reef islands are low-lying; on many Pacific atolls, and also
on the Cocos (Keeling) Islands, only about 33% of the reef
island surface is more than 2 m above mean sea level, and
<8% exceeds 3 m above mean sea level. In the Maldives
the islands appear even lower, with around 4 and 1% of
the total island area above 2 and 3 m above mean sea level,
respectively (Woodroffe, 2008).
Island sediments
Atoll reef islands are built from sediments that are entirely
calcareous, being derived from the skeletal fragments of
organisms living on the reefs, such as coral, coralline or
calcifying algae, molluscs, and foraminifera. Genera of
benthic foraminifera, such as Calcarina, Amphistegina
and Baculogypsina, produced on the reef crest and the reef
Atolls, Figure 6 Reef island cross sections surveyed across a selection of atolls and illustrating the variability in surface topography.
Several of the reef islands have been modified through the excavation of pits for cultivation of taro.
ATOLLS
61
on the Cocos (Keeling) Islands, only about 33% of the reef
island surface is more than 2 m above mean sea level, and
<8% exceeds 3 m above mean sea level. In the Maldives
the islands appear even lower, with around 4 and 1% of
the total island area above 2 and 3 m above mean sea level,
respectively (Woodroffe, 2008).
Island sediments
Atoll reef islands are built from sediments that are entirely
calcareous, being derived from the skeletal fragments of
organisms living on the reefs, such as coral, coralline or
calcifying algae, molluscs, and foraminifera. Genera of
benthic foraminifera, such as Calcarina, Amphistegina
and Baculogypsina, produced on the reef crest and the reef
Atolls, Figure 6 Reef island cross sections surveyed across a selection of atolls and illustrating the variability in surface topography.
Several of the reef islands have been modified through the excavation of pits for cultivation of taro.
ATOLLS
61