40 Transactions. 



The whole country in the vicinity of Lake Tekapo has been heavily 

 glaciated. Extensive areas of the lower levels are masked by a veneer of 

 moraine ; large travelled blocks everywhere dot tha landscape, and some 

 are exposed, partially submerged, along the shores of the lake. Owing ti- 

 the completeness of this covering, exposures of rock in situ are rare below 

 the steep slopes of the mountains. Scoured and grooved surfaces and 

 smoothed landscapes are visible at higher levels. Numerous shelves of 

 comparatively small elevation are characteristically developed as the valley 

 widens out, especially on the section between Coal River and the Macaulay. 

 These are strongly reminiscent of those to be seen near the Potts River in 

 the Rangitata Valley, and near Lake Heron in the valley of the; Upper 

 Ashburton. In these cases the type of sculpture is associated with the 

 erosion of a valley which has been at one time filled with non-resistant 

 Tertiary sediments. Farther up-stream, however, a modified form of this 

 sculpture is apparent where the ice has overridden the end of the spur 

 between the Macaulay and the main valley, the rock being entirely 

 gceywacke, so that it is not dependent altogether on the presence of easily 

 eroded rocks. A feature similar to this is recorded by Park (1909, p. 19) 

 as occurring near Ben More, in the Wakatipu district. In this case, 

 however, he attributes the feature entirely to glacier erosion, whereas the 

 Tekapo occurrence seems partly due to erosion and partly to the derjosit of 

 morainic matter on the shelves so formed. 



The extreme freshness of the evidence of ice-action suggests that the 

 retreat of the ice was comparatively recent, a fact which is emphasized by 

 the modifications of the valley-sides. The youthful stage of the drainage of 

 some of the tributary creeks, too, with their deep, narrow, rock-bound gorges 

 incised into the abraded surfaces, so smooth by contrast, strongly supports 

 the hypothesis that the ice has but recently retreated from this region. 

 This feature is specially well exhibited in the Waterfall Creeks, which enter 

 the Macaulay from the east, just at the point where it is emerging from the 

 rocky precipitous country on to the down area which lies on the flank 

 of Mount Gerald. 



One somewhat surprising feature is the absence of halting-stages in the 

 retreat. There are no terminal moraines apart from the great one at the 

 foot of the lake, and the coating of angular material seems to be somewhat 

 thin. It is as if the ice disappeared simultaneously from long stretches of 

 the valley and dropped the covering of moraine which then masked its 

 surface. This loose material would be rapidly occupied by plants from 

 the adjoining open spaces, so that the formation of a plant covering 

 should not lag long behind the disappearance of the ice. The rapidity 

 with which a bare shingle river-bed is covered with vegetation shows that 

 no objection can be raised to the hypothesis of a recent rapid retreat of 

 the ice on the ground that plants would not have had time or opportunity 

 to spread and establish themselves on the glacier-swept areas. The 

 evidence of rapid retreat with few or no halting-places is observable in the 

 valleys of the other main rivers of Canterbury, especially the Rakaia and 

 the Waimakariri. 



On the higher country the usual forms resulting from glacial sculpture 

 are to be seen, notably corries in all stages of complete and arrested 

 development and of destruction by present-day ice and frost. The cirques, 

 originally heading them after the retreat of the ice, are attacked by these 

 agencies, the clear-cut walls disappear, the hollows becoming filled with 

 debris Especially is this the case when they are partially filled with snow. 

 Rocks roll down its frozen surface, especially in winter, and accumulate 



