NOTES ON THE lQl6 ERUPTION OF MAUN A LOA 487 



The 1916 eruption was of small magnitude compared with 

 earlier action originating near its source. There are accumulations 

 of ancient pumice far greater in depth and spread than that ejected 

 at this time. The older double semicones round about are higher 

 and greater and their gashes and fissure systems on a larger scale. 



One such ancient source — -whimsically designated in field notes 

 as "the lunar crater" because of a steep and relatively high peak of 

 riven blocks which stood near the center of its large, circular 

 depression, or crater-like area — had been the spring of a lava flood 

 vast in proportion to the recent flow. All about this old depres- 

 sion, except for its gap at the south, was a high rampart built of 

 huge cinder blocks piled confusedly, and outward from the top of 

 this a slope built of small cinders and pumice fragments fell away 

 gradually. 



Also the cones at Puu o Keokeo point to action of far greater 

 magnitude at the time of their building than recently — greater 

 than any action of historic date on the south flank of the mountain. 

 These cones, however, are only a conspicuous group in the well- 

 marked belt extending from the summit down the slope below 

 them. Though perhaps these are the largest of all, there are others 

 of comparable size, both above and below. The suggestion, there- 

 fore, attributed to the late S. E. Bishop, that Puu o Keokeo is a 

 vent distinct from Mauna Loa, but subordinate to it, probably 

 must be dismissed. This point, though a digression, is interesting 

 and important, since it might be considered to bear on the question 

 of the genesis of the 1916 eruption. 



In connection with this same point it is worthy of note that the 

 eruptions of 1868 and 1887 (and probably of 1907 also) were pre- 

 ceded by outbreaks of fumes and lava much higher up the moun- 

 tain than their eventual heads of flow — action similar to that 

 preceding the 1916 flow. 



In 1868 such action broke out in the evening of March 26, with 

 a further outburst in the early morning of March 27 "a little to the 

 southwest of the summit," followed by outflow from low sources, 

 at the southwest on Kilauea on April 2, and at the south-southwest 

 on Mauna Loa on April 7. This upper outbreak was very near 

 the summit. 



