 All glaciers in the park are relatively small glaciers that occupy areas that are in almost permanent shade , such as north- and northeast @-@ facing cirques . Lyell Glacier is the largest glacier in Yosemite ( the Palisades Glaciers are the largest in the Sierra Nevada ) and covers 160 acres ( 65 ha ) . None of the Yosemite glaciers are a remnant of the much , much larger Ice Age alpine glaciers responsible for sculpting the Yosemite landscape . Instead , they were formed during one of the neoglacial episodes that have occurred since the thawing of the Ice Age ( such as the Little Ice Age ) . Climate change has reduced the number and size of glaciers around the world . Many Yosemite glaciers , including Merced Glacier , which was discovered by John Muir in 1871 and bolstered his glacial origins theory of the Yosemite area , have disappeared and most of the others have lost up to 75 % of their surface area . 
