Geography
The islands are located on a shallow continental shelf with an average depth of 200 metres. However, in the Spratlys, the sea floor drastically changes its depth, and near the Philippines, the Palawan Trough is more than 5,000 metres deep. Also, there are some parts that are so shallow that navigation becomes difficult, and prone to accidents.
The sea floor contains Paleozoic and Mesozoic granite and metamorphic rocks. The abysses are caused by the formation of the Himalayas in the Cenozoic.
Except one volcano-island, the islands are made of coral reefs of varying ages and formations.
Read more about this topic: South China Sea Islands
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