S. Powers — Explosive Ejectamenta of Kilauea. 243 



another section is seen. These sections are given for com- 

 parison : 



Kaalualu 





Honuapo 



Top: possibly 



another 



flow 



Top: an erosion surface 



5-10 feet ash 







3-15 feet ash 



2^- 3 " lava 







10-15 " lava 



7-10 " ash 







10 ± " ash 



? lava 







12 ± " lava 



10 ± " ash, base not seen 



At Pahala and at Naelehu the cane-fields are situated on a 

 yellow ash bed over 10 feet in thickness, but south of Pahaha 

 in the grazing- land from the highway to the recent flows from 

 Kilauea the ash is very thin. It is owing to the fertility of 

 the ash that cane can be raised with a very small supply of 

 water. 



Although a thorough reconnaissance of the entire Mohokea 

 territory is impossible on account of the impenetrable tropical 

 jungles in which one walks on decayed vegetable matter and 

 never sees fresh rock, it is thought that the interbedded ash 

 deposits and lava flows came from some source now concealed 

 in the Mohokea region. It is not possible to discuss here the 

 possibility of the former existence of a crater in the Mohokea 

 area of down-faulted blocks, but the ash beds might be used as 

 evidence favoring the crater theory. 



Summary. 



It has been shown that the ash deposits on Hawaii are found 

 on the flanks of all the volcanoes, but especially on Mauna Kea 

 where the closing stages of activity were marked by enormous 

 ash-eruptions ; on the southwest slope of Mauna Loa ; near the 

 crater-like depression Mohokea ; and on the summit of Kilauea. 

 In the first instance the ash beds now exposed appear to be 

 almost entirely surficial ; at Mohoka it is interbedded with 

 the lava ; at Kilauea it occurs interbedded with the flows and 

 on the outer rim. of the sink. 



The visible Kilauean ejectamenta have been described as 

 principally surficial. The interbedded deposits are exposed 

 in only a few places in the walls of the sink, but they suggest 

 many catastrophic periods in the older history of the volcano. 

 The ejectamenta on top of the walls of the sink cover the sur- 

 rounding region and have a maximum thickness of 36 feet 

 near the present crater Halemaumau. These deposits represent 

 two eruptive periods : the older, of pre-historic age, comprising 

 most of the deposit and consisting of basal thread-lace scoria at 

 the northeast part of the sink, overlain by ash which surrounds 



A.M. Jour. Sci. — Fourth Series, Vol. XLI, No. 243. — March, 1916. 

 18 



