Roy Plotnick has a new post over on Medium. This one is about the Chicago's rich geological history. There is a list of significant sites near Chicago that can be visited easily... even during a pandemic.
I recently participated in a workshop on America’s Geoheritage. What is geoheritage? One definition is that this an area with geologic features with “significant scientific, educational, cultural, and/or aesthetic value.[i]” One form of geoheritage sites is: “places where geologic features or landscapes played a role in cultural or historical events”. Although there is an unofficial list of geoheritage sites maintained by the National Park Service[ii], the naming of such sites is still in its infancy (thus the workshop). Many locations in Chicago and the surrounding region are prime candidates for eventual designation as culturally and historically significant geoheritage sites. I will discuss some that can be easily visited, even during a pandemic.
The geology and topography of Chicago were shaped by two major episodes in geologic history, separated by hundreds of millions of years. Some 420 million years ago, during the Silurian, the region and indeed most of North America was covered by a shallow tropical sea. Like shallow tropical waters today, in places reefs grew to the surface. Huge deposits of lime mud were deposited, which were transformed over time into the carbonate rock dolomite. These rocks have great economic value; they can be used for building stone, as gravel, or processed to form cement and plaster. Since these deposits were located close to the surface, numerous quarries sprang up across the region as the city grew. The oldest and longest surviving of these was the Bridgeport (Stearns) Quarry, located near 27th and Halsted St., which opened in 1833 and remained operational until 1970, when it was purchased by the city. Reaching a depth of 350’ and conveniently close, the former quarry was an ideal landfill site. After reaching capacity, it was transformed into an inviting park (Palmisano Park) that opened in 1998. One of the remarkable features of the park is a portion of the original highwall of the quarry, that you can go up to and touch in one area.
