russeli,] AGE OF THE LATER LAVA FLOWS. 105 
Creek Valley. The eastern wall of this water body, which is about 
200 or 300 acres in area, is formed by a wall of aa and pressure ridges; 
its western shore is composed of alluvium washed from the mountains. 
When the lava that entered a lateral valley terminates in a thin edge 
the alluvium from the mountains usually extends out upon it, conceal- 
ing its actual margin, and no lake results. 
The reason why more lakes are not present about the border of the 
lava is twofold: First, on account of the small rainfall the streams are 
usually weak and disappear in summer, and are unable to form per- 
ennial lakes even under favorable conditions; and, second, the lava is 
fissured and nonretentive. 
As will appear later, the changes produced in the topography where 
the recent lava flows from the Cinder Buttes meet the mountains 
seem to explain many similar changes, frequently on a far grander 
scale, produced by the lava flows which came from much older craters. 
RELATIVE AGE OP THE LATER LAVA FLOWS. 
As has been stated, at least six large streams of lava flowed from 
the Cinder Buttes at a. recent date. Among these certain differences 
in age are readily distinguished. In reference to three of the main 
flow, namely, the two most westerly on the north side and the great 
stream which was supplied from two sources on the south side of the 
buttes, no tangible differences in age have been recognized. Each of 
these three great flows is as fresh as if it had congealed and come to 
rest but yesterday. The lava appears black to one walking over it, 
but at a little distance, and in certain stages of illumination, has a 
light-gray appearance as if uniformly and lightly covered with dust. 
That this appearance is due to dust, however, seems improbable, as it 
does not reveal itself on close inspection. This surface " bloom," 
whatever its cause, is certainly an indication of youth, as it is absent 
on lava flows known from other reasons to be older. These recent 
flows are totally bare of soil, lapilli, volcanic dust, etc., and only to a 
slight extent have lichens taken root upon them. No positive evidence 
was obtained to show that the dead trees which occur along their bor- 
ders in certain instances were killed by their heat. The remnants of 
the craters from which the lava was poured out are tree clothed, and 
on the supposition that the lava outflows immediately followed the 
explosive eruptions which built the craters, the lava is older than the 
trees, many of which are fully 20 inches or 2 feet in diameter. 
Although it is impossible to make a well-founded estimate of the time 
that has elapsed since the last eruption, it seems probable that it is no 
more than one hundred or possibly one hundred and fifty years. 
Next older than the three lava streams just referred to, so far as one 
can judge, is a stream which skirts the base of the highest of the buttes 
on its western side and expands on the plain to the southward. This 
