38 



RISTVET 



2 



^ SOUTHWEST 



\ PaSSAGE 



SOUTH 

 CHANNEL 



10 



20 STATUTE MILES 



CONTOUR INTERVAL 100 FATHOMS 

 DATUM IS MEAN LOW TIDE 



Fig. 1 Location map of Enewetak Atoll, Marshall Islands. 



Meanwhile, expeditions in other areas of the world 

 were contributing to an understanding of atoll geology. 

 Darwin (1842), during the voyage of the HMS Beagle from 

 1831 to 1836, studied reef building organisms and reef 

 morphologies. He established a three-fold classification of 

 reefs that is still used today: fringing reefs, barrier reefs, 

 and atolls. Darwin (1842) integrated his findings into a 

 theory of atoll formation on subsiding island foundations 



with antecedent fringing and barrier reef stages. However, 

 other workers (cf. Agassiz, 1903; Daly, 1915; and Gar- 

 diner, 1931) later proposed alternate theories postulating 

 that atoll reefs grew upwards from still standing submarine 

 summits of various origins. 



By the turn of the century, direct subsurface sampling 

 became a paramount issue to understanding the origin of 

 atolls. Funafuti Atoll, in the Ellice Islands 2400 km south 



