First-time visitors to Yosemite Valley stare in astonishment at El Capitan’s sheer granite wall and Half Dome’s cleanly sliced face, understanding, perhaps vaguely, that it must have taken rain and glaciers a long time to cut and shape that scene. But how long did it take?
https://scitechdaily.com/berkeley-analysis-reveals-the-age-of-yosemite-valley/