesy of John “Doug” Powell