A MOUNTAIN LAKE Geo AMONG THE MOST route10 ANCIENT ROCKS IN LAKE PINARRA AND PUERTO VIEJO c Sobrarbe Geopark

Texts: Luis Carcavilla Urquí (IGME) and Ánchel Belmonte Ribas (Scientific Coordinator Sobrarbe Geopark). Figures and illustrations: Albert Martínez Rius Photographs: Luis Carcavilla Urquí Translation into French and English: Trades Servicios, S.L. Design and layout: Pirinei, S.C.

CBC project -Monte Perdido, World Heritage (PMPPM) GEO- of the 2007-2013 POCTEFA Program. ROUTE NETWORK OBRARBE GEOPARK GEO-ROUTE S NETWORK The Sobrarbe Geopark is located in the north of the province of and coincides with the district of the same name. This area is noted for its many cultural and natural values, most notably its spectacular geology. Indeed, the Geo-Route network of the Sobrarbe Geopark was created to learn about and understand its geological heritage in greater depth. This is a network of 30 self-guided routes that allow visitors to access the most outstanding geological sites in the district and understand their origin, meaning and significance. All Geo-Route have been designed so that they can be covered on foot and are clearly signposted; in most cases they are based on official short-route (PR) or long-route (GR)except PN 1, PN 4, PN 5, PN 9, PN 10 and PN 11 that combine a stretch of road and vehicle with trails paths. There is a brochure on each route in order to facilitate the interpretation of each stop on the way. In addition, 11 of these geological routes are located in the Ordesa and Monte Perdido National Park, including the territory of the Geopark, and 3 of the Geo-routes are of a cross-border nature, allowing visitors to enjoy the geological heritage of the Pyrenees-Monte Perdido, declared a World Heritage Site by UNESCO.

In addition to the Geo-Route network, there are mountain bike (MTB) routes in the Geopark, some of which feature small information panels along the way and there is also a brochure that Taken together, these routes will enable visitors to enjoy the most beautiful parts of the Sobrarbe district and also obtain further information on its long geological history dating back over 500 million years. THE SOBRARBE GEOPARK In 2006 the Sobrarbe District was declared a Geopark and became part of the European Geopark Network, sponsored by UNESCO. A Geopark is a district with unique geological features for which a sustainable development strategy has been developed. Consequently, the key objective is to preserve its natural and cultural heritage and promote development through the appropriate management of the geological environment. There are currently 60 Geoparks in Europe and 100 in the word. The Sobrarbe Geopark features an exceptional geological environment, with over 100 places of geological interest that have been inventoried; many of which can be visited on the Geo-Route network. More info: www. geoparquepirineos.com

1 AP OF THE SOBRARBE GEOPARK M GEO-ROUTE NETWORK

Gèdre

Gavarnie

Bujaruelo Pineta Monte Viadós Perdido Río Cinca A-138 Bielsa PARQUE Víu Torla P.N. DE ORDESA Y NATURAL MONTE PERDIDO DE POSETS- Escuaín MALADETA Gistaín Ara Saravillo Nerín Plan Río Puértolas Lafortunada Fiscal Laspuña

N-260 Ascaso

Escalona

Labuerda San San Juan de Toledo Boltaña Victorián Foradada Aínsa N-260 Campo

Las Bellostas Embalse de Tierrantona Mediano PARQUE NATURAL Arcusa DE LA SIERRA Y Palo LOS CAÑONES DE Paúles Samitier GUARA de Sarsa

Río Esera

Bárcabo Lecina Embalse de

A-138

GEO 1 Geo-Route PN 1 Geo-Route in National Park of Ordesa and Monte Perdido

The various Sobrarbe geo-routes vary in length, difficulty, theme and duration. Consequently, almost everyone will be able to find a route that suites them.

2 Nº GEO-ROUTE TRAVEL DIFFICULTY DURATION THEME*

1 Geopark Interpretation Centre Geopark area - 1 hour All Aínsa: a town between two rivers. 2 Urban geology Aínsa Low Short R T F Samitier castle and 3 Low Medium TF Geology: A bird's eye view hermitages 4 Inside the canyon Congosto de Entremón Medium Short TR Vero River canyon 5 Breath-taking landscapes of water Low Medium RF and rock viewpoints 6 Sobrarbe at your feet Ascaso- Nabaín Medium Medium TF

7 Crossing the Jánovas Gully Near Jánovas Medium Short TR

8 Iron Age Elements Viu-Fragén-Broto Low Short GR Medium- 9 Long Whims of water for lonely mountaineers Ordiso Valley High GKR A lake among the oldest rocks in 10 Sobrarbe Lake Pinara and Puerto Viejo Low Medium GR

11 The hidden lake Lake Bernatuara Medium Long RGT

12 A road with tradition Bujaruelo Pass Medium Medium RGT Fiscal-Gradatiello- High 13 A privileged vantagepoint Peña Canciás Long RT

14 Secrets of the Guara Mountains Las Bellostas-Sta. Marina Low Long FRT Low 15 Geology for the Saint Espelunga de San Victorián Short RT

16 A passage between two worlds Collado del Santo Medium Long RFT Low 17 Water inside the Earth Badaín-Chorro de Fornos Medium KR Basa de la Mora Low 18 The Jewel of Cotiella (Ibón de Plan) Short GR

19 Treasures of the Posets-Maladeta Viadós-Ibones de Millars Medium Long GR Nature Park GEO-ROUTE IN NATIONAL PARK OF ORDESA AND Nº MONTE PERDIDO TRAVEL DIFFICULTY DURATION THEME*

Torla-Cola de Caballo- Low- RGF PN1 Ordesa Valley Góriz Shelter Medium** Medium Góriz Shelter-Mount Perdido PN2 Mount Perdido High Long TRKGF

PN3 The Roland Gap Góriz Shelter - Roland Gap High Long TRKGF

PN4 Cutas Viewpoints Torla-Viewpoints-Nerín Low** Medium KRGFT Low** PN5 La Larri Bielsa-La Larri Valley Medium RGT High PN6 Balcon de Pineta Pineta-Balcón de Pineta Long FTG Medium PN7 Añisclo Canyon (lower part) San Urbez-Fuen Blanca Long RGT

PN8 Añisclo Canyon (upper part) Fuen Blanca-Añisclo Pass High Long RGTF Escalona-Puyarruego PN9 Circuit Añisclo Canyon Low** Medium RTK Tella, Revilla-Escuaín PN10 Escuaín Valley Low** Medium TK Broto -Bujaruelo- PN11 Otal Valley Otal Valley Low** Medium GTK * Theme: T- Tectonics; F- Fossils;K- Karst; R- Rocks; E- Stratigraphy; G- Glaciarism ** Combining vehicle and hiking

3 GEOLOGICAL HISTORY OF THE SOBRARBE GEOPARK The geological history of the Sobrarbe Geopark goes back over 500 million years. Many geological events that have affected the current landscape and relief took place over that vast period of time. The geological history of Sobrarbe can be divided into 6 different episodes, each of which includes significant moments that led to today's geological landscape.

THE REMOTEST PAST 1 (between 500 and 250 million years ago) Over a long period of the Palaeozoic, the land now occupied by Sobrarbe was a seabed where silt, mud, clay and sand accumulated. Today these sediments have become the shale, sandstone, limestone and quartzite that form the northern mountains and valleys of the District. These rocks were intensely altered by the Variscan orogeny: an episode of intense tectonic activity that affected much of Europe and resulted in a huge mountain range. Numerous folds and faults attest to this past together with granite that was also formed in that era.

Folds in Palaeozoic rocks

TROPICAL MARINE SEDIMENTATION 2 (between 250 and 50 million years ago) The giant mountain range formed in the previous stage was heavily eroded and almost disappeared. Once erosion has almost swept away the mountain range, the resulting flat land was covered by a shallow tropical sea. Coral reefs appeared and the calcareous mud we see today in the shape of limestone, dolomite and marl, containing abundant marine fossils, accumulated. The sea fluctuated several times and there were many time when its depth increased and decreased; however, it practically covered the area throughout this episode. Fossils of marine organisms in the Cretaceous limestone

THE FORMATION OF THE PYRENEES 3 (between 50 and 40 million years ago) The marine sedimentation process continued during this episode, but under very different conditions to previous episodes. The sea, which separated what is today the Iberian Peninsula from the rest of Europe, gradually dried up. About 45 million years ago, as this sea became narrower and sedimentation occurred on the seabed, thousands of Typical landscape of turbidites outcrops metres below the surface, on land, the Pyrenees began to develop. I

In Sobrarbe we can find exceptional examples of turbidites, rocks formed in that sea as it accumulated huge amounts of sediments resulting from the development of the mountain range, while the mountains continued to develop.

PALAEOZOIC 542 m.a. 488 m.a. 443 m.a. 416 m.a. 359 m.a. 299 m.a. 251 m.a. 199 m.a. 145 m.a. 65 m.a. 23 m.a. 2,5 m.a.

Cambrian Ordovician Silurian Devonian Carboniferous Permian Tria Jurassic Cretaceous Palaeogene Neogene Quaternary EPISODES: 1 4 SOBRARBE GEOPARK THE SOBRARBE DELTAS (between 40 and 25 million years ago) 4 The formation of the mountain range caused the gradual disappearance of the sea, which was becoming shallower and elongated. About 40 million years ago, a system of deltas marked the transition between the area that had emerged and later stages of this marine gulf. Although this period was relatively short, huge amounts of sediment accumulated, which can be found today in the southern part of the District converted into marl, limestone and sandstone. Once the sea had retreated definitely from Sobrarbe, the relentless effects of erosion became all the more intense if possible. About 25 million years ago, active and dynamic torrents accumulated huge amounts of gravel that, over time, became conglomerates, such as those that form the bulk of Conglomerates: rocks formed from rounded Peña Canciás. fragments of other rocks

THE ICE AGES 5 (last 2,5 million years) Once the mountain range and its foothills had formed, erosion began to transform it. The river valleys widened and the present river network began to be formed. On several occasions during the Quaternary, mainly over the last two and a half million years, various cold spells occurred, covering the mountains with snow and ice. The last major ice age reached its peak about 65,000 years ago. Huge glaciers covered the valleys and mountains and shaped the landscape, effectively eroding some places and accumulating sediment in others. The landscape of the entire northern section of the District was shaped by those ancient glaciers.

Glaciers like the ones we see today in the Alps covered the Pyrenees at that time 6 TODAY Today, erosion processes are slowly and gradually wearing away the mountain range. This erosion occurs in many ways: through the action of rivers, erosion on the slopes, karst dissolution, etc. The landscape that we see today is only an instant in a long evolutionary process that is on-going, but now with the participation of man who is changing the environment like no other living being is capable.

Río Cinca, agente modelador actual

MESOZOIC CENOZOIC 199 m.a. 145 m.a. 65 m.a. 23 m.a. 2,5 m.a.

Tria Jurassic Cretaceous Palaeogene Neogene Quaternary 2 3 4 5 6 5 PISODES REPRESENTED IN THE GEO- E ROUTES

Nº GEO-ROUTE EPISODES

PN1 Ordesa Valley 2 5 6

PN2 Mount Perdido 2 3 5 6

PN3 The Roland Gap 2 3 5 6

PN4 Cutas Viewpoints 2 3 5 6

PN5 La Larri 1 3 5

PN6 Balcon de Pineta 2 3 5 6

PN7 Añisclo Canyon (lower part) 2 5 6

PN8 Añisclo Canyon (upper part) 2 3 5

PN9 Circuit Añisclo Canyon 3 6

PN10 Escuaín Valley 3 6

PN11 Otal Valley 1 3 5 6

Episode 1: Variscan orogeny - Episode 2: Tropical marine sedimentation - Episode 3: The formation of the Pyrenees - Episode 4: The Sobrarbe deltas- Episode 5: The ice age - Episode 6: Today Nº GEO-ROUTE EPISODES

1 Geopark Interpretation Centre 1 2 3 4 5 6 Aínsa: a town between two rivers. 2 Urban geology 3 6 3 Geology: A bird's eye view 2 3 6

4 Inside the canyon 2 3 6 Breath-taking landscapes of water 5 and rock 2 4 6 Sobrarbe at your feet 6 3 6

7 Crossing the Jánovas Gully 3 6

8 Iron Age Elements 5 6

9 Whims of water for lonely mountaineers 5 6

10 A lake among the oldest rocks in Sobrarbe 1 5

11 The hidden lake 1 2 5 6

12 A road with tradition 1 2 5

13 A privileged vantagepoint 4 6

14 Secrets of the Guara Mountains 2 6

15 Geology for the Saint 2 3 A passage between two worlds 16 2 3 Water inside the Earth 17 2 6 The Jewel of Cotiella 18 2 5 6 Treasures of the Posets-Maladeta 19 Nature Park 1 5 6

7 8 A MOUNTAIN LAKE Geo10 AMONG THE MOST route ANCIENT ROCKS IN SOBRARBE

LAKE PINARRA AND PUERTO VIEJO

About 65,000 years ago, time, you can make your way up to glaciers covered much of the Puerto Viejo, on the border with Pyrenees. Today, only a few France and the boundary of the glaciers remain as a reminder of Pyrenees National Park, from where past Ice Ages, but these mountains you can enjoy a magnificent view are full of evidence of their glacial of this beautiful area, which has past. Valleys, ridges, cirques, some of the oldest rocks in basins, waterfalls, mountain lakes... Sobrarbe that originated over 480 are all remnants of when great million years ago. glaciers covered the region. This geo-route takes us to Pinarra Valley, where the traces of past glaciers are clear to see, and it leads to the small and usually solitary mountain lake of the same name. If you have a little more

9 FRANCE 6 FRANCE

5 4 3 2 1 i

LEGENDE N 500 m Parking i Home Geo-Route Tour Geo-Route Optional Tour 1 Number of stop Signpost STARTING POINT: The car park on the right-hand side of the road to France, near the southern i end of the Bielsa-Aragnouet tunnel on the A-138, which connects Aínsa with the French border. Next to the car park, which can hold half a dozen cars, there is a Tunnel control building.

CHORRO DE PINARRA 10’ stop1 The track starts on the north side of the building. Some signs on the façade indicate the direction of the track. We shall leave the waterfall behind. At the beginning of the route, there is a signpost indicating PR HU PR 182 Puerto Viejo, Puerto de la Forqueta. The track zigzags uphill, gaining in altitude and offering better views of the waterfall. Stop 1 does not correspond to any particular place, but to any place that offers a good view of the waterfall; approximately 10 minutes after starting out (Fig. 1).

Outcrops Mount Viejo ( Pico Viejo)

QUARTZITE Waterfall

Fig. 1. View of the Chorro de Pinarra waterfall (right) and the quartzite outcrops. Mount Viejo can be seen in the background. The headwaters of the ravine that provides the water to the waterfall can be seen at the foot of the mountain.

The waterfall (chorro o Churro de the most important rivers in Aragon. The Pinarra) is visible from the car park. The ravine and its headwaters are really an water from the Pinarra Ravine drops 60 ancient glacial valley. About 65,000 years metres into the valley. Here it combines with ago, the glacier flowed into the cirque water from the Salcorz Ravine (located on where we commenced this Geo-route. the other side of the valley) and flows south to the River Barrosa, which originates in the When the ice retreated, this valley of the same name. Finally, this river tributary glacial valley ended up higher flows into the River Cinca at Bielsa. The than the floor of the valley into which the torrent that creates the waterfall is the glacier flowed, and that drop is now northernmost tributary of the Cinca, one of bridged by the waterfall.

11 PINARRA VALLEY

FRANCE

BARROSA

VALLEY

Fig. 2. Pinarra Valley and location of the Stops on the Geo-Route. 12 These mountains are made of which zigzags up to a grassy plateau, which quartzite rocks from the metamorphism corresponds to the top of the waterfall (25 (changes to rocks when subject to high minutes from the car park). Although we pressures and/or temperatures) of quartz cannot see it from the path, we will be able sand (see episode 1 on page 4). These to hear it. A short detour will enable us to rocks are very resistant to erosion and often see the top part of the waterfall. From this create outcrops, as on both sides of the position, we can appreciate the waterfall. physiognomy of the main valley and the difference in altitude with respect to the We shall continue along the path, ravine we are now going to climb.

QUARTZITE FIELD 3’ stop2 The track runs parallel to the stream. About 200 metres from the previous Stop, we shall come to a field on our right.

Outcrops

Fig. 3. View of the rock field and quartzite outcrops in the background. The greenish hue is caused by lichen covering the rocks.

This field (Fig. 3) contains large quartz blocks and its appearance is similar to a huge natural scree. Among the rocks, we can see some blocks of quartz and white quartz that stand out from the rest. Almost all the blocks are flat, elongated and covered in lichens, giving them a distinctive greenish hue.

The flat shape is due to the fact that quartzite derived from the meta- morphism of sedimentary rocks set out in strata and it usually breaks up along these Fig. 4. Detailed view of a white quartzite block (indicated with an arrow in planes. the image on the left).

13 Fig. 5. General view of the rock field.

The origin of this rock field lies in the than today, as these conditions only occur quartzite outcrops that exist directly above during the coldest months of the year. We it. The water seeps into cracks in the rock know that the rock field is inactive now, i.e. (mainly following the strata lines) and there is no significant movement or accumulates there. At night or on cold accumulation of rocks because they days, the water freezes, increasing in present a more or less homogeneous layer volume. Hence, the water acts as a natural of lichens. In rock fields with regular wedge that subjects the rock to movements and new blocks, the distribution considerable stress. This effect, repeated of lichens is more irregular, as these thousands of times, caused the rock to organisms only grow on the surface and, if break and roll down the hillside. The blocks the blocks move, we would see rocks that are very angular, which is evidence that are not covered in lichens. Moreover, the they have not travelled far, i.e. they have layer of lichens on a rock that has recently accumulated at the foot of the outcrops fallen onto the field would be less dense. from where they have fallen. Further on and on the opposite This rock field formed in a colder slope, we shall see more rock fields. We climate than today's, but not cold enough may even see one that is noted for its for the valley to be covered in ice. This reddish hue as the area contains fragments means that the freeze-thaw cycle that of red sandstone instead of blocks of fractured these rocks was more frequent quartzite.

14 A GLACIAL VALLEY 15’ We shall continue along the path and, after a few tight bends, we shall reach stop 3 higher ground. This will also enable us to see the rock field from above. Now, we shall come to a small ravine and waterfall on our right. It is the only advisable place to obtain water on the entire route, as the other springs are usually used by cattle (15 minutes from the previous Stop).

The waterfall (Fig. 6), which measures These features originated because a dozen metres high, usually carries water all glaciers do not erode valleys homogeneously. year round. As in the case of the Pinarra waterfall, the quartzite forms an outcrop at the top of the cascade. Here, it is easy to observe the inclination of the strata and their varying thicknesses. However, the foot of the waterfall consists of another type of rock, also metamorphic, but less resistant and, in this case, dark grey, known as shale. While quartzite quartzite derives from metamorphic rocks rich in quartz, shale comes from subjecting clay to high pressures and temperatures. schist If we look towards the valley, we shall s see a depression bordered by escarpments below (Fig. 7). This is typical of glacial valleys, Fig. 6. Waterfall. The dashed lines show the strata lines, tilted to the which have a stepped profile, alternating north. drops and flat areas.

escarpment Ice direction

flat areas escarpment

Fig. 7. View of the valley from Stop 3, displaying an irregular profile full of cliffs, drops and flat areas that originate the waterfalls and meadows that are typical of glacial valleys. 15 WHITE QUARTZITE 20’ stop 4 We shall continue along the track up the valley until we reach a small hut (20 minutes from the previous Stop).

The track continues uphill from the waterfall and passes next to some shale outcrops that are easily visible from the path (Fig. 8).

The hut (Fig. 9) is built in the shelter of an outcrop of white quartzite that, from schists a distance, appears greenish as it is covered in lichen.

However, if we get closer and observe the area in detail, we shall see the Fig. 8. Detailed view of shale, a metamorphic rock that is less intense whiteness of the rocks. Quartzite is resistant to erosion than quartzite. highly resistant to erosion and, therefore, the stream that crosses the Pinarra Valley has carved into the rocks creating a white quartzite narrow canyon.

The quartzite we can see along the route was formed in the Cambrian and Ordovician, at least 460 million years ago. They are among the oldest rocks we can find in the Pyrenees in Aragon, far earlier than the granite or limestone found in some of the most famous peaks. In fact, this area and the area around Mount Posets are the best places in the Geopark to observe Fig. 9. Hut built in the shelter of white quartzite rocks, which are very resistant to erosion. these ancient rocks.

Fig. 10 White quartzite rocks at the outcrop (left) and a separate block (right), both next to the hut. Lichens give them a greenish hue but a closer look will reveal their intense whiteness.

16 LAKE PINARRA 25’ stop 5 We must continue along the track until we see the valley floor. In order to approach the lake, we shall have to turn off the track and cross some Alpine fields. The path is unmarked but not difficult. The best option is to follow the path towards Puerto Viejo, indicated by a signpost that also indicates the turn-off to Puerto de la Forqueta. We shall eventually see a large rain gauge at the bottom of the cirque, on our left. We must head in that direction if we want to go directly to the mountain lake, which is hidden behind a moraine beyond the rain gauge (a small stream connects the lake and the rain gauge and can be used to find the former). If, on the other hand, we prefer to make our way up to Puerto Viejo, we will have to continue along the clearly visible track and, on the way back down, we can turn-off to visit the lake (it takes about 20 minutes to go from the hut to the rain gauge and about 5 more to reach the lake).

When we cross the floor of the cirque, we shall see a coloured pole about 3 metres high not far from the rain gauge. Similar poles exist in other cirques in the Pyrenees in Aragon. They are used to measure the thickness of the snow in winter; hence the coloured sections measuring half a metre each. They were installed in the 1980s to calculate the water resources from snow in the Spanish Pyrenees, a project that was unfortunately abandoned.

On reaching the rain gauge, we shall climb a short slope to reach the lake; a small circular lagoon with a diameter of approximately 50 metres. The lake is located in a small depression blocked by a moraine, i.e. an accumulation of sediment Fig. 11. Pole used to measure the thickness of snow in winter. carried there by a glacier (Fig. 12).

This moraine, today covered in grass but recognizable by its shape, is a natural dam. However, a tiny stream flows out of the lake towards the rain gauge through a small gap. All mountain lakes in Aragon are situated at altitudes that range to mountain lake from 2,200 to 3,000 metres, as their origins are connected to the erosion caused by glaciers on the valley floors, where they often created basins surrounded by moraines, as in this case. Fig. 12. Rain gauge, which can be used as a reference point to find the lake.

17 FRONTAL MORAINE FRONTAL MORAINE

MOUNTAIN LAKE ( IBÓN)

Fig. 13. Lake Pinarra, blocked by a small moraine. Puerto Viejo in the background, where the next Stop is located.

PUERTO VIEJO (2 472 M) 30’ stop 6 A climb for those who wish to extend the excursion. Whether we have previously visited the lake or not, the path to the mountain pass is very clear (30 minutes from the lake or from the snow post).

The path leads up to the pass, a valley flowed into the main valley and small gap on the ridge that marks the connected with the glacier from Barrosa, as border between and France. now happens with the streams that flow through these valleys. To the north is Gèla Valley, in the Pyrenees National Park (France). Looking At Bielsa, they joined the glacier towards the Spanish side, we shall see that that came from the north face of Mount the valley we have just crested has the Perdido (Pineta Valley), creating the Cinca typical shape of glacial valleys: irregular, Glacier, which used to be 23 kilometres stepped floor, steep walls and a U shape long and over 350 metres thick at its peak (Fig. 14). The absence of trees, due to the about 65,000 years ago (Fig.15). We are altitude in part, enables us to observe all now at the northernmost part of that these aspects. The glacier that formed this impressive glacier.

Profile of U Ibón de Pinarra

Fig. 14. Glacier topography at the head of the Pinarra Valley.

18 BARROSA PINARRA BARROSA PINARRA VALLEY GLACIER RIVER VALLEY BIELSA BIELSA GLACIER PINETA REAL TUNNEL PINETA GLACIER VALLEY GLACIER BIELSA FRANCE FRANCE VALLEY

Fig. 15: Left: Current aspect. Right: Reconstruction of the extent of the glaciers 65,000 years ago when the Pinarra Valley was covered in ice.

Fig. 16. View of Pinarra Valley from the area around Puerto Viejo.

19 ! A MOUNTAIN PASS FOR TRADE... AND TO ESCAPE. ! There is a small plaque on the Puerto Viejo mountain pass commemorating the forced exile of many people fleeing from the horrors of the Civil War. It is interesting to realize the intensity of that war in the farthest reaches of the Pyrenees.

During April and June, 1938, the town of Bielsa was besieged, creating what was known as the "Bielsa Pocket". The night of the 15 to 16 April was especially dramatic as many inhabitants from Bielsa had to cross the mountain pass, still covered in snow, to escape the bombardment of the town. The Bielsa town hall features an ethnographic museum that dedicates part of its exhibition to explaining this tragic event, with a wealth of documents, items and photographs.

Apart from this tragic event, this mountain pass was also the standard border crossing between Bielsa and France until the tunnel was built in 1976. Although this place may seem remote and distant, there used to be a bustling trade between the inhabitants of the Bielsa and Gela (France) valleys. The Puerto de la Froqueta (Forqueta Pass), towards which we previously saw a turn-off, was used for smuggling as it was steeper and less frequented.

A MOUNTAIN LAKE AMONG THE MOST ANCIENT ROCKS IN SOBRARBE LAKE PINARRA AND PUERTO VIEJO

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> PRACTICAL INFORMATION ROUTE: Southern end of the Bielsa Tunnel to Lake Pinarra and Puerto Viejo. PR HU-182 TYPE OF ROUTE: Linear (return along the same route). There are three options: (1) visit the mountain lake, (2) visit Puerto Viejo, (3) combine both and visit the mountain pass first and then visit the lake on the way down. DIFFICULTY: Low-medium for all options. The path is not difficult and the gradient is moderate (a rise of 750 m on the longest option), although the various options proposed may make the route shorter. Visiting the lake requires crossing an unmarked area that is easy and clearly identifiable; however, in foggy weather it may be difficult to find your way. Avoid climbing to Puerto Viejo if there is heavy snow, as the mountainside may be unstable and avalanches may occur. DURATION: 1.5 hours (out) if you visit the lake. Add another hour for the return journey. 2 hours if you visit Puerto Viejo. Add another 1.5 hours for the return journey or 2 hours if you stop to visit the lake.

LENGTH: 4 km (one way) to the lake; 4.5 (one way) to the mountain pass; 10 km (both ways) if you combine both visits.

GRADIENT: 400 m on the way up (and the same distance on the way down) to access the lake; 710 metres up and the same distance down for the mountain pass. If you combine both visits, the difference in altitude will be 750 metres (up and the same distance down).

STARTING POINT: The car park on the right-hand side of the road to France, near the southern end of i the Bielsa-Aragnouet tunnel on the A-138, which connects Aínsa with the French border. Next to the car park, which can hold half a dozen cars, there is a Tunnel control building. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> COMMENTS It is not advisable to replenish your water except at the place indicated due to the presence of cattle.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> PROFILE GEO-ROUTE 2500 6 5 2250 4 3 2000 1 2

1750

10GEO-ROUTE ofof SobrarbeSobrarbe www.geoparquepirineos.com