The Cinca River and its tributary the Sosa river are the two rivers that cross the region and give it character, intervening in the recent development of the relief.

Other important elements of the landscape are the hills, sasos and muelas, as is the Terreumuela in Conchel (culminating point in the south region, altitude 477 m), the tabular reliefs made ââof sandstone layers or limestone with continental origins that are built on layers of clay. All these materials date back to the Tertiary (Miocene), except for the clongomerate (Plio-Quaternary). At its base, extended erosive ramps and large flat areas where saline soils abound are found.

In Almunia de San Juan, Cofita and Fonz we find chalky materials like Keuper (lower Oligocene) that are part of Barbastro- Balaguer anticline.

Finally, in the north part of the village of Fonz,  eocenelimestones, cretaceous and triassic from the Carrodilla appear in the southern buttresses of the Sierras Exteriores del Pirineo in Huesca forming the south border at the mantle of Gavarnie. It is here that the highest point of the region (La Cruceta, 826 m altitude) is found.

Forms of erosion and sedimentation

1. Gullies. They are created as a result of repeated storms. The superficial water flow channels first flows through the streams made on the ground (grooves), here is where they start extending and canalizing. If the speed and flow acquired because of the elevated steep slopes, the erosive effects evolve towards the formation of a gully network of variable dimensions. They are very striking on the north side of the Muela de Terreu in Conchel.

2. Tafoni and alveoli. Cave-like vertical scarps caused by mechanical weathering of sandstones under semiarid climate which causes disintegration and flaking of the rock notables in the sasos surrounding Monzón.

3. Ripas. Vertical scarps formed by the river's linear incision which cuts abruptly tertiary structural materials of the Monegros platform. One of the most noctorious is the one in Alcolea de Cinca with multicolored shale strata at the base.

4. Valleys. Flat-bottom gullies in gypsum soils whose present morphology has been filled with fine sediments from the slopes.

5. Paleochannels. Correspond to twisted fluvial channels filled with fine materials and they are from the Miocene age.

6. Sinkholes. Typical forms of erosion in limestone karst landscapes. The rainwater perforates and dissolves the rock leaving a micromodal with grooves and ridges of varying dimensions and sinkholes in the land. In our county they are of small dimension (The Fonz Carrodilla), they can also occur in gypsum like the Gesas in La Almunia.

7. Alluvial fans. Deposits formed at the base of the steep slopes of the sasos and muelas due to the abrupt decreasing of the slope and thus, the speed of the water which forms alluvial fans.

8. Glacis erosion. They are formed between the slopes of the sasos and the lower depressed areas.  Debris of quaternary origin is generated by a coldly semiarid climate and smooth ramps or nearly horizontal esplanades due to irregular regimin and sometimes extreme rainfall. The deposits have abundant clay matrix and a variable content in stones.

9. River terraces. Alluvial sediments that hang over the course of the river as it flows through the low water channel. The changes are attributed to different climatic phases in which the dynamics of the river changed with the flow modification related to the Quaternary glaciations cycles (at least four). The river terraces consist of silt, sand and gravel,these with great lithological variety, sedimentary stones, metamorphic, plutonic and volcanic.

Use of geological strata, forms of erosion and rocks

Carved in situ of potent sandstone strata for various uses has been ongoing in our region since prehistoric times. We found caves used as dwellings, shelters, storage tillage or wineries, columbarium (spectacular series of small niches carved into the rock, for example in the Joy Hermitage in Monzón). Also found were water pipes or tanks, thirteen of which have been inventoried to Almunia de San Juan, where one can also see the steps of an ordeal stone in this type of rock. In the Adamil of Monzón there are iberan sandstone tombs.

From the Gesa gypsum plaster, were extracted for production. The gypsum was baked in ovens and the same was done with the limestone to produce lime Carrodilla. With the establishment of the cement industry in Monzón, the quarries in Fonz were exploited and are still in operation. With the clay, so abundant in the region, tiles and adobes are manufactured.

There are some unique buildings or private houses in the villages throughout the county built with blocks and other architectural elements carved in the rock extracted from nearby quarries or brought from further areas. The limestone was the most appreciated, but sandstone, conglomerate, large boulders and plaster edges were also used,the latter in some pastoral coats. The rough, porous rock appreciated for bread ovens was extracted from other mountain areas (in nearby Litera is in the Gabasa).

The alluvium deposited in the river terraces (sand, gravel), especially the most recent, have been intensively exploited, sometimes uncontrolled, in order to extract aggregates for construction.

Agricultural practices in the areas that erosion has been carving in the gesas, filled with fine fertile sediments, have produced their deterioration.The springs are rare; the most notable ones are in Conchel and Fonz (Ojo de la Fuente, which supplies water to the town), plus some as the Saso fountain in Monzón or the Lions in Albalate. Its location often coincides with a change in the permeability of the strata in the Eye of the Source, using the contact between limestone and gypsum rocks.