1725-1815

French geologist who demonstrated the volcanic nature of columnar basalts in France's Auvergne region (1765), thus establishing that not all rocks are sedimentary. This was in opposition to Abraham Werner's neptunian theory. Desmarest's most original contribution to geology was a history of eruptions and lava flows from Auvergne's volcanoes (1775). His three-stage physiographical history extended historical geology to volcano studies. As an agent of the French department of commerce, Desmarest served as Inspector of Manufactures at Limoges (1788-91).