CORAL REEFS 



175 



LEVEL 



(Fig. 35), the force of the sea would throw boulders of 

 coral limestone on to the surface of the flat around the 

 edge and here dry land would begin to be formed. Gradu- 

 ally the boundaries of the reef would be extended in all 

 directions, more stones and boulders would be thrown up, 

 some of which would be worn down by the action of the 

 weather to form a soil in which seeds carried by the sea, 

 or in floating timber washed ashore, or in soil attached to the 

 feet of sea birds which alighted here, would establish 

 themselves and grow. And so the beginnings of plant life 

 would appear and, by the binding action of their roots, would 

 establish the dry land yet more securely, while their decay 

 after death would 

 provide further, and 

 richer, soil. Mean- 

 while the centre of 

 the reef flat would 

 become hollowed out 

 to form a lagoon in 

 essentially the same 

 manner as the 



channel is formed F IG « 37- — Diagram to illustrate the formation of 



. an atoll according to Murray's theory. A, original 



between the fringing mound on sea-bottom ; B1-B4, increase in mound ; 



f A +V1 1 A C I_ C3» outward extension of atoll by accumulation of 



reel ana tlie lana. talus falling down the side. Lagoon hollowed out by 



The water pouring in solution or eroding action of sea, etc. 



between the various islands forming the atoll ring (see Fig. 

 34), would scour and dissolve away (Murray laid great 

 stress on the latter process) the dead coral in the centre 

 and, with the aid of boring animals and plants gradually 

 eat out a shallow lagoon. And so the process would go 

 on, the atoll extending outwards like a " fairy ring " of 

 fungus on grass, the broken fragments or talus falling 

 down the steep slopes outside and furnishing a foundation 

 for the further increase of the reef. In exactly the same 



ill ill i 





