bussell.] KECENT VOLCANOES. 47 
instances similar elevations are composed principally of lava cakes 
formed, as already explained, by the cooling of splashes of liquid lava 
after coming to rest. Examples of cones or craters formed exclu- 
sively or in large part by the two methods just cited, however, are so 
rare that special names for them do not seem to be necessary. 
It frequently happens that a volcanic hill or mountain is composed 
of projectiles of all the classes considered above, as, for example, when 
large angular blocks of lava are ejected, together with lapilli and dust, 
and at some time in the life of the volcano plastic or liquid lava is blown 
into the air and forms scoria, bombs, lava cakes, etc. Such composite 
cones or craters built of the products of explosive eruptions are illus- 
trated by several characteristic examples among the Cinder Buttes. 
There is one feature of lapilli and scoria cones which does not seem 
heretofore to have attracted attention. Interbedded with the frag- 
mental material in the walls of such craters there are sometimes irreg- 
ular sheets of compact and usually reddish lava, ranging in thickness 
from a few inches or less to many feet, and presenting all variations 
in extent from a few square inches to several hundred square yards, 
and resembling true lava flows. These compact layers occur both in 
the outer and inner slopes of a crater, and at times a single bed in 
one part belongs with the steeply sloping layers of the inner cone, and 
changing its dip in the part beneath the crater's rim, passes into the 
outward-dipping series of beds. As may be seen at the Cinder Buttes, 
such beds of compact lava sometimes contain scoriaceous masses, and 
on their edges become thin and terminate irregularly in accumula- 
tions of lapilli or scoria. Some of these features may be recognized 
in the small sample from the wall of a cinder cone, shown in PI. X, B. 
The range in size of the compact beds just described, the presence 
in them of scoriaceous masses, and the manner in which they termi- 
nate, etc., show that they are due to an accumulation of liquid or 
highly plastic splashes and clots of lava, which united one with 
another as they fell. In harmony with this explanation is the fact 
that in many instances a sheet of lava of the nature under consider- 
ation is completely inclosed in lapilli or scoria. In sections of lapilli 
and scoria cones to be seen among the Cinder Buttes numerous 
examples of interbedded sheets of compact lava may be seen which 
are due to the running together of liquid or highly plastic splashes 
and clots in the manner just explained, and similar occurrences were 
seen elsewhere, particularly at the Jordan Craters described below. 
The notes presented above are intended as a supplement to the 
more general account of the Cinder Buttes contained in Bulletin No. 
199 of the United States Geological Survey, and I trust will be fol- 
lowed by a detailed survey of that unique region. In the publication 
just referred to, several isolated craters and groups of craters situ- 
ated in southern Idaho are described, and the list of these recent vol- 
canoes is here extended by an account of three similar centers of 
eruption in southeastern Oregon. 
