Conor Watkins And J. David Rogers
Colorado Plateau Research
Black Mesa, AZ Landsliding

Black Mesa is a high, coal rich plateau in northern Arizona ringed by Toreva block style landslides.  The mesa consists of Mancos Shale capped by the resistent Mesaverde Sandstone.  These formations are the same as those present at the Hopi Mesas, the type locality for the Toreva block.  This type of landslide, also known as a rotational slump block, was noted by Parry Reich in his 1937 Journal of Geology article titled The Toreva Block, a distinctive landslide type.  Reiche mentions the presence of similar slides at Black Mesa and elsewhere.   As with the Toreva blocks surrounding the Hopi Mesas, those near Black Mesa failed in the weak Mancos Formation. Black Mesa was viewed from the air during a research trip in August 2004.  These landslides appear quite old and dissected but this appearance may be caused in part by increased precipitation at the higher elevation of the plateau, which acts to erode the landscape.

Repeating slumps appear as vegetation covered ribs surrounding the margins of Black Mesa.

A closer view of Black Mesa reveals several slump blocks that have been dissected by surface streams.  The process responsible for their formation appears to have been dormant during recent geologic time.

Additional view of slump blocks surrounding Black Mesa.

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