Geoparque Unesco

11 The Origins of the Peña Montañesa (Road from Escalona to Buerba)

The origins of Peña Montañesa (Ctra. Escalona - Buerba)

Localización: Ctra Escalona Buerba.

Coordenadas. 262729 4710335 31 N

Textos Esperanza Fernández (Geopage)

Solitary and imposing is how walkers describe the Peña Montañesa, visible for much of their route. This mountain has a long history which includes a "journey" known in geological terms as a thrust fault.

Aspecto general de Peña Montañesa con Peña Solana a su izquierda. Fotografía: Esperanza Fernández.

Detalle de Peña Montañesa, donde se observan los materiales resistentes a la erosión que forman la cima desnuda de vegetación. Estos materiales se originaron a decenas de kilómetros de distancia y fueran movidos y colocados en este punto durante la formación de los Pirineos. Fotografía: Esperanza Fernández.

What is a thrust fault, it and how is it formed?

1/ The layers of sedimentary rock in the Earth's crust are stacked one on top of another, with the lowest layers being the oldest.

2/ When compressional forces occur, these layers are folded and/or broken. Low angle fractures are the most common type of fault. In this case, compressional forces have pushed the rock directly above the fracture up and over the one on top. This movement can take place over tens of kilometres.

3/ The result is three-fold:

  • A) The Earth's crust is shortened and thickened, forming high mountains.
  • B) Some rocks are come to rest far from their place of origin.
  • C) Ancient rocks, originally located at the base of the mass in movement, slide over the top of more recent rocks, originally located at the highest part.

4/ The Pyrenees have many thrust faults. Peña Montañesa is part of a major thrust fault that affects the entire Cotiella Massif and whose displacement has been estimated at about 40 kms.

Esquema de formación de un calbagamiento, consistente en una falla de bajo ángulo y en el desplazamiento del bloque que queda sobre ella. El resultado está siendo erosionado por los agentes geológicos externos, que han destruido las rocas más endebles permaneciendo las más duras, entre ellas Peña Montañesa y Peña Solana. Esquema de Albert Martínez.

Did you know that…?

It has been estimated that the collision between the Iberian Peninsula and Europe shortened the Earth's crust by about 150 kms. As a result, there are several peaks in the Pyrenees with altitudes above 3000 m, and these would be even higher if it were not for the continuous action of erosion on these materials.

Recomentations in your visit to Sobrarbe-Pirineos Geopark

  • Safe visits, unforgettable experiences. There are companies who collaborate with the Geopark where you can hire specialized guides to make your tour a unique and safe experience.
  • Respect the geological outcrops. Do not break off samples of rock, mineral or fossils.

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