Over the past 2.6 million years, there have been multiple glacial periods in Yellowstone and most of North America. A glacier deposit at Tower Fall in Yellowstone is 1.3 million years old, which is rare to be found. The area was covered by the Bull Lake glaciers between 151,000 and 160,000 years ago. The Pinedale glacial, the last significant ice age in the Yellowstone region, is estimated to have ended 21,000 years ago in the east, 20,000 years ago in the north, and maybe as recently as 15,000&ndash16,000 years ago in the south. Sadly, glaciers in Yellowstone, Yosemite, and the Waterton Glacier International Peace Park are likely to disappear by 2050.