MAGNIFICENT MILE — Even though it was built 90 years ago, Tribune Tower building is much, much older than that — if, like any good paleontologist, you look at its "bones."
The stonework used in many of Michigan Avenue's largest, oldest and most striking buildings tells a story about the environment in Chicago hundreds of millions of years ago, and that's not a coincidence, said Asa Kaplan, who leads a fossil tour down Michigan Avenue several times a year, including one on Saturday.
"What's great about looking at rocks that are used for buildings is they're almost always local rocks, because if you look at the cost of rock, there's getting them out of the ground, and then they cost a ton of money to transport," Kaplan said. "So everywhere you go, the buildings that you look at are made of the local heritage. They represent what used to be happening right here 200 million years ago."
A Flossmoor native now living in Pulaski Park, Kaplan studied paleontology at the University of Michigan, but eschewed academia in favor of spreading his love of fossils and geology outside the field.
"Academics, all they do is write journal articles and then occasionally come out into the light of day to talk to a few people about their work," Kaplan said. "I respect that that institution is needed, but man, do we need integration into daily life. So I'm trying to help out with that."
When he moved back to Chicago in 2009, Kaplan started researching the history of the stonework in downtown Chicago, tracing the heritage of slabs he spotted on walks down Michigan Avenue that looked more like fossils than concrete.
In 2011, he launched his fossil tours, which start at the Millennium Monument in Grant Park.
There are many buildings within walking distance that are made up of fossils. How so? "Any piece of stone containing remains of past life is a stone that contains fossils," he said. " ... It may be hard to accept this as the reality of every block of stone making up buildings you walk past every day, but it is so: They are made literally and entirely of fossils."
Buildings with stones "composed entirely of animal skeletons" include the bridgehouses, Chicago Cultural Center and the Tribune Tower, he said.
While the Tribune building is well-known for the embedded fragments from famous structures from around the world, including the Pyramids and the Great Wall of China, the stone blocks making up most of the building are 300-million-year-old Indiana limestone.
The tour also includes Water Tower Place, where a giant slab of limestone inside the Macy's entrance had rings that looked familiar. Kaplan later identified it as a fossil from the Cretaceous period.
Another building with examples of fossils that are millions of years old is the Pittsfield Building, 55. E. Washington St., which contains ammonite —an extinct, shelled relative of squid and octopus — near its entrances.
Fossils are everywhere, he says.
"I'm encouraging people to always be looking critically," he said. "Your windowsill is probably made of fossils."
Kaplan said he initially aimed his tours towards adults, but has had lots of interest from families and success with children. "You say the words 'fossil' and 'poop' together in a sentence, they love it," he joked.
He says the tour's material is suitable for all ages and contains some information that will be new even to amateur geologists and life-long Chicagoans.
"I don't want fossils to be something that you only see in a museum," he said. "I want our relationships to be something that you can experience as you're walking down the street."
Ticket's for Saturday's 1 p.m. tour cost $15 per person. Saturday also marks the last day of Earth Science Week, which included "Fossil Day" Wednesday.
Participants are encouraged to bring in rocks or fossils they'd like to identify.
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