Tag Archives: pretty rocks

Denali Road Droop

Denali Park Road at Pretty Rocks; August 2021

The above picture is of the Denali Park Road at the Pretty Rocks formation last August. That was the last time any gravel had been dumped in this section of road that is dropping due to melting ice under the roadbed.

Denali Park Road at Pretty Rocks; Spring 2022

This spring, maintenance crews discovered that the road had dropped as much as 40 feet at the troublesome section near Pretty Rocks. It had already been decided that the park road would be closed for the 2022 season due to the roadbed situation, but the drop was more impressive than forecast.

A new bridge will be installed over the section with the melting ice formation, and will be secured into solid rock on either side of the great melt. I expect that the road into the heart of Denali Park to remain closed through the 2023 season.

Pictures credit: Denali National Park & Preserve


The slumping of the Denali Park Road

A drill rig taking core samples at Pretty Rocks

The Denali Park Road has a slump in it. The road was cut into the rocks 90 years ago, and a section at Mile 45 in Polychrome Pass, in an area that is known as Pretty Rocks, is built over an underground rock glacier. The existence of the glacier was unknown at that time, but it has been melting at an accelerating rate the past three years.

In 2018 the road was dropping an inch a month, by 2019 that had grown to an inch a day. This August, the road has been dropping over a half inch an hour. More than 100 dump truck loads of gravel were dropped over this span every week this summer, but even that proved pointless, and the Park Road was closed to traffic at Mile 43 in August. The landslide has moved far enough down the hillside to expose the ice below the roadway.

Winter should put the freeze into the ground once again, so that the road can be used early next spring, but the plans are for the road to be closed for all of the summer of 2022. There is solid rock on either side of the glacier, so a bridge will be anchored into those to span the slump zone.

Time lapse of the landslide in Polychrome Pass

Photo and time-lapse credit: NPS