THE KARST PHENOMENA MAKE UP THE MAIN DISTINCTIVE QUALITY OF THE FAMENNE-ARDENNE GEOPARK, AT THE HEART OF A UNIQUE GEOLOGICAL AND TOPOGRAPHICAL SETTING.
Karst terrain is made up of a series of surface and underground formations and landscapes associated with limestone : sinkholes (closed depressions), chasms, caves, underground rivers, stalagmites...
FIG 1 The landscape is determined by the geology. From south to north, the resistant sandstone rocks of the Ardenne dominate the landscape, shales form depressions and the limestone of the Calestienne gives way to the shales of the northern Famenne. The principal rivers, the Ourthe, Lesse, Lomme, Hilan, Biran and Aisne flow down from the Ardenne to cross the various geological formations.
FIG 2 In the limestone areas, the meanders of the main rivers may plunge underground (caves of Han, Rochefort, Bohon). Streams flowing down from the sandstone heights disappear into sinkholes (chantoirs) to form underground rivers that emerge at the bottom of deep valleys (caves of Hotton, Fond des Vaulx, Laide Fosse).
FIG 3 Swallow hole of the Lesse at the Gouffre de Belvaux.
FIG 4 The underground river in the Cave of Hotton.
FIG 5 Laide Fosse sinkhole. The stream carves out a shallow valley and disappears underground as soon as it meets the limestone.