EROSION AND ITS SIGNIFICANCE. 135 



On the same wide and low lying block as that which holds 

 Lake Te Anau lies Lake Manapouri, and both lakes have 

 their deepest portions in situations along which the greatest 

 stream scour could not have taken place. On the other 

 hand the locations of maximum stream (ice or water) 

 scour have been along channels whose bases lie above or 

 near lake level. In a word, the lakes lie on an old age 

 surface, and such wide surface is separated from other 

 dismantled old age surfaces by the wildest topography 

 imaginable. 



The region has been intensely glaciated in recent times. 

 It is difficult to assign the exact share that earth move- 

 ments and erosive activities have had in producing this 

 magnificent topographical feature, but it is evident that 

 corrasion has had only a minor share in producing the total 

 result. The lake in quite recent times was much larger 

 than at present, and from a consideration of the principles 

 discussed in the present note it appears to represent the 

 filling by water of a great senkungsfeld having the moun- 

 tainous country on the western portion of the lake proper 

 as one wall, the eastern wall of the lake for another, and 

 the rugged and youthful Takitimu Range for another wall. 



The beginning of the fiords which break its western and 

 northern walls may also have been in heavy cross faulting, 

 but it is certain that the liords have been intensely glaciated 

 during the recent Ice Age, and that the long and profound 

 canons discharging into the fiords may be easily explained 

 by erosive processes alone. 



Similar reasoning may be extended to the case of Lake 

 Wakatipu where faulting appears to have been most pro- 

 nounced especially about Arrowtown, The Grown Terrace, 

 and the great west front of The Remarkables. Heavy 

 erosion by ice, however, is evidenced on the lower hills, the 

 thickness of the ice stream having been several thousands 



