 Glacial systems reached depths of up to 4 @,@ 000 feet ( 1 @,@ 200 m ) and left their marks in the Yosemite area . The longest glacier in the Yosemite area ran down the Grand Canyon of the Tuolumne River for 60 miles ( 97 km ) , passing well beyond Hetch Hetchy Valley . Merced Glacier flowed out of Yosemite Valley and into the Merced River Gorge . Lee Vining Glacier carved Lee Vining Canyon and emptied into Lake Russel ( the much @-@ enlarged ice age version of Mono Lake ) . Only the highest peaks , such as Mount Dana and Mount Conness , were not covered by glaciers . Retreating glaciers often left recessional moraines that impounded lakes such as the 5 @.@ 5 miles ( 9 km ) long Lake Yosemite ( a shallow lake that periodically covered much of the floor of Yosemite Valley ) . 
