CHAPTER XV 



DESCRIPTION OF THE GEOLOGICAL AND GENERAL PHYSICAL 



features {continued) 



The North-east Portion of the Island 



This large area, which extends for a distance of nearly forty- 

 miles from the eastern slopes of the Mount Thurston Range to 

 Undu Point, forms the region closing in Natewa Bay on the north. 

 It would be difficult to imagine an area of this size with a greater 

 variety of surface or showing such a lack of arrangement of its 

 principal features. The hills and mountains on the north side 

 gather at the coast, and extensive inland plains, raised but a few 

 feet above the sea and strewn with silicified corals, occupy a portion 

 of its interior. A long valley with a very small gradient extends 

 nearly across its breadth ; and the rivers are for the most part 

 tidal estuaries fed, except in one or two cases, by insignificant 

 streams. There is, however, a lofty range of ridge-mountains in 

 its broadest part attaining a height of 2,500 feet ; whilst away to 

 the east stretches the great Undu Promontory singular for the 

 straightness of its form. 



Volcanic rocks of acid types, such as oligoclase-trachytes, 

 quartz-porphyries, and white pumice-tuffs prevail in the northern 

 part between Undu Point and the promontory opposite Mali 

 Island. In the southern part, from the foot of Mount Thurston 

 and Vuinandi to the vicinity of Tawaki, massive rocks and tuffs and 

 agglomerates of basic characters predominate. Although my 

 acquaintance with this area is incomplete, the data below given will 

 be sufficient to enable a general idea to be formed of its structure. 

 The more conspicuous features in its geology will gradually come 

 into prominence as the various localities visited are described. 



