Plate 16.—The volcanic plain is a hybrid type which is usually found as a part of an upper 
basin, but its distinctive characteristics leave no doubt as to its identity. The canyon type is very 
distinctive and it has only a very narrow range of associations. 
COLORADO PLATEAU 
VOLCANIC PLAINS TYPE 
COLORADO PLATEAU 
CANYON TYPE 
Fig. 2.20 Volcanic plains type. This Is an area of lava 
flows and cinder cones, at an elevation of 7,000 ft. in the 
vicinity of volcanic mountains. Vegetation is completely 
lacking or extremely sparse, and the land cannot be used as 
livestock range. The soils are undeveloped and composed of 
well drained" cinders and fragmented lava. The climate is a 
transition between temperate and semi-desert. Snow does not 
remain after winter storms and light rains fall sporadicly 
from July to September, usually coming as thunder storms. 
Roads are infrequent. Occasionally roads lead to cinder' 
pits for road surfacing material. Lava beds are almost im 
passable. Water supply is precarious. North of Springer- 
vllle, Arizona. October 1949. 
Fig. a.21 Canyon type. This is a deep canyon cut through 
horizontal sandstone strata at elevations between 5,000 and 
5,000 ft. Vegetation is almost entirely lacking, except in 
wide canyon bottoms, which may have a brush or sparse grass 
cover, used for winter range. Soils are absent except in flat 
bottoms which have alluvial deposits of sand and silt. The 
climate is arid with precipitation of 10" - 15", with warm 
winters and hot summers. No agriculture is found except in 
occasional fields in wide bottomed canyons where there is ir 
rigation. This canyon is inhabited by the Havasupai Indians, 
who irrigate the lower canyon bottom. Supai, Arizona. 
October 1947. 
GVII-100 PHOTOGRAMMETRIC ENGINEERING