Caves and potholes in the Montsec d'Ares geological unit

The Montsec d'Ares is a unit of the Prepirineu, the western sector of the great Montsec anticline, a limestone wall furrowed by gorges, pits and caves. It comprises 87 cavities: 42 pits and 45 caves, with a total passage of 7403 m and a maximum depth of 166 m. The dominant lithology is limestone (78), followed by sandstone (7), travertine (1) and dolomite (1).

Among the longest cavities are the Grallera Gran del Corralot (1977 m), the Graller del Boixeguer (870 m), the Cova Colomera (475 m), the Cova Negra de Corçà (325 m) and the Cova del Brugal (279 m). The deepest are the Grallera Gran del Corralot (166 m), the Graller del Boixeguer (148 m), the Grallera de Corona (119 m), the Grallera d'Alsamora (98 m) and the Cova Colomera (78 m).

Several cavities are located in Sant Esteve de la Sarga, such as the Grallera Gran del Corralot, the Graller del Boixeguer, the Cova Colomera, the Grallera de Corona, the Grallera d'Alsamora and the Cova del Brugal; the Cova Negra de Corçà is in Àger.