GLACIAL ACTION IN AUSTRALASIA. 235 



THE ANCIENT GLACIERS OF NEW ZEALAND. 



A few details of what we know about the ancient glaciers of 

 New Zealand may be interesting, and 1 will begin with Nelson and 

 work southwards. 



Nelson. — The most northerly ice-marks yet discovered are near 

 Mount Olympus, in Collingwood county. I have not seen them 

 myself, but they are thus described by Mr. .lames Park, F.G.S. : — 

 *' Glacier detritus is found only in the upper basin of Big Boulder 

 River, where it covers an area of perhaps 150 acres in extent. The 

 morainic matter occurs mostly on the west side of Boulder Lake at 

 the eastern foot of Lead Hill, but the remains of old moraines, 

 principally composed of large angular fragments of granite, are 

 found on the opposite side of the lake resting upon the slates. It 

 is evident that at one time thi< valley was occupied by a large 

 glacier, which must have excavated the fine rock basin in which 

 the present lake rests. The line of roches vnoutonnees on 

 the west side of the lake near the outlet are as fine an example 

 of ice-erosion as anything of the kind to be seen elsewhere in 

 New Zealand."* 



Mr. A. D. Dobson, -who was the first to call attention to these 

 ice-marks, says that Boulder Lake, or Te Warau, is 3.200ft. above 

 sea level, and that Lead Hill is a mass of granite, which rises to a 

 height of 4,4o0ft. above the sea. The glacier, when it attained its 

 fullest size, was about four miles long.f 



Several other small glaciers also formerly existed in the same 

 district at the heads of the Anatoki River. 



"■ The Mount Arthur Range, which attains its greatest height 

 (5.8()0ft.) in the Mitre Peak of Mount Arthur, gave rise to many 

 small glaciers." Those on the eastern sl()23es descended to 3,600ft. 

 and 3,000ft. above present sea level, while those on the western 

 side were larger and their terminal faces are 3,000ft. and 2,700ft. 

 above the sea. Some of the terminal moraines are almost com- 

 pletely hidden by detritus from the mountains. :J: 



The St. Arnaud and Spencer Mountains, wliich rise in places to 

 over 8,(KJ0ft. above the sea, gave origin to many glaciers. The 

 principal ones on the north-west were those which filled the valleys 

 now occupied by Lakes Rotoiti and Rotorua Lake Rotoiti is 

 2,()60ft. above the sea, and its former glacier was about twelve 

 miles in length by two in breadth. On the eastern side a glacier 

 came down the Rainbow Hiver, which is a branch of the Wairau, 

 and others down the Clarence and Waiau-ua. The old glacier 

 of the ^^'^aiau-ua or Dillon must have been not less than fourteen 

 miles in length, with a branch five miles long in the valley of the 

 Ada. The terminal moraine at one time held back a lake which 



• Keports Geal. Exploration, 1888-9, p. 242. 



+ Trans., N.Z. Inst., vol. 4 (1871), p. 337. 



X Dobson, 1. c, pp. 338-9. 



