Impressive wall map of Wisconsin, showing the state's geology and published at the start of the twentieth century.
This geological map, produced by the Wisconsin Geological and Natural History Survey, shows some fifteen different types of strata and their distribution around the state. Below the map are three cross-sections, running across the state at different levels. Explanations of the strata appear in the lower left, while a detailed essay describes the geological history of the state.
The geology of Wisconsin is characterized by its position in the North American craton, a vast swath of old and strong crust that has not seen much deformation in the last several hundred million years. As such, most of the strata and structures in the region are very old. The youngest non-drift deposits on the map are Devonian in age, or over 350 million years old. Some rocks in the region predate the Cambrian and the evolution of animal life.
The map was produced under the direction of William Hotchkiss, who was a state geologist between 1909 and 1925. He was in charge of surveying with regard to economic geology in the state, as well as the building of early highways.