300 
TOPOGRAPHIC TERMS OF SPANISH AMERICA 
are as follows, beginning at the north and east: The Montana 
cordillera, the Colorado cordillera, the Guadalupe cordillera, 
and the cordillera of the eastern Sierra Madre. Each of these 
grades westw’ard into a great mesa or plateau region. The Co- 
lumbia plateau borders the Montana cordillera. The Colorado 
plateau lies w'est, southw’est, and southea.st of the Colorado cor- 
dillera. The Guadalupe cordillera is bordered on the west by a 
relatively smaller, but nevertheless extensive, plateau, known as 
the Sierra Diablo, which appears as a diminutive feature on the 
map. The eastern Sierra Madre of Mexico likewise flattens out 
westward into an extensive plateau region, which, for the want 
of a better name, I call the Parras plateau. The plateaus become 
tilted in places into cuestas, and, by faulting, the latter grade into 
sierras of the basin-range type, separated by bolsons. Each of 
the plateau regions is thus bordered on the west and south by 
great regions of bolsons and basin ranges. The Colorado plateau 
is h»ordered on the w'est and southwest by the Great Basin region 
of Powell and Gilbert, and on the southeast by the Coahuilan 
bolson region. 
There are also internodal areas of mesa-like topography be- 
tween the ends of the cordillera masses of the Rocky mountain 
systems, such as that lying between the southern end of the 
Colorado cordillera and the northern end of the Guadalupe 
cordillera. The great cordillera in Ave.stern Mexico known as 
the Sierra Madre passes at its northern end into the Colorado 
plateau (not into the California sierras, as often supposed), and 
constitutes a partial barrier between the Coahuilan bolson region 
of Mexico, Trans-Pecos Texas, and New Mexico, and the great 
bolson (basin) region of Utah and Nevada. 
The plateaus of the plains lying east of the Rocky mountain 
region south of Arkansas river are collectively a series of mesas 
overlooking broad plazas and separated from them by escarp- 
ments. The conspicuous plaza regions are the Canadian and 
Pecos valleys of New Mexico. The great Central Denuded region 
of Texas, Oklahoma, and southern Kansas is also mostly a plaza 
region. On the east are Cretaceous prairies of Texas, which w’e 
have described as dip plains; these are incipient cuestas. The 
Central Denuded region lying between tbe westward-facing 
scarps of these prairies* on the east and the eastward-looking 
scar})s of the plains on the w'est is collectively a great plaza 
country. 
•The old border of Appalachia forms the eastern boundary of this region, north of 
the Ouachita mountain system of Indian Territory. 
