glaciers cover about 16% of the 6 million acres of denali national park and preserve. there are more extensive glaciers on the southeastern side of the range because more snow is dropped on this side from the moisture-bearing winds from the gulf of alaska. the 5 largest south-facing glaciers are yentna ( long), kahiltna (), tokositna (), ruth (), and eldrige (). the ruth glacier is thick. however, the largest glacier, muldrow glacier ( long), is located on the north side. nonetheless, the northern side has smaller and shorter glaciers overall. muldrow glacier has "surged" twice in the last hundred years. surging means that it has moved forward for a short time at a greatly increased rate of speed, due to a build-up of water between the bottom of the glacier and the bedrock channel floating on the ice (due to hydrostatic pressure).