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The Quaternary Period

The Quaternary belongs to the Cenozoic Era, but due to its many geological events, crucial to our species, we consider it worth a special mention.

From the Quaternary, the deposits of glacial, periglacial and fluvial origin stand out.Glacial sediments, such as moraine, are unconsolidated accumulations of clay and sandstone with debris and blocks of different sizes. For example, in the Ara Valley, we find lateral moraines in Viu, 300m above the current bottom of the valley.

Sedimentary deposits from Quaternary. Fluvial terrace of the Cinca River by Aínsa.

North of Bielsa, we find moraine remains in the Santa Cruz and Sarra Gorges, 200m above the current river floor. The main glacial deposits belong to the maximum glaciation in the Pyrenees, though we can also find minor deposits at high elevations related to later stages, such as the Little Ice Age. .

On the slopes or at the foot of the main summits, dejection cones and terminal moraines stand out. They are unconsolidated accumulations of debris and blocks of different seize, made up mainly of limestone rock fragments from the Upper Cretaceous and the Paleocene..

Terraces of the Ara River between Jánovas and Aínsa. Fluvial terraces are related to climatic changes during the Quaternary.

At the bottom of many valleys, we find present and sub-present deposits related to the periglacial morphology, such as scree or solifluction flows.

Rivers in Sobrarbe continue to erode the shafts in La Fueva, Susía and Arcusa; terraces are formed on marlstone terrain along the Cinca and Ara Rivers and gorges are carved in the hardest rock.

The highest valleys in the county were partially covered by glacial ice during the maximum glacial in the Pleistocene, and at some other times. From the Palaeolithic, Sobrarbe's inhabitants have faced different climatic changes. /p>