S. Powers — Explosive Ejectamenta of Kilauea. 235 



The center of dispersion of the threacl-lace scoria is appar- 

 ently a point within the Kilanea sink, southwest of the Volcano 

 House. Kilanea Iki does not appear to be the source of the 

 material, judging from the sections at the Crater Hotel and 

 along the automobile road to the crater. The thread-lace 

 scoria is replaced by ash with a small amount of black olivine 

 sand west of Uwekahuna, and in the vicinity of Keanakakoi. 



Overlying the thread-lace scoria on the northeast side of 

 Kilauea and directly overlying the basalt flows on the south 

 side is a deposit of ash which is continuous over the whole 

 area, although it may not all have been ejected in the same 

 eruption or from the same vent. The ash is quite uniformly 

 dark yellow in color, and of fine grain, but layers of coarser 

 material grow abundant near the main source, and thin bands 

 of thread-lace scoria, ordinary scoria, and olivine-bearing sand, 

 and occasionally Pele's hair appear on close examination. 

 Large bombs are comparatively rare in this deposit. Some of 

 the ash is composed of pisolites, showing that rain fell at the 

 time the ash was blown out. 



The distribution of the ash is shown in fig. 3. The maximum 

 thickness exposed is 25 feet on the "Peninsula" south of 

 Halemaumau and west of the automobile road. The deposit 

 thins rapidly in all directions. It has a thickness of from 12 

 to 23 feet along the southwest and southeast sides of the sink 

 as seen in the fault-scarps nearest Halemaumau ; 6 to 9 feet 

 on the edge of the monoclinal slope nearby, a mile southwest 

 of the crater ; 6 feet at the foot of the trail to the floor of the 

 sink from the Volcano House; and 1 to 3 feet over the sur- 

 rounding region as along the 1868 cracks on the west, Uweka- 

 huna, the Volcano House, the first of the pit craters on the 

 southeast. 



The source of the material is not conclusively shown, but 

 the great thickness at the "Peninsula" suggests that the prin- 

 cipal eruption came from the vicinity of the present Halemau- 

 mau. There is no indication of a source at Keanakakoi, but 

 the thickness of about 12 feet at Byron's and Waldron's ledges 

 suggest a vent in this vicinity. 



The ash is overlain by a deposit of course ejectamenta com- 

 posed of fragments of basalt such as is seen in the modern 

 flows, and in the large blocks which must have come from 

 some distance underground ; bombs ; scoria ; and a small 

 amount of ash. The deposit resembles gravel and many of 

 the blocks are rounded like stream pebbles, but the material 

 was never rounded by water. 



The relation of the ejectamenta to the ash is probably a dis- 

 conformity because very local unconformities are seen in the 

 " Peninsula " and on the Kau desert, both on the top of the 

 monoclinal slope south of Halemaumau and farther southwest. 



