118 The Tarawera Outbreak. 



The views that he formed after he had examined the 

 district are summed up by him as follows : — He concludes 

 that the eruption was (1) a purely hydrothermal phenomenon; 

 (2) that it was not of deep-seated origin; (3) that it was a 

 quite local movement; and he also tells us that the great 

 fissure was the most characteristic feature of the outbreak. 



What I propose to do is to discuss Dr. Hector's views as 

 to the nature of the eruption as far as the facts disclosed in 

 these two reports will enable us to do so. 



We will, in the first place, consider the statement that it 

 was a purely hydrothermal phenomenon. 



Now, what is a purely hydrothermal phenomenon ? 



Must a phenomenon, to be termed purely hydrothermal, 

 have heated water, and nothing else, as its cause, and also 

 heated water, and nothing else, as its effect ? If so, then hot 

 springs and geysers alone are purely hydrothermal pheno- 

 mena, and Dr. Hector's meaning must be that Tarawera 

 was merely a geyser. 



But it is certain that Dr. Hector might mean to describe a 

 phenomenon of which the sole cause was heated water, 

 although the visible effects included the emission of many 

 kinds of matter besides steam and water. Such a pheno- 

 menon would be a volcano, and if I accepted Dr. Hector's 

 words in this sense, then his meaning would be that the sole 

 cause of the Tarawera outbreak was the action of heated 

 water. But such a statement would be the merest truism^ 

 and therefore it is unlikely that he would make the assertion. 



Consequently, it will be necessary to weigh the language 

 of the context to enable us to decide whether he means to 

 say that Tarawera was a mere geyser, or that the Tarawera 

 volcano was actuated purely by steam. 



Thus he tells us that it was a hydrothermal phenomenon, 

 but upon "a gigantic scale." Now, if it were a geyser erup- 

 tion, it certainly was one upon a gigantic scale ; but if it were 

 a volcano, its scale was not at all gigantic, but very ordinary. 

 Therefore, from the use of this adjective we would infer 

 that he is describing a geyser. 



Again, he states that the outbreak was "not deep-seated." 

 This raises th6 question as to whether volcanoes are ever 

 superficial in their origin. I shall discuss this point further 

 on, and at this stage I will only say that such a statement 

 confirms the impression already made on my mind that a 

 geyser, and not a volcano, is conceived of by the author of 

 the report. 



