Erankio Cueva

The Erankio sector has two cave-mines, whose working was abandoned 50 years ago. Erankio Mina-cueva 1 has 185 metres of passage development and -20 metres of vertical extent, and has two entrances. The UTM coordinates of the upper entrance are: N 4,773,700; E 586,640; alt.: 440 m.a.s.l. Reference Map: Berastegi 89-II, scale 1/25,000, IGN. 20 metres to the N-W of this point is a second mine (Erankio Mina-cueva 2), with 40 metres of development and -4 metres of vertical extent. The greatest interest is presented by cave-mine 1, since apart from its greater development it has an underground river and natural passages. Mine 2 is almost entirely artificial, with less development of the dark zone and only slight enlargements or modifications due to seepage and collapses. Cave-mine 2 has a much simpler layout. It consists of a 26-metre-long passage, with a small parallel excavation, and an ascending side chamber that communicates with the outside through a small second entrance. The total development is 40 metres. The main passage ends in a collapse.

Cave-mine 2 has few and small speleothems of goethite, bronze in colour. Next to the upper entrance small efflorescences of epsomite are observed, forming crusts and small tufts.

Cave-mine 1 has an underground river. In cave-mine 2, shortly before the collapse that closes the main passage, small seepages have formed a shallow pool of water.

Interesting and complete study carried out by Carlos Galán of Sociedad de Ciencias Aranzadi, dealing with topics such as Biospeleology, Cave Fauna, Geology, Mineralogy and Speleothems. The terrain is carbonaceous slate with ferruginous materials, of Paleozoic age, associated with the Cinco Villas Massif, but it also has inclusions of other minerals. The Paleozoic slates are close to a contact with Permo-Triassic argillites and Keuper ophites. In the entrance zone of both entrances there are disintegrated blocks with abundant quartz grains and marcasite twins.