Читать книгу Walking in the Yorkshire Dales: North and East. Howgills, Mallerstang, Swaledale, Wensleydale, Coverdale and Nidderdale онлайн

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The most intriguing features of karst landscapes are those that result from the solubility of the bedrock in rainwater. The rain’s slight acidity dissolves the stone, exploiting crevices and vertical stress fractures, and ultimately creating the awe-inspiring potholes and caves for which the area is famous. Whole rivers are swallowed into the ground, either in abruptly sensational falls such as Gaping Gill, or merely disappearing intermittently into their beds, as does the River Nidd in its higher reaches.

Just as magical are the Nidd’s resurgences lower down, the river having coursed between two points deep underground in the dark and constricted passages and fissures that are the province of intrepid potholers and cave divers. At Stump Cross, these dramatic passages are sufficiently accessible to have been opened as show caves, allowing visitors to marvel at fantastic stalactites, stalagmites and other formations, created as incessant drips of lime-rich water evaporated over millennia, leaving the lime behind. Occasionally, similar deposits are also seen on the surface in the form of tufa, where calcite is precipitated from the cascading water. And at How Stean Gorge, the river runs through a dramatically narrow canyon, which is explained as a collapsed cave.