If the shivers don’t run down your spine when you hear the magic
"BU56", then you are 1) not a caver or 2) a speleological barbarian.
The BU56, situated in the Spanish
has been discovered nearly 24 years ago but it still remains a mythical
cave. Once it was the deepest of the planet (-1408 m) on even now it
is still a cave of which we all speak with a lot of respect.
And why is the BU56 so special?
Caves of over 1000 meters deep are, these days, not exceptional anymore:
there are over 50 of them.
But in most cases, these are vertical caves in which you go down
on a rope; all the way to the bottom.
Underground progression in such a cave, becomes a technical
thing, and climbing out of such a cave is quite monotonous; hanging
on a rope for 15 hours or more is … just boring.
But in some caves, to reach the magical depth of one thousand meters,
you must progress for many kilometres and deal with many obstacles such
as waterfalls, pitches, big piles of boulders, narrow and difficult
winding meanders. Roaring underground rivers, beautiful flowstone formations,
giant underground rooms are the icing on the cake in such caves.
Often they have multiple entrances which offer extra possibilities
such as through-trips.
These are the caves we all love.
Gouffre Berger (-1271 m), Réseau Jean-Bernard (-1602 m), Systema Badalona
(-1050 m), Réseau de la Pierre-St-Martin (-1342 m) are some of those
fantastic and “complete” caves, that are on every cavers’ wish-list.
And then… there is the BU56.
BU56 is one of those “great” caves. But, it is yet different from the
There is only one entrance known.
You go in there, and you’ll have to go out there.
No cheating is possible; no through-trips. And the bottom of the cave, or better the terminal sump at a
depth of -1325m, is about 8 kilometres away from that entrance… so you
are heading for a 16 km trip.
The entrance… means 400 m of pitches, with some long and very narrow
meanders in which you will loose hours and a lot of sweat.
The entrance…is situated at an altitude of 1980m and you need a very
long walk (about 3 ½ hours) and a +900m climb to get there.
Once you arrive at the bottom of the pitches, you find an underground
river of exceptional dimensions. The more you go down in the cave, the
bigger it gets until becoming a raging river in which progression gets
nearly impossible. In Canyon
Belagua at a depth of -1200m,
you have to traverse 20 meter high above the thundering river, over
a distance of nearly 200 m, on a narrow ledge.
Around -1250m the river, this river (1m³/sec) crashes down in
a series of big waterfalls. The discoverers of the cave wrote about it: “Emotion guaranteed".
The progression in the cave is no Sunday walk. The river alternates
with big and chaotic galleries, in which you climb up and go down huge
piles of boulders all of the time.
In Salle Roncal at -750 m, the pile of boulders is no less than
80 m high (that’s as high as a 30-story building!),
and once you are up, you have to go down the other side … for
an incredible 110m! When
taking all these ups and downs into account, the depth difference you
make in the cave is almost 1600 m!
Most of the classic “big” -1000m caves, such as Gouffre Berger, can
be done in one (long) trip by a well trained team in less than 20 hours.
In case of the BU56, this is not possible.
If you want to make it in one trip, then you are heading for
a 35 hour trip or more!
That’s why most teams split the trip up in parts, making it a
two or three day trip.
But, sleeping in
a cave means taking a lot of extra stuff with you: food, sleeping bags,
tents and so on.
In short: a trip to the bottom of the BU56 is a
Finally: the cave is located in the world-famous Pierre-St-Martin area,
and so it is closely related to the history of the PSM… a library full
of exciting and breathtaking stories.
It is evident that a caver who loves the PSM, cannot ignore the
in caving club Avalon, there are quite some people who lost their heart
in the PSM .
The entrance is discovered by Jean-François Pernette and I. Ortilles in 1979. That day Pernette reaches a depth of
-92m after passing the extremely narrow meander N. In the following two years, expeditions follow in which many
famous French cavers participate; such as J-F Pernette, Richard Maire,
Serge Fulcrand, Gerard Bouteiller, Georges Marbach.
They push the cave to a depth of -1338 m; making it the deepest
of the world. Fred
Vergier dives the terminal sump of the cave and two following sumps.
In 1986 and 1987 a Bulgarian expedition dives three more sumps,
stopping before sump nr 7. This
fantastic achievement brings the depth of the cave to -1408 m.
entrance pitches go from 0 to -387m. There is a serious obstacle at
-80m; the "Méandre N"
which is 60 m long and very narrow.
At the base of the pitches (-387m) begins "Méandre Oprimido"
which is over 300 m long and is so difficult that you need +/-
two hours to get through.
Once through the meander, you arrive near -452 m in a gallery
with boulders. This becomes
bigger and bigger and soon you find the river that runs on the “primary
socle” of hard schist rock.
The progression is not easy, many sumps have to be avoided by
lateral or superior passages, often narrow and time-consuming.
For some waterfalls you need to use a rope and so you finally arrive
in the first big room of the cave: Salle Arcaute at -575 m. There you
go down a 19 metre pitch and continue to follow the river that thunders
down steep toboggans.
Near -700 m the gradient becomes less steep; but the flow rate
of the river (more than) doubles because of a big inlet, coming from
Sima de la Hoya
Portillo. Then the
river flows softly in a wide and high canyon. A 30 m long lake can be
avoided by taking a low and muddy shunt at the left.
Then it disappears between the boulders, which we climb up to
arrive in the biggest room of the cave: Salle Roncal.
This room is over 500 m long and about 50 m wide. A giant and
very steep pile of boulders, over 80 m high on the East side,
and 110 m on the West side, is a tough obstacle to take!
Near --780 m, Salle Roncal narrows, the floor becomes flat: this
is the usual place to camp. Further on, we arrive at a very decorated balcony dominating
the thundering river. We
go down a 20 m pitch and enter Canyon Roncal.
In this very narrow canyon, the progression is very spectacular
and wet, and if water levels are high, even quite difficult!
250 m of most exciting “white water” caving, a 10 metre pitch besides
a powerful waterfall brings you to Salle Paquiza. This is the most decorated
room of the cave with hundreds of three metre long straws.
This room, continues into other big rooms and galleries such
as Salle Ukerdi, enormous and very steep!
Near -1000 m however, the passage suddenly lowers and becomes
very narrow. The
only way on is a real squeeze, situated just at the waterlevel.
This passage floods quickly, up to 10 metres of height, when
it rains outside! This
is really the point of no return.
Then, another series of big rooms and galleries... Belagua Gallery is
beautifully decorated, with big “stairways” of flowstone and gour pools
where you walk on. A final
big inlet, Rio Linza, again increases the flow rate of the river, which
is meanwhile swollen to an average of 1 cubic metre per second!
Linza (80x80m) and Salle Maz.
(120x50m) are quickly traversed. Then the river crashes down into Canyon
Belagua. It is impossible
to progress in this canyon because of the raging river.
One must traverse on a ledge, 20 metres above the river, for
the incredible distance of +/- 200 metres.
Secured by handlines, tied to stalagmites, high above the roaring
river, this is one the most frightening and impressive passage that
can be encountered in a cave at such a depth (-1200 m !)
Finally, a 17 m pitch puts you back into the river again.
Another wild water part follows, untill finally the water goes
down, with unbelievable power, two consecutive waterfalls, 18 and 16
metres high! They can be
avoided by a fossil upper level ( Galerie Lapazarra) leading to the
terminal sump of the cave at the depth of -1325 m. 5 other sumps follow, leading to a 7th, non-dived
sump at -1408 m.
For us, normal cavers, the only way on is….back to the entrance… 8 kilometres
away and 1325 m higher!
The SC Avalon “BU56 project”
After having made several serious caving trips in big caves situated
in Pierre-St-Martin area (late 80’s and beginning of the 90’s), such
as Pierre-St-Martin, Couey Lotge, and Lonné Peyret); the BU56 seemed
like the next logical step to take for our club.
Indeed, about 10 years ago Annette and I played with the idea to bottom
that BU56. But the project
never got off the ground and ended up in the freezer…
In 1997 we “rediscovered” the PSM-mountains once again, with a bottom
trip in the Anialarra System (-648m). And this time we stayed, year
after year we continued exploring the Anialarra cave and its giant and
In the meantime, we had become “old”, mid forty, but much to our surprise
those PSM-caves were still a piece of cake for us.
We realized that we still had the potential to do the BU56… but
it was also clear that if we waited another 10 years, it would be too
late! So, in 2002 I again
suggested to my fellow clubmembers that we should go and bottom that
BU56 cave once! And
yes, some others immediately agreed: Mark Michiels, Rudi Bollaert
and Mario Lebbe would join us in this ambitious project..
We thought it would be better to have an even number of participants,
and if possible somebody that had already done the cave. We ended up with Koen Mandonx of Spekul caving club, who we knew
very well because he had been an Avalon-member for several years. Koen
had once done the cave(20 years ago!), but only to -1000 m; and he was
very keen on taking a revenge on the cave and do it all the way to the
bottom this time!
The “administrative” side of our project was soon settled, thanks to
our ARSIP-friends that quickly arranged the permissions form the Spanish
authorities (the cave is situated in a nature reserve).
We also fixed the date: we choose mid-September , because a)
in August we had our annual Anialarra-expedition and b) the BU56 is
very flood-prone, and in general September is the month with the least
We decided on our strategy. It would be a three-day trip (after two days of gear-carrying and rigging)
Day 1: to -800 (camp in Salle Roncal)
Day 2: from -800 to the bottom (the sump is at -1325m) and back again
to Salle Roncal
Day 3: from Salle Roncal to the exit.
Then another two or three day for de-rigging and carry all gear down
So, one week should be enough… but there was no possibility for resting,
or waiting in cave the weather was bad.
It looked as it was going to be a very tough week
The underground camp
Of course, this plan means a lot of gear. Underground camping means:
sleeping-bags, a lot of food, cooking gear, a tent etc…
After a lot of thinking we decided to use two very compact and
light home-made tents, made by Annette. Each could shelter 3 persons
and had only a weight of 1,5 kilograms. We tested one of these tents in the Anialarra-System, a
similar cave as the BU56 and we had a comfortable night. Condensation
hardly occurred, and with a candle we could easily raise the temperature
in the tent from 4 to 8 degrees Celsius.
Anyway, needless to say that each participant will be carrying a very
big and heavy tacklebag when going down the BU56…
At the end of our Anialarra-expedition,
in August 2003, we already went to the entrance.
We were guided by two legends of the PSM-area: Michel Douat and
Richard Maire. For
several hours we walked through a magnificent landscape, to arrive finally
at the entrance, on which the number “BU56”, painted by J-F Pernette
in 1979, is still visible. Of course, that day we already carried
a lot of gear with us, such as 450 metres of rope, two tents and so
Within one month or so, you will be able to read in our Hot News, if
we succeeded in our plan to bottom the BU56 in only one week.
Paul De Bie