Adkin. — Former Glaciation in the Tararua Range* 315 



General Conclusions. 



The former glaciers of the Tararuas owed their existence to the then 

 greater elevation of the country and to the more rigorous climatic con- 

 ditions. At the present time the snow-line in the latitude of the Tararuas 

 is about 8,000 ft. above sea-level. " The late Sir Julius von Haast, in his 

 ' Geology of Canterbury and Westland,' estimates that during the glacial 

 period the snow-line was 1,000 ft. lower than it is in New Zealand at the 

 present time."* This estimate involves only a slight reduction of the 

 annual temperature — a reduction presumably induced by cosmic or ex- 

 ternal causes or conditions — and appears to have been based on such, other 

 factors being neglected. The evidence furnished by the configuration of 

 the bed of Cook Strait (as shown by soundings) and by the physiography-] 

 of the lowlands at the western foot of the Tararuas indicates that the ele- 

 vation of that part of the country has been reduced since the glacial period 

 by at least 1,000 ft. Taking for granted that these estimates are correct, 

 and that they represent the sum of the influences that lowered the snow- 

 line, the snow-line in the Tararuas during the glacial period was, in re- 

 lation to the present sea-level, 2,000 ft. lower than at the present time ; 

 in other words, the snow-line of the Tararuas formerly stood at a height 

 of 6,000 ft. above the present sea-level. But it is evident from the known 

 altitude and position of the extinct glaciers of the Tararuas that the lower 

 limits of the permanent snowfields that fed them were at the most 4,000 ft., 

 and perhaps only 3,500 ft., above the present sea-level. By taking as 

 correct even the greater altitude — i.e., 4,000 ft. above the present sea- 

 level) — there is a discrepancy between it and the foregoing of 2,000 ft. 

 This lack of agreement between the tentatively adopted and the actual 

 altitude of the former snow-line may be removed by accepting one 

 of the following amendments : that during the glacial period the 

 snow-line was lowered (in each case with reference to the present sea- 

 level) — (1) by more rigorous climatic conditions 3,000 ft., and by the 

 greater elevation .of the land 1,000 ft.; (2) by climatic conditions 

 1,000 ft., and by greater elevation 3,000 ft. ; or (3) by climatic conditions 

 2,000 ft., and greater elevation also 2,000 ft. The last of these is probably 

 nearest the truth, since the estimate that the snow-line was lowered by 

 climatic influences only 1,000 ft., as pointed out by Mr. H. Hill (Trans. 

 N.Z. Inst. vol. 27, p. 453), " is a very small one, representing, as it does, 

 only a difference of about 3 degrees of temperature ; and this certainly 

 would not be sufficient to bring about a glacial climate in the South Island " ; 

 and, of course, still less so in the North Island, unless it can be shown that 

 the latter stood at an enormously greater elevation in the early Pleistocene 

 period. 



The former glaciers of the Tararua Ranges give some indication of the 

 extent and nature of the Pleistocene sflaciation of the North Island : they 

 show that in these respects it was limited, localized, and moderate. On 

 comparison this view is found to be in harmony with the known extent 



* H. Hill, " On the Hawke's Bay Pleistocene Beds and the Glacial Period," Trans. 

 N.Z. Inst., vol. 27, 1S95, p. 452. 



t G. L. Adkin, " The Post-tertiary Geological History of the Ohau River, &c," 

 Trans. N.Z. Inst., vol. 43, 1911, p. 49fi. 



