Guettard (Sept. 22, 1715 - Jan. 6, 1786) was a French geologist and mineralogist who made the first survey to make a geologically map of France and to study the exposed rock strata of the Paris Basin.
He was first to identify several fossil species from the Paris area. Noting that certain plants occurred only in association with certain minerals and rocks, he travelled and mapped plant distributions and the occurrence of various minerals and rocks. The publication of his map in 1751 marks the beginning of the science of geology.
He also recognized erosion by running water, how subterranean water made caves and the battering of cliffs by the seas. He discovered the volcanoes of the Auvergne and the surrounding landscape shaped by past eruptions, cinder layers, old soils and solidified lava. From Today In Science History. image