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The Pretty Rocks landslide intersects the Denali Park Road near its midpoint at Mile 45.4 and displaces 100 yards (90 m) of the full width of the road. In recent years this landslide has evolved from a minor maintenance concern to one that has caused substantial road restrictions. To learn more about the bridge construction expected to begin at Pretty Rocks in 2023, see the Polychrome Area Plan.
The Pretty Rocks landslide has been active since at least the 1960s, and probably since well before the Denali Park Road was built through this area in 1930. Before 2014, the landslide only caused small cracks in the road surface and required moderate maintenance every 2–3 years. However, in 2014, road maintenance crews noticed a substantial speed up. By 2016 the movement had increased further, a slump had developed in the road, and a monitoring program was begun. The rate of road movement within the landslide evolved from inches per year prior to 2014, to inches per month in 2017, inches per week in 2018, inches per day in 2019, and up to 0.65 inches per hour in 2021.
By late August, 2021, park managers recognized that adding hundreds of truckloads of gravel into the slumping road to maintain a drivable surface was no longer tenable or safe, and they enacted a road closure west of Pretty Rocks. Since then, the movement of the landslide has continued to carry that section of road farther down the hillside and the road closure has remained in effect.
