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Astove Island is part of the Aldabra Group of the Seychelles. It is 38 km SSE of Cosmoledo Atoll, located at (). It is a raised coral island of most peculiar form: a single stretch of land, more than 1 km (nearly one mile) at the widest, almost entirely encloses a shallow lagoon. This has a maximum depth of 3 metres (10 ft), and the only exit is a winding passage in the southwest, called ''Gueule Bras Channel''. Astove Island measures nearly north to south and about at most east to west. The land area is 4.96 km2 (1.92 sq. mi.), and the total area including the lagoon 9.5 km2 (3.7 sq. mi.). The only settlement, on the western coast, has been abandoned since the 1980s. There is a grass airstrip on the north east point of the island, and remnants of a former coconut and sisal plantation. Today, the island is rarely visited - usually by scientists researching the lagoon's ecology - but the near-vertical drop-off from its outer reef edge is an occasional destination for diving cruises. ==Geology and geography== Astove's unusual structure has raised questions about its formation. It was suggested that Astove is not a true raised atoll, but rather a reef flat, with the lagoon being washed out later. In any case, the lagoon indeed grows slowly, owing to rainwater, acidic from the soil's humic acids, dissolving the lagoon's carbonate rock bottom. This causes the unusual milky-white color of the lagoon's waters.〔Piggott (1961)〕 On the large land mass towards the western tip, exposed reef rock raises to some 5 m (15 ft) ASL. Elsewhere it is largely covered by gravelly debris. Dunes of up to 18 m (60 ft) line the windswept eastern rim of the island, and the eastern part of the lagoon is especially shallow due to the inblown dune sand. Astove Island's fringing reef is just about 180 m (300 ft) wide. As noted above, beyond the reef's outer edge the seafloor drops down steeply, with a depth of 550 m (300 fathoms) a mere 300 metres (900 ft) away from the shoreline.〔 The climate is dominated by the southeast trade winds which are most pronounced between April and November. Temperatures are around in the shade during that time, and slightly higher during the northwest monsoon season. At that time, tropical cyclones with torrential rain sometimes hit the island, but overall it is very arid.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Astove Island」の詳細全文を読む スポンサード リンク
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