Rock, usually limestone, composed of oolites.

岩石岩石，通常指石灰岩，由鲕粒岩组成。

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All fibrous formations form from saturated solutions being squeezed out of pores in the bedrock (usually limestone) and depositing at they hit air.

所有纤维状沉积物都是由基岩(通常是石灰岩)的孔隙中受压的饱和溶液形成的，当他们遇到空气，就结晶沉积下来。

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Usually, it happens when the substrate is formed by limestone, carbonate rock, salt beds or any other rock that is easily eroded by water streams.

通常，它发生在基板是由石灰岩，碳酸盐岩，盐层或任何其他岩石，很容易被水侵蚀形成的溪流。

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Usually this layer is a soluble carbonate rock, such as limestone or its purer form, chalk.

BBC: Who, What, Why: How are sinkholes formed?