Devils Lake: A Billion-Year-Old Landscape
Near Baraboo, Wisconsin
South of Baraboo rise the pink and purple cliffs of Devils Lake, and the rock within them is almost unimaginably old. Geologists call it Baraboo quartzite, and they date it to more than one point six billion years, making these some of the most ancient rock outcrops in all of North America. It began as ordinary sand, washed by rivers into shallow seas, pressed into sandstone, then squeezed and baked under enormous heat and pressure until it hardened into quartzite, a rock so tough it resists nearly everything nature throws at it.
These bluffs form the Baraboo Range, the worn-down remnant of mountains far older than the Rockies or the Appalachians. The lake itself is much younger. About fifteen thousand years ago, near the close of the last Ice Age, a lobe of the Wisconsin glacier pushed up this ancient river valley and stopped.
When it melted, it left behind ridges of rock and gravel, called moraines, plugging both ends of the gorge like earthen dams. Water gathered in the bowl between them, and Devils Lake was born, a deep, clear lake with no natural stream flowing in or out. Today it anchors the largest and most visited state park in all of Wisconsin.
