CHAPTER VI. 
THE UINKARET PLATEAU. 
Common features of the Sheavwits and Uinkaret, with the latter as the type. — The boundaries of the 
Uinkaret defined. — The three groups of facts presented hy the plateau, basaltic eruptions, the 
Hurricane fault, and the Permian remnants. — The foundation of the plateau is of Carboniferous 
strata, with many remnants of Lower Permian beds. — The volcanic masses. — Ancient basaltic 
plateaus. — The Trumbull, Logan, and Emma platforms. — View of the recent cones from the sum- 
mit of Trumbull. — Grouping of the cones. — Their linear arrangement. — The lava caps of the 
plateaus. — Their antiquity. — Relations of the younger to the older basalts. — Former extensions 
of the lava caps and their denudation. — Similar facts presented by the Sheavwits Plateau. — The 
distribution of the younger basalts. — A long interval of repose between the old and young 
basalts. — Basaltic eruptions of very recent age. — The Hurricane fault. — Its appearance at the 
Grand Canon. — Its northward extension. — Its great displacement at the Virgen River. — Distor- 
tion of the strata at the fault plane. — Details of the dislocation. — Action of the fault in the 
Queantoweap. — Relations of the fault to the lavas. — It cuts the ancient basalts, but not the 
recent ones. — Lava cascades across the fault-plane — The Permian remnants. — Comparative 
smoothness of the denuded platform. — Infrequency of lateral drainage channels. — Base-levels of 
erosion. — Effect of an arid climate upon the topographical features — Geological history. 
The two western subdivisions of the Grand Canon district, the Sheav- 
wits and Uinkaret Plateaus are much alike in their physical features and 
in respect to the groups of geological facts which they present. To study 
and describe both of them in detail would extend the discussion into a weari- 
some repetition without adding anything of sufficient value to justify it. 
The groups of facts which they present are displayed in a more compact, 
intelligible, and, on the whole, more complete manner in the Uinkaret than 
in the Sheavwits, and the former subdivision is selected for description in 
some detail as the representative of both. It will be necessary, however, 
to make frequent allusions to the Sheavwits. 
The position of the Uinkaret is between the Sheavwits on the west and 
the Kanab Plateau on the east. For the most part, its boundaries are well 
defined. Throughout its entire western border the great Humcane fault 
and the resulting cliff known as the Hurricane Ledge is the boundary ; 
with equal definiteness the Grand Canon temiinates it upon the south. On 
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