The coral reefs in Sanyawan can be divided into 5 microfacies: organic framework reef, bioclast, reefdebris, coral detritus, and the strongly reformed bioclast.
三亚湾珊瑚礁可以分为5个微相：生物骨架岩、生物屑、礁岩屑、珊瑚碎块、强烈改造的生物屑。
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For instance, when hurricane Bebe hit Tuvalu in 1972 it deposited 140 hectares of sedimentary debris onto the eastern reef, increasing the area of the main island by 10 per cent.