OCEAN CONTOURS, S.W. PACIFIC. 441 



rocks. The Kermadec islands have shown some activity within 

 historic times. Sunday Island was subjected to eruptions in 1872. 

 On Curtis Island steam jets show that activity is only subdued tem- 

 porarily. The soundings show no elevated ridge to the east as at 

 the Tonga islands. Depths of 1,500 fathoms are shown close to the 

 islands. 



As previously mentioned the sea floor between this ridge and New 

 Zealand is less than 1,500 fathoms deep, but there is little sign of a 

 ridge as ISew Zealand is approached. The structure of Tonga is 

 reproduced in the East Cape and hot lake district of New Zealand, 

 for here the volcanoes are west of the structural ridge of the land. 

 The Miocene limestones are at a higher level than the older slates 

 which lie between them and the volcanic zones. A deep submergence 

 (3,000 ft.) would therefore in this part of the land cause two lines of 

 islands to be separated — the easterly line would consist of Miocene 

 limestone; the westerly of volcanoes. The slates between them would 

 be entirely submerged. 



Traced further south these features entirely change. Even in the 

 North Island the volcanic series stops abruptly at Ruapehu, and in 

 the direction of its continuation is a series of late Cainozoic strata 

 resting almost horizontally. Here, too, the altitude of the argillite 

 peaks is far greater than that of the Cainozoic rocks that are still 

 found to the east of them. 



On the southern shore of Cook Strait the difference is more 

 marked still. The range of argillites is still continued in the Kai- 

 koura Mountains. The Cainozoic sediments to the east are now of 

 still less importance. The volcanic rocks to the west, which even in 

 the south pai't of the North Island is replaced by late Cainozoic sedi- 

 ments, do not extend across the strait ; but their place is occupied by 

 first the gravel deposits at the head of Tasman Bay, and then by the 

 great folded zone of the Southern Alps. 



North of the Tonga Islands this great ridge bends round to the 

 westward towards Fiji. It appears, so far as may be judged by 

 soundings, to be entirely cut off from the Samoa Islands by water 

 2,000 or 3,000 fathoms in depth. 



In New Zealand the volcanoes which lie on the strike of the 

 Tonga-Kermadec ridge have not emitted any lava within historic 

 times. There is not even any evidence of molten lava reaching the 

 crater of any of the volcanoes except during the eruption of Tarawera 

 in June, 1886 ; but even on this occasion there was no outflow of hxva, 

 though bombs of andesite were ejected. Those mountains that have 

 had explosive eruptions within modern times in addition to Tarawera 

 are the following : — Ruapehu, Ngauruhoe, Tongariro (Te Mari crater), 

 and Wliite Island (Whakari). During the most violent recorded 

 eruption of Te Mari, in 1895, Dr. Von Friedlander, who was then on 

 a visit to the region, failed to see any reflection of hot rock on the 

 steam clouds. Similarly in March, 1907, I failed to see any reflection 

 on the clouds of steam and ashes rising over Ngauruhoe, which was 

 then in explosive eruption. Stress has been laid by Trotter, Dana, 

 and Jensen, as well as many others, on the well-knowai fact that four 

 days after the Tarawera eruption Whakari showed unusual signs of 

 activity, and that two months later there was an eruption at Niouafu, 



