The Origin of Lake Pavin: Two Centuries of Controversy

Abstract

The Lake Pavin, having a circular shape, unusual size and depth, pure water and dark forest draping the slopes down to the shore, has always impressed visitors. This unusual lake garnered a fame that attracted the attention of geologists very early. After the discovery of extinct volcanoes of Auvergne by Guettard (Mém Acad Roy Sci, Paris:27–59, 1752a) in the Chaîne des Puys, naturalists and geologists quickly recognized that most of the Auvergne mountains were volcanic edifices (Desmarest, Mém Acad Roy Sci, Paris (parts 1 & 2 [published in 1774]):705–775, 1771; Dolomieu, J des Mines 7:393–420, 1797). Lake Pavin was also supposed to be of volcanic origin, but the cause of its unusual shape was controversial: according to Montlosier (Essai sur la théorie des volcans d’Auvergne. Landriot, Riom, 1788), the lake was the product of a large explosion but Legrand-d’Aussy (Voyage fait en 1787 et 1788, dans la ci-devant haute et basse Auvergne, aujourd'hui départemens du Puy-de-Dôme, du Cantal et partie de celui de la Haute-Loire. Edn. Chez le Directeur de l'Imprimerie des Sciences et arts, Rue Thérèse, près la rue Helvétius, Paris. 3 volumes 1794–1795) considered it as the result of a collapse. These two assumptions have been defended throughout the nineteenth century: Poulett Scrope (The geology and extinct volcanoes of central France., vol in-8°. Pl. and maps. 2nd edition 1858 edn. Murray, London 1827), Lecoq (Description pittoresque de l’Auvergne. Baillière, Paris, 1835) and Vimont (Annuaire du Club Alpin:337–349, 1874) advocated the explosive origin, while Lacoste (Observations sur les volcans de l’Auvergne suivies de Notes sur divers objets; recueillies dans une course minéralogique faite l’année dernière, an X. Delcros, Granier et Froin, Clermont-Ferrand, An XI, 1802–1803), Dufrénoy and Elie de Beaumont (Ann. des Mines. 3, 3, 1833) and Boule (Bull Soc Géol France XXIV:759, 1896) supported the collapse model. Other explanations have also been proposed such as a local geomorphic anomaly (Huot, Volcans in Desmarest, Nicolas: Encyclopédie méthodique. Géographie-physique, vol V. Chez Mme veuve Agasse, an III, Paris, 1828) or a glacial origin (Julien, Des phénomènes glaciaires dans le Plateau Central de la France et, en particulier, dans le Puy-de-Dôme et le Cantal. Paris, 1869; Giraud, Annales de la Station Limnologique de Besse 1:147–161, 1909). As he studied the deposits associated to the Lake Pavin, Glangeaud (C R Acad Sci Paris 162:428–430, 1916) demonstrated that explosions did produce them, an interpretation accepted by most geologists for the twentieth century and thereafter. It was not before 1973 that Camus et al. (C R Acad Sci Paris, sér D 277:629–632) reconciled the two explanations in the light of modern maar models, in which violent explosions trigger concentric collapses, which in turn enlarged the crater.