The visitor who seeks to encounter nature in Jacetania you will find a territory full of landscapes in which geology, climate and culture have left their mark, generating a territory full of personality. Surely anyone who decides to embark on discovering their essence will find a space with which they can identify.
To speak of Jacetania is to speak of the most northwestern region of the province of Huesca, bordering to the west with Navarra and to the north with France, it is one of the four Pyrenean regions along with Alto Gállego, Sobrarbe and Ribagorza. Administratively it is located in the provinces of Huesca and Zaragoza. It is made up of 20 municipal areas, among which is Jaca, the largest town, which brings together the main services of the territory.
Geographically, Jacetania would be included between the interfluves of the Veral rivers, to the west, and Gállego in the neighboring region of Algo Gállego. As in the other four Pyrenean regions, it is not possible to talk about Jacetania without mentioning the natural border of the Pyrenees. We are in the transition zone between the western and central sectors of the Pyrenean mountain range. As you know, the Pyrenees is born and dies in the sea. As you advance from the Atlantic Ocean towards the Mediterranean Sea, the mountain range begins to gain height little by little until reaching the great peaks of the granitic plutons of the Maladetas, in Ribagorza. It is here, in Jacetania, where the first peaks that exceed 2000 m in altitude appear after Ory in Navarra; Already in the Aragón River basin, the peaks reach over 2500 m (2667 m of Bisaurín peak or 2886 m of Collarada) while in the Tena valley they exceed 3000 m.
This western area does not escape the complexity of having suffered over time two orogenies that wrinkled the crust forming a series of mountainous alignments and depressions in an ENE – WSW direction. The coexistence of the Hercynian and Alpine cycles is evident in the territory. An axial, Paleozoic axis, formed by the Hercynian folding with the presence of Silurian, Devonian, Carboniferous and Permian sediments, to which the so-called Interior Sierras are attached to the north and south as a result of the later alpine orogeny, made up of a set of alignments of materials ranging from the Upper Cretaceous to the Eocene.
The oldest materials, the Paleozoic, reappear in Jacetania in Oza after having been “lost” in Roncesvalles and continue through the Ibón de Estanés, Candanchú, Canal Roya, Formigal and Panticosa. These materials share a presence with the most modern, the lower Eocene limestones that form the crest of the Sierras Interiores that runs from Ezcaurri to Tendeñera, passing through Alanos, Bisaurin, Bernera, Aspe, Collarada and Tendeñera.
To the south, between the Middle Depression and the Interior Sierras, appears the flysch . In this east-west extension band, it forms a set of mountain ranges with rounded profiles covered with vegetation. The flysch was formed by the deposition of materials from the Pyrenean sedimentation resulting from the Alpine orogeny. These are turbiditic deposits that filled the existing sea trench. These materials were deposited at different rates. In each sequence the coarser materials did so more quickly than the fine ones, giving rise to that characteristic structure of alternating marl and sandstone. The Sierra de los Dos Ríos or the Garcipollera are made up of these materials.
It is a soft material that leaves large deposits of rectangular blocks that form the banks of many rivers, such as the Estarrún.
If we talk about its climate, we must again resort to the concept of transition. This region is characterized by being a transition area between the Atlantic and Mediterranean climates. From the marked features of a mountain climate and the high oceanic mountains that stand out in the most northwestern extreme above 1600 m, we pass towards the east to a more Mediterranean climate. It is a transition that takes place in two directions: north-south and east-west. From north to south, the barrier represented by the interior mountain ranges that leaves a more humid climate to the north, together with the progressive loss of altitude, facilitates a notable decrease in the rainfall. In the second direction, the distance from the cooler and more humid Atlantic masses and the succession of interfluves favor the hygrometric decrease of the masses loaded with humidity. To the east of the Aragón River and above 1600 m, the high oceanic mountain is replaced by an identical, more Mediterranean and continentalized mountain. Below 1600 m, a continental Mediterranean climate dominates that occupies the entire mid-mountain, replaced by the sub-Mediterranean climate below 1000 m. The highest average temperatures are those recorded in the Berdún channel (Jaca 11.4ºC) with a progressive decrease towards the north (Hecho 9.4ºC; Canfranc 8.4ºC). The presence of snow in these areas cannot be overlooked due to its importance. The snow cover usually extends between the months of November and June. It is, due to the situation of the 0º isotherm, from 1600 m onwards where the winter snow reserve is created.
* Chema Martinez, biologist and good friend, based in Jaca great fan of nature and very knowledgeable about nature
