NOTES ON THE IQ16 ERUPTION OF MAUN A LOA 477 



our efforts on this occasion were devoted in large measure to 

 observation of details and to the examination of evidence bearing 

 on the physical-chemical conditions and the mechanisms of flowing 

 in the lava streams near their head. The ideas considered in this 

 connection are best left for future discussion by the writer's com- 

 panion on this expedition. Here it will suffice to say that much 

 was seen tending to confirm, and some things tending to modify, 

 the writer's conception of the mode of flow of a-a, as exempli- 

 fied by the action observed at the front of the Honomalino 

 branch, described above. Consequently, the space here devoted 

 to this more thorough work is small in proportion to its relative 

 importance. 



On June 27, 19 16, we set out from the observatory and went by 

 motor to Honomalino, and thence with horses up the southeast 

 flank of Loa to a point in Kahuku, above Papa, at an elevation of 

 about 6,500 feet above sea-level. Here we made camp on barren 

 ground a little above tree-line on this part of the mountain, close 

 beside a short narrow branch of the new flow — the most north- « 

 western of all its definite branches. The six days, June 28 — July 3, 

 we spent in exploration of the source region. On July 4 we returned 

 on horseback to Honomalino and by motor to the observatory. 



This camp site was situated on the regular, gentle slope of the 

 mountain dome, between i| and 2 miles below the junction of this 

 branch of flow with the rift source. Everywhere here the old sur- 

 face was of ancient, rusty-red pahoehoe and a-a commingled in a 

 complicated pattern — except for an area of gray pahoehoe, younger, 

 but still very old, found about if miles above camp. Nearly all 

 our way upward from camp to the source led alongside the new flow 

 over slopes below the limits of the great flat above Puu o Keokeo, 

 but as the 1916 source was closely approached these slopes graded 

 into this upland plain west of the new rift cracks. 



The sources of all the branches of the 19 16 flow lie in the new 

 rift segment. The 19 15 rift here is a newly developed fissure, or 

 in most places a very narrow system of closely spaced fissures (the 

 primary group together nowhere more than 30 feet wide and nearly 

 everywhere much narrower) which extends from the northern base 

 of Puu o Keokeo for a distance estimated closely at 3! miles in a 



