Students on a field trip complete a scavenger hunt in The Northwoods ROCKS exhibit at the Cable Natural History Museum. Photo by Joshua Hintze.  

Thirty second graders tumble off their big yellow bus and onto the sidewalk in front of the Museum. Hot sunshine makes it feel like summer, and after tomorrow, (their last day of school) it will be. “Welcome to the Cable Natural History Museum,” I shout over the noise of traffic and excitement. “Check out that big banner. What’s the biggest word up there?” I ask pointing to the front of the Museum.  

“ROCKS!” They answer as a group.   “Raise your hand if you like rocks,” I command, and suddenly a forest of fingers waves vigorously. With big smiles, Kali and I walk the students into the Museum’s classroom. Kali is a very recent graduate of Northland College’s geoscience program, and is one of our two summer interns. Kali is helping to lead our school field trips about…ROCKS!  

The learning starts with a skit that Kali and I designed to cover about 3 billion years of geologic history in Northern Wisconsin. “BILLION?” the kids exclaim, suitably impressed. Yes, billion. Three billion years ago the first continents were forming, including a small continent that would become the heart of North America. That Superior Continent bumped into another small continent.  

At this point Kali and I kneel at either end of a large sheet of cardboard painted dark brown. “Do you know what happens when to continents bump into each other?” I ask the students. A girl in the back acts it out with her hands experimentally, fingers meeting, then steepling upward. “When continents bump into each other they push up mountains like Mount Everest!” Kali and I each push an end of the cardboard toward the middle, and a well-placed fold pops up, tenting into a peak.  

“Those continents pushed up huge mountains right here in Northern Wisconsin. They were so big that their peaks were covered with snow.” At that point Kali drapes a piece of pure white flannel over the cardboard mountain. “They were bigger than the Rocky Mountains, and maybe bigger than Mount Everest, too. And they were RIGHT HERE.”  

At this point in the skit, I take a look around the room to watch eyes go big and round, foreheads crinkle in thought, and heads shaking in disbelief. Geology is astounding, that’s one reason Kali and I both studied it at Northland.   “A couple billion years later (give or take) something else happened on this new continent,” I continue. “It started to rip apart. The crust stretched and thinned.”

At this point, Kali pulls a section of the brown cardboard “continent” away, revealing swirling shades of red and orange in the gap. “Lava pushed up from within the Earth,” I continue, “broke through the thin spots, and volcanoes erupted TONS of lava into the area where Lake Superior is today.”  

“That lava cooled and hardened into a dark gray rock we call basalt. Have any of you picked up a dark gray rock off the ground?” Heads nod. “That rock was molten lava 1.1 billion years ago.” Eyes go wide.   “

After that lava hardened, rain, snow, ice, wind, and gravity started to break the high places into smaller pieces and wash them downhill. Have you ever seen water carrying sand and rocks away?”

Some students nod more vigorously than others while I pull our cardboard mountain flat, and Kali whips out another piece of carboard to cover up the lava. This sheet is painted tan with speckles to represent the sandstone that formed in the rift basin that would become Lake Superior. “So much sand piled up that it squashed together and turned into sandstone.”  

“Finally, many years after that,” I continue, “huge mountains of moving ice came down from Canada.”

Kali hands me a pale blue bed sheet and asks for four volunteers. Once a student is holding each of the corners, we have them carry the sheet down the length of our cardboard continent. “Those glaciers scraped across Northern Wisconsin, flattened off the high spots, broke the rocks into pieces, and carried the pieces away with them,” I narrate as the student-powered glacier moves.  

“And then, when the glacier finally melted…” at this point Kali and I quickly flip over our brown cardboard and swirl the glacier sheet off to the side. This reveals a green landscape dotted with small lakes and a sinuous river. “The glacier left behind the lakes, rivers, and hills we see today.”  

“How many of you like to go fishing? Paddling? Tubing? Mountain biking? Skiing? Four-wheeling?” Little hands raise and wave excitedly when I call out their favorite recreation. “The lakes and rivers and hills that make those activities so fun in Northern Wisconsin are all thanks to the way that the glaciers and geology shaped our landscape!”  

After that, I take the students into our new exhibit “The Northwoods ROCKS: Where Geology is the Foundation for Fun,” to learn even more.  

Raise your hand if you like rocks…awesome! You’re invited, too!  

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too. For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our new exhibit: “The Northwoods ROCKS!” is open now! Our Summer Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.