Written in Stone: Exploring the Geology of Door County

By Lynn Michelsen, Business Manager, Crossroads at Big Creek

Door County’s landscape is written in stone. From the towering bluffs along the bay of Green Bay to the smooth rocks scattered across Lake Michigan beaches, the peninsula’s unique character was shaped hundreds of millions of years ago. Ancient tropical seas deposited layers of limestone and dolomite; glaciers sculpted the land, and wind and water continue to shape it today. This week’s Summer at Crossroads theme, Rocks, invites visitors to discover the fascinating geological story beneath their feet and explore how Door County’s rocky foundation influences everything from its caves and cliffs to its forests and wetlands.

The week begins with a Tale. At 2 pm on Monday, July 27, Door County Librarian Beth Lokken will read “When You Find the Right Rock,” written by Mary Lyn Ray and illustrated by Felicita Sala. Through vibrant illustrations and thoughtful, evocative text, this story encourages readers to discover beauty and meaning in something as simple as a stone. From mountain paths to lakeshore beaches, each rock carries a story and invites us to slow down, make connections with the natural world, and appreciate small discoveries. For those unable to attend Story Time, the pages of the book will be featured on our Trail Tales storybook walk all week long beginning at the West Trailhead.

On Tuesday, July 28, at 1 pm, Journeys with Joan will explore Rocks & Caves of Door County. Naturalist Joan Wilkie will guide participants through the geological history hidden just below the surface. From the dolomite bedrock of the Niagara Escarpment—the very feature that helped create Door County’s distinctive shoreline—to caves, crevices, and cliffs shaped by water and ice, participants will discover how sedimentary rocks form over time and how erosion continues to shape the peninsula today.

At 1:30 pm on Wednesday, July 29, hikers joining Wandering Wednesday will hit the trails with a naturalist for a guided hike on the trails. Explore the beauty of Crossroads at Big Creek while learning about the plants, animals, and natural communities that make this landscape unique. Along the way, hikers will discover seasonal highlights and gain a deeper appreciation for the natural environment that surrounds them.

Thursday’s 2 pm Talk on July 30 features Brian Forest of the Door County Land Trust presenting Geology 101 – Learning Rocks. This hands-on program will introduce participants to the three major rock types—igneous, sedimentary, and metamorphic—and explain how they form and what they tell us about Earth’s history.

Focusing on Door County’s geology, Brian will explore how limestone and dolomite bedrock, along with glacial deposits, influence the peninsula’s landforms, soils, groundwater, and ecosystems. Participants will gain a deeper understanding of how these ancient geological processes continue to shape the places we love to explore today. Whether you’re new to geology or simply curious about the rocks beneath your boots, this program offers a fresh perspective on familiar landscapes.

Throughout the week—and all summer long—visitors can also enjoy Tinkers, our self-led, hands-on activities designed for curious minds. Guests can sort and examine different types of rocks, compare textures and shapes, and participate in simple challenges that encourage observation, classification, and discovery.

As visitors explore Door County’s landscapes this summer, they may also want to mark their calendars for Crossroads’ annual Trails & Ales event on September 12, combining great beer, local food, live music, and the natural beauty of Crossroads’ trails. Early Bird tickets are available now through July 31, offering a chance to save while supporting Crossroads’ mission of connecting people with nature. Learn more and purchase tickets at: https://www.ticketsignup.io/TicketEvent/TrailsandAles.

Rocks may appear still and unchanging, but they are part of a dynamic Earth system. Formed through heat, pressure, time, and the movement of water and ice, they provide the foundation for every ecosystem. In Door County, that foundation is especially visible—etched into beaches, bluffs, caves, and shorelines that tell a story far older than human history. By learning about rocks, we gain a deeper appreciation for the landscapes that shape our community and the life that depends on them.

Thanks to the generosity of our donors, we can offer free programming for all ages and our trails are open all day, every day, free of charge.