' UTAH PENEPLAINS 
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PENEPLANAL AFFINITIES OF HIGH PLATEAUX 
OF UTAH 
By Charles Keyes 
The High Plateaux of Utah ^ are especially noteworthy phy- 
siographically because of the fact that they are last, though great, 
unconsumed remnants of a vast highland plain which once spread 
out over the entire western one-third of the north American con¬ 
tinent. Throughout most of this boundless area all traces of this 
wide regional plain are now extinguished. Over other very con¬ 
siderable portions of the tract only the most resistant masses are 
not yet completely reduced to the level of the present plains-sur- 
face. These arid monadnocks, as they really are, stand forth as 
the desert ranges in the Great Basin, and on the Mexican Table¬ 
land. The Rocky Mountains constitute a rejuvenated highland. 
Throughout the entire Cordilleran region, during Tertic times, 
prodigious outpourings of very mobile basic lavas give rise at 
later date to curious idiosyncracies of landscape. Among the 
many novel features especially striking are those strange isolated 
tablelands — mesas they are called by the Spanish-speaking dwell¬ 
ers of the region. Physiographically mesa-land is almost unique. 
It is an accentuated phase of the inselberglandschaft of the South 
African veldt. It is a specialized type of enisled relief, and it is 
a topographic expression peculiar to the desert. 
Nowhere else are climatic conditions more favorable for exten¬ 
sive plains genesis. ’ From the very beginning of each geographic 
cycle the plain is the characteristic and dominant landscape type. 
Plateau plain of the desert is really a reminiscent stage of inter¬ 
cycle planation such as is preserved during no other attainment 
to base-level. Because of the fact that so few plateau plains 
have close contemporaries it is not always easy to fix their position 
1 Paper presented before the Geological Society of America at the Chicago, or 
Thirty-third Annual, Meeting. 
