 On the sheltered slopes of the highest peaks of Glacier National Park in Montana , the eponymous glaciers are diminishing rapidly . The area of each glacier has been mapped for decades by the National Park Service and the U.S. Geological Survey . Comparing photographs from the mid @-@ 19th century with contemporary images provides ample evidence that they have retreated notably since 1850 . Repeat photography since clearly show that glaciers such as Grinnell Glacier are all retreating . The larger glaciers are now approximately a third of their former size when first studied in 1850 , and numerous smaller glaciers have disappeared completely . Only 27 % of the 99 km2 ( 38 sq mi ) area of Glacier National Park covered by glaciers in 1850 remained covered by 1993 . Researchers believe that by the year 2030 , the vast majority of glacial ice in Glacier National Park will be gone unless current climate patterns reverse their course . Grinnell Glacier is just one of many glaciers in Glacier National Park that have been well documented by photographs for many decades . The photographs below clearly demonstrate the retreat of this glacier since 1938 . 
