29 



nel (width 23 miles). It is 2100 miles southwest of San Fran- 

 cisco in latitude 21° 30' north and longitude 158° west. Il 

 is somewhat north of the geographic center of the main group, 

 and is third in size, but it is pre-eminently the most important 

 member of the group. 



"In shape Oahu is somewhat trapezoidal. The bases oi 

 the trapezoid are at the northeast and the southwest, and the 

 legs are at the south and northwest, the latter being at right 

 Jingles to the base. The longer base is about 2i7 miles long; 

 tlie shorter, about 22 miles. The legs at the south and north- 

 west are about 29 and 22 miles in length respectively. The 

 shortest distance across the tableland from Kaiaka Bay at 

 the north of Pearl Lochs at the south, which extends 5 miles 

 inland, is about 15^ miles. The total area of Oahu is 598 

 square miles, as compared with 4015 square miles for Ha- 

 waii and 728 for Maui. 



MOUNTAIN RANGES, 



"Oahu Island has two distinct mountain ranges, a feature 

 which makes it unique as compared with the other islands, 

 none of which has any distinct mountain range. The Koolau 

 range at the northeast extends the full length of the island, the 

 crest being approximately parallel to the shore and only 3 or 

 4 miles inland. The Waianae range extends almost the en- 

 tire length of the southwest side, the crest being from 1 to 5 

 miles from the shore. These ranges are separated by a table- 

 land which rises to an elevation of 800 feet in the saddle near 

 the center of the island, from which point it slopes gently 

 downward to the north and to the south. Both these ranges 

 are at right angles to the northeast trade winds which blow 

 for about nine months of the year, and both are exposed more 

 or less to the severe southwestern storms, or konas, which 

 prevail at times. Each shields the other to a greater or less 

 extent, and this helps to explain some of the present physical 

 features. 



"The Waianae mountains are very much older than the Koo- 

 lau mountains. They are probabl}^ as old as Kauai, and orig- 

 inally formed a single island much larger and higher than the 

 present Waianae mountains. Erosion had probably eaten 

 deeply into, the northeastern and southwestern slopes and com- 

 pletely obliterated all trace of the original crater long before 

 the Koolau mountains on the east had emerged from the ocean. 

 The successive lava flows from younger Koolau then piled up 

 along the eastern base of Waianae, filling the valleys and cov- 

 ering the ridges, thus obliterating the effects of earlier chan- 

 neling on that side. On the southwest side, however, nothing 

 of the kind has occurred. The original valleys have been 

 broadened, deepened, and extended farther into the heart of 



