The “Classification” of Mountains in the Alpine Region during the 18th Century

One of the most significant topics of the history of geology in the Alpine region is the question as to how the primarily structural "classification" of formations and mountains began in the late 18th century to incorporate the sense of geohistory that the formations recorded. Some recent studies on the 18th century scientific literature and unpublished primary sources on the Alps and the pre-Alps have shown that rocks and formations were central elements in a "proto-stratigraphy" which was not yet based on the prominent use of fossils. During the second half of the 18th century, German, Italian and Swedish geologists and mineralogists developed the first classifications or sub-divisions of mountains, which also included the classification of their different rock types. These sub-divisions supported the idea of the relative chronology of the sequence of the studied strata. Consequently the most recent or the most ancient formation could be deduced not only from its position within the sequence, but also from its lithological and morphological features (such as, for example, folds or fractures). The terms "primary" or "primitive", "secondary" and "tertiary", which were used by the Earth-scientists for indicating categories of mountains, were also used for stratigraphical units, rock-units and formations. The "classifications" of mountains contributed to introduce the idea of geological time connected to a complex history of the Earth, also with providing a chronological scheme for the successive formation of different types of rocks that formed different kinds of mountains. The aim of this paper is to analyze and compare some significant 18th century studies on the Alpine and pre-Alpine region in order to evaluate their role within the early development of historical geology.