Southern Guam geospatial information server

Beaches in Southern Guam

Beaches are coastal deposits of loose sandy sediment. They are important natural habitats and some of Guam’s most beautiful scenery. In southern Guam, beach sand is a mixture of terrigenous (land-derived) sediments and and biogenous sand composed of disintegrated calcium carbonate shells of marine organisms. Observing this pepper-and-salt colored sand under magnification reveals that dark-colored grains are minerals eroded from rocks on land and light-colored grains are pieces of corals and calcareous algae, mollusk shells, echinoderm fragments, etc. Sand in some areas is largely derived from land. Beach in Talofofo Bay, for example, has parts of entirely black sand rich in mineral magnetite.

Beaches are generally barren. Very few plants can grow in loose and salty coastal sand. Vines such as Ipomoea pes-caprae and Canavalia spp. may extend from their roots in the backshore and creep seaward to take advantage of unshaded, open space on the beach. Near the water, beach sand is locally cemented by natural processes into hard deposits known as beachrock. They are usually coated with slippery films of algae. Green algae, especially Ulva, occasionally bloom in the intertidal zone.

Text above is slightly modified from "Environments of Guam" by Danko Taborosi, David R. Burdick, Claudine M. Camacho, Frank Camacho, published by BessPress, 2013.


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