Sometime before 5am on February 20, a landslide occurred on US 89, about 25 miles south of Page, Arizona near the town of Bitter Springs. The area is known as the Echo Cliffs, and is close to the area where adventurous folks put in on white-water rafting expeditions down the Colorado River. The landslide has closed the highway, resulting in a 45 mile, 1-hour detour to get between Flagstaff and Page. The geoblogosphere has lit up over this landslide, and the best coverage has been on the Arizona Geology Blog, run by the AZ State Geologist himself. A summary of some of his coverage is listed below. [Image
The likely geologic unit that is causing the problems is the Petrified Forrest Member of the Chinle Formation, a Triassic-aged unit that weathers into some pretty high-plasticity clay and has been known to cause slope problems all around the State. ADOT’s geotechnical engineers and geologists are looking at the site, and one of their on-call geotechnical consultants has been tasked with the emergency project to design a geotechnical repair to get the road re-opened. I was hoping it would be my employer, Golder Associates (not affiliated with GeoPrac) that would get the nod, but it wasn’t our turn in the rotation I guess.
- US89 slide may be failure in a larger ancient slide block – Source: Arizona Geology
- Highway US89 collapse south of Page, Arizona – Source: Arizona Geology
This is the first coverage of the event by the Arizona State Geologist’s blog. Their posts were some of the most interesting and informative (for geoprofessionals anyway) compared to the regular media coverage.
- Photos of Highway US89 slide – Source: Arizona Geology
This post had some photos shared with the AZGS by the Arizona Department of Public Safety.
- Another view of highway US89 landslide near Page – Source: Arizona Geology
This post has a nice Google Earth image giving a great overview of the topography and geology of the area near the landslide. The ancient landslide is clearly visible in the image.
- US89 Geologic Map – Source: Arizona Geology
This geologic map covering the project area lets you see the various Triassic-aged geologic units in the area of the landslide, including the likely "bad actor", the Petrified Forest Member of the Chinle Formation.
- Geologic references for Bitter Spring landslide – Source: Arizona Geology