230 /S. Powers — Explosive Ejectamenta of Kilauea. 



minimized in the least by the possibility of contemporaneous 

 activity on the southwest rift-line marked by the 1808 and 

 older fissures. 



The ejectamenta of Kilauea are readily divided into two 

 classes : those in the walls ; and those outside and on top of 

 the walls. The former are of great age, and only exposed in 

 the faults bounding the main sink ; the latter are in part 1789, 

 but mostly pre-historic. 



Older Ejectamenta. 



The ash-sections in the walls of Kilauea are difficult to find, 

 and more difficult to trace, both because of their similarity to 

 the lava-flows and to the eroded surfaces of these flows ; and 

 because of the vertically and inaccessibility of the walls. 

 The most extensive section is at the base of the cliffs, south- 

 west of the Uwekahuna fault-blocks. Another is found at 

 the northeast end of the fault-blocks. 



The former section (fig. 1) is exposed to a thickness of only 

 17 feet and for a length of about 500 feet, at the base of a 

 cliff 170 feet in height. The beds are composed principally 

 of yellow ash with some rock-fragments 1-2 inches in diameter, 

 lava droplets, thread-lace scoria, and a few bombs 6 inches in 

 length. At either end the section dips beneath the floor of 

 the sink. The tilting of the beds probably took place with the 

 faulting at Uwekahuna, as the pahoehoe flow immediately 

 above the ash follows the contour of the ash without varying 

 in thickness. 



On the northeast side of the Uwekahuna fault-blocks, above 

 a talus slope, is exposed an unconformity (fig. 2), which 

 appears to be a fault formed during the construction of the 

 dome of Kilauea. Above the unconformity is a bed of ash, 

 varying in thickness from 1-6 feet, and the flows above the 

 unconformity end against the ash. The stratigraphic relation 

 of this section to that above described is difficult to determine 

 on account of the Uwekahuna fault-blocks which conceal 

 the conformity. 



A generalized section of the ash beds as seen in fig. 2, where 

 they rest on a horizontal surface of thin pahoehoe flows, shows 

 coarse and fine ash with fragments of scoria and basalt 1-3 

 inches. This bed of ash continues around the north wall of 

 the sink, at a height of about 35 feet above the floor. The 

 character of the material changes and the thickness is variable. 

 The fine ash is replaced by scoriaceous lava fragments as well 

 as fragments of rock, until on the north wall of the sink, near 

 a 2-foot dike, the ash has become a red scoriaceous breccia, 5 

 feet thick. Beyond the first dike the breccia loses its identity 



