The purple cliffs standing over Devil’s Lake are Baraboo quartzite, sand laid down and then pressure-welded roughly 1.7 billion years ago, making this some of the oldest exposed rock in North America and one of the most important geological sites in the Midwest. The glaciers dammed the ends of an old gorge to make the lake. This is a STATE PARK: collecting is not allowed, but as a place to read a billion and a half years off a cliff face it has few equals.
Quartzite (Baraboo Range)
See it on the map
Other places on the map within a couple of hours.
