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The beautiful Vermillion Cliffs. I found this information of interest:
POSSIBLE CAUSES OF SLOPE INSTABILITY ALONG THE VERMILION CLIFFS
A wetter climate during the Pleistocene likely heightened groundwater levels within the cliffs. This may have led to gross instability because of reduced effective stress and loss of cohesion in the the Chinle and and Moenkopi Formations.
Saturation and strength loss of the Petrified Forest Member of the Chinle Formation might have been caused by lava dams in the western Grand Canyon. These dams impounded reservoirs with a pool elevation of up to 1200 m (4000 ft), easily saturating the base of the Vermilion Cliffs. This effect was likely more pronounced at the eastern end of the cliffs near Lee's Ferry, which are at a significantly lower elevation than the western portion near House Rock, AZ.
Evidence suggests that some lava dams failed catastrophically. Pore pressure imbalances caused by rapid drawdown during these failures may have triggered the earth flows common near Lee's Ferry.
At least three of the dozen or more lava dams inpacted the Vermilion Cliffs Region. Reservoir induced seismicity caused by the filling of such large lakes may have played a role in triggering the landslides.
Seismic activity related to nearby volcanism may have been instrumental in triggering the slides.
Strain softening caused by relaxation of slopes may have acted to reduce the strength of the Chinle Shales in combination with other processes. It is possible that straining of the Chinle Formation is responsible for the open joint planes seen near the edge of the Paria Plateau atop the cliffs. http://web.mst.edu/~rogersda/cp_megalan ... causes.htm
POSSIBLE CAUSES OF SLOPE INSTABILITY ALONG THE VERMILION CLIFFS
A wetter climate during the Pleistocene likely heightened groundwater levels within the cliffs. This may have led to gross instability because of reduced effective stress and loss of cohesion in the the Chinle and and Moenkopi Formations.
Saturation and strength loss of the Petrified Forest Member of the Chinle Formation might have been caused by lava dams in the western Grand Canyon. These dams impounded reservoirs with a pool elevation of up to 1200 m (4000 ft), easily saturating the base of the Vermilion Cliffs. This effect was likely more pronounced at the eastern end of the cliffs near Lee's Ferry, which are at a significantly lower elevation than the western portion near House Rock, AZ.
Evidence suggests that some lava dams failed catastrophically. Pore pressure imbalances caused by rapid drawdown during these failures may have triggered the earth flows common near Lee's Ferry.
At least three of the dozen or more lava dams inpacted the Vermilion Cliffs Region. Reservoir induced seismicity caused by the filling of such large lakes may have played a role in triggering the landslides.
Seismic activity related to nearby volcanism may have been instrumental in triggering the slides.
Strain softening caused by relaxation of slopes may have acted to reduce the strength of the Chinle Shales in combination with other processes. It is possible that straining of the Chinle Formation is responsible for the open joint planes seen near the edge of the Paria Plateau atop the cliffs. http://web.mst.edu/~rogersda/cp_megalan ... causes.htm