Tuscania Nature Reserve

Geology

The whole Province stretches mainly over a territory formed by the explosive activity of three major volcanic complexes: Vulsino, the northernmost, at whose centre lies the vast lake basin of Bolsena, Vicano, having at the centre the Vico lake, and Cimino, to the immediate south-east of the Provincial Capital. The beauty and richness of the whole province are closely linked to the geological nature of its territory which, besides stretches of fascinating scenery, offers a soil enriched by volcanic activity which has made it especially suitable for the development of farming activity.
As to its geology, the Tuscania Nature Reserve is quite diverse: side by side with materials of volcanic origin which are relatively recent, resulting from the volcanic activity of Vulsino (between 0.7 and 0.3 million years ago) and Vicano (0,8-0,09 million years), there are also some areas marked by sedimentary rocks of much more ancient origin.
The geological origin of the territory is due mainly to the volcanic ashes often projected to great distances which formed a thick plate of layered tufa, of varying colour and consistency, which blanketed the underlying terrain. Since tufa is a tender material and easily eroded, the numerous streams flowing down spoke-fashion from the slopes of the volcanic mountains have over the course of the millennia cut out deep valleys or gullies, the 'forre'. Thus the tufa plains and the 'forre' are the main elements which mark the area's scenery.
The system of the 'forre' stands out clearly from the rest of the territory and is often of great naturalistic importance. The tufa valleys host plant and animal species of great interest and offer a sure refuge for the native vegetation and animals, which at one time lived also on the surrounding plains; what is more, they act as important corridors for the movement of wild animals.
The complex activity of the volcanic areas has influenced the presence of numerous rock types, which differ as to chemical composition and grain size. These are mainly lava flows, scoria cones, lapilli, clayey tufa and ignimbrite deposits, the latter being the only formations present linked to the activity of the Vicano district. This ignimbrite appears typically as a red tufa with black scoria due to the presence of big black pumice stones with large blisters. This formation comes to the surface exclusively along the canyon cut by the Fosso delle Doganelle torrent.
The clay-conglomerate-sandstone complex on the other hand includes sedimentary deposits dating from the Pliocene and Cretaceous-Paleocene flysch deposits, covered by vulcanites from the Vulsino and Vicano volcanoes, whereas the alluvial complex, dating back to the Holocene, surfaces along the whole course of the Marta river and the gullies and river valleys cut by some of its tributaries.
Volcanic activity has also left some hydrothermal traces, such as the sulphur spring of 'Acquaforte', along the Acquarella gully.