Fault at Waimea, Oahu — Palmer 
89 
If the region is later faised, or tilted, so 
that the stream is given a steeper gradient 
and a great velocity, the stream will revert 
to a predominance of deepening over widen¬ 
ing, and will cut a new, inner, narrow valley 
along the trough of the older, outer, broader 
valley. This process results in what is known 
as "two-cycle topography,” or "valley-in¬ 
valley topography,” characterized by the 
break in the transverse profile where the 
upper and lower valley sides meet. The upper 
valley was cut during an earlier cycle of ero¬ 
sion and the lower valley during a later cycle. 
The hypothesis that there is a fault at 
Waimea supposes the block on the northeast 
to have been raised. If this is true, the rais¬ 
ing should have rejuvenated the streams and 
should have produced two-cycle topography. 
Such topography is found between Pupukea 
and Kaunala, in an area extending for about 
3 miles parallel to the shore line, and lying 
inland from the crest of the wave-cut cliff. 
Unfortunately the contour intervals of the 
maps do not permit constructing a profile 
that will show the inner and outer valleys. In 
Figure 7, the inner valley runs from right to 
left. The photographer stood on a part of 
the older, upper valley slopes which extend 
to the middle distance. The pineapple fields 
on the far side, and the pasture to the right 
of the pineapple fields, are also on the 
older, upper valley slopes. The sides of the 
younger, inner valley are too steep to be 
tilled, and are partly in brush, partly in grass, 
and partly bare of vegetation. 
THE FAULT SCARP 
Where faulting has recently raised one 
crust block with respect to the adjacent block, 
a cliff or fault scarp separates the two blocks, 
and at first is likely to be a conspicuous 
feature of the landscape. As time goes on, 
however, the scarp becomes weathered and 
eroded back, and changes into a more Or less 
subdued and inconspicuous land form. Such 
is the scarp of the Waimea fault, now that 
it is rather old. The best place known to the 
writer from which to view this subdued 
scarp is the bridge across the small Lauhulu 
Fig. 7. View of two-cycle or valley-in-valley topography on the upthrown fault block. 
