52 



FOYE. 



The basaltic rocks of Susui and the agglomerates of the outer islands 

 are fresher than the andesitic rocks to the west. The dips of the 

 agglomerates, closely adjacent to the limestone islet, indicate that 

 these beds once surrounded the small island. The directions of dip 

 indicate that the eruptive center lay in the eastern island, ]Munia. 

 From these facts it is concluded that the basalts of eastern Susui were 

 erupted after the elevation of the limestones of the Exploring group, 

 and thus during the later volcanic period already seen to be important 

 in the history of the group as a whole. 



Scattered Imestone islets lie within the lagoon, inside the curve 

 formed by the three large islands of Vanua Mbalavu, Malatta, and 



Figure 23. Profiles of Four Limestone Islands of the Lau Group. 

 Numbers indicate possible terraces. 



Susui. On the northern border of the lagoon a few A'olcanic islands 

 occur. The only other island of any size, except Munia which will 

 be described later, is Thikombia-i-lau. 



The accompanying outline sketches (Figure 23) were made at a 

 distance from the islands shown, Thikoml)ia-i-lau, Avea, Vanua 

 Mbalavu, and Naiau. Fi\e miles away, one would say immediately 

 that the breaks in the outlines of the islands represent sea-cut benches, 

 yet a closer view causes doubt as to whether they have significance or 

 not. Many of the supposed "l)enches" represent a chance align- 

 ment of several cliffs and hills which cannot be traced witii any 

 regularity about the islands. 



Tliiko)iihia-i-Iau. Thikom])ia-i-lau is shaped like a Scotch bonnet 

 with a central, north-south depression cutting entirely across it. The 



