bussell.] KUNA BUTTE. 109 
aceous basalt and occasionally waterworn pebbles of quartz and of 
dense igneous rock resembling diorite. In certain layers of the tuff 
and intimately mingled with small angular fragments of scoriaceous, 
glassy basalt, there are large quantities of angular quartz grains 
and other fragments, which appear to be feldspar. In some layers 
the sand grains far outnumber the lapilli fragments, and if the material 
did not occur in the walls of a crater it would certainly be taken for a 
bed of sandstone containing a limited amount of lapilli. The non- 
volcanic included material indicates that the conduit of the volcano 
was opened through coarse gravel, such as Snake River is now spread- 
ing out near at hand, and finer sediments, probably lake beds, con- 
sisting largely of sand. 
The moderately compact tuff is sufficiently soft at a depth of a few 
feet below the surface to be cut with an ax and has been quarried at an 
adjacent locality on the bank of Snake River for building purposes. 
There are several houses in Menan built of rough-dressed blocks of 
this stone. 
The plain about the base of the butte is smooth for a distance of 
1,000 to 2,000 feet, on account of the lapilli blown and washed down 
from its sides; outward from this belt, except on the south, where 
alluvial deposits laid down by Snake River have modified the surface, 
is a rough plain of basalt with only a thin covering of wind-deposited 
material in the depressions. 
The crater of the larger of the two cones, as stated by Bradley, is of 
somewhat greater size than that of the one just described, but is not 
so deep. The two volcanic cones are united at their bases and are 
undoubtedly of about the same age and moderately recent. Although 
comparatively young lava flows form the neighboring plain, it is not 
apparent that either of the volcanoes gave origin to a lava stream. 
Kuna Butte.- — Rising from the Snake River Plains about 17 miles 
northwest of Mountain Home, and 7 miles west of Cleft, as indicated 
on fig. 1, is an isolated cinder cone, 230 feet high, known as Kuna 
Butte, shown on PI. XVII. This conical elevation, rising from a 
nearly level and seemingly limitless plain, is a conspicuous object 
and a prominent and well-known landmark throughout a region several 
hundred square miles in area. 
The butte is composed mainly of scoriae and lapilli, but, so far as 
can be distinguished beneath the soil and drifting sand about its base, 
did not give origin to a lava flow. Lava was blown out in a highty 
plastic condition, however, as is shown by irregular, flattened cakes 
of highly scoriaceous basalt at the summit, which are 3 or 4 feet 
across and several inches thick. At the top of the cone there is a 
remnant of a once comparatively large crater, the walls of which 
have now fallen in, and its crest has become rounded and notched by 
erosion. There is a suggestion of compact lava in a gully on the 
