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914 PHYSIOGRAPHICAL GEOLOGY. — [Boox VIT. 
external scenery may be instructively studied. In many instances — 
each anticline forms a long ridge, and each syncline runs as a corre-— 
sponding and parallel valley. It will usually be observed, however, 
that the surface of the ground does not strictly conform for more 
than a short distance to the surface of any one bed; but that, on 
the contrary, it passes across the edges of successive beds, as in 
Fig. 430, This relation—so striking a proof of the extent to which 
S.E. N.W. 
OENSINGEN. BALLSTHAL, MUNSTER. RAMEUX. 

(The ridges coinciding with anticlines and the valleys with synclines.) 
the surface of the land has suffered from denudation—may be fol- 
lowed through successive phases until the original superficial contours 
are exactly reversed, the ridges running along the lines of syncline 
and the valleys along the lines of anticline (Figs=3375838). Among 
the older rocks of the earth’s crust which have been exposed alike to 
curvature and prolonged denudation, this reversal may be considered 
to be the rule rather than the exception. We may suppose that 
the tension of curvature produced an actual rupture of the crest of 
an anticline along which the denuding agents might operate, 
The Uinta type is a variety of this structure seen to great per- 
fection in the Uinta Mountains of Wyoming and Utah. It consists 
of a broad flattened flexure from which the strata descend steeply or 
vertically into the low grounds, where they quickly resume their 
horizontality. In the Uinta Mountains the flat arch has a length 
of upwards of 150 and a breadth of about 50 miles, and exposes a 
vast deeply trenched plateau with an average height of 10,000 to 

Fic. 431.—Uinta Type or FLEXURE. 
a, Paleozoic rocks; b, Mesozoic; c, Tertiary ; f, fault. 
11,000 feet above the sea, and 5000 to 6000 feet above the plains 
on either side, ‘This elevated region consists of nearly level ancient 
‘Paleozoic rocks, which plunge steeply below the Secondary and 
Tertiary deposits that have been tilted by the uplift (Fig. 481). 
Powell believes that a depth of not less than three and a half miles 
of strata has been removed by denudation from the top of the — 
arch. In some places the line of maximum flexure at the side of 
the uplift has given way, and the resulting fault has at one point a 
vertical displacement of 20,000 feet. ; 
' Geology of Uinta Mountains, p, 201. There is in this work a suggestive discussion 
of types of mountain structure. See also Clarence King’s Report on Geology of 40th 
Parallel, vol, i. ) 
