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Decorah sits on top of a 470 million year old crater

River to River, hosted by Ben Kieffer

Hear about innovations in plastic "upcycling" research and two geologists' work to explain a mystery in northeastern Iowa.

Geologists refer to Iowa's rugged northeastern section as part of the Paleozoic Plateau. But there's a layer of shale in Decorah that had some geologists scratching their heads.

Shale is relatively abundant, accounting for roughly 70 percent of the sedimentary rock in the Earth's crust. But there's virtually no shale in the Paleozoic Plateau. This lead a team from the Iowa Geological Survey to try to get to the bottom of this strange formation. What they found was a meteor that crash-landed 470 million years ago.

On this episode of River to River, host Ben Kieffer speaks with two geologists about that crash, how it changed the landscape and the fossil record of the creatures that lived in the crater.

We also hear from Aaron Sadow, a chemist at the U.S. Department of Energy’s Ames Laboratory, about his team's workto develop new value-added means of recycling plastic.


  • Aaron Sadow, professor of chemistry at the Ames Laboratory U.S. Dept. of Energy
  • Paul Liu, retired geologist with the Iowa Geological Survey
  • Bob McKay, retired geologist with the Iowa Geological Survey
Ben Kieffer is the host of IPR's River to River
Zachary Oren Smith is a reporter covering Eastern Iowa