Briefly, this system drains the enclosed depression of Matienzo at its northern end via Cueva Carcavueso (length 250m). The water flows into a boulder choked sump and after 800m joins with the water flowing from the areas longest cave, Cueva Uzueka (13km). This cave starts in the Riaño valley as a maze of smallish phreatic passages but soon breaks into some impressive sandy floored tunnels in which double decker buses could pass each other. After 600m the 'serious' cave starts with wet crawling and a kilometre of back-breaking progress in the Gorilla Walk. The route to the known end of Uzueka is then magnificently continental - 500m of stomping passage; 220m of crawling; a kilometre of wading, together with climbing and walking, passing the 101.6m high and 30m diameter Astradome Aven (height found by helium balloon); a phreatic grovel up into the huge boulder-strewn passage of Armageddon, where the buses left in the near series would be dwarfed; a 5m pitch down out of the pile; a tight shaley constriction into Giant's Causeway, where leaping from slab to slab along the down-dip passage is the easiest method of progress; Duckham's Sump and its hole in the roof get-out; and finally 500m of Rocky Horror where progress had stopped in '77 at a seemingly blank wall with the stream rushing away eastwards to its connection with the Carcavueso water.
About 400m east of this point in Uzueka, the combined waters emerge out of the upstream sump in the 3rd valleys main cave - Cueva Llueva (3km). Above the phreatic tube of the river course is a large boulder-floored tunnel which eventually descends to the water at a chamber where access was first gained to the cave from the surface. There is only one passage downstream of this chamber and this requires swimming (or boating) in a gloomy mud-walled passage for a couple of hundred metres. A climb up through a boulder choke and the water is met again in a superb 15-abreast gravel floored stream passage. Idyllic prgress is stopped after 200m at a 25m deep sump pool. The water then flows through uncharted passage to rise at Los Boyonnes Cave in the 4th valley - Secadura.
A short cave can be entered at the rising but the 38 survey stations in its 100m length and moving boulder choke that the cave basically is, makes any progress here very uncertain.
In 1979, efforts were made to extend Uzueka beyond Rocky Horror and some progress was made. The team came out on low lights and according to the log book left behind 'a choke with a draught vanishing straight up; an old phreatic tube with a howling draught' and 'a choke that looked possible and could lead into the continuation of the main passage.
Two teams at the end of the expedition went into Llueva to try to continue the push upstream - Phil Papard dived in the sump finding the way on still open. The second group looked around in a large chamber 200m from the sump. Barry Davies' account of the trip - 'Patrick had free climbed to a ledge in the fault about 60ft above stream level but his light had gone out. I climbed up to give him some light and when he got down I traversed to the right of the ledge to an immense jammed block. Up this some heavily stalled blocks led up easily to aqnother jammed Herbert which looked decidedly unstable; 20ft above this was a large inviting black hole with the draught screaming up into it'. Bolting will be required this year in order to reach this passage which is heading towards Uzueka.
On reaching Spain this year, we were presented with 1:5000 maps of the area which ad been previously obtainable and after a few days of rescaling cave surveys it became clear that Cueva Celláron could be a key to the downstream continuation of Llueva. The bottom end of the 93m deep pot (found in 1978) is only about 40m above the possible stream level. This cave and area will receive close attention in 1980. The new maps also made it reasonably easy to check the accuracy of our surveys and by using them and our set of speleophones, 2 points were checked in Uzueka. A memorable 2 hours were spent on a Matienzo hillside in pouring rain thrashing through gorse bushes - but the ten minute conversation with the team 130m below and 7km into the cave made it all worthwhile. The survey was found to be accurate to within about 30m in 7000!
Two attempts were made to make Uzueka a shorter trip: Fuente las Varas Pot on the hill above Uzueka was pushed to an impossible draughting hole; and inside Uzueka, a 500m long bypass to Armageddon was found - although it is doubtful whether this makes the cave any easier because of its 'phreatic nature with knee-deep mud' and the fact that all exposed surfaces are covered with an abundance of mud, indicating that it spends most of its time completely submerged.
Water entering the Matienzo depression does so via Cubio de la Reñada (4km). The source of the water is not known but many parties have spent hours on the hills above the cave investigating the numerous depressions and holes that must enter Reñada. Three new pots were discovered this year - Torca del Omoplato (dug into, but ending too tight at 20m depth); Torca del Avellano (30m deep, ending at a wet, strongly draughting low crawl with 4cm air space); and Salamander Pot (dug through to a walking-sized passage to an immediate boulder choke).
The prospects for our 11th visit are as exciting as in any previous expedition - the joining of Uzueka and Llueva; the search for the water beyond Llueva and that behind Reñada. A new phase of exploration will also be starting with the establishment of a second camp on the hills to the south-east of Matienzo, where the rock dips towards Cueva Cobrantes, a 30 x 30m fossil resurgence at the head of San Miguel valley.
Acknowledgements: We were generously supported with grants from the
Sports Coucil and the Ghar Parau Foundation. We would also like to thank
Bob Machin for the loan of a prototype set of speleophones. Finally, to the
caving authorities in Spain and the overwhelming hospitality and friendship
shown to us by the people of Matienzo and surrounding districts.
References: MUSS Journals 7, 8 and 9
Matienzo Journals 1974 and 75.
Further details will appear in MUSS Journal 10 to be published shortly.
amended from an original article by Juan Corrin in Caves & Caving 8 (May 1980).