by wave action so that broad platforms were formed 

 around the land (Fig. 9) . When the ice age passed, 

 the sea level rose to its normal position and engulfed 

 the platforms. As it became warmer, the present day 

 reef began to grow upon these new bases, which w^ere 

 all at a depth of under 175 feet and therefore suitable 

 for coral growth. 



PREGLACIAL 

 FRINGING RLZF 

 NOW EXPOSED 



PREGLACIAL 



sea" level 



^, GLACIAL 



SEA LEVEL 



iCAJ^iS;"' FC^pM 



Figure 9. Section illustrating the formation of a platform by wave action 

 in the marginal seas, during glaciation. 



In general it may be said that Darwin's theory of 

 land subsidence, combined with Daly's glacial control 

 theory, is adequate to explain most known reefs but 

 that there are also undoubted cases where the platforms 

 have been formed by agencies of a different nature such 

 as those provided by other theories. Final proof is 

 very difficult to obtain and even deep borings made 



33 



