82 THE CLIFF RUINS OF CANYON DE CHELLY [ETH. ANN. 16 
GEOGRAPHY 
The ancient pueblo culture was so intimately connected with and 
dependent on the character of the country where its remains are found 
that some idea of this country is necessary to understand it. The limits 
of the region are closely coincident with the boundaries of the plateau 
country except on the south, so much so that a map of the latter,! 
slightly extended around its margin, will serve to show the former. 
The area of the ancient pueblo region may be 150,000 square miles; 
that of the plateau country, approximately, 150,000. 
The plateau country is not a smooth and level region, as its name 
might imply; it is extremely rugged, and the topographic obstacles to 
travel are greater than in many wild mountain regions. It is a coun- 
try of cliffs and canyons, often of considerable magnitude and forming 
a bar to extended progress in any direction. The surface is generally 
smooth or slightly undulating and apparently level, but it is composed 
of a series of platforms or mesas, which are seldom of great extent 
and generally terminate at the brink of a wall, often of huge dimen- 
sions. There are mesas everywhere; it is the mesa country. 
Although the strata appear to be horizontal, they are slightly tilted. 
The inclination, although slight, is remarkably persistent, and the 
thickness of the strata remains alinost constant. The beds, therefore, 
extend from very high altitudes to very low ones, and often the forma- 
tion which is exposed to view at the summit of an incline is lost to 
view after a few miles, being covered by some later formation, which 
in turn is covered by a still later one. Each formation thus appears 
as a terrace, bounded on one side by a descending cliff carved out of 
the edges of its own strata and on the other by an ascending cliff 
sarved out of the strata which overlie it. This is the more common 
form, although isolated mesas, bits of tableland completely engirdled 
by cliffs, are but little less common. 
The courses of the margins of the mesas are not regular. The cliffs 
sometimes maintain an average trend through great distances, but in 
detail their courses are extremely crooked; they wind in and out, form- 
ing alternate alcoves and promontories in the wall, and frequently they 
are cut through by valleys, which may be either narrow canyons or 
interspaces 10 or even 20 miles wide. 
The whole region has been subjected to many displacements, both 
flexures of the monoclinal type and faults. Some of these flexures 
attain a length of over 80 miles and a displacement of 3,000 feet, and the 
faults reach even a greater magnitude. There is also an abundance of 
volcanic rocks and extinct volcanoes, and while the principal eruptions 
have occurred about the borders of the region, extending but slightly 
1See Major C. E. Dutton’s map of the plateau country in 6th Ann. Rept. U.S. Geol. Survey, pl. xi. 
His report on ‘‘ Mount Taylor and the Zuni plateau,” of which this map is a part, presents a vivid 
picture of the plateau country, and his descriptions are so clear and expressive that any attempt to 
better them must result in failure. The statement of the geologic and topographic features which is 
incorporated herein is derived directly from Major Dutton’s description, much of it being taken bodily. 
