Hill. — Taupo Plateau and Lake. 453 



the time of the eruption, and went through the awful experiences 

 from which he escaped only with his life. The photographs 

 show a downthrow and a subsidence, the latter of more than 

 90 ft., the sides being vertical. Here the difference is seen 

 between a force acting upwards and overcoming the downward 

 pressure, and a force acting downwards and overcoming the 

 upward pressure. The former is explosive at the surface, and 

 the latter simply shears and shows a steep face or faces along 

 the boundary-area that subsides. If the whole of the area 

 affected by the Tarawera eruption is traced, two separate and 

 distinct activities are seen to have taken place — one upward and 

 the other downward. The great quantity of material thrown 

 out from the numerous vents and shafts, exclusive of Roto- 

 mahana, shows the existence of underground movement. The 

 scoria, blue mud, ashes, and many varieties of volcanic rocks 

 were distributed for miles over the district affected by the 

 explosions ; but the material did not come from great depths, 

 and appears to have been acted on by superheated steam of so 

 high intensity that dust,, and scoria, and steam rose over the 

 seat of explosion to a height of many thousands of feet. 



But all the phenomena of the Tarawera eruption such as 

 were found in the mountains, in the rifted valleys, and about the 

 subsided areas, were no more than the display that took place 

 daily at Te Tarata and Otukapuarangi, or the White and Pink 

 Terraces, but on a much grander scale than was daily displayed 

 at those places. The explosions along the great fissure with 

 its centre at Rotomahana were most likely the direct result of 

 stoppages in various parts of the volcanic area, but which were 

 manifested along the line of greatest weakness — a weakness that 

 perhaps had its origin in the frequent shakings that had taken 

 place in the immediate vicinity of Rotomahana. Mr. Percy 

 Smith, in his excellent resume of the Tarawera eruption, points 

 out that the fissure seemed to prefer the face of a hill to the 

 bottom of the valley ; but the reason is that the valley passes 

 across the lava-flows, and not in the direction taken by them as 

 they move over the land when flowing from a volcanic orifice. 



The Wai-o-tapu Valley is at present separated from the line 

 of fissure by deposits from two volcanic mountains known as 

 Maunga-kakaramea and Maunga-ongaonga, both of which show 

 many signs of recent activity. Thus the valley of the Wai-o-tapu, 

 with its crateral lakes, its mud volcanoes, terraces, fumaroles, 

 geysers, and boiling springs, is only separated from the great 

 fissure at Tarawera-Rotomahana by a comparatively low ridge 

 of volcanic debris, and the earthquake-cracks at Pareheru and 

 Waikorua are at the apex of the two valleys. The Wai-o-tapu 

 stream begins in the crateral lakes at the foot of Kakaramea 



