The 1988 Expedition was another success in terms of passage discovered and surveyed
- 7km were logged and yet more exciting prospects opened up. Matienzophiles will find last
years area map, published in Caves & Caving 41, a helpful companion to the
The Four Valley System
All the water draining from the Matienzo depression sinks in a bouldery mess in normal
water conditions but, in flood, flows on eastwards for 200m to sink around the Carcavuezo
entrance. Underground the passages and water trend to the north and east and form part of
the Four Valleys System.
This year, partly by pushing back westwards over the stream, the system was extended by
4km to 37.2km and an interesting set of passages entered (The Western Series extension).
The breakthrough came while surveying some bits around the Afternoon Stroll. A small rift
passage was followed back towards the Carcavuezo streamway where water could be heard down
a deep rift which was then traversed and descended to connect with the river. Whilst
surveying out, a bedding was entered and followed back over the streamway which, instead
of pinching out, got bigger and entered a 5 x 5m passage. The survey was hastily abandoned
and the main passage, Gobsmacker, was stomped along for 400m to where a major change in
direction provided a natural place to call a halt. In all, 909m was surveyed, not quite
the magic K! A big push the next day resulted in another 700m; cave of similar dimensions
heading in a westerly direction towards Volvo (Cueva de Bollon, site 98), a postulated old
sink for the valley. Subsequent trips increased both the length of the Western Series to
3km and the amount of speleogenesis bull.
It would now appear that block faulting at the northern end of the valley has allowed
development within each block, mainly strike orientated, with the northerly dip and faults
on 60 degrees allowing the water to head towards the synclinal axis which collects both
the Cueva Riaño (105) and Uzueka (107) streamways.
Further into the cave, around the Sewers of Doom, 750m was surveyed in a maze area
where cave density is 500m in a 50m square - about 2.5km remain to be surveyed. In Cueva
de Riaño, 220m of new passages were surveyed and the cave extensively photographed, the
first time since its discovery in 1973.
Toad In the Hole
This system, at the southwestern side of the depression, was where the second big
discoveries were made. A series of pushes extended the cave 700m to the northwest under
the high ground of Calzadillas; an unexpected extension under an 'unknown' area! In all,
2km of cave were surveyed, mostly on the main route. Some splendid stal formations were
discovered and a number of leads remain to be pushed. The speleogenesis is anyones
guess, but it does seem that water has come from the west and south along faults where
phreatic mazes are found and has headed north down dip in good walking passages until
other faults and their associated phreatic mazes are met. Ongoing passages beyond these
faults have developed in the Orbitolina beds which show characteristic breakdown and
Two streams have been heard at the far end and these may be dye tested next
year. Water may resurge in the Matienzo depression, via Cueva Mostajo (71) and the Rio
Tuerto inlet in Cueva de Agua (59); may drain into the Four Valley System; or may flow to
Fuente Aguanaz (713) at San Antonio.
Fuente de Aguanaz
The entrance to Fuente Aguanaz lies 7km to the northwest of Toad, well outside the
depression. The cave is a water supply and various permissions are needed. The initial
route, behind the true resurgence, passes through a collapse and reaches the stream. The
passage allows swimming 5 abreast with the airspace being 5 x 5m. After 500m a series of
cascades allow a brief rest before another 250m of swimming to a supposed sump. On the
first full trip, the cave was explored and hyperthermically and sportingly surveyed in four
and a half hours - the next trip is likely to use floatation to reach and explore the side
passages and search beyond the sump.
Some other discoveries
Cueva de Mostajo was extended to 6.5km. The passages ended, in the middle of Enaso, at
a pitch which has yet to be explored.
The holes on Muela continue to be explored at a slow rate. Of the hundreds of sites
there must be one which will eventually lead to a horizontal development! One possible
lead is Alpine Chough Pot (site 99) which yielded some passages with undescended pits.
Codisera (39), a very old and large cave perched at the southern end of the depression
yielded a number of 95m shafts which did little but keep a team occupied for a number of
Also on the hill to the south of La Vega, Torca de Azpilicueta (333) devoured a team
for some days. A series of extremely muddy pitches found in 1987 were re-explored but no
further progress was made amongst the slime and calcite belay points. A case for bringing
We had hoped to spend much more time shaft bashing but the tools we invested in were
not up to the job. A pair of Black & Decker hammer drills were used to drill holes for
8mm stud anchors. The equipment was no match for the Cretaceous limestone and the
rechargeable battery packs only managed 3 holes at best. The 1989 expedition will try
Bosch drills and use 6mm studs for aven climbing.
Because of using more than one type of self-drilling anchor a problem which emerged was
the cones from different manufacturers not snugly fitting all drills. By mixing parts the
resultant anchor would stand proud or be less well held - neither condition was
satisfactory and could be dangerous.
Shaft dropping was facilitated by using CBs and we now have an indication of the local
range of the equipment around the rim of the depression. Numbered, plastic, 21p ear tags
for cows were used for the first time as an alternative shaft marker. They may provide an
answer to relocating holes in a landscape where accurate map reading can be difficult.
Molephones, or rather BURPs (Bolton Underground Radio Phones), were used to good
effect. Survey points and underground / surface communication was established in the new
passages of both Toad in the Hole and Carcavuezo.
Computer facilities were used in the bar to convert survey data to x, y and z
co-ordinates and to plot out the line plan and elevations. A hardcopy would normally be
available within a couple of hours of emerging and could encourage (or discourage) further
trips the following day.
The scientific suppliers, Philip Harris, lent data logging equipment worth nearly
£2000. This was used to monitor temperature, rainfall and stream level and to assess its
potential for more extensive use.
Apart from underground and overground exploration to the west of Carcavuezo and within
Volvo to build on the 1988 discoveries, higher levels within the Four Valleys System have
yet to be entered and explored to any great extent. The 2km long Trident Passages in
Uzueka are the longest length above base level and they give some indication that there is
much more to be explored around this altitude. Serious consideration has also to be given
to possible Mostajo, Carcavuezo, Uzueka, Suviejo links which would open up the probability
of a system 100km or more in length. Toad in the Hole is another magnet for exploration
and will require a number of long trips to unravel the secrets at its western end.
One of the major problems with a long term series of expeditions (Matienzo has been
running for nearly 20 years) is that all kinds of people visit the area during the summer
for all sorts of reasons! This can lead to resentment amongst the older hands,
the new-comers need some guided tours of the caves before any serious exploration can be
started. There is obviously much work to do in and around the depression but the
discoveries are only going to proceed at a satisfactory pace if cavers integrate and
commit themselves to the area (or a system) over a number of years. What are NOT needed
are cavers who 'milk the area without putting anything back into the exploration,
survey drawing, and writing program.
Finally, our thanks must go to the authorities and the villagers who allow us access
and offer hospitality during the six week invasion.