BASALTS OF THE UINKAEET. 
109 
descended form very striking and suggestive spectacles. Each of them 
holds many streams, but so blended together in appearance that they might 
at first glance be supposed to be each a single coulee of vast proportions. 
There are five of these passes descending into the Toroweap; tvro from the 
southern end of the Uinkaret to the esplanade of the canon, and two 
descending into the Queantoweap. The largest of all is upon the western 
side of the Uinkaret, leading down into the Queantoweap from a cluster of 
large cones standing in the interval which separates the Logan from the 
Mount Emma platform. This lava cascade is about two and a half miles 
wide and descends about 2,600 feet. 
Among the basalt fields which lie north and east of Trumbull there are 
two which attain notable proportions. One of them begins about two miles 
north of the mountain, and has at its summit a multiple cone consisting of 
five or six vents. This cone has been considerably wasted by erosion, and 
its interior structure is in great part laid open to view. It shows the familiar 
arrangement of tufaceous and scoriaceous material around a central pipe, 
the layers dipping downwards and inwards from the rim of the crater 
towards the pipe, and downwards and outwards from the rim towards the 
base. The anatomy of the multiple mass is also shown, and the growth of 
new craters upon the cone previously formed. From these vents a great 
number of eruptions have taken place, and they have built up a turtle- 
shaped mass of lavas having a thickness of 700 to 800 feet, and spreading 
out to the north, the east, and the west of the cone four to six miles. 
Towards the borders of this field the thickness steadily diminishes and at 
last vanishes in a thin irregular edge. East of Trumbull is another and 
somewhat larger field. This has many large cones upon it, standing in 
clusters of three to five, arranged in a line. I’he largest individual coulees 
seem to have emanated from these craters, and their aggregate thickness 
may exceed 500 feet. In the outer portions of the volcanic area the lava 
fields are all of small extent and usually very thin. From the cones on 
the Kanab Plateau the eruptions have been of very small volume and the 
lavas do not extend more than half a mile from their bases. 
Between the epoch of the extravasation of the ancient basalts of the 
Trumbull, Logan, and Emma platforms and the epoch of eruptions from 
