University Place

Wisconsin State Parks: Gateways to the Ancient Past

– Today we are pleased to introduce Scott Spoolman as part of the Wisconsin Historical Museum’s History Sandwiched In lecture series. The opinions expressed today are those of the presenter and are not necessarily those of the Wisconsin Historical Society or the museum’s employees, Scott Spoolman is a science writer who has focused on the environmental sciences especially those stories of natural science and the environment related to Wisconsin and surrounding states. He grew up in northern Wisconsin and after earning a master’s degree from the University of Minnesota School of Journalism he worked for several years as an editor in the publishing industry specializing in textbooks and other educational materials. Since 1996 he has worked as a freelance writer for a variety of outlets and has co-authored several editions of a series of environmental science textbooks. So please join me today in welcoming Scott Spoolman. (audience applauding)

– Good afternoon and welcome. And thank you for coming here tonight, today, it’s great to see you, it’s such a nice turnout. And thanks to the Wisconsin Historical Museum for hosting us. We’re here to talk about geology and natural history of Wisconsin as evidenced in our state parks. And that reflects the title of my book “Wisconsin State Parks: Extraordinary Stories of Geology and Natural History” published by the Wisconsin Historical Society Press. And I want to tell you how extraordinarily grateful I am to them for taking an interest in this book idea and I’m happy to have a few of them here today. One other person I’d want to thank is my wife, Gail, who’s in the back there. And she’s given me good feedback and some ideas that have been incorporated into the book. She’s also provided some nice snacks back there. And she’s also been a great coach, she’s coached me in these presentations. And she’s excellent, she’s really good. However, what that means is that whatever happens here today you can blame on Gail. I’ll talk about the history and the geology and the book a little bit and then after that we can have some time for questions and answers and a book signing if you’re interested. Just one more thing before we get started. I wanted to pay a tribute today to a great teacher and writer who recently passed away, Dr. Robert Dott co-authored the “Roadside Geology of Wisconsin. Among other great books including the definitive historical geology textbook called “Evolution of the Earth.” Those books were most helpful to me in this project as was Bob himself who graciously answered a lot of questions for me. So here’s to you Bob. People often want to know why I wrote the book and the main reason is that I’ve always been fascinated by Wisconsin’s various landscapes and beautiful natural settings.

My parents got me going on this when I was young by taking me to the places they enjoyed such as this beautiful little place called Morgan Falls up in the North Woods, up in Ashland County. This was the beginning of my exploration of the state’s beautiful natural settings. And since then, Gail and I have carried on the family tradition taking our kids to the places we like to go to including Devil’s Lake State Park. And we’ve all grown a bit since that picture was taken. These experiences have also helped to shape my career as an environmental science writer. One of the things that caught my eye a few years ago was this beautiful map produced by the Wisconsin Geology and Natural History Survey. It vividly shows Wisconsin’s diverse and distinctive landscapes. And it occurred to me that the zoom in on these areas and study them, one could use Wisconsin’s wonderful state parks as entry points. I think of the state parks as time portals or gateways to the ancient past. You walk through the gates of the park and travel back in time. And that idea fascinated me and I thought that by doing that by exploring the parks and telling their stories in a book I could share my fascination with Wisconsin’s geology and Natural History. I would bet that many of you will agree that what’s also fascinating is the enormity of the processes that shaped these various landscapes… such as the deep north, the deep woods of northern Wisconsin and the cliffs on Door County on the east side of the state. The Central Sand Plain with its buttes and spires and sandstone mounds. In the Driftless Area of Southwestern Wisconsin with its deep valleys and river bluffs. Understanding and appreciating these processes involves some key geological concepts.

And one of those is the immense time scale of the Earth’s history. I ask you to take yourselves out of our daily time frame that we divide into hours and minutes and seconds and smaller and smaller fractions of a second and to put yourself into a much larger frame that is measured in centuries and millennia and millions and billions of years. For our purposes today there are four spans of time that I want to focus on. First is the Precambrian age which is the first, excuse me, the first four billion of the Earth’s 4.6 billion-year history. And it involved continental collisions that built ancient North America. And in the Wisconsin region it involved volcanic activity and mountain building. The next period is a period of the invasions of the area by inland seas starting with the Cambrian Period. When life began to evolve in the first of those seas, the earliest of those seas that invaded our area. It was a 50 million-year span during which at least a couple of ancient seas invaded and then retreated from Wisconsin. And it was followed by about 135 million years of more invasions by inland seas and more accelerating evolution of the life that lived in those oceans. During the next roughly 400 million years, the last of the seas had departed and Wisconsin was more or less high and dry. Erosion took over as the main geologic force and erased the record, the fossil record of all of that time. So for example, we don’t know if dinosaurs roamed in Wisconsin during the Jurassic. I mean, we assume they did it, they probably did, but we don’t have any record of dinosaurs in our area, thanks to erosion, it’s all gone. And finally the two and a half million year Quaternary Period, the ice age, becoming the glaciers. And within the last 200,000 years the emergence of humans. These periods are all explained much more fully in my book in the introductory chapter which tells the bigger geologic story of Wisconsin. And gives an overview and introduces this and other key concepts that help you to fully appreciate the park stories. Another such key idea was the fact that for much of its history the Wisconsin region was tropical. I want to thank the UW Press for the use of this image. Author David Mickelson and his co-authors used it in their fabulous book the “Geology of the Ice Age National Scenic Trail” which some of you have probably seen. Early in its history the crust of the earth was fractured into several large pieces called the tectonic plates. And they were jostled and bumped around, jostle and moved around on the mantle of the planet which is the plastic hot rock that underlies the crust of the Earth. And the term plate tectonics refers to this movement of the crustal plates driven by the intense heat of the planet’s interior. The plate on Wisconsin road was south of the equator in Precambrian time. And it did kind of a curlicue path as it moved around over time across the equator which is right here. (laughter) Yes, it did. About 350 million years ago and continued on up to its current latitude between 70 and 10 million years ago. And we’re still moving by the way. Wisconsin is moving generally southwest now and about the rate at which your fingernails are growing.

[laughter] For this project, I divided the state into five geographic regions. Each park has its own story and for each region I picked the five or six stories that I thought best represented the dynamic processes that occurred in the regions. For example, in the northwest corner of the state. Copper Falls State Park was formed largely by a volcanic activity and that’s Brownstone Falls in that park. And the rocks underlying and all around that falls are volcanic. In the northeast corner of the state, the parks lie on the sediments of ancient sea creatures that were converted into very hard rock and then later unearthed by the glacier and other processes creating features like these cliffs that make Door County famous. This one is in Peninsula State Park. In the rolling countryside of southeastern Wisconsin, glaciers formed the landscapes such as this cone-shaped hill called a kame. This one is Dundee Mountain up at Kettle Moraine State Forest. In the south-central region several processes help to shape the land, many of them related to the glacier. For example, even during glacial times, during summer months, water flowed into cracks and crevices of rock and then during the very cold winters of that time froze and expanded and widened the cracks and crevices and eventually pried rock pieces apart. And over the centuries this freeze thaw cycle with its pickaxe effect literally sculpted rock features such as the Balanced Rock at Devil’s Lake State Park. The same process created the talus slopes of those piles of fractured quartzite that are draped along the cliffs up there at Devil’s Lake. And finally in the southwest corner of the state the Driftless Area where the glaciers never invaded, the slow steady process of erosion formed features such as Enee Point at Governor Dodge State Park.

This is a sandstone mass sculpted by wind and water erosion over uninterrupted from hundreds of millions of years. And that’s my son Will in the photo there, he was helping me that day. All of these processes are explained more fully in my book. I devoted a chapter to each of the regions that I just reviewed. Each chapter includes an introduction with more details on regional geology and natural history, followed by five or six park stories. Each story that in turn has an introduction that gives more details on the geology and natural history of the park area. And in many cases I also included some early human history explaining how Native Americans lived in the park areas and how they too viewed them as special and even sacred. For example, the Trempealeau Mountain up at Perrot State Park on the Mississippi River north of La Crosse. This has long been sacred ground to the Ho-Chunk and access to it is restricted in honor of that. Another area that is rich in Native American history is the Driftless Area covered in chapter three of the book. That chapter introduction includes some material that archeologists have found that tells the story of how people lived in the distant past. It’s extraordinarily good archeological information. And there are similar information from the other regions of the state as well. Now in the parks you will want to see the evidence of the geologists and scientists and historians have used to construct these park stories, and you can do that by hiking the trails. I’ve provided trail guides in my book at least one for each park. And these preview what you’ll see including rock types and formations and how things have changed over time. So right now let’s go through one of those time portals and we’ll hike through one of the parks going to Interstate Park. It’s the oldest of Wisconsin’s parks, a joint venture with the state of Minnesota established in 1900. What we’ll see as we go is a progression of extraordinary processes including volcanic eruptions, invasions by ancient seas, centuries of erosion, crushing glaciers and finally a catastrophic flood. The chapter in which this park is located is chapter two and the following paragraph from the introduction to that chapter sets the stage.

The northwest corner of Wisconsin was shaped by unimaginable forces of extreme heat and cold. Heat so intense that it melted rock deep in the Earth forced it to the surface and forged massive new layers of rock thousands of feet thick over much of the area. And cold so intense that it defied the sun, captured and froze the Earth’s water for centuries and built a crushing deep field of ice that spread over most of the state. The interactions of these great masses of rock and ice were largely what created the fascinating landscape of northwestern Wisconsin. Chapter two, the story of Interstate Park is in chapter two and it’s called the rift zone. The chapter introduction explains that a little over 1100 million years ago, that’s 1.1 billion years ago, a massive plume of magma or hot liquid rock rose up from deep in the Earth toward the crust where it pried open this long crevasse called the Midcontinent Rift. It stretched from lower Michigan all the way up through what would be the Lake Superior basin and then southwest all the way down into Nebraska and Kansas. This rift could have split the continent in two just as another earlier rift split another earlier ancient continent and created the Atlantic Ocean. And you notice the long ridge that lies along the center of that oceans floor, that was built of lava that was spurting from that rift. But something stopped the process in the Upper Midwest… probably a continental collision to the southeast that pushed everything back together again. But this rifting process was responsible for much of what we see there now in northwestern Wisconsin. Over a period of 25 million years lava spurted from the rift. And in northwestern-most Wisconsin the lava spread across a wide area that included Interstate Park which is right about there. Right in the middle of it all. That lava would become basalt, a dark-colored fine-grained very dense rock that underlies northwestern-most Wisconsin. Over those millions of years multiple flows of this lava built up to make a mass of basaltic rock that was up to 20,000 feet or nearly four miles thick in some areas.

The next major process that affected the Interstate State Park area was the coming of the Cambrian seas. Now during the Cambrian at least a couple of shallow seas invaded and retreated in the Wisconsin region and they might have resembled this mudflat area on the east coast of the United States. Now remember the area was, the area that would become Wisconsin was lying close to the equator was something like a tropical desert, there was no land vegetation. So untold quantities of sand were deposited by these shallow seas accumulating for millions of years. And eventually becoming layers of sandstone totaling thousands of feet thick. And this is an example of Cambrian sandstone. After the Cambrian period came more inland seas that deposited more sandstone but life was evolving in these oceans and becoming more diverse. In Silurian time, one of those periods that followed the Cambrian, the seafloor might have looked something like this right here in Wisconsin teeming with life. This is a diorama on display in the Milwaukee Public Museum and it’s really worth a trip over there to see this and all their other great geological exhibits. Seafloor life included a variety of shelled animals such as clinging brachiopods and crawling trilobites and these tall, flower-like things here. These are actually animals called crinoids or sea lilies and the chief top predator in that system was this long octopus looking like critter called cephalopod. The remains of these creatures collected on the sea floors for many millions of years and eventually became limestone which by chemical reactions was converted to something called dolomite. A harder rock more resistant to erosion and often rich in fossils. Now all of Wisconsin was once covered by dolomite and much of it has been eroded away during that long period of erosion, exposing the older, deeper sandstone in some areas including the Interstate Park area.

Eventually forests covered the land and the area around Interstate Park was a rolling forested plain lying on land stone, just lying on sandstone, just before the glaciers came. This is actually a picture of the Wisconsin River Valley, I took that photo in Wyalusing State Park. But before the climate cooled and the glaciers arrived the ancient St. Croix River Valley might have looked something like that. Well then came the glaciers. There were several glaciers during the roughly two and a half million-year Ice Age. Some of you all just think as many as 15 major ice sheets flowed down from Canada. But the most recent one is called the Wisconsin Glaciation because Wisconsin contains some of the best examples in the world of what a glacier can do to the land, how it can change the landscape. This glacier entered Wisconsin about 30,000 years ago. And at its peak the ice sheet over Interstate Park was well over 1,000 feet thick, so that’s roughly the height of the Empire State Building. And it might have looked something like this glacier in Greenland. Eventually the climate warmed again and the glaciers began to melt. It retreated in fits and starts and finally melted out of the northernmost part of Wisconsin between 11,000 and 10,000 years ago. An interesting side note, if you did the math, you realized that that glacier just the most recent one, the Wisconsin glaciation was in the state for 20,000 years. That’s about four times as long as the all recorded human history, so it gives you some perspective. Now when glaciers melt away the melt waters form lakes called glacial lakes in low-lying areas. And big glacial lakes can form against the retreating ice wall and sit for centuries, thousands of years in fact. One such lake was Glacial Lake Duluth which occupied various portions of the Lake Superior basin for centuries. At its southern end was a dam made mostly of ice with some rocks and sand and gravel from the glaciers, and it was located about 80 to 100 miles north-northeast of the Interstate Park area which is right here. With the climate warming and the ice melting that dams days were numbered. And when the rising glacial lake waters finally overwhelmed the dam, the resulting flood was a catastrophic force of nature.

Icy melt waters roared down this valley of the ancient St. Croix River. When the flood from the glacial lake arrived at the park area it probably engulfed all of is now Interstate Park. It tore away much of the softer sandstone and then went to work on the underlying basalt bedrock, the harder rock. Began chiseling at this basalt by working at its vertical cracks. And chunks of the basalt would come loose and be tumbled down the riverbed by the massive flood. And as the channel became deeper the water acquired more force and this chiseling digging effect became stronger and the carving quickened. In this way the icy blast of water dug a deep narrow gorge piece by piece. It probably took a few hundred years, which in geologic time is quick. And this was the result. And this is what I mean by going back in time. This little canyon at Interstate park called the Dells of the St. Croix was carved by that post-glacial flood that I just mentioned, described. And you can get this stunning view by hiking on a trail called the Potholes Trail. And on that trail of course you can also see some of Interstate Parks famous potholes. And this one is about five feet across and goes down about eight or nine feet. It was formed by gravel and rocks that got stuck an eddy of the massive flood and there were whirling ferociously against the bedrock for decades or centuries until this hole was literally drilled into the bedrock. There are many other potholes in the park and some of them are much bigger than, than this one. At this point on the Potholes Trail you are about 100 feet above the river.

And this is how we know that the post-glacial flood must have spread across the entire park for centuries, drilling holes here and there while it was excavating that gorge. When glacial Lake Duluth finally drained to a certain level, the river level also dropped leaving the potholes high over the river where they are now. Now a little south of the potholes on another trail called the Skyline Trail, you can visualize the great flood filling the valley. These little tick marks here represent the southeast rim of the valley, the ancient St. Croix River Valley or actually the current St. Croix River Valley. And this, the other, the northwest rim of the valley is along this highway in Minnesota. And Skyline Trail skirts the southeast rim of the valley. The Skyline Trail guide includes the following: “As you hike on the trail along the rim of the River Valley, imagine the great flood of ice water that rolled through filling the valley almost to the brim as the glacier retreated 10,000 years ago.” “The surrounding land would have been tundra, no forests, hosting only extreme cold weather species such as lichens, some grasses, stunted alder and spruce trees, musk oxen and caribou.”

And it might have looked something like this… current day meltwater flood going on in Iceland. From still another trail called the River Bluff Trail you can look across the St. Croix River for a good view of one of the walls of the gorge and the mass of basalt that was laid down over that 25- million-year period. This is just the top… Where’s my pointer? There it is. This is just the top 100 feet or so of a mass of basalt that’s probably thousands of feet thick at this point. And you can also see how the basalt was fractured into blocks by these vertical and horizontal cracks. Do you see the rock climbers in this photo? There’s one right in the middle going straight up, there’s one over here making an angular move. Notice those people are working their way up this rock face using those crack and crevices, some of which were formed long before humans even existed on the planet. Let alone before some humans decided it was a good idea to go climb rock walls. [laughter] Rock climbers love this kind of rock. So we’ve come to the end of our hike through Interstate Park. This is one of several pine groves that you can visit in the park. After the last glacier retreated, great pine forests became established over most of Wisconsin and stood for thousands of years as I’m sure you know. Since they were logged in the early 20th century, the forest in the park area has reclaimed the land and some nice stands of red and white pine like this can give you a sense of the ancient forest.

I’ll leave you with the following paragraph which reflects one of my most memorable experiences hiking in the parks. And this is from the Interstate Park story. What covers much of Interstate Park now is 2nd and 3rd growth forests that have their own remarkable beauty if not the majesty of the ancient pine forest. Nevertheless when you are hiking on one of the many trails in the park that passed through small groves of red or white pine, stop for a moment and close your eyes. Smell the scented air and listen for the delicate song of the wind in the pines. You might then imagine yourself to be in that vast deep forest that once stood here the top gravel and soil dropped by the glacier… on top of sandstone and limestone deposited by ancient seas. On top of bedrock laid down a billion years ago. Thank you.
(audience applauding)