ERTJPTIOX OF MOUNT TA.EAWEEA. 



185 



white streaked with green. This decomposed rhyolite is a very 

 common surface-rock in the district. The second kind is a soft, 

 dead-white, fine-grained, compact rock, with minute black specks of 

 hornblende or black mica, and crystals of pjTite, as well as occasional 

 small grains of quartz. The ground-mass is a white glass, with 

 innumerable small glass-inclusions, which are pale pinkish violet by 

 transmitted light. It contains quartz, pyrites, and, rarely, sanidine 

 not twinned. The vesicular state of these rocks is white glassy 

 pumice with quartz grains more or less abundantly developed. 



From the mountain came, chiefly, vesicular fragments of pumice 

 and scoria, the latter in much larger quantities than the former. 

 Many of the fragments, even those of small size, are composed partly 

 of pumice and partly of scoria with well-defined junctions. The 

 ash that accompanied these fragments is pale brownish grey, and 

 contains much white and brown glass as well as quartz, sanidine, 

 plagioclase, augite, and what appears to be a weakly pleochroic brown 

 hornblende. 



Prom the craters on the plains came angular fragments of 

 compact rocks and lapilli, chiefly rhyolite, without any pumice or 

 scoria. The ash that accompanied them is pale French-grey, and 

 contains much devitrifled glass and abundance of quartz with 

 occasionally sanidine, plagioclase, and green augite. 



The different ejectamenta are, of course, mixed together ; but still 

 a difference in distribution can be made out. That from the 

 mountain spread to the south-west only as far as Kakaramea, but 

 along the coast it extends from Katikati on the north, to Tolago Bay 

 on the east. It is tolerably evenly spread, the heavier scoria at the 

 bottom and the lighter ash at the top, and thins out very gradually. 

 On the Kaingaroa plains, about ten miles south-east of Mt. Tarawera, 

 the thickness of the deposit is five or six inches ; while at the 

 Southern Cross Petroleum Co.'s works, near the "Waiapu Biver, 

 between 89 and 90 miles distant, it is one inch thick, but, of 

 course, much finer. This ash fell dry, and it was warm for a 

 distance of eighteen miles from the mountain. The compact rocks 

 from the craters on the plains were not thrown more than two or 

 three miles, and the ash is much more limited in its distribution 

 than that from the mountain. On the south-west it went to the 

 base of Kakaramea ; to the west it follows nearly the same line as 

 that from Tarawera, while its easterly limit lies through the east 

 end of Eotoiti to ITaketu, but it gradually passes into the deposit 

 from the mountain. Eound the craters it fell hot and dry, but 

 further off as intensely cold mud, almost freezing ; and further off, 

 again, it fell as dry dust. The mud seems to have fallen in pellets 

 more or less rounded. I collected some of these out of the trees at 

 Pakaraka, near Eotokakahi ; they were of all sizes up to an inch in 

 diameter, and some had a small piece of scoria in the centre. They 

 must have formed in the air like rain-drops. One of them had a 

 leaf halfway through it, which it had knocked off in its fall, 

 proving that it was not frozen hard. On the morning when the 

 mud fell there was a severe frost, and it fell so hard that it was 

 Q. J. G. S. No. 170. o 



