•Hill. — Rotomahana and District revisited. 285 



Okaro Lake, the steam-vents are powerful and excessively active ; and 

 along the entire chasm there are many signs of unusual activity, steam 

 being forced through the rock at very high pressure. 



The water of the lake is of a greyish-green colour, and contains a fair 

 amount of mud in suspension. The lake is bounded by high walls of pale- 

 blue mud, which are easily washed away in time of heavy rain. This may 

 account for the colour of the lake-waters ; but the Haumi Stream also 

 carries down plenty of mud^ — in fact, during heavy and stormy weather 

 the stream must carry down an immense quantity of material from the 

 soft pasty mass of the area which the stream drains. 



The country, wherever it was covered with material from Rotomahana, 

 presents a curious appearance. The blue clay is mixed with scoria that 

 was thrown from the mountains, and they appear to have fallen together 

 in many places. The surface becomes hard and gritty, and yet in time 

 of rain deep ruts or gutters are quickly formed, and there appears surface- 

 characteristics that are not seen under ordinary physical conditions. Every 

 rut represents a drainage-basin from two adjacent slopes that may not be 

 more than 2 ft. or 3 ft. wide, but of fair length ; and the drainage from 

 this miniature watershed and basin forms in time ruts of extreme depth, 

 resembling a crevasse in the ice. These provide pitfalls to the unwary, 

 and it is inipossible for a horse to pass across country where these ridge- 

 like places abound. As time goes on, these miniature-basin areas will 

 merge, and the basins will grow fewer and fewer as erosion breaks down 

 the ridges. In some places where grass was sown there are few ruts, and 

 ■comparatively little damage to the new surface has taken place. But the 

 lesson to be learnt is that resulting from the action of the weather upon a 

 surface that has to be supplied with a covering of vegetation in nature's 

 own way, and the growth of an ordinary river-basin by the merging of 

 hundreds and even thousands of tiny miniature basins where the old basins 

 have been obliterated presents even to-day an object-lesson of the utmost 

 interest in the physical evolution of surface-features in a country. 



At the time of the eruption the mountains presented the appearance 

 of having been torn and wrenched by some great titanic force. The south 

 end of Mount Tarawera, known as " The Chasm," ran towards the lake from 

 nearly the front crest of the mountain. This chasm is now quiescent, and 

 but for the colour of the material and traces of scoria it would be difficult 

 to suppose that the rift had been made within the past quarter of a cen- 

 tury. Immediately above the chasm there is a fringe of black lava that 

 h.as evidently flowed into its present position. It passes over the crest, 

 and is lost in a dip of the mountain which has been filled with scoria and 

 other material thrown from the craters further along the mountain. The 

 appearances suggest that, before the chasm burst, an opening in the moun- 

 tain further to the north had been made from which lava — a heavy dark 

 lava^had commenced to flow. The late Mr. Blythe stated that he saw 

 a, stream as of moving lava, and was supported by ^thers. Between this 

 place and the first of the craters is a dip from which one rises to the flat, 

 where the first crater is seen. This flat area is ridged, and shows a series 

 of earthquake-cracks running north-east and south-west. The depressions 

 have formed places of safety for lowly forms of vegetation, and several 

 varieties of ferns were collected among other specimens of plants. The 

 two craters on Tarawera are separated from each other by a kind of rock 

 pai-tition. The walls of the craters on the west and north more parti- 

 cularly show varying coloured bands of scoria and cinders, which have a 



