The Place of Glaciers in Natural and Cultural Landscapes

In the fi rst half of the nineteenth century, glaciers taught us a great lesson about the earth. In the 1820s and 1830s, Swiss naturalists established the existence of the Ice Age. Their key insight was the fact that the small glaciers found at high elevations in mountainous regions were remnants of vast sheets of ice that once had covered large portions of the earth’s surface. They combined many sources—Alpine villagers’ intimate knowledge of mountain landscapes, earlier research by other geologists, and their own extensive explorations—to document the remote periods of the past, when areas that now are towns, fi elds, and forests had lain under miles of ice. Once they understood that this now-vanished ice had transformed the earth’s surface, they were able to explain features such as the parallel scratches found on rock faces that were engraved by glaciers and the long walls of rocks, stretching across valleys, that were carried by glaciers. Later researchers traced multiple Ice Ages and linked them to the cyclical fl uctuations in the earth’s orbit. This fi rst lesson, then, was of the dynamic quality of the earth. Geologists found common elements in the study of the ice sheets and other discoveries that were made 1