Photographer: J. Richard Gaskill, MD, Los Gatos, Calif. This granite ridge has been gouged and polished by glaciers that flowed down Tenaya Canyon into Yosemite Valley. En route, they swept away massive amounts of crumbling granite, exposing the sheer northwest face of Half Dome, in the distance. The loose rocks in the foreground are glacial erratics, deposited as the glaciers receded.