346 Transactiom. — Geology. 



both, and that it has even been carried to within a few miles of 

 New Plymouth. Volcanic mud is of common occurrence all 

 over this country, but now so altered in aj^pearance by decom- 

 position as to be difficult of recognition, were it not for the 

 underlying strata of pumice. It will be seen later on that the 

 recent deposit of mud in the neighbourhood of Wairoa throws a 

 good deal of light on the method of deposition of these beds of 

 mud. 



The changes in the central zone of volcanic action since this 

 vast mass of ejecta was scattered all over the country have been, 

 doubtless, very great. It is difficult to believe that all this 

 material has issued from the extinct volcanoes, the remains of 

 which we now see. It is far more reasonable to suppose that, 

 during the ages which have passed since the later Eocene 

 period, other volcanic vents have existed, and added to the 

 immense mass of remains now visible, and that they themselves 

 have disappeared, or been covered up by subsequent outbursts 

 of the present volcanoes. We cannot assign, for instance, to 

 the action of Euapehu and Tongariro the cliffs of pure pumice 

 on the east of Taupo, which are 400 feet high, nor have the 

 vast lava floes of the west side of the lake come from those same 

 sources. Is it not far more reasonable to suppose that we now 

 see in this long belt of country a great depression, due to the 

 sinking of the whole surface, which carried with it the numbers 

 of points of eruptions whose remains are now all that is left to 

 denote their whereabouts? But to follow out this line of rea- 

 soning, and show from the evidence obtainable that this is 

 probable, would occupy more time than is allowable. If this 

 slight notice of some of the principal features of this great 

 volcanic area has shown that changes have occurred in the past 

 on a stupendous scale, it will prepare us for the acceptance of 

 the idea that similar changes may always occur in that locality, 

 and of this we have had recent evidence in the outburst at 

 Tarawera. 



Premonitory Signs. 



New Zealand has been colonized so short a time, compared 

 with the geologic ages of the past, that observation has not yet 

 been continued sufficiently long to record any great changes in 

 the volcanic region alluded to. 



It is true that, from time to time, slight eruptions of Tonga- 

 riro, (or rather Ngauruhoe,) have been noted ; earthquakes have 

 occurred on a larger or smaller scale ; the hot springs have been 

 occasionally more or less active ; floods and landslips, involving 

 loss of life, and due more or less directly to volcanic agency, 

 have occurred ; but no great catastrophe has been recorded, to 

 bring home to us the fact that any great changes are going on. 

 But, nevertheless, a general opinion has been curx-ent to the 



