30 



C. II. HITCHCOCK — GEOLOGY OF OAHU 



esteemed it the equivalent of the older basalt, and that consequently the 

 divergence of dips was suggestive of a fault between the two. It is re- 

 corded in some of my notes that the dike materia] cuts across the red 

 clinker. Part of the dikes are drab and part of an olive green color. 

 Some of them seem to me to be identical with the chrysolite basalt. 



Perhaps these several facts may justify the following conclusions re- 

 specting the relative age of the several rocks : 



1. The Koolau basalt, in horizontal sheets. 



2. Amygdaloidal basalt. 



3. Chrysolitic basalt, and some, if not all, of the vertical dikes. 



4. Reddish agglomerate with chrysolitic pebbles. 



5. Red clinker and the latest dikes. 



From the base of the Pali one can follow the course of the red clinker 

 stretching up the sides of the mountain much above the road. 



Secondary Craters 



CLASSIFICATION 



In almost every section of Oahu there are evidences of late volcanic 

 activity as manifested in craters, layers of ashes, tuffs, and dikes. Cer- 

 tain of these phenomena happen to be present in the midst of the settled 

 district, and therefore they are familiar to everybody. When Koolau 

 and Kaala are thoroughly explored others may be added to their num- 

 ber. Geographically they may be grouped as follows: 



1. Laeloa series.. 



2. Salt Lake group. 



3. Tantalus and the Pali. 



4. Punchbowl. 



5. Diamond head. 



<>. Rocky hill, Mauumae, and Kaiinuki, 



7. Kaneohe and the Koko heads. 



The} 7 may be described also as tuff cones, basaltic craters, volcanic 

 ashes, and dikes. 



LAELOA SERIES 



At the south end of the Waianae mountains is a group of 6i*aters, the 

 Laeloa, named from the southwest point of the island. They are Kapolei, 

 Palailai, Makakilo, Kapuai, Kuua, and others not specially named. 



Kapolei is a low crater, open to the south on the south side of the gov- 

 ernment road and north of the railroad, 162 feet above the sea and over 

 100 above the limestone plain at its base.* The rock is solid basalt with 

 red clinker. There are irregularities in the positions of the layers, so 

 that the normal form of the double quaquaversal dip is not readily seen. 



* It is very near the houses occupied hy laborers from California, who are making an experiment 

 as tu the ability of white men to succeed in actual work in the cane field. 



