J. W. Powell—Types of Orographic Structure. 425 
In Atlas, plate No. 4, we have a stereogram representing 
these displacements, and in a subsequent chapter the subject 
is more fully discussed. 
any other areas far more complex than these have been 
discovered, where a zone has been broken into blocks, and 
these blocks tipped and contorted in diverse ways and direc- 
tions, like the blocks of ice crowded in an eddy of a northern 
river at the time of its spring flood. The topographic features 
found in such areas are zones of irregular hills. 
Figure 6 is a diagram illustrating the general types of dis- 
placement heretofore discussed. A represents a Simple Anti- 
clinal displacement; B, a Uinta displacement; C, a Kaibab 
displacement ; D, a Basin Range displacement; and HE, a Zone 
of Diverse displacement. 
MOUNTAINS COMPOSED IN WHOLE OR IN PART OF EXTRA- 
VASATED MATERIAL. 
carrying away the softer sedimentary material, and leaving the 
harder volcanic rocks in the midst of the valley; and this may 
< an elevation less or greater than that of the adjacent 
‘ountry beyond the rim of the valley. : 
_ A fine example of a table mountain is found in Pilot Butte, 
in Wy oming Territory. 
VIIL— UVinkaret Structure. 
=. and serve as a protection to the sedimentary 
ae Immediately underlying them, and as the erosion of the 
ijacent country not thus protected progresses, new vents may 
ves of such sheets and at a lower level. 
Sut, and still at lower levels, until a mountain is left. nn 
“ith its central mass composed of sedimentary material, bu 
