80 PRATT. 



surface material was removed from the crater, allowing only a shallow 

 depth for the new lake, to make up the volume of the solid ejecta. The 

 appearance of the ejected mud, its low temperature, and its irregular 

 character, all bear out the conclusion that it consists almost entirely 

 of the material removed from the surface.^* The few incandescent stones 

 may have come from slightly lower down in the volcanic throat, but even 

 these were probably originally thrown out by former volcanic activity 

 and were only worked over recently. 



It is improbable that Taal has ejected original molten material within 

 historic time, although among the last of the geologically recent beds 

 in its crater wall there is a thin layer of basaltic lapilli. It is true that 

 accounts of the eruption of 1754 mention floating pumice and scoria on 

 Lake Bombon, but patches of scoria were observed on the lake surface 

 after the recent eraption during which no scoria were thrown out. 

 These patches of floating pumice in the recent activity resulted from 

 the action of the water wave on the bed of lapilli near the ground surface 

 of the island and the lake shore. The scoria of the former eruption may 

 have been due to a similar action. 



If no part of the solid ejecta of the recent eruption was newly cooled 

 lava (either as scoria or ash), there seems to the writer to be a difficulty 

 in explaining this explosive outburst by the more commonly accepted 

 theory of explosive volcanic action; i. e., as the sudden escape of steam 

 and other absorbed vapors from molten lava. It is incredible that gases 

 should escape from a liquid magma "wdth such violence and not bring with 

 them fragments of that magma either as ash or scoria. 



Although hot and heavily mineralized,-^ the water which is flowing 

 into the new crater probably is seepage from Lake Bombon through the 

 crater walls. Since Lake Bombon stands a few meters above sea level, 

 the new crater lake M'ill probably rise in time to about sea level. It is not 

 apparent that this larger body of water in the crater will have any material 

 effect on the activity of the volcano. It will probably tend to' muffle 

 the minor surface violence, by yielding more readily to pressure and 

 dissipating more rapidly the heat that reaches the upper part of the 

 volcanic throat, than the rigid, heat-insulating earth which it replaced. 



The large column of rock or "obelisk" which appeared in the crater 

 of Taal Volcano during this eruption is at present a striking object (it 



^^A fresh sample of the mud was sent to Mr. H. D. Gibbs, chief of the 

 division of organic chemistry of this Bureau, to be tested for radio-activity, 

 with the idea that if the material were of deep-seated origin it might be radio- 

 active. The test, made within three days after the eruption, showed no radio- 

 activity. 



'^ A sample of the water from one of the streams was taken, and has been 

 analyzed. See the article by Dr. Alvin J. Cox in this number. 



