As rain and snow continue to erode the sedimentary rocks surrounding the Tower's base, more of Devils Tower will be exposed. Nonetheless, the exposed portions of the Tower still experience certain amounts of erosion. Cracks along the columns are subject to water and ice erosion. Erosion due to the expansion of ice along cracks and fractures within rock formations is common in colder climates, a prime example being the columnar "hoodoo" formations at Bryce Canyon National Park. Portions, or even entire columns, of rock at Devils Tower are continually breaking off and falling. Piles of broken columns, boulders, small rocks, and stones, called scree, lie at the base of the tower, indicating that it was once wider than it is today.