GEOMORPHOLOGY
The Madriu-Perafita-Claror Valley is of glacial origin with geomorphological interest throughout almost its entire extension.
The relief of this area, which is very uneven, sits on a substratum of siliceous rock (granitic at Gargantillar-l’Illa and metamorphic at Port Negre), on which the modelling action of the firns has worked. The U-shape of the valley, the cirque glaciers, the rocky firns, the hanging valley of L’Estany Blau, the plateaus of the Camp de Claror or the dynamics of the avalanches are clear examples of the glacial origin of the valley. There is also a large number of mountain peaks where the peak of La Portelleta stands out, at 2,905m, the highest in the protected area.
In the Camp de Claror, the interest lies in the fact that it has models similar to subpolar latitudes and tundra regions (Spitzberg). They are geometrical figures (polygons and circles of stones), which are exceptional and rare testimonies of high scientific value in the Western Pyrenees.
Ensagents (fund: Dona Secret)
The Rocky Glaciers of the Madriu Valley
When we talk about the Madriu-Perafita-Claror Valley, we are talking about a unique natural and cultural heritage, declared a World Heritage site by UNESCO. Its lakes, forests, and historic paths are well known, but they hide a geological treasure that often goes unnoticed: the rocky glaciers.
These formations, which we might easily confuse with simple screes, are actually fascinating remnants of a glacial past. In the valleys of Ensagents, Perafita, and in the Madriu valley itself, especially on the northern slopes, we can find some of the best examples in the Pyrenees. They are, we could say, “textbook glaciers” for scientific study.
What is a rocky glacier?
A rocky glacier is a tongue of ice and blocks that was formed around 11,000 years ago in this area, during a cold and dry climatic period. The snow, scarce but persistent, compacted into ice at the foot of the cliffs, while simultaneously mixing with the constant fall of blocks. The result: a dense flow of abundant rocks and ice that acted like cement, slowly descending down the slope.
What we see today is only its “fossilized skin”: lobular masses of blocks that still retain the shape of a tongue and contrast with conventional screes.
The Madriu Valley, a Natural Laboratory
Madriu is a true open-air museum for anyone wanting to discover these formations:
- In the Ensagents valley, we find perfectly defined rocky glaciers at the foot of the shaded cliffs of the valley.
- In Perafita, the presence of metamorphic material has allowed for the spectacular preservation of these tongues, which remind us of a lava flow descending the mountain slope, even though they are in no way volcanic!
- In the shaded slopes of the Madriu valley, the colder climatic conditions of the area and the granitic material have left scientifically valuable traces: this is where we can study “textbook glaciers,” ideal for understanding the difference between a scree and a rocky glacier.
This set makes the valley a reference point for geological and climatic research in the Pyrenees, as well as a draw for curious visitors.
How to differentiate them from a scree?
If in doubt, there are two key indicators:
- The lobular shape, like a tongue that moves slowly due to gravity.
- The origin of the blocks: many times, they have traveled dozens or hundreds of meters from the rocky cliffs where they fell, which is impossible in a simple scree where blocks roll down until they stop.
Additionally, the granitic rocky glaciers, like those in Madriu, are the ones that have best withstood the passage of time, and we can observe their original structure almost intact.
Are they still active?
Despite their spectacular nature, the rocky glaciers of the Madriu Valley are relics: they no longer contain ice inside. The only active rocky glaciers in the Pyrenees are found in Besiberris, Posets, and Cotiella. But this does not diminish their interest; on the contrary, it allows us to read the climatic history of the Pyrenees and understand what life was like during much colder periods.
A visit with added value
Walking the trails of Madriu is not only stepping into an exceptional cultural and natural landscape: it is also traveling back to the glacial past of the Pyrenees. Those who know how to observe will find, beyond lakes and forests, traces that explain how the mountain reacted to the last major cold snap.
The rocky glaciers of Madriu, Ensagents, and Perafita are a geological and tourist treasure that combines science and beauty. One more reason to discover, with new eyes, this privileged corner of the Andorran Pyrenees.