Geir Hestmark (UiO): Discovering the Ice Age - nature as a historical source

The discovery of ice ages counts among the greatest breakthroughs in the Earth sciences and our understanding of dramatic climate changes. The pioneer contribution here was Danish-Norwegian geoscientist Jens Esmark's 1824-paper on the Scandinavian ice age, a totally new reading of the Nordic landscape. The genesis of his paper has however remained much of a mystery due to the parsimony of the published record and the scarcity of unpublished written sources. To understand both what he discovered, and how he made his discovery, I here take a closer look on the observational basis of his claims, in other words on 'nature itself', and discuss the significance of essential locations also for the meta-perspective of the historian of science. An important part of the inquiry was the actual identification and confirmation of Esmark's locations, many which have remained unknown until now.