520 NOTES ON THE RECENT ERUPTIONS IN THE TAUPO ZONE, N.Z., 



It is noteworthy that the explosive centres are travelling to 

 the N.E. : Ruapehuand others formerly active, but now extinct, 

 and Tongariro at present still slightly active lie to the S.W. 

 Then the hot springs of the Kuharua country, the geysers and 

 hot springs of the Waikato, and, with still increasing activity, the 

 Rotomahana marvels continue the chain to its N.E. culmination 

 in the ever active insular volcano of White Island. 



This gradual decrease in activity as we move to the S.W. 

 along the line of disturbance seems to be in harmony with the 

 view that the present condition of Taupo is only a more 

 advanced stage of the same series of which we see some of the 

 preceding steps in the late explosion, and that in the course of 

 ages Tarawera and Rotorua will come to reproduce a basin of 

 equal tranquillity for themselves. 



If there has been in the case of Tarawera no actual eruption 

 of lava from crater or fissure, there seems to have been at least 

 an enormously increased energy of thermal action, involving the 

 actual incandescence of steam and other gases, and of the 

 materials which their discharge shot up in the clouds. And it 

 does not seem probable that so great and so sudden a paroxysm 

 could have been produced by any cause short of a real rise of 

 the fluid rhyolitic lava, either up unseen funnels left by 

 former explosive action, or up new rents, whose rupture might 

 have caused the shocks of earthquake which appear to have been 

 so frequent and so violent. 



To what extent this lava may have been itself charged with 

 steam under intense compression may be a question difficult of 

 determination. But seeing how the whole country teems with 

 springs, there is no difficulty in supposing that such a column of 

 white-hot lava moving upwards would meet with abundance of 

 percolating waters which it could almost instantaneously change 

 into explosives of prodigious power. 



The cessation of upward movement in the lava column, which 

 must be consequent on so vast a loss of heat as is involved in the 

 expenditure of so much steam power, will naturally give some 

 intervals of comparative repose to the surface. But after a time 



