The Supramonte of Urzulei form together with the other supramonti of Orgosolo, Oliena, Dorgali, Baunei, a wide carbonated plateau, which is formed essentially by limestone and dolomite, which go back to the Mesozoic. In order to understand its present form, we have to run through the stages of the last 170 million years again.

Rare remainings of river- and lake pebbly drifts, as well as sand and clay, have been accumulated over a flat base formed during the Permian Era because of the erosion of a large group of mountains of which Sardinia was just a small part of it (Ercinic Chain). The fossils of plants, fern and other trees similar to todays cypress, testify that during the medium Jurassic Era (150 M.a) the climate was temperate.

During the Upper Jurassic, these deposits were covered by the sea, which lead to the deposition of grey dolomite and white limestone within an environment filled with corals and shellfish, which nowadays are absorbed as fossils in the rocks.

The landscape of the next geological period, the Cretaceous, about 140 million of year ago, was different. The lowering of the sea level determined the emersion of the sea bottoms where carbonatic mire was sedimenting with clay, which once dried originated a rock called loam rock. This conclusion is supported by the layers on the upper surfaces, which are very similar to the structures that can be found on the bottom of dry pools.

The sedimentation of limestone due to the accumulation of remainings of coralline reefs and loam rocks started again in the Cretaceous Inferior, when the sea level increased. At the end of the Cretaceous (65 M.a), because of the relevant tectonics activity connected with the movements that led to the creation of the Alps, the Supramonte emerged. These tectonics movements have given the landscape some marks that can still be recognized today. These are the reliefs of Munnoro and of Serra Azzaudeli, which are on the ridge of wide anticlinal folds, and the canyons of Riu Flumineddu and of Codula Orbis which follows the main lines.

However, it is because of the different climatic periods during the Tertiary and Quaternary, and because of the action of the man, that Supramonte assumed the unique "moon-like" appearance that makes it so picturesque. During the hot and humid periods, the solvent action of the water manifested itself through karst processes, dolines of various dimensions (in Planu Campu Oddeu, Campu de su Disterru, and Cuile Sedda Arbaccas), caves such as the caves of Ivy, of su Mamucone, and of Orbisi.

Dolomite and limestone are the rocks that have been mostly affected by karst phenomena, because of their physical properties they can be easily damaged by such a chemical action. During the cold periods of the Quaternary Era, when the temperature was much lower than today, physical processes such as collapses and fragmentations of the rocky banks, which were mainly caused during the cycles of cold and thaw, which is called crioclatism by the geologists. The result of such a strain can be seen in the enormous detrital accumulation at the feed of the Costa Silana and in proximity of the Gorge of Gorropu.

The Gorge of Gorropu is without doubt the most striking shape of this part of the Supramonte. This cut in the rock, which was caused by the action of the River Flumineddu, form the most lowered area of the entire Sardinian Supramonte. Its steep cliffs are as high as 450 meters, and enclose the agitated bed of a river with several crags and pools where water is present also in summer.

All these natural elements together with the modifications made by human activities, give this land a harsh and deserted aspect. The ruthless cutting of thousands and thousands of trees that has been done during the last few centuries, the excessive pressure of sheep-farming, and the fires, have transformed the land which once used to be full of trees and forests, into a bare land with rocks and rare vegetation due to the intense erosion.

Luckly enough, some parts which are more remote and difficult to reach, haven't suffered the human influence too much and have preserved parts of ancient forests of holm-oaks and, to a less extent, juniper, yew and some other almost extinct floras, such as the holly, which is typical of much colder climates. Animals, such as the royal eagle e the mouflon, which in other areas are already extinct, are present here. The Supramonte of Urzulei could be one of the main attraction points of the planned National Park of Gennargentu. A necessary condition for its success is that the administrations and local people really believe in an alternative economical development based on a correct usage of their own natural resources.