Geomorphic Contrasts in Koolaus — -Palmer 
307 
in- the southeastern part. Obviously there was 
originally a considerable area above what is 
now the 3,000-foot level, most of which has 
been removed by erosion and perhaps in part 
by down-faulting. Though this part of the 
range still has the points of greatest altitude, 
it has much less area above either the 1,000- 
foot or the 2,000-foot contour lines than the 
northwestern part (Fig. 5). One may again 
Fig. 3. Nuuami Gap, a deep indentation of the 
Crestline of the Koolau Range, as seen from the Ha- 
waiian Pineapple Company cannery. 
conclude that erosion has been at work much 
longer in the southeastern part, for it has 
been more fully and deeply dissected despite 
an originally greater altitude. 
Dips of the lava flows suggest that the 
original summit lay distinctly northeast of the 
present Crestline in the southeastern part of 
the Koolau Range, but close to the present 
Crestline in the northwestern part of the range. 
THE LEEWARD VALLEYS 
The leeward valleys of the southeastern end 
of the range are notably wider, deeper and 
Fig. 4. The smooth Crestline of the northwest end 
of the Koolau Range, as seen from Laie Point. 
flatter floored than the valleys of the north- 
western end (Fig. 6a-e). These characters 
increase from Kalama Valley, northeast of 
Koko Crater, to Manoa or Nuuanu (Figs. 
6a and 6b), perhaps because of greater stream 
erosion where higher altitude caused greater 
rainfall and provided larger collecting basins 
for streams (Fig. 7, isohyetal map of Oahu). 
In all this southeastern part of the Koolau 
Range, stream erosion has been able to cut 
so strongly partly because of greater steepness 
of the original slopes leading to greater velo- 
city and thus to stronger erosional power. 
Fig. 5. The 1,000-foot (dotted line) and 2,000-foot 
(solid line) contour lines of Oahu. 
The rather wide and level floors of Palolo, 
Manoa, Nuuanu and Kalihi Valleys (Fig. 6b) 
result in part from infilling by rather young 
intra-valley lava flows, but mostly from sedi- 
mentation in drowned valleys subsequent to 
a submergence of this part of Oahu. These 
valleys, and those to the east of Palolo, were 
cut to much their present form when this part 
of Oahu stood 800 or 1,000 feet higher rela- 
tive to sea level than now, as shown by well 
logs in the Honolulu area (Palmer, 1946: 
25-29). Subsidence changed the mouths of 
the valleys into bays, in whose quiet waters 
sediment accumulated to a considerable 
depth. Wailupe Valley (Fig. 6a) is a classic 
example of such a flattish valley floor (Davis, 
1928: 174, fig. 74). 
