.238 8. Powers — Explosive Ejectamenta of Kilauea. 



but the depressions made in the underlying deposit may be 

 seen to greater advantage.* They do not extend on to the Kan 

 desert beyond the monocline, but they are found on ITweka- 

 huna with a diameter of 1 to 5 feet, and a quarter of a mile 

 north of the edge of the pit one was found 44- feet long, 4 feet 

 wide, and -3 feet high. 



The youngest deposit of coarse material, "gravel," is diffi- 

 cult to separate from the thick deposits underneath. The top 

 of it forms a hard crust over the gravelly plains of the desert 

 area near Halemaumau. On the Kau desert a thin coating of 

 this gravel covers the thread-lace scoria which is unconform- 

 able upon the older deposits. 



Age of JEjectamenta. 



The relative ages of the basal thread-lace scoria at the Vol- 

 cano House, the ash overlying, the coarse material, and the 

 1789 ejectamenta remain to be considered. The first three 

 deposits appear to belong to the same period of eruptive activ- 

 ity. They are all altered in places where steam has issued or 

 is now issuing, they are all faulted alike, the local unconformi- 

 ties between them merely represent brief periods of repose, 

 and they are all overlain by the Keamoku flow from Mauna 

 Loa. It cannot be stated whether the three kinds of material 

 represent three or many eruptions. Judging from the amount 

 of ash ejected by one of the explosive type of volcanoes in a 

 single eruption, as Sakurajima in 1914, all the older Kilauean 

 ejectamenta might represent a single eruption lasting only a 

 few days. 



The surficial deposits of pumice, coarse ash, and bombs are 

 separated from the others because they appear to be less 

 altered, and less consolidated (except where rain-water has 

 made a surface crust), and because they are found to rest 

 unconformably on the other deposits, especially in places 

 where the older beds are faulted and the younger material fills 

 the fissures. 



If the explosive material represents two eruptions or series 

 of eruptions which took place at widely separated periods of 

 time, as is argued above, was the first series before the forma- 

 tion of the present sink of Kilauea? On first thought this 

 seems quite impossible, but an examination of the meager evi- 

 dence may lend some support to this view. 



The pre-historic deposits of ejectamenta are found on the 

 fragments of the former summit of the volcano: the plains 

 and the fault-blocks outside the present sink of Kilauea and 



* These depressions have been photographed and described by Perret in 

 this Journal (4), xxxv, 614, 1913. 



