Expedition Name (& Club): Tresviso 2021 (Bradford Pothole Club, Cardiff Hill Divers and Sheffield Uni)

Destination country: Spain
Region: Eastern Massif, Picos de Europa, Northern Spain.

Lat: 43.2500 Long: -4.6600 Elevation: 2425 m
MEF funding: none

Leader: Mr. Phil Walker

Brief Expedition objectives:

List a short summary of the main Expedition objectives.

The Picos de Europa is a well known mountain range amoungst Spanish and British cavers. The Western Massif contains the major cave systems of Ario, which, until recently, formed the deepest caves explored by British teams. The Central Massif contains the Cerro del Cuevon system, the deepest in Spain at 1586m.

But it was in the Eastern Massif that British cavers first breached the -1000m mark with Sima-56 (LUSS) in the 1970's. Further, they also began to uncover the delights of Cueva del Nacimiento (or Agua), a resurgence cave of considerable length, dimensions and complexity. If a link could be found between the high alpine potholes (such as Sima 56) and the resurgence this would create a truely classic cave system with a depth potential of over 1600m showcasing all that is great about caving - alpine potholes, impressive shafts, stunning phreatic passageways and a true sense of journey.

Recent discoveries in Cueva del Marniosa, a major feeder to Nacimiento, suggest this may be key

How can the GPF support your Expedition?:

Please explain the aspects of the trip which make it eligible for Ghar Parau funding.

As in 2018, the core team will be bolstered by a large group from SUSS (both old and new) to aid the exploration of the vertical systems located above Nacimiento. SUSS intend to camp high in the Vegas de Andara (Sara depression) on the Andara plateau, requiring additional logistics. The caves will be as rope hungry as any alpine pothole. Thought must be given to the charging of drills & lights, a problem not encountered during the original LUSS camps!

The exploration of Cueva del Nacimiento, over previous years, has required a strong team to camp in the further reaches of the cave (Death Race). This is a remote location and is also a gear hungry place, with poor rock quality and lots of traversing/bolt climbing requiring large amounts of rope, hangers and bolts. Each year consumes bolts, anchors and rope and in 2019 some gear was lost in a flood.

Detailed description of objectives:

Give a more detailed account of the purpose of the trip, including any particular known caves you intend to visit, specific areas where you will explore for new cave, and scientific experiments you will attempt.

Sadly, the dreamed for connection has not proved an easy one to achieve. In fact, since the resurgence of the alpine potholes was located in 1974 it has so far taken 46 years to not achieve it. I do not believe that this year will be any different. However, trip by trip, more of this puzzle has been revealed and with persistence, I feel it is entirely possible.

In an area as complex as this, it makes more sense to discuss the general aims of the project, rather than individual projects, digs, and passages. Here we will discuss the 4 main areas targeted by current exploration:

1. Exploration deep in the far reaches of Nacimiento. This is ancient phreatic passage, and was originally hoped to be heading towards the Andara plateau and potholes. However the further we progress in this region the less likely it appears. Never the less, a strong draught remains present throughout the upper system and whistles away down a diggable constriction - this is a major aim. Access to this location has been considerably improved over the 2018 expedition and a dig at this location has moved from the realms of fantasy and desperation to reality. The second major lead in the region can be found by following an immature streamway down and away from the 'terminal' dig. This immature stream eventually reaches a massive pool in what is thought to be an airbell of the main water table. Progressing along a rift here in 2018 lead to a very large ramp (unclimbed) heading into the distance. This ramp is currently perpendicular to the rest of the cave and heading south west, between Cueva del Marniosa and the Andara range - whether this is key to unlocking this area of the map remains to be seen.

2. Cueva del Marniosa is a largely linear streamway cave, currently 6.2km in length and a main feeder for Agua, recent discoveries have returned it to the limelight and a real possibility that it is a crucial link of the known system - there is less than 400m between the downstream end of Marniosa and the upstream sump in Agua. In 2017 it was connected to a higher entrance, revealing some major vertical development. The connection point between the two systems was a short 3m climb only mildly obscured from the streamway. Thus, a full survey and probing of inlets in Cueva del Marniosa during the last expedition (2019) lead to the discovery of a major new inlet (42 Streamway) Exploration stopped in open passage at a short climb.

3. Pushing the downstream sump of Marniosa - which will almost certainly lead to the upstream sump in Nacimento, (which being very deep and at considerable altitude is no mean feat) it is hoped that prior to this deep connection, the Marniosa feeder stream will intersect a main drain from higher up the mountain. The two divers feel this is an incredibly remote location and are currently pondering how to carry enough gear to drop the pitch that barred progress in 2017. Another option would be to resume exploration of the far upstream sump, another serious undertaking.

4. With the expansion of the expedition by a large contingent of SUSS cavers, exploration of the alpine potholes, will continue. There has been plenty of re-surveying and tidying up of loose ends over the past few years which has resulted in discovery of some stunning pitches and extensions. There is also an ambitious plan to dive the final sump in Sara, by all reports the largest streamway of any of the alpine pots and a high contender for the main drain of the region. The only stumbling block being that it has not been visited in over 40 years.

It is worth noting that given the current Coronavirus effect it is entirely possible that the expedition will be reduced to a skeleton crew. In the case of a diminished team, efforts will be focused on Marniosa, as there is the potential here for the highest yield for lowest man hours.

There will undoubtedly be new leads picked up during the course of the expedition, some hopefully as interesting as those listed above. However, for those new leads which are not immediately seized and acted upon it is important that they are fully logged and described.

Alongside the exploration of new passage, one of the overarching aims of the Tresviso Caves Project is to collate and document, providing an online database for all the caves in the region. To date 79kms of cave across 1095 sites have been described, logged and made publicly available along with relevant surveys, descriptions and possible leads. This is by no means an exhaustive list - but is pretty close! As this work progresses and the data becomes more complex, it has become apparent that the hydrology of the area is far more varied and far less understood than previously though. Apart from some simple (and perhaps inconclusive) dye traces conducted in the 70's and 80's very little has been done to further this knowledge. As more sumps and waterways have been discovered over recent years it is perhaps time to begin more conclusive dye tests.

Previous work in this area:

Give details of any previous work in this area by your own and other teams. Include references to reports and articles published on the area, and the names of any local cavers or academics with whom you have discussed the Expedition.

Under the banner of the Tresviso Caves Project, all available reports to the area have been filed, documented and converted into more up to date technology, with many leads highlighted and key surveys redrawn and updated in Survex and Therion files. In total there are nearly 200 articles and reports on cave exploration in the area. The key reports have been uploaded online (Spanish reports translated into English) and can be found here http://tresvisocaves.info/index.html.

A full bibliography of publications can be found here: http://www.tresvisocaves.info/bibliography/

Going through old reports/data is not only essential for future discovery, but ensures that the rich exploration history of the area is maintained and added too.