A story that begins in the time of the dinosaurs

The Park's mountains are made up of sedimentary rock - mainly limestone - formed almost 150 million years ago, at the time of the dinosaurs during the Jurassic period. The Alps did not yet exist, and a sea called the Tethys lay where the Alps are today. It was at the bottom of this sea that marine sediments accumulated hundreds of metres thick to form the rocks we see today. A gigantic collision of two tectonic plates then completely changed the face of the region. As a result of this collision, which began after the disappearance of the dinosaurs 65 million years ago, the floor of the Tethys Sea was raised, folded and fractured to form a mountain range.

Dynamic processes and an evolving landscape

Ever since they were formed, the Alps have been exposed to a variety of natural elements, such as glaciers, rivers, rain, avalanches, frost and wind, all of which have contributed to giving the mountains their current shape through erosion and the transport and deposition of materials. Many of the Park's outstanding natural sites have been created by the simultaneous action of several processes. Lake Lioson, for example, owes its existence to the passage of a glacier that has now disappeared. The enormous weight of the ice carved out a depression that subsequently filled with water. In the cirque de la Pierreuse and the Lapé forest, whole sections of mountain have collapsed after being weakened by cycles of freezing and thawing. In the alluvial zone of the Ramaclé, it is the free-flowing, ever-changing course of the Sarine that creates an enchanting landscape. The diversity of relief created by these processes is highly favourable to biodiversity, with different species able to find ideal conditions.

Spectacular and sometimes mysterious sites

The gorges of the Jogne and Chauderon rivers and the waterfalls of the Dâ, Tâna and Ramaclé are spectacular sites linked to the presence of particularly resistant rock that the rivers have great difficulty in eroding. Two rare types of landscape are unique to Gruyère and Pays-d'Enhaut: marshes and karstic formations (caves, lapiés, etc.). Marshes are linked to the presence of an impermeable subsoil that retains water on the surface. The marshy landscapes of the Col des Mosses region are the largest Alpine expanse of marshland in French-speaking Switzerland. As for the karstic forms, such as the lapiés de la Pierre du Moëllé, the opposite is true: they depend on the presence of permeable rock in which water can carve out its path and form underground galleries, the vast majority of which remain unexplored to this day!