REEFLESS COASTS OF EMERGENCE 



539 



The Gulf of Carpentaria, on the northern coast of Australia, is shown 

 on the geological map of Queensland by Jack and Etheridge (1892, map, 

 sheet 5) to be mostly bordered by low alluvial delta flats, often occupied 

 by mangrove swamps. The shallow sea-border is free from reefs, and 

 thus presents a strong contrast to the eastern coast of Queensland, where 

 reefs abound along a bold embayed coast fronting deep water. Whether 

 this example belongs under coasts initiated by emergence or by submer- 

 gence I can not say. Young volcanic islands may be treated under coasts 

 of emergence ; their shorelines are comparatively simple, and the detritus 

 washed from their slopes may form a gravelly or sandy beach. Ambrym, 

 in the New Hebrides, culminating in an active volcano from which 

 streams of lava and showers of dust have been given forth in recent years, 

 has a beach and bluff cut in loose ash deposits along part of its circuit; 

 here reefs are absent and the surf becomes dark and turbid as it falls on 

 the black volcanic sand. 



THE REEFLESS COAST OF SOUTHEASTERN INDIA 



The Madras district of southeastern India, of which Gushing (1911, 

 1913.) has given excellent descriptions, is a remarkable example of a 



Figure 13. — Diagram of the reefless Coast of Madras 



reefiess coast of subrecent emergence. It is bordered by a belt of marine 

 strata, forming a coastal plain the shoreline of which is either fronted 

 by sand reefs or built forward by deltas, roughly shown in figure 1 3 ; but 

 coral reefs are almost wanting in spite of the high temperature of the sea- 

 water. Furthermore, a much more ancient emergence of this region, by 



