Benasque Valley

Geographical location

The study zone has 290 km² and is located in the Spanish Central Pyrenees. It mainly covers the Ésera river high basin (also called Benasque Valley). It is a rugged area, from the 3.400 m of the highest summit to the 1.100 m or the deepest valley. It is 3 hours away (by car) from Zaragoza.

The area is made up of Paleozoic materials: slate, limestone and granite. These materials are the basement of the Alpine Cycle Sediments in the Pyrenees. Today, this basement comes to the surface in the Axial Zone, tectonically piled up southwards through Alpine age thrusts.

In this Axial Zone, there are the highest Pyrenean peaks (Maladeta 3.308 m, Aneto 3.404 m, Russel 3.205 m, Salenca 3.010 m) exactly, within the Maladeta Granite Massif. There are four Igneous bodies: Posets-Millares Granite Massif (very similar to the Maladeta one), Lys Granite Massif and Cerler Volcanic Complex. All of them intruded during the Carboniferous cutting the upper Paleozoic materials.

The relief is controlled mainly by two factors: lithology and processes (fundamentally glacial). In the northern part, where the granite lithologies are common, the glacial and periglacial morphology has more entity. The south half is made up of less strong and firm materials, thus the generated relief is not so rugged as before. The standing out morphology consists of fluvial incision, circular breaks and mass movement.