Typology of karst systems :
" One of the most original features of the Famenne – Ardenne Geopark is, incontestably, its karst. This term refers to a series of natural forms: massive river losses (swallow holes), closed depressions, massive spring resurgence, caves and potholes, and subterranean rivers, all of which develop primarily in calcareous rocks. Together, they form an ensemble known as a karst system. This in turn may be defined as the area of underground drainage that leads to an emergence, encompassing the initial loss of the river or stream, the infiltration surfaces and the resurgence of the water from underground..."
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