Sistema Arriluxe

At the contact of the stream with the series of limestone materials, water has infiltrated, creating a 3x2-metre doline and a 7-metre shaft. Once this step has been descended, progression continues along a small gallery opened along a joint that communicates with the "Sala del Buque" through a narrow passage with an air current; a chamber of 60x35 m has formed. The galleries advance winding and forming continuous curves and meanders. The water has excavated a small canyon that runs along a large gallery in which the river has become entrenched. The gallery opens into an abyss into which the river plunges toward a pit of -135 metres, whose dimensions are 40x10 metres at its head and 20x10 metres at its base. The base of the vertical is a cone of blocks. The morphology of the cavity changes abruptly after a series of small steps between blocks and a meandering gallery; the air is lost and the gallery ends by narrowing and sumping, reaching a depth of -325 metres with a total of 2,265 metres surveyed.

This gallery shows great activity, as it rapidly absorbs rainwater. It can be seen how the flow of Arriluxerreka increases after receiving successive small seepages until reaching the Galería de los Fantasmas, where it receives the first important input at a place of large block collapse. This is the AR-16 stream, which collects the waters of the small closed basin of Taplaburu and joins the Arriluxe system through a N-S fissure. It is not possible to access from the outside through this sink, since it is an impenetrable joint; however, the oral and visual communication is evident. About 800 metres of sinuous meanders are estimated to have been traversed; after 1 km, another important input is received: the Meandro Argal. It joins the Arriluxe system on its left side and has a development of 600 metres of tortuous meanders with widths of less than one metre and continuous pools and forced passages. The highest point of the meander is only 15 metres of elevation difference from the AR-16 bis sink. At the base of the vertical the rain is constant.

Once the 7-metre step has been descended, progression continues along a small gallery opened along a joint that communicates with the "Sala del Buque" through a narrow passage with an air current. One continues through a succession of wide galleries connected by narrow passages. Returning to the main gallery, the most interesting part of the cavity is reached. In no more than a hundred metres the river plunges into the impressive Pozo Iluntxeta. At the base of the vertical a great air current is noticeable.