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Abstract

Every book containing some historical volcanology tells the same story: Jean-Étienne Guettard, studying the geology of Auvergne, was the first to postulate, in 1752, that basaltic rocks were the products of ancient volcanic activity. However, expedition diaries from two Jesuit missionaries, Eusebio Kino and Juan María de Salvatierra, and a Spanish captain, Juan Mateo Manje, tell another – forgotten – story. In 1701, they led an expedition through the Sonoran Desert in quest for a land connection to California, at the time still believed to be an island. They reached the area now known as the Pinacate volcanic field, which contains hundreds of cones, lava flows, and maars, over an area of 1500 km². The diaries of the three men contain descriptions of rocks showing, without ambiguity, that they understood perfectly their volcanic origin. Unfortunately, these writings took a long time to emerge from Mexican archives. In 1919, Kino’s life finally got some attention after historian Herbert Eugene Bolton translated his memoir in English. Twenty years later, Ives translated the diaries of Salvatierra and Manje and was the first to point out that the three men had understood the volcanic origin of the lava rocks they observed. But since then, Ives’ discovery has itself been forgotten. This presentation aims at unearthing it and, more broadly, at asking this question: in a world were millions of people have lived close to active volcanoes for millennia, is it reasonable to think that nobody ever made the connection between active lava and basalt?