Made up mostly of limestone formed from the skeletal remains of sea creatures, the submerged regions of the tidal flats are carved by channels where water flows between land.

这些群岛主要是由海洋生物残骸形成的石灰岩构成，潮汐滩的水下部分被流动的水分割成河道。

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He was describing the multitude of caves that puncture the limestone slopes that spread across Asturias, Cantabria and Castilla y Leon regions in northern Spain.

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