1 6 W. N. BENSON 



the effects of glaciation are also evident. It seems clear, how- 

 ever, that this was restricted to the highlands and the valleys 

 among them reaching sea-level only along the west coast of 

 the South Island. The ice did not advance to form a large 

 confluent piedmont glacier beyond the eastern slopes of the 

 Southern Alps, though it deployed into sheets of considerable 

 area in the lake basins and associated depressions, notably that of 

 the above-mentioned Lake Te Anau. The view that an ice sheet 

 extended to the low southeastern portion of the island does not 

 appear to be acceptable. As a result of glacial erosion, the valleys 

 in the mountainous portions of the South Island, though originally 

 determined as explained in the previous paragraph, have since 

 been considerably modified. The topographic features character- 

 istic of glaciation have been developed, and there are even indica- 

 tions of the effects of more than one cycle of mountain glaciation. 

 It is not clear what extent of glaciation may have been present in 

 the North Island, but there seems to have been little if any. 



In the rain shadow of the Southern Alps an area of very small 

 precipitation occurs in the center of the province of Otago, and 

 here topographic features characteristic of semi-aridity may be 

 seen. 



Piedmont aggradation. — Concurrently with the degradation of 

 the mountains, there has been much sedimentation, forming 

 piedmont plains. A series of gravels formed during the elevation 

 of the Southern Alps have been unconformably covered by the 

 gravels of the Canterbury Plains. These consist of a great sheet of 

 detritus over 130 miles long and 30 miles wide, the confluent fans 

 of the rivers draining the eastern slopes of the mountains, at the 

 foot of which they rise to a height of 1,000 feet above sea-level, 

 but they have been built out over a sea floor which has subsided 

 at least 600 feet during their formation. Less extensive plains of 

 gravel and alluvium occur in other districts, each with special 

 features of interest. 



Loess. — Of lesser importance are the deposits of loess along the 

 central portion of the eastern coast of the South Island. The loess 

 is composed of the rock-flour carried by the dominant northwesterly 

 winds from the dried pools in the braided valleys of the glacier-fed 



