THE CONTINENT 



The basalts occur as dykes or flows chiefly on the 

 flanks of Mount Erebus and Mount Bird. The same 

 series is found also on the mainland, notably near Cape 

 Adare. Interesting magnetite basalts are met with at 

 Cape Barne and Tent Island in the west of Ross Island. 

 Jensen is of the opinion that the heavier lavas, such as 

 the basalts, flowed from fissures in the sides of the 

 main crater, tapping lower portions of the magma. 

 The upper portions gave rise to the lighter Kenytes, 

 which are the most typical eruptive rocks of East Ant- 

 arctica. (See Figure 8.) 



Mount Erebus and Its Kenytes. — No description of 

 the geology of the Ross Sea area would be complete 

 without some reference to the dominating volcano of 

 Erebus. This towers over thirteen thousand feet above 

 the Ross Sea and together with its extinct neighbor, 

 Mount Terror, practically forms Ross Island. The 

 main bulk of the cone is built of the remarkable lava 

 called Kenyte, which is closely allied to the rhomb 

 porphyries of Norway, and also to Gregory's series 

 from Mount Kenya in East Africa. The chief char- 

 acteristic of the Kenytes is the presence of large crystals 

 of anorthoclase felspar, usually about one inch long. 

 On almost all the outcrops these felspars weather out 

 of the fine-grained ground mass under the action of 

 frost so that the surface of the Kenyte resembles a 

 medieval church door studded with huge nailheads. 

 The chief constituents as given by Prior are silica 56 

 per cent, alumina 21 per cent, soda 7 per cent, and 

 potash 4 per cent. Data as to the period of the initia- 

 tion of these eruptions are wanting. They are con- 



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