Читать книгу Walking in the Yorkshire Dales: South and West. Wharfedale, Littondale, Malhamdale, Dentdale and Ribblesdale онлайн

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The most intriguing features of karst landscapes are those that result from the solubility of the bedrock in rain water. Its 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 ‘evaporating’ before your eyes as does the stream emanating from Malham Tarn or the River Skirfare in its passage through Littondale. Just as magical is their reappearance further down the valley, the river having coursed between the two points deep underground in dark and constricted passages and fissures that are the province of intrepid potholers and cave divers. In places, some dramatic passages are sufficiently accessible to have been opened as show caves, allowing visitors to marvel at the fantastic stalactites, stalagmites and other formations created as incessant drips of the lime-rich water have 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.