Geomorphic Contrasts Within the Koolau Range 
of Oahu, Hawaii 
Harold S. Palmer 1 
Laymen as well as geologists have ob- 
served various striking topographic contrasts 
between the southeastern and the north- 
western parts of the Koolau Range of the 
island of Oahu, Hawaii. These familiar con- 
trasts are discussed in this paper, but atten- 
tion is also called to certain less obvious 
contrasts, and to the bearing of all the con- 
trasts on the geologic history of the Koolau 
Range. 
I am indebted to Messrs. Doak C. Cox, 
Stephen B. Jones, Gordon A. Macdonald, 
Erik Palmer, Howard A. Powers, and Horace 
Winchell for careful reading of a draft and for 
valuable criticisms and suggestions. 
In addition to the usual placing of references 
to the literature and to figures by items in 
parentheses, it was thought well to give help 
in locating of unfamiliar place names. There- 
fore references to the figures on which places 
may be found are given in parentheses after 
the place name in the text. 
A chart was made of the 100-fathom and 
200-fathom submarine contour lines around 
Oahu, but it showed no discernable contrasts 
between the two parts of the Koolau Range. 
THE WINDWARD SIDE 
Simplified maps of four parts of the wind- 
ward, or northeast, side of the Koolau Range 
with a contour interval of 500 feet show 
1 Department of Geology, University of Hawaii. 
Manuscript received January 10, 1955. 
significant contrasts (Fig. 1a-e). The south- 
eastern part has rather continuous, high cliffs, 
that curve inland a little to form wide alcoves. 
Davis (1928: 171) aptly described these wind- 
ward-facing cliffs as "receding in several 
bights between blunt cusps.” At Waimanalo 
and Kailua (Fig. 1 a) the alcoves or bights 
are a mile and a half to two miles wide, but 
those from Haiku Valley to Waiahole (Fig. 
lb) are only a mile or a little less in width. 
In both these areas the reentrant depths of 
the alcoves are about three-quarters of a mile, 
and, because of the steepness of the cliffs, 
the 500- and 2,000-foot contour lines are in 
general only half a mile apart. For much of the 
way, a smooth curve generalizing the 500- 
foot contour line would depart from the 
actual contour lines by only a third or a half 
of a mile. 
In the area from Kualoa to Kaluanui (Fig. 
lc) narrow valleys are found instead of wide 
alcoves. At the ends of the ridges the 500-foot 
contour line is only a quarter of a mile from 
the shore, but it swings inland two or three 
miles in the valleys. Whatever cliffs there are, 
instead of facing the sea, face one another 
across deep valleys, strikingly, for example, 
near Sacred Falls in Kaluanui Valley. 
From Hauula to the northwest end of the 
range (Fig. Id) there are neither alcoves nor 
valleys with high and steep walls. Here the 
valleys are more numerous but shallower and 
narrower. 
304 
