HEWETT] RIO GRANDE VALLEY, NEW MEXICO 17 



striking scenery from the geologic point of view to be found in the 

 Southwest. 



In most places the color of the tufa blanket ranges from yellow to 

 gray, varying with the exposure. In the neighborhood of the basaltic 

 contact, areas of (hvrk brown occur and in some places patches of 

 almost pure white ash are to be seen. The greater part of the for- 

 mation, the material of which originated ui the cones of the Jemez 

 mountains to the west, seems to have been laid do\ni somewhat 

 imiformly as a rather coarse ash, nowhere approaching commercial 

 pumice, usually much mLxefl with spicules of silica. The formation 

 presents every degree of compactness — the light gray ash that can 

 be removed with a shovel, somewhat harder porous masses in which 

 are thousands of natural caves formed by wmd erosion (the advan- 

 tages of which for shelter constituted probably one of the first induce- 

 ments for the peopling of the region), and finally the fairly compact 

 imbroken strata hundreds of feet thick, as seen m the canyon walls at 

 the Rito de los Frijoles, the North Alamo, and the Puye. The soft 

 honeycombed formations afforded, with but little additional exca- 

 vation, dwellings for the first inhabitants, while the more compact 

 masses furnished the light buildijig stone for the great community 

 houses of more recent times that were built upon the mesa tops, in 

 the valleys, and on the talus agamst the massive walls, as at the sites 

 above mentioned. 



Many formations of unusual character are found' here and there, 

 giving variety and character to the scenery. Such are the mud 

 flows which occur as brownish stratified masses, and the remarkable 

 tent-shaped rocks, of which the finest examples are at Otowi, but 

 which occur also at many other places (pi. 8-10). Those at Otowi 

 are especially noted for havmg been used as human habitations. 

 They are to be seen in all stages of formation — the porous stratum 

 in which they originate still covered with the cap of more compact 

 tufa, the detached masses with fragments of the cap as balanced 

 rock remainmg upon the apex, and the completely isolated finished 

 cones. A whole vUlage of these is to be seen m Otowi canyon. 



Two natural caverns of considerable size are found m the southern 

 part of the plateau, one in the Rito de los Frijoles and one in the 

 Cafiada de la Cuesta Colorada. Both were utilized by the inhabitants 

 for ceremonial purposes. This portion of the plateau embraces the 

 most stupendous canyons, the wildest scenery, and affords the 

 grandest panoramas to be seen in New Mexico, and in fact scenes that 

 can scarcely be paralleled anywhere. 



The principal eastern tributaries of the Rio Grande are Taos, Santa 

 Cruz, Pojoaque, Santa Fo, and Galisteo creeks, small streams \\ith 

 narrow flood plams. .\11 of these usuaUy carry a small amomit of 

 67519°- Bull, 54—13 2 



