September 8, 1762 the young son of the Yolle's, herding the flock of sheep, disappeared near the village of Laval in the province of Dauphiné (France). Only the poor remains of the boy, partially eaten by a mysterious creature, were recovered.
The pastor of Laval, named Raphaël, later described an encounter with this creature:
"the size of a very large wolf, just lighter in color than that of burnt coffee, with a strip of black fur along the back, the belly is white, the head very big and hairy and the tail covered with fur like that of an ordinary wolf but longer and raising towards the end"
Then in 1764 a young shepherdess was killed by the village of Saint-Étienne-de-Lugdarès, Vivarais, near the border to the province of Gévaudan. As other attacks soon concentrated in the border area of the provinces of Gévaudan and Auvergne, the creature became known as the Beast of Gévaudan.
Fig.1. The Cathedral of Saint-Flour, build with dark volcanic rocks abundant in the region. In 1764-1767 the beast of Gévaudan, haunting this area, was considered by some pepole a supernatural creature or even a divine punishment.
Fig.2. Landscape with eroded volcanic cones in the moor of Narse.
Fig.3. Lac Pavin, an ancient volcanic caldera filled by a lake.
It was in part this terrain, hard to venture in and overlook, which for a long time hide the creature. In 1765 the supposed beast - a large wolf - was killed near the royal abbey of Les Chazes in southern Auvergne. However the mysterious killings contuined until 1767, when another large wolf was killed.
The realm of the beast was shaped by ancient volcanoes and the geology of the Auvergne played a major role to understand the significance of volcanism on earth. The chains of Le Puys was recognized in 1752 to be a series of extinct volcanoes and the Massif Central is the eroded remain of a large volcanic complex.
Fig.4. Outcrop of volcanic tephra in the extinct volcano of Puy de l'Enfer.
However also another important geological concept can be observed in the Auvergne - deep time.
In 1820 the British geologist George Poulett Scrope (1797-1876) proposed a chronology of lava flows, showing that there had been a continuous history of volcanic eruptions, forming blankets of lava, and subsequent slow river erosion, forming deep valleys.
Fig.5. Longitudinal profile of lava flows from the Puy de Dôme (Auvergne), Scrope interpreted these profiles as successive phases of volcanic accumulation and subsequent erosion, from "The Geology and Extinct Volcanoes of Central France" (1858), image in public domain.
At the time the age of the earth was still unknown, even if some naturalist already proposed a very old earth. Most geologists however believed in a young earth, maybe just some million years old. However to erode hard volcanic rocks this age seemed not enough. In 1822 William Daniel Conybeare (1787-1857) and William Phillips (1775-1828) argued that "to believe them [the valleys in general] to have been formed by their actual rivers, however long their action may have endured, involves the most direct physical impossibilities" and proposed a catasrophic origin of the river valleys (presumably a large flood). A catastrophic, unknown origin was also favored by geologist William H. Fitton (1780-1861) in 1823 "The effects of water upon the solid strata of the globe have been the subject of much geological debate; but it is now almost universally admitted, that valleys have been excavated by causes no longer in action."
Fitton was right when he argued that whatever created the valleys was no longer in action in the unglaciated Massif Central. However in 1837 the French naturalist Jean Louis Rodolphe Agassiz observed that U-shaped valleys, similar to the one descending from the local mountain ranges, can be found also in the Alps and traced them back to the glaciers. So indeed the valleys of the Auvergne were repeately cut by ancient glaciers, long tima ago melted, into the former lava flows and more recently reshaped by rivers.
Fig.6. Glacier-valley on the Puy Mary (1.785 m /5.800 feet) in the Cantal mountain range, a large and ancient volcanic mountain.
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