Journey with Joan

By Coggin Heeringa, Interpretive Naturalist, Crossroads at Big Creek, Inc.

Things are changing—some quickly and some with glacial slowness—at Crossroads at Big Creek, and this week our programs will reflect on some of those changes. So what is glacial slowness? Geologists estimate that during the last Ice Age, the glacier moved over the Door Peninsula at one to four inches per day—when it wasn’t stalled, which it sometimes was.

The topic of the family program Journeys with Joan at 1:00 on Monday, July 28, is butterflies, and  for them, change happens quickly. Participants will likely see monarch butterflies flitting among common milkweed blossoms, sipping nectar—though monarchs tend to prefer other flowers for feeding.

More likely, females will be searching for tender milkweed leaves on which to lay their eggs. Joan will explain that a monarch develops from a tiny egg about the size of a grain of sand to an adult butterfly in  29-32 days, depending on temperature. Other butterfly species may develop even faster, but in the grand scheme of things, it’s an impressively rapid transformation.

The next day, the Journey with Joan program will focus on glaciers—the iconic example of slow change. But the formation of the Great Lakes has been slow also.  The retreat of the last glacier began more than 10,000 years ago, and the landscape is still recovering.

The ice sheets were so massive that they depressed the Earth’s crust. When the ice melted, the land began to rebound, while the volume of water in what is now Lake Michigan fluctuated wildly for millennia. Today, the land around Sturgeon Bay is still rising a few millimeters per year, while nearby areas are sinking  ever so slightly.

On Wednesday, the Journey with Joan program will discuss caves, another testament to slow geologic change. Approximately two millions of years ago, glaciers scoured away the overlying soil and rock, exposing the region’s Silurian dolomite bedrock. Since then, slightly acidic rainwater—formed when rain mixes with carbon dioxide in the atmosphere and soil—has slowly widened fractures in the dolomite, creating the caves and sinkholes we see today.

Finally, our Nature Trek with Terrie will transform participants into “Nature Detectives.” Learners of all ages will explore Crossroads’ diverse terrestrial and aquatic habitats, searching for clues about who lives there, what they eat, and where they go.Looking ahead, on Saturday, September 6, the community is invited to further explore our habitats during the Second Annual Trails & Ales event. We encourage early registration—discounted pricing is available through the end of July. Proceeds support programming and outreach at Crossroads at Big Creek. For details and tickets, visit the Crossroads website.