bussell.1 CAKES OF LAVA. 79 
although still retaining .something- of their spherical form, such as 
occur abundantly about the Ice Spring crater in Utah/' 
Lava cakes. — The thin, flat cakes of compact lava, mentioned above, 
occur in abundance on the side of some of the cones and crater walls 
forming the Cinder Buttes. They may be seen especially on the 
southwest slope of the highest cone, where they occur in thousands. 
These lava cakes, as I term them for lack of a better name, are usually 
composed of compact or but slightly vesicular black lava, but at 
times the} T are scoriaceous; although usually flat, they frequently 
have thin inclined ridges or offshoots on their upper surfaces; in 
thickness they vary irregularly from perhaps a fourth to half or, in 
the larger pieces, two-thirds of an inch. Their margins are usually 
broken, but sometimes thin out to a sharp edge. They are of all sizes, 
up to 14 inches or more across. On their under surfaces there are 
sometimes adhering fragments of lapilli, and occasionally similar 
fragments are inclosed between projecting ridges, or in the center of 
a mass composed of two or more adhering cakes. These thin lava 
cakes occur in abundance not only on the lapilli cones among the Cin- 
der Buttes but on the adjacent lapilli fields and hills, where no dis- 
tinct crater can now be seen. Similar cakes were observed, also in 
abundance, around a small and very recent volcanic cone about 10 miles 
north of Bliss, named on a previous page the Blanche crater. Their 
abundance in the instances mentioned indicates that they form no 
inconsiderable part of the fragmental or quasi -fragmental material 
thrown out by volcanoes of a certain type, namely, those which are 
supplied with highly liquid lava. In some instances the splashes of 
lava, after striking the earth, were still sufficiently fluid to flow and 
united one with another so as to form irregular sheets. Compact lay- 
ers, usually of a reddish color, seen in vertical sections of some of the 
cones of lapilli and scoriae were found to have originated in this manner. 
Only the more conspicuous variations exhibited by the fragmental 
material, including bombs, so abundant about the Cinder Buttes have 
been noted, but it would not be difficult to select a series showing a 
complete gradation from angular scoriaceous fragments produced by 
the breaking and ejection of a frothy, brittle crust, formed on the 
surface of the lava within a crater, to the irregular lava cakes resulting 
from the hardening of material blown out in a liquid condition. Such 
a series would illustrate the fact that the wide variations presented by 
the material blown from volcanoes depend principally on its degree 
of rigidity or fluidity on leaving the parent crater. The range is from 
brittle scoria to highly fluid lava. The variations in shape assumed 
by lava ejected in a plastic or fluid condition depend on the length of 
its aerial flight and on the manner in which it rotates. 
"These flattened bombs are referred to by G. K. Gilbert, in his monograph on Lake Bonneville, 
Mon. U. S. Geol. Survey, Vol. I, 1890, p. 321. 
