Different aspects of the sedimentary layers that make up @glaciernps. Looking at Sperry Glacier from Logan Pass — over sediment, shale, snow, boulders, tree covered slopes, grass and old glacial remnants. Swipe right and pinch & zoom for a closer view of the layers in the glacier. [from wiki] Once one of the largest glaciers in the park, the surface area of Sperry Glacier has retreated 75 percent since the mid-19th century. 2005 measurements of the surface area of the glacier resulted in an estimated area of 216 acres (0.87 km2), whereas the glacier is estimated to have covered an area of 930 acres (3.8 km2) at the end of the Little Ice Age in the mid-19th century. The glacier lost almost 35 percent of its surface area between 1966 and 2005. The glacier is named for Lyman B. Sperry, a professor from Oberlin College, who in 1895 participated in an expedition to explore the geography and map the region where the glacier is located. Like all other glaciers in the park, Sperry has significantly retreated, though it leaves many minor glacial features, including large moraines and streams and lakes colored a milky aqua from glacial flour.