266 S.' Powers — Notes on Haivaiian Petrology. 



tween Maui and Kahloolawe. Another line appears to 

 extend in the direction of the summit of Kahoolawe^ as 

 if that island had arisen on the line as a volcano subsidi- 

 ary to Haleakala. Few cones are found on the western 

 side of the mountain, toward West Maui, and fewer cones, 

 except those composed of trachyte, are found on the 

 deeply-dissected West Maui Volcano. 



Hawaii. — The Kohala Mountains, forming the oldest 

 volcanic center on Hawaii, also show a number of radial 

 rows of young cones. On the northwest flank of the vol- 

 cano a row of large cones, from which lava flows have 

 come, points directly toward Haleakala, which is a much 

 younger volcano than Kahala, and suggests that Halea- 

 kala may bear the same subsidiary relation to Kohala 

 that Kahoolawe bears to Haleakala. 



Mauna Kea has more cones on its flanks than any other 

 volcano in the Hawaiian Islands. The original summit 

 sink, if one existed comparable to Mokuaweoweo on 

 Mauna Loa, was completely buried by the ash eruptions, 

 at the closing stages of activity in pre-historic times. 



Mauna Kea lavas are not exposed in deep gulches and 

 therefore only the surficial flows may be studied. From 

 an ascent of the mountain, Daly finds evidence of a ba- 

 saltic base capped by younger flows of trachyandesite 

 which are partly covered by ash. 10 One of the younger 

 flows has never been noted — a flow at Laupahoehoe which 

 is younger than the wave-cut cliff which bounds Hawaii 

 from Hilo to Waipio valley. The Laupahoehoe basalt 

 issued from fissures near the mouth of the valley by that 

 name and spread out into a small peninsula which pro- 

 jects beyond the sea-cliffs. This is the most recent flow 

 near the base of the mountain. 



Hualalai was last in activity with a lava flow in 1801, 

 the flow being observed by one of the earlier mariners, 

 but smoke issued from the mountain as late as 1823 and 

 possibly as late as 1840-41. 11 Instead of a single flow in 

 1801, as has been previously supposed, two main streams 

 of lava poured from the mountain and several ash cones 

 were formed. An ascent of the mountain in 1915 from 

 McGuire 's ranch, together with a review of the Hawaiian 

 traditions concerning the activity at the time, has shown 

 that the eruption took place along one or more radial 

 fissure-lines extending from near the summit of the moun- 



10 Magmatic differentiation in Hawaii, Jour. Geol., vol. 19, p. 299. 



11 J. D. Dana, TL S. Exploring Expedition 1838-42, Geology, p. 215. 



