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.