Localización: Mirador del Tozal de Guaso, junto al esconjuradero e iglesia.
Coordinates . 30T0677471 UTM 4616060
Textos Esperanza Fernández (Geopage)
This viewpoint is an excellent place from which to observe how the geological substrate, the product of a long and complicated history, has determined the shape of the Sobrarbe region. Looking around us, we can see an ocean of rocks, within which we can distinguish various landscapes with characteristic geological and anthropic features.
This forms the wall of grey rocks (limestone) and ochre rocks (sandstone) that we can see in the background. It contains some emblematic, mostly limestone, mountains such as the Macizo de Cotiella, Monte Perdido or, closer to us, Peña Montañesa.
These are formed of ancient rocks from the Palaeozoic, which are very hard and resistant to erosion. In fact, they are the ruins of an old mass that has now been almost completely destroyed, and which stand out in relief because the surrounding rocks have eroded away. The range can be identified by its height, the escarpments and the fact that it often lacks plant cover.
This consists of younger, mostly Eocene, materials of the kind called turbidites or flysch. Two alternating types of rocks are present in turbidites: marls, which erode easily when they are not protected by vegetation, creating a landscape full of gullies, and sandstones, which are more resistant.
They create gentle reliefs cut through by narrow valleys, with plant cover and occasional headlands (such as the one on which we are standing) when a sandstone layer protects the marl that lies beneath.
We are standing on the western shore of the Ara River, again in the mid-mountain range. Looking to the right (south) and left (north), we can see a succession of peaks; these are the result of the presence of turbidites, with their alternation of hard sandstones and soft marls. On this side, there are also deposits of marl with occasional layers of limestone, where surface runoff has produced a landscape marked by gullies and bare rock.
This is the lowest area, through which the Ara and Cinca rivers flow. Both rivers have taken advantage of a stretch of very clayey materials to carve out their riverbeds. Above them are located the fluvial terraces: deposits from the rivers themselves that form areas of different sizes and heights. It is difficult to distinguish these at first glance but they usually have a red outline and can be identified by the fact that they are used for growing crops. Among them is situated the wide, gravel-covered riverbed of the Ara River.
These are the mountains at the end of the horizon to the West. They are formed by the Sierra de Guara, consisting mostly of Eocene limestones, where the rivers are carving out deep canyons.
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