Did Glaciers Make Devil’s Lake?

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“Did the glaciers make the lake?”, Well, that’s one of the most common questions asked about Devil’s Lake. Good question. I mean, in school we’re all taught about glaciers in a very general sort of way, and we know they covered parts of Wisconsin and there are signposts with mammoths all over the place.  It’s no surprise folks think that the glaciers made the lake, but no, the story is just a bit more complicated than that.

Let’s start with the bluffs surrounding the lake which are part of the Baraboo range, or as we say, the “Baraboo hills”. They were here way, way, way before the glaciers we all know and love. In fact, the Baraboo hills are what’s left of eroded mountains and are about 1.6 BILLION YEARS OLD! They are older than the Rocky Mountains and older than the Himalayas!!  They are so old, that you won’t even find fossils of dinosaurs in the rocks. The dinosaurs weren’t even around back then!

Now, the very short story is that when all the earth’s land was a single continent called Pangea, tectonic plates came together and slowly pushed up our mountain range. They were much bigger once upon a time than what you see today. What you see now it what’s left over eons of erosion.

(Map is modified from Paleogeography and Geologic Evolution of North America, by Ron Blakey.

(Map is modified from Paleogeography and Geologic Evolution of North America, by Ron Blakey.

At another point far back in history it is believed that our bluffs were covered by a shallow sea then slowly the sea receded and they were dry once again. We can see remnants of this all over the bluffs in the form or ripple marks left in the stone. These “ripples” where once the sand on the shallow floor of the sea.  You can see modern ripple marks being created right now on the beaches of Devil’s Lake.  Just walk into the water and look beneath your feet! It’s even thought that in another slice of time, much of central Wisconsin was a desert scoured by high winds and sand! So many stories over so many years!  A billion years is a long, long time…

As the millennia rolled on, now some 500 million years ago, Pangea was breaking up and the Baraboo hills (parts of them anyway) were islands in an archipelago that jutted out into a tropical sea. Way back then, the North American continent was turned sideways.  What we see as facing south today, was actually facing west.  (See the map above.)  It is believed that at that time, the gorge where Devil’s Lake sits was actually a thin channel between 2 islands created in part by the east and west bluffs. Back then powerful tropical storms and massive waves tossed onto the shore. We can see those rocks are various places along the east bluff trail, now frozen in time.

If you spin the clock ahead again, time will cover, uncover, recover, freeze, thaw, dig out and freeze again the bluffs over millennia until about 10,000 years ago during the last Ice Age. (That’s the one everyone talks about).  At that time a river (Probably not the Wisconsin River we see today!) flowed through the gorge we call Devil’s Lake. While up to 2 miles high further north, the glacier was on its last legs when it arrived here and the Baraboo hills actually got in the way.  The Glacier wrapped around the bluffs and dammed up the river on both the north and south ends.  These dams are called “terminal moraines” and you can see them both quite clearly today.

The melt water of those old glaciers are long gone, evaporated and recycled all over the earth. The water in the lake today comes from modern sources, rain, springs and a small stream on the south-west end of the lake.  That doesn’t stop it from feeling cold as glacial melt water some days!

You see, the Baraboo hills and Devil’s Lake were created and molded over a billion years through many upheavals. They’ve traveled the world on moving tectonic plates, sat at the bottom of warm, tropical seas and survived many glacial periods. Certainly, the last glacial period, over 10,000 years ago, has done a lot to shape our part of Wisconsin but the place we call “Devil’s Lake” has been around in one form or another much longer.

** Credit goes to Charles R. Van Hise, Paul Herr, Ken Lange, Sue Johansen, Keith Montgomery, Alton Dooley and a host of other researchers, writers, bloggers, naturalists and geologists whose concepts I’ve generalized and mangled to create this very short overview of Devil’s Lake State Park geology…

Read On!