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20. Basalt Formations of the Vivarais, 1778

Faujas-de-St.-Fond, cit. Barthélemy (1741-1819). Recherches sur les volcans éteints du Vivarais et du Velay. Grenoble: Chez Joseph Cuchet, 1778.

East of the Auvergne region, in south-central France, lie the mountainous districts known in the eighteenth century as the Velay and the Vivarais. After Desmarest explored the Auvergne region, Faujas-de-St.-Fond made a similar geological journey through the Velay and Vivarais, and he found columnar basalt, lava, and what appeared to be volcanic craters everywhere in evidence. He came to be a strong advocate for the theory of the volcanic origin of basalt.

The many fine engravings in his sumptuous folio publication show mostly columnar basalt formations. The plate displayed shows a bridge over the Bridon river , which is near Vals and Antraigues in the Vivarais. Columnar basalt is everywhere, suggesting to Faujas-de-St.-Fond that the river was carving its way through an extinct lava flow.