Geology.] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 689 



sandstones, and the component grains are formed of quartz which has the structure 

 of schist quartz. It is therefore reasonable to infer that some area of metamorphic 

 rocks was then exposed above the ocean-surface. During the Miocene period sub- 

 mergence was in progress, and the final stratified rocks of the series consist of 

 almost pure oceanic limestone, without a trace of detrital matter. This appears 

 to imply that all the land was submerged towards the close of the period. Volcanic 

 action broke out about the end of the Miocene period. At first the volcanic action 

 was submarine, and the marine fossils imbedded in the fragmental matter which 

 was first ejected show that the water was relatively shallow, and that the sea-floor 

 was inhabited by a fauna comprising much larger species of Mollusca than are at 

 present found there. Elevation probably continued during the period of volcanic 

 activity, for the scoria-beds which separate some of the upper lava-flows are highly 

 oxidized. After the cessation of volcanic action the ordinary processes of destruc- 

 tive actions by degrees modified the surface, and before long glaciers were formed, 

 and the valleys were deepened and widened. To what extent the present drainage- 

 system had been developed before the glacial advance is not indicated, so far as. 

 the observations made by the present expedition are concerned. It is certain that 

 a climate of mild temperate character prevailed at the commencement of the 

 volcanic period, and it is probable that a considerable interval of time would 

 elapse before conditions would change to a sufiicient extent to allow of the forma- 

 tion of glaciers. 



Much discussion has from time to time taken place as to the cause of glaciation 

 in New Zealand. Captain Hutton always held to the opinion that the extension of 

 the glaciers — ^the only glaciation of which we have evidence — was caused by a greater 

 elevation of the land, without any important change in climatic conditions. He 

 quoted the southern islands in support of this theory, for he failed to detect any sign 

 of glaciation in them. Haast explained the glacial advance in New Zealand as due 

 to the greater amount of land-surface then above the snow-line, for he supposed 

 that the elevated land was then dome-shaped and little dissected by erosion. Hector 

 appears to have regarded the glaciation as a result of the same general cause to which 

 the formation of glaciers in the Australian Alps and in Tasmania were due. It is 

 well known that this cause has not yet been clearly defined, and that there is no 

 consensus of geological opinion about it. 



So far as Campbell Island is concerned, no evidence in favour of greater 

 elevation was found, except, perhaps, an elevation sufficient to raise the floor of 

 Perseverance Harbour above the sea-level — ^that is. 180ft. As before stated, there 

 was considered to be abundant evidence of glaciation. The period of this glacia- 

 tion appears to have been about contemporaneous with the Pleistocene glaciation, 

 by which so many different parts of the temperate regions of the world were 

 affected. It is therefore reasonable to consider the formation of glaciers on the 

 island as a result of a general cause which resulted in the refrigeration of so many 

 regions of the earth's surface. 



By ice erosion the surface of Campbell Island acquired the majority of 

 the features which it now possesses. The volcanic plateau ! which formerly 

 composed the island was dissected, the lava-flows were cut up into isolated 

 fragments, the underlying rocks were exposed, and the present features were the 

 result. 



45— S. 



