The U.S. Board on Geographic Names officially recognized the last active glacier in Idaho in a meeting last month.
Borah Glacier, located on Borah Peak—about 40 miles northeast of Sun Valley, as the crow flies—measures 30 acres in size, according to the U.S. Geological Survey.
The dense ice patch on the north slope of Borah Peak was first discovered in 1974 by Bruce Otto, a geology student at Boise State University.
According to a Portland State University report, regular climbers of Borah Peak found the glacier’s blue ice to have shrunk dramatically between the mid-70s and early '90s. In a 2016 survey, however, Salmon-Challis National Forest employee Joshua Kelley and Student Conservation Association Intern Mathew Warbritton confirmed the ice mass was still active.
“Our survey confirmed the continued presence of the perennial ice mass originally identified in 1974, and concluded that the ice mass is indeed a glacier that continues to move under its own weight,” the pair wrote.
Mount Borah is Idaho’s tallest peak at 12,667 feet.