Cantabria in Northern Spain is without doubt one of the finest caving regions in Europe. Matienzo is of course well known, but equally famous are the caves of the nearby Ason gorge. Here there are some world-class through trips: Cueto-Coventosa, Tibia-Fresca, and Tonio-Cañuela. A couple of years ago Tom Baker, Mike Bottomley, Carmen Smith and I did the Cueto-Coventosa trip [see 'A tale of three pots', CPC Record 88, 17-19 (Oct 2007)]. At Easter this year (2009) I managed to do the Tonio-Cañuela trip with Becka Lawson from the RRCPC.
Overview
The trip falls naturally into two parts. The first part is a descent of Sima Tonio. This is almost completely vertical and consists of about 18 pitches interspersed with a few climbs. There are two pitches where one has to swing onto a traverse line. However the traverse lines are easy to spot and navigate. The final 20m pitch drops spectacularly though the roof of the enormous Salle Olivier Gillaume, at -280m. The second part of the trip consists of wandering through the vast galleries of Cueva Cañuela, compass in hand. The development in Canuela is on such a grand scale that there is actually quite a lot of up and down, in fact a lot more down than up since the Canuela entrance is at -400m with respect to the Sima Tonio entrance.
The through trip is dry, although in very wet conditions a couple of the pitches can apparently acquire a bit of spray.
BE WARNED there is a constricted 13m pitch about half way down Sima Tonio. To Becka and myself it seemed similar in character to the top half of the Link Pot entrance pitch, or the narrow section at the top of the first pitch in Bar Pot. In Sima Tonio though the narrow section continues for almost the full 13m and it is necessary to 'follow your feet' down, perhaps with a descender on a cow's tail. If you struggle with Link or Bar Pot, then maybe Sima Tonio is not for you!
Location
Unlike the other through trips which are located in the Ason gorge, the Tonio-Cañuela through trip is more accurately described as lying in the Bustablado valley to the west of the small town of Arredondo, at the start of the Ason gorge. The bottom entrance – Cueva Cañuela – can be reached by a footpath from hamlet of Bustablado itself. The top entrance – Sima Tonio – can be reached by a path from the hamlet of Socueva which lies on a terrace at the start of the Ason gorge (it seems possible that Sima Tonio could also be reached directly from Bustablado but this is an option we did not have time to explore).
If two cars are available, one can conveniently be left in Bustablado before setting off from Socueva. In our case we only had one car but found it quite easy, but rather long, to walk back to Socueva from Cañuela.
Socueva to Sima Tonio
Cars can be parked opposite the small church in Socueva. The path can be seen climbing in zig-zags up the amphipheatre above. To reach the path, follow the ascending lane through Socueva and swing right in front of a farmhouse, then left again once past the buildings. Pass a path on the right, indicated as not being the right way by an X. The lane climbs steadily and swings right again, reducing in size until it becomes a donkey track where the onward (and upward) route is now obvious. Well-graded zig-zags take you to the top of the amphitheatre where the track levels out and eventually passes a small cliff on the left. At this point one is looking west over a small dry green valley, descending from south to north towards Bustablado. On the skyline across the valley are a scattering of barns. Sima Tonio is located in the field below the farthest of these barns. To reach the entrance follow the track as it contours around the dry valley. The track climbs slightly and starts to swing left (south) as it enters an area that is best described as moorland, continuing eventually to Sima Cueto. At the point where the track starts to swing left, leave the track, and head right (north-west) towards the aforementioned barns. An area of deep grykes can be passed on the right, keeping some large dolines to the left. The entrance to Sima Tonio is in a steep field below (north of) the farthest (westernmost) barn. The entrance can be seen from the path. Climb the wall and descend the field to the entrance. A water trough lies near the bottom of the slope in the western half of the field. The entrance is a modest narrowing rectangle, becoming more constricted after a ledge about 2m down. A pull-through anchor is just below the lip. You can find photographs of the entrance on the internet.
From the point where you first view the dry valley it should take about 15 mins to reach Sima Tonio. Allow 1 – 1½ hours from Socueva. It took us about 2 hours but without a GPS we couldn't find the entrance until we got some advice from a farmer who happened to be around.
Descent of Sima Tonio
The first pitch (15m) narrows just below the entrance but opens out again towards the bottom. The base of this pitch is notorious for harbouring large spiders! The next two pitches (18m, 10m) follow one after the other. The fourth pitch is a big one (48m), but is descended only for about 36m to an obvious traverse wire which takes you onto a sloping gravel ledge. From here the traverse wire is followed up an easy 5m climb to the top of a 10m pitch. At the base of this pitch one has to climb up slightly and squeeze into a narrow rift to the tight 13m pitch mentioned above. This opens out only at the bottom. What looks to be an easy descending tube is next, but it is best treated as a 8m pitch since it ends over a hole. The hole is not descended, instead follow a fixed rope up a 4m climb and down and across another hole (again do not descend) to reach two short pitches of 6m and 4m respectively. These bring you to a small antechamber / ledge looking out over the second of the big pitches (55m). Again this is descended only for about 36m to an obvious traverse wire which takes you to a 'bridge' where the shaft effectively splits in two. From here a 5m pitch lands on a spacious ledge. The remaining pitches are extremely straightforward. A short 6m pitch leads to a 20m + 13m pitch probably easiest treated as one drop (we did not have a problem pulling the rope down). Next an 18m pitch lands onto blocks. Between the blocks in one corner is a 22m pitch that brings you to the base of this pitch series. From here a short narrow meander leads to a small climb and the final 20m pitch into the Salle Olivier Gillaume. The draft blowing through this short length of passage is ridiculously powerful! The take-off for the final pitch is a bit awkward, but shouldn't present any real difficulties. The descent of Tonio took us about 3½ hours.
At the base of the pitch it is worth slogging up the slope to the top of the underground hill which is in the middle of the largest part of the Salle Olivier Gillaume – maybe 120m in diameter at this point.
The route through Cueva Cañuela
From the base of the pitch follow a faint trail down the steeply descending boulder slope. Where this starts to level out make for an initially invisible exit in the wall to the north. The temptation is to head towards the obvious continuation of the chamber which is east. A compass is very useful at this point! The exit is not really apparent until you are close up against the wall, where it then becomes obvious that there is a steeply descending route (including a rope climb down). From here follow the obvious and very large passage north, passing a place where a stream can be heard in a canyon in the floor. After about 400m (10-15 mins) one arrives at a large balcony to the right overlooking the Sala del Vivac. Trend left here up an easy rope climb past a large hole on the right. At the top of the rope climb keep heading north. The passage reduces in size and apparently comes to an end in a boulder ruckle. This is actually hiding an easy climb up past the boulders back into large passage again. Continue straight (north) past a junction with a passage heading right and back towards the Sala del Vivac. Soon one reaches a short scramble down to effectively a cross-roads. The easiest route (marked by reflectors) is to bear right and up an easy 8m climb into a magnificent flat-floored rift passage (Galeria del Bulevar) leading north-east. This swings north again through some large chambers, to arrive at the final pitch (15m). (This pitch can apparently be bypassed by a tube off to one side.) From the base of the pitch, head east and soon daylight can be seen in the entrance passage. The final obstacle is a straightforward traverse with fixed rope which takes you across a large sloping ledge high on the right avoiding the Canuela entrance pitch. The remaining passage to the entrance is a huge phreatic tunnel, initially of monstrous proportions but reducing in size as one approaches the relatively more modest entrance portal.
From the base of the Tonio pitches to the Cañuela entrance took us about 1½ hours. There is no point rushing as there is plenty to see, including the famous scimitars – sword-like stalactites whose bizarre growth is no doubt governed by the strength of the prevailing draft.
Cueva Cañuela back to Socueva
The path from the entrance descends steeply down then veers left (west) through a bit of a wood before descending to cross the river and reach the Bustablado road. To get back to Socueva, one may follow the road, or alternatively we left the path at a clearing in the woods cut for a line of pylons, heading east. This brings you into a network of fields where one keeps heading east, through several gates and past various barns, to reach the Socueva road where it starts ascending the hill. We dumped rope and SRT gear when we reached the road to avoid carrying it all up the hill (but beware that the Socueva road is not that quiet – it is quite a popular viewpoint for looking over Arredondo). The walk back took us 1½ hours. Hence the total round trip car-back-to-car was about 8½ hours.
Gear
We took two 60m lengths of 9mm rope plus 60m of 3mm emergency pull-down cord, plus a few maillons and a couple of slings. In hindsight, rope lengths of 40m + 60m would be fine. It is useful to have the long rope as it means that all but two of the pitches can be done on one rope (or all but three pitches if the 20m + 13m pitches are done as one). All the pull-thru anchors are in a pretty good shape.
Access
[Oct 2018] A permit used to be required even for tourist caving in Cantabria but as far as I know this is no longer the case. The following is therefore just kept as historical reference. A permit was relatively easy to obtain and there was not really an excuse for not trying to get hold of one: it was in no-one's interest to jeopardise the good relations that the Matienzo expedition has built up with the authorities. Spanish and English versions of the permit application form can currently be downloaded from www.espeleocantabria.net. Most of the required information is obvious, eg the names of the caves : Sima Tonio, Cueva Cañuela, etc ('City Hall' means municipal region – enter 'Arredondo' for the caves of the Ason). For this 2009 trip the completed form was scanned and converted to PDF, and emailed to the address indicated. It was returned by email, having been officially counter-stamped, after about 10 days.
GPS
The Ramales Speleo Group website gives the location of the Cañuela entrance, and three (!) possible locations for the Tonio entrance, though one – labelled Boletín Cántabro – is clearly not even on the right hill. Based on our knowledge of the location of the Tonio entrance relative to the surface features, we have come up with our own coordinates using Google Maps. In summary:
UTM (WGS84) 30T 449120 4790390 Sima Tonio
UTM (WGS84) 30T 449660 4791720 Cueva Cañuela
Our Tonio coordinates are reasonably close to the consensus Ramales Speleo Group coordinates.
More information
The caves of the Ason have predominantly been explored by French expeditions, and a lot of information is in French caving magazines. A French description of the Tonio-Cañuela traverse can be found in Spelunca No 34, pages 25-30 (1989). More recent descriptions can be found in Spanish caving guides. A lot of information (in Spanish) including a reasonable survey can be found on the Ramales Speleo Group website – search for Sima Tonio.
Adapted from CPC Record 97, 23-25 (Jan 2010).
Copyright © (2010) Patrick B Warren and Craven Pothole Club Ltd.