Old Sun Glacier lies in Glacier National Park in Montana, immediately east and northeast of Mount Merritt, occupying high terrain between about 9,400 and 8,600 feet above sea level. It was named for Ntas, a Blackfoot sun priest whose name is translated as Old Sun. The glacier is marked by numerous crevasses and has been noted for a healthy accumulation zone, where persistent snowfall feeds the ice. Like many glaciers in the park, it has changed in recent decades. Between 1966 and 2005, it lost 12 percent of its surface area, showing measurable retreat while remaining an active part of the mountain landscape.