Park. — Rate of Erosion of Hooker and Mueller Glaciers. 395 



Art. XXVIII— The Rate of Erosion of Hooker and Mueller Glaciers, New 



Zealand. 



^ By Professor James Park, F.G.S., Otago University, Dunedin. 



Rfud before the Otago Institute, 5th December, 1916 ; received by Editors, 30th December, 

 1916 ; issued separately, 30th November, 1917.] 



In a paper on the rate of erosion of the Hooker and Mueller Glaciers, pre- 

 sented to the Otago Institute in August, 1912, Dr. Marshall* records the 

 results of thirteen determinations of the amount of suspended matter carried 

 by the Hooker River, which drains the Hooker and Mueller Glaciers. The 

 first sample was taken on the 17th November, 1911, and the last on the 

 25th March, 1912. The lowest result gave 1 part of suspended matter in 

 885 parts of water, and the highest 1 in 39,141. He concluded that the 

 whole of the suspended material was the product of glacier erosion due to 

 the slow movement of the ice over the rocky bed. From his meagre data 

 he calculated that the rock bed over the whole neve and glacier area of 

 the Hooker and Mueller Glaciers was being removed at the rate of £§ in. 

 annually, equal to 1 ft. in 756 years. 



In the discussion which followed the reading of the paper I pointed out 

 that both the Hooker and Mueller Glaciers were heavily dirt-laden, and 

 that in all probability a large proportion of the suspended matter ascribed 

 by Dr. Marshall to glacial erosion was in reality released from the melting 

 neve. 



Since that date I have again examined the Mueller and Hooker Glaciers. 

 The Mueller Glacier, especially in its lower portion, is covered with an 

 extraordinary quantity of transported material, rai ging from large angular 

 flaggy slabs of a rgillite and greywacke to small angular grit mixed with fine 

 particles of fresh unoxidized rock. Ten pannings of the finer material, taken 

 at different points near the terminal end of the neve, contained from 0-08 to 

 3-60 per cent, of material sufficiently fine to form suspended matter when 

 placed in water moving at the rate of 3 ft. per second. 



The Hooker Glacier also carries a large load of frost-shattered rocky 

 material, and in many places is interstra titled with thousands of thin bands 

 of fine material that alternate with thin bands of almost clear neve. These 

 dirt bands descend through the body of the neve to an unknown depth. 

 When the neve melts they discharge their load into the river draining the 

 glacier. 



Experimental tests of the material forming the dirt bands showed the 

 presence of from 0*16 to 2-34 per cent, of material sufficiently fine to form 

 suspended matter in slowly moving water. The lowest observed velocity 

 of the water at the Hooker bridge was 5*6 ft. per second. 



The neve is constantly melting at the terminal face and on the walls 

 and roof of the ice-tunnel under the glacier. Moreover, the glacier river 

 flows in the ice-tunnel with a great velocity, as may be seen at various 

 places where the sides have collapsed. The wear-and-tear and pounding 

 of the larger fragments of argillite when they fall into this turbulent stream, 

 in the two miles between the terminal face and Hooker bridge, must be 



;: P. Marshall, Note on the Rate of Erosion of the Hooker and Mueller Glaciers, 

 Trans. N.Z. Inst., vol. 45, 1913, pp. 342-43. 



