Geology
Elephant Rock - East Bluff
Have you ever visited Devils Lake? If not, you should. Devils Lake is a natural wonder. It is as interesting as any other feature on our planet. One of my tour guides worked at the Grand Canyon as a park ranger a few years ago. He said the Grand Canyon is more scenic, but the Devils Lake area has a better story to tell. Want to hear one of the incredible, unbelievable, BUT TRUE stories about the Devils Lake area?
Drive in the north entrance of Devils Lake and you will be greeted by an emerald "tunnel" cut through a dense oak woodland. Around the first bend you will see something unusual for the Midwest–thick layers of a super-hard, pink rock called Baraboo Quartzite. The rock layers are not flat, like most rocks in the Midwest, but tilted at a 20-degree angle.
Pull your car off to the right shoulder. If you park on the bicycle trail to the left, the rangers will give you a ticket. Get out of your car an walk up to the quartzite. Touch it. Did you get the shivers? Geologists, like myself, get light-headed when we touch the Baraboo Quartzite because of its mind boggling story. Don’t think of it as rock, but as a time capsule to transport you to an alien world that existed in Wisconsin 1.7 billion years ago.
You are standing at the top of a mile-thick layer of quartzite. This tilted layer plunges deep below the town of Baraboo, Wisconsin, curves back to the surface, and re-emerges a few miles north of Baraboo. If you could pull the quartzite layer out of the ground, you would see that it is bent downward into a giant fold, just like a buckled piece of paper but immensely larger and thicker. The quartzite was crumpled into this shape by colliding continents 1.5 billion years ago.
How excited should you get when you touch the quartzite? The following hypothetical situation will give you some idea. Imagine you are digging in your garden when you hear a "clunk". You dig down to discover an ancient urn filled with papyrus scrolls. Would you be excited? Sure you would. You would call the media, your friends, everybody. "Get over here quick, I just found a 3,000-year-old urn filled with papyrus scrolls from a lost civilization."
The pink quartzite is like a "papyrus scroll", only its incredibly older. If you got excited about the urn, you should be ecstatic about the quartzite. If you know where to look, it will tell you about an alien red planet covered with sticky mats of iron eating bacteria at a time when Wisconsin lay on the edge of the continent.
Lets start our examination of the rock scroll by first figuring out its origin. By looking at the quartzite, you would never guess that it started its "life" as beach sand. It is easier to imagine when you learn that the sand got buried five miles inside the earth and the individual sand grains became tightly fused together under immense pressure. The quartzite is beach sand that got pressure-cooked. Under a microscope, the individual, rounded sand grains are still visible.
The quartzite is loaded with perfectly-preserved ripple marks. On the east bluff at Devils Lake you can see four layers of quartzite, each with a different orientation of ripples. This means that the wind and currents were moving in different directions on each of these days 1.7 billion years ago. When you visit Devils Lake, run you hand over the ripples and realize that you are touching one day in the life of the earth 1.7 billion years ago. This ancient story is beautifully and perfectly preserved. Our customers generally let out an "oooh, aaaah" when we tell the ripple story.
The ripples are preserved because the quartzite got baked, but not too baked. Most ancient rocks like the Baraboo Quartzite have been buried so deeply inside the earth that they’ve nearly been re- melted. When rocks get over-cooked, their story gets erased. The Baraboo Quartzite, however, was only gently "browned". It was cooked enough to preserve and solidify the ripples, but not enough to destroy them.
The story of the ripples is not over. There is another, more-incredible, message in the ripples. Did you know that ancient rocks, like the Baraboo Quartzite, are often loaded with ripple marks. Younger rocks, younger than 600 million years old, don’t have as many ripple marks. Do you know why? It has something to do with life (or lack of it) on our planet 1.7 billion years ago.
Bacteria were the only life forms in the ocean when the quartzite ripples were made. Bacteria are too small to disturb ripple marks. In modern-day oceans, the ocean bottom is home to all kinds of burrowing creatures–shrimp, fish, worms, clams, etc. As soon as ripples get buried in modern oceans they often get destroyed by the burrowing action of these animals, just like the soil in a field gets churned by earthworms.
The ripples in the quartzite didn’t get churned because there was nothing around to churn them. The ripples carry the signature of a time before life as we know it. Touch the ripples again and realize their incredible message. Time for another "ooooh, ahhhhh".
The concept of "billion-year-old quartzite" is hard to comprehend, even for geologists. The age is determined using a technique called "radiometric age dating". Unless you are a physicist, it probably doesn’t mean much to you. Fortunately, we can get a gut feeling for the age of the quartzite by looking at the quartzite itself. The Devils Lake area is one of the best places in the world to get a gut feeling for the age of the earth. You will not need a Ph.D. in physics to understand this story.
The Baraboo Quartzite juts out of the ground to form a 25 mile-long, 800-foot-high ridge. It forms a ridge because it is so hard and resistant to erosion. Devils Lake is located in a gorge cut through the midpoint of the ridge.
The eastern half of the quartzite ridge was overrun by the last glacier. The glacier acted like a giant piece of sand paper–thousand of feet of ice with boulders embedded in the bottom. As the ice slid forward, it scratched the top of the quartzite ridge and polished it to nearly a mirror-like surface. Even though the glacier melted back 13,000 years ago, you can still see your reflection in the polished quartzite. 13,000 years of wind, rain, frost and acids in the soil haven’t even taken the shine off of the quartzite.
Now lets look at the quartzite layer we are standing next to at the north enterance. The quartzite layer angles out of the ground and then stops. It has been decapitated. How much time did it take to decapitate a mile-thick layer of quartzite that once extended high into the sky and connected with other quartzite layers across the Midwest.
If 13,000 years doesn’t even take the shine off the quartzite, how much time did it take to destroy a mile-thick layer of it? How does a billion years sound? Do you know how many 13,000-year periods there are in a billion years? There are seventy-seven thousand, 13,000-year periods in a billion years. It takes this long to get rid of the super-tough Baraboo Quartzite.
Now for the final chapter of our story and the most amazing part. I hope you are convinced that the Baraboo Quartzite is old. Do you know what is even older than the quartzite? YOU!!
The iron-eating bacteria that stained the quartzite red also developed some of the early chemistry of life. This chemistry still "ticks" in every cell of our bodies. Part of our DNA is inherited from these ancient bacteria. In a sense, you and I are living fossils–even older than the Baraboo Quartzite.
It took three billion years of life on our planet to develop human beings. We are the culmination of 3-billion years of evolution. We are part of an incredible, 3-billion-year, continuous chain of life. If anything had happened during this immense period of time to cut the chain of life, we would not be here. If the sun had burped in the direction of earth or if the meteor that killed the dinosaurs had been a little bit bigger, we wouldn’t be here.
We are incredibly lucky to have made it this far, yet human beings today are endangering the chain of life. We are punching holes in the ozone layer that shields us from the deadly rays of the sun, we are causing global warming with our emissions of greenhouse gasses, and, with genetic engineering, we are tinkering with the very basis of life. Unless we are careful, we will cut the chain of life.
Hopefully, by seeing the ancient rock "scrolls" and hearing their incredible story, we are more likely to appreciate how lucky we are to be here and less likely to fiddle with the chain of life!. Life is a precious thing. We shouldn’t waste a single minute of it.
I hope you enjoyed this journey through time. Next time you are in the Dells/Baraboo region, give us a call. We have many more incredible stories to tell.
- contributed by geologist Paul Herr
