This is perhaps the only geology trek on the list that takes you into the future as well as the past. Glacier's majestic peaks were carved by great glaciers more than 12,000 years ago.
Today's remaining glaciers date back to about 7,000 years ago and numbered about 150 when the park was established in 1910. By 2010 there were only 25 glaciers left larger than 25 acres. The U.S. Geological Survey estimates that all of the glaciers could be gone by the year 2030.
If you want to visit these endangered glaciers before they are gone, among the most accessible is Grinnell Glacier, which can be reached via the Many Glacier information station. For more information on retreating glaciers of Glacier National Park visit here.