Idrija Geopark – European Geoparks Network

Website: www.geopark-idrija.si

The Idrija Geopark covers an area of 294 km² and includes the entire Municipality of Idrija, which lies in the west of Slovenia – more precisely, in the pre-Alpine hills of Idrija and Cerkno. It is located at the junction of two mountain ranges, the Dinarides and the Alps. It is the exceptional location that creates such a unique geoheritage – deep gorges where various rocks are discovered in remarkable stratigraphic cross sections, tectonic phenomena as well as mineral and fossil deposits. Water is also extremely important since it contributes to the variety of the terrain with numerous springs, rivers and Karst features. In a relatively small area, visitors have the opportunity to observe the rocks forming the terrain in the region. It has a typical thrust structure and is very diverse with deep gorges, high Karst plateaus, many caves, abysses, sinkholes, and hilltops that offer beautiful views from the Alps all the way to the Adriatic Sea.

In the Idrija region, Carboniferous, Permian, Triassic, Cretaceous and Paleocene-Eocene rocks can be found. Extensive tectonic movements began in the Middle Anisian and lasted throughout the Middle Triassic period. The paleo-geographic conditions were highly complicated in this period during which the famous Idrija mercury ore deposit (the most valuable and unique geo-site) was formed. Due to extensive and complex tectonic events, the calm carbonate sedimentation was interrupted in Upper Cretaceous. Typical flysch rocks were formed in the foreland basin. In the Miocene Epoch, the pushing of the Adriatic microplate under the European plate first transformed the rocks of the Idrija region into a huge recumbent fold and, by further displacements, later cut them up into individual nappes and intermediate nappe horses, which moved in the SW direction. The final structure of the terrain of Idrija was formed by numerous strong normal and then right-lateral faults. The strongest and best known fault from this area is the Idrija Fault.

The richly developed and often somewhat specific karst phenomena in the Idrija region are the reflection of complex rock composition as well as tectonic and morphological stratification of the highly variegated Idrija region. The high karst comprises several karst plateaus, which pass into shallower limestone karst. Typical of the high karst are deeply karstified carbonate rocks, particularly limestones, with all the characteristics of classical karst. On the surface, numerous sinkholes can be found in various geological structures, whereas the underground karst is characterised by deep abysses, occasional sub-horizontal short caves, as well as short sinking streams and swallow holes (‘covered karst’) along the thrust edges. Special mention should be made of the 400-metre-deep Habeček shaft and the Divje jezero (Wild Lake), a cave, spring and lake in one.

Idrija, together with Almadén in Spain, has been inscribed on the UNESCO List of World Heritage for its exceptional mercury heritage. A great many rare and even unique specimens of technical heritage have been preserved. The town of Idrija and its surroundings feature a large number of cultural heritage sites which testify to the exceptional significance of this area for mercury production. The continuously emerging challenges in ore extraction and metal production attracted prominent European researchers to Idrija. Idrija also developed as a town with all the necessary educational institutions offering opportunities to capable locals to get the necessary education at home. Mining activities occupied the male labour force, but also brought lacemaking activities to town, which were developed by women and provided them an additional source of income.

The surroundings of Idrija were inhabited by rural population. Preserved till today are the homesteads of powerful, wealthy farmers in Spodnja Idrija and large, solitary homesteads in the nearby villages. The existence of residential and all necessary farm buildings testify to the economic independence of these farm units. The influential historical processes that brought political and social changes also left their marks in the shape of immovable heritage sites. These include military facilities from the First and Second World Wars – military routes, boundary fortifications and burial grounds. Although of younger origin, these sites bear witness to the turbulent historical events in this area in the recent past, too.