Conor Watkins And J. David Rogers
Colorado Plateau Research
Vermilion Cliffs, AZ Landsliding
Description of Sliding


THE EASTERN VERMILION CLIFFS


  This eastern cliffs contain numerous earthflows.  Earthflows did not did not occur along the western cliffs although the although the stratigraphy is similar.  Large slump blocks have formed instead.


Earthflows consisting of highly disaggregated Chinle, Moenave, and Navajo Formations are present along the Vermilion and Echo Cliffs near Lee’s Ferry.  Strahler (1940) suggested that these flows occurred when rotational slumps developed in the Chinle dropped dropped over the over the Shinarump bench, which has not been excavated and exposed along the western cliffs.  But, earthflows are also present well above the Shinarump.


Earth flows above the Shinarump bench


Earth flows have cascaded over the edge of the Shinarump bench along the Vermilion Cliffs as suggested by Strahler (1940).


Additional paleo earthflow fan below the Shinarump escarpment


The earthflows have occurred during rapid drawdown, when the lava dam impoundment inundating the cliffs suddenly drained away.  The Moenkopi beds near Lee's Ferry and Navajo Bridge appear rounded by inundation.


Telephoto view of the potentially water smoothed bedding planes in the Moenkopi Formation between Navajo Bridge and Lee’s Ferry.


Close-up of potentially water smoothed bedding planes in theMoenkopi Formation at Navajo Bridge.  The Moenkop doesn’t doesn’t exhibit this texture elsewhere in the Colorado Plateau.


Smoothed Moenkopi beds near Marble Canyon, AZ with nearby residence for scale


 
THE WESTERN VERMILION CLIFFS


This aerial photo shows a landslide complex along the face of the Vermilion Cliffs near House Rock.  The rotational Torevaor slump type block becomes more common as one moves west along the cliffs.


Dissected slump blocks near House Rock, AZ


Some secondary earthflows appear to emanate from parent back-rotated blocks.


The rotational slump blocks near House Rock occurred well above the level of any Pleistocene lake caused by nearby lava dams. Some other cause may be responsible.  The nearby lake may have allowed groundwater levels to rise nearby, causing a different form of landslide.  Similar slides exist throughout the southern Colorado Plateau and appear related to some widespread cause.  These include slides described by Rieche (1937) at Toreva, AZ and Black Mesa in the Mancos Shale, and others in the Grand Canyon region.


The Vermilion Cliffs become shorter in height and turn northward along the House Rock Valley in their far western reaches.  This section is devoid of landslides since the Chinle Formation has not yet been excavated to a point where it can strain.  This confinement has prevented sliding from occuring.

Questions or comments on this page?
E-mail Dr. J David Rogers at rogersda@umr.edu
or Conor Watkins at cwatkin@umr.edu.