342 Transactions. — Geology. 



approached the separate cones of which it is formed at the 

 top become more distinct. (See Plate XXVIII.) The lower 

 slopes of the mountain are composed of lava-streams, which 

 stretch as far as Eotoaira, the lake to the north ; indeed, the 

 formation of the lake appears to be due to the blocking of the 

 drainage-channel by a lava-stream. These lower slopes are 

 covered with tussock-grass, which affords a certain amount of 

 support to animal life, so that the slopes of the mountain 

 have been employed as a sheep-run. On the north side there 

 is a large area of forest. Amongst the tussock-grass small 

 herbaceous plants with bright -coloured blossoms grow in far 

 greater abundance than is usually seen in New Zealand except 

 in alpine districts. The summit of the mountain is all but 

 devoid of vegetation. 



That portion of Tongariro which lies to the east is often 

 termed by the natives Te Mari, whilst the part to the west 

 is Tongariro proper. The top of the mountain is marked by 

 seven large craters, as well as some smaller ones. The dis- 

 tribution of these will be best gathered from the accompanying 

 sketch-map (see Plate XXIX.), which will, I believe, be found 

 sufficiently accurate for our present purposes. 



The ascent of the mountain is most easily accomplished by 

 way of Ketetahi, a hollow at the height of 4,900ft. on the side 

 of the cone which forms the north-west angle of Tongariro. 

 Ketetahi is not, properly speaking, a crater, though explosions 

 of steam seem to have assisted in the excavation of the hollow : 

 it resembles rather the enlarged head of a gully. There are 

 many hot spi'ings and a powerful escape of steam here, whilst 

 the overflow of the w^ater forms a warm stream. The volume 

 of steam rising from Ketetahi is usually very considerable — so 

 copious, indeed, as to render the spot visible for a distance of 

 fifty miles. 



Two other places on Tongariro are marked by the escape 

 of steam, which betrays the volcanic forces dormant within 

 the mountain. One of these is on the northern slope of Te 

 Mari, the other is in the Eed Crater ; but neither shows so 

 much activity as Ketetahi. Above Ketetahi the slope of the 

 cone becomes steeper. It is formed of lava having a compara- 

 tively smooth surface of step-like formation, which greatly 

 facilitates the ascent. 



On reaching the summit of the cone a remarkable sight 

 presents itself. The top is formed by a circular area half a 

 mile in diameter, which at first strikes one as being perfectly 

 flat. Closer examination, however, shows minor undulations, 

 the surface of the wind-swept ground being strewn with fine 

 sand-like volcanic ashes and lapilli. To the north, and, again, 

 on the opposite side, towards the south, a cliff of lava rising 

 perhaps to 100ft. above the crater-bottom forms the boundary 



