J. D. Dana — Geological History of Oahu. 93 



the mountains, as if the source were somewhere in that direc- 

 tion ; but just where, remains in doubt ; and it may be even 

 questioned whether there may not have been two or more 

 great craters along the line. 



No point or region has a more reasonable claim for consider- 

 ation in this respect than the head of Nuuanu valley. In situ- 

 ation and width, and the features at its head, it is just what 

 should be looked for in a great discharge -way. On my recent 

 visit I sought for facts bearing on the question and found the 

 dip of the beds to diminish from 3° to 1° toward the top, and 

 at the " pali," the beds were very nearly or quite horizontal. 

 This is favorable to the conclusion that the crater was either 

 at its head or near by it, just beyond the precipice. The low 

 land below, over the Kaneohe peninsula and between this pe- 

 ninsula and the " pali," is a region of tufa hills and other small 

 cones, unlike any part elsewhere of the north or northeast 

 coast. In addition, at the head of Nuuanu valley, very near 

 the top of the " pali," there are the remains of a red cinder 

 cone. Besides this, on descending the steep " pali " by the 

 path, there is to the east of the path a long broad slope, 35° to 

 40° in angle, consisting of reddish layers of volcanic cinders, 

 scoria, earth and stones — indicating cinder ejection from some 

 point above. 



It is therefore most probable that the center of volcanic ac- 

 tivity for East Oahu was in the vicinity of the " pali," above the 

 low region a little to the northeast of it. The cinder cones 

 above mentioned may have been results of the last efforts of 

 the declining fires, like those of Haleakala and Mt. Kea. 



In 1840, I was led to locate the central crater on the Kan- 

 eohe peninsula, because the head of the " pali " was so near 

 the southern foot of the mountain ; I thought it must have 

 been farther off. But the fact that the volcanic mountains of 

 East and West Maui are eccentric in ground-plan, and that 

 the same feature quite certainly characterized this Oahu cone, 

 makes the position near the " pali " the most probable. In 

 Haleakala the center of the crater is only six miles from the 

 southern shore ; and this distance in the Oahu crater, on the 

 above supposition, would be about seven miles. The idea of 

 an eccentric cone fourteen or fifteen miles in the transverse 

 diameter through the crater is thus strongly favored. On fur- 

 ther comparison with Haleakala, we find that the part of the 

 longer diameter of the mountains which lies northwest of the 

 center of the crater is about 19 miles in length on Maui, and 

 on Oahu it would be nearly 25 miles. The small dip of 1° to 

 3° prevails widely about the mountains at Kualoa point and 

 to the northward, as well as in the upper part of the Manoa 

 valley, west of the Nuuanu ; and from this it may be inferred 



