126 



COLLEGE ZOOLOGY 



atomic bombers took off for the bombing of 

 Hiroshima and Nagasaki in Japan. Many of 

 the finest landing strips on the Pacific is- 



lands have been paved with coral. Coral has 

 also been used for making roads and side- 

 walks. 



High tide 



yLagooDy 

 :\::Coral reef;w/Vw:v':; 



>Vol 



came IS 



land^ 



Lagoor 

 ::v.Coral reef'- 



Cross section of a fringing reef 



Cross section of a barrier reef 



High tide 

 Low tide 



OOI 



■■^:^" " Lagoon ^"•:^^^^:;i:^" . /- fj}^^ 



/<C^:V."-l-i'-:V^^;=^Coral reef v^^::^^•::^v:;V:^v^^v^^ 



Cross section of an atoll reef 



Figure 64. Coral reefs are grouped in three general classes: fringing, barrier, and atoll. The 

 fringing reef lies close against the shore; the barrier reef lies off shore and is separated from the 

 land by a lagoon; the atoll reef is a barrier reef which encloses a lagoon; it may be a continuous 

 reef, but it is usually divided by water channels, extending through it from the ocean to the 

 lagoon, as shown in this illustration. Vegetation grows on accumulated debris. One coral reef 

 is known to be 690 feet in depth. (Modified from drawings by P.G. McCurdy.) 



There are three types of coral reef forma- 

 tions: (1) fringing reef, (2) barrier reef, 

 and (3) atoll reef (Fig. 64). 



A fringing reef is a ridge of coral built up 

 from the sea bottom, located so near to 

 land that no navigable channel exists be- 

 tween it and the shore. Frequently, breaks 

 occur in the reef and irregular channels and 

 pools are created which are often inhabited 

 by many different kinds of animals, some of 

 them brilliantly colored. 



A banier reef is separated from the shore 



by a wide deep channel which may afford 

 passage for relatively large boats. These 

 coral reefs may constitute a great danger to 

 shipping, however. The Great Barrier Reef 

 of Australia, which is the largest, is an enor- 

 mous coral structure, 1350 miles in length, 

 and, in places, 25 to 90 miles from the main- 

 land of Australia. The channel is from 60 

 to 150 feet deep. A barrier reef may en- 

 tirely surround an island. 



An atoll is one or more islands, consisting 

 of a belt of coral reef surrounding a central 



