Current Issue -

Decorah History: Deep Time Edition

By Clara Wodny | Summer 2025 Inspire(d)

While the discovery that Decorah sits atop an ancient impact crater and was once home to the world’s oldest-recorded sea scorpion, Pentecopterus decorahensis, may seem like old news (literally!), the excitement surrounding this fascinating history is alive and well.

In fact, Decorah even has its very own crater “taskforce” – a small, informal group of local scientists and crater enthusiasts. Dedicated to public education and outreach, taskforce members recognize how important and unique it is for residents and visitors of Decorah to be aware of the area’s history and timeline, and to understand how a connected, invested community made it happen. 

“From the beginning to where we are now, these incredible discoveries required collaboration among people of all different backgrounds and from all walks of life,” says Birgitta Meade, a local Winneshiek County Instructor in Environmental Education.

The whole story from initial hunch to published scientific findings unfolded in about 20 years – warp-speed in the world of science. In 2004, amateur geologist and long-time Decorah resident Jean Young was working with the Iowa Geological Survey to analyze stratigraphic data (rock layers) of well-drilling cores as a way of mapping local geography and helping to predict the best locations for constructing wells. In the Driftless area, the various layers of rock underneath the ground’s surface typically follow an established, predictable sequence. But Jean began to notice something odd – all of the samples within a 3.5-kilometer diameter circle contained mysterious layers of shale (a fine-grained rock primarily composed of clay and silt particles especially conducive to preserving fossils) that wasn’t present in any of the samples outside of that area. 

Jean wasn’t the first person to notice this unexpected anomaly, but when everyone else brushed it off and moved on, she honored her hunch that the shale was pointing her towards a bigger discovery and began to investigate. 

“That was the start of every crater-related discovery that has been made in Decorah,” says Laura Peterson, Professor of Environmental Studies at Luther College and a member of Decorah’s informal crater enthusiasts group. “We only know everything we do now because Jean paid attention to something that was unusual and didn’t match the expected pattern, and trusted herself enough to pursue that.” 

Eventually, Jean and her collaborators at the Iowa Geological Survey discovered copious amounts of breccia – a conglomerate rock made of fragments of many other rocks and minerals  – underneath the shale. Not only is breccia a problem for the construction of deep geothermal wells, as it can interfere with water movement and the way heat is transferred, it is also a strong indicator of impact events. It was one of the major pieces of evidence that led to the discovery of Decorah’s impact crater, which is estimated to be around 465 million years old. Jean passed away in 2007, but the impact, pun intended, of her dedication should be recognized in the Decorah community for, well, the rest of time.

The presence of the crater, which is buried around 100 feet below the surface of Decorah, is likely the reason that the layer of Winneshiek Shale, and all of the fossils encased within it, has been preserved in this area, even though it eroded away everywhere else. Currently, the area inside the impact crater is the only known location of Winneshiek Shale in the world. For the most part, the shale is deep enough underground that it can only be reached by taking core samples, meaning that only very small fossil fragments are able to be excavated. But Jean and her team were lucky enough to discover one area where the shale rose to surface level – the fact that it was underwater was not enough to deter them. They were able to dam the flow of water, allowing access to large portions of shale. This excavation led to the discovery of a wide variety of ancient creatures and organisms, many of which had never been documented before.

Pentecopterus decorahensis / Illustration by Clara Wodny

One such find, of course, was that of the Pentecopterus decorahensis, a giant six-foot long eurypterid (yew-RIP-ter-id) – the scientific name for a group of extinct marine arthropods that feature segmented bodies, jointed limbs, and a flexible organic exoskeleton. Pentecopterus decorahensis is the largest organism that has been found in Winneshiek Shale, and the second-largest eurypterid that scientists have discovered in the world so far. But that’s not all – one of the greatest contributions that Pentecopterus decorahensis has made to the discipline of paleontology is related to its extremely old age. As the oldest known eurypterid by nearly nine million years, this fossil confirmed suspicions that eurypterids evolved a lot sooner than had been previously estimated and documented.

Pentecopterus decorahensis is something of a celebrity in the Decorah area, especially since the arrival of a life-sized model, affectionately known as Scorpy, that now resides at Luther College. Decorah’s crater taskforce was thrilled when the model was able to permanently return to Decorah, providing a fantastic tangible resource to help locals and tourists learn more about the crater and its creatures. 

But why stop there? Steve St. Clair, a Decorah resident and member of the taskforce, had a vision for another Pentecopterus decorahensis model – one that would be able to withstand traveling and being touched. So, he reached out to the original Scorpy artist, Dennis Wilson of Pangaea Designs, and the new, more durable Scorpy will arrive in Decorah soon, with the intention of making appearances at various public events such as parades, school visits, and local festivals. 

The new Scorpy is just one step towards engaging the community in our area’s incredible history, and teaching future generations about all of the possibilities within the field of science. Hopefully, Scorpy’s story will inspire the development of future scientists who will carry on Decorah’s wonderful tradition of groundbreaking discoveries!

Clara Wodny


Clara Wodny is a 2025 graduate of Luther College, where she studied English and Visual Communications. She loves creating tangible expressions of community, both with words and stories as well as visual art. She can often be found elbows-deep in clay or printmaking ink and is excited to see where life after college takes her. 

    Check out the info & illustration by Clara Wodny below to learn even more fun facts and deep time history of Decorah’s impact crater and Pentecopterus decorahensis, aka Scorpy!

    Fun Facts about Decorah’s Crater & Scorpy!

    • Decorah’s ancient impact crater, one of fewer than 200 impact structures on the entire planet, sits about 100 feet below the earth’s surface. This means that the crater itself is not visible or present in Decorah’s current topology. Instead, the city’s bowl shape is a result of many years of erosion, rather than the meteor strike.

    • While it is true that there are a lot of cool, ancient fossils found inside the impact crater, the impact itself is not what killed or preserved them. Instead, they probably lived many thousands of years after the impact and are preserved in a mysterious layer of shale that includes rocks, sediments, and fossils from many different time periods, all combined into one. Because the shale was deposited in deep, oxygen-free waters, it provided unique conditions that allowed for the preservation of very fine fossil features.

    • Pentecopterus decorahensis might be the most famous organism extracted from Winneshiek Shale, but it is far from the only one. Conodonts are a fully extinct group of jawless marine vertebrates. Because the only portion of Conodonts that become fossilized are their teeth, scientists must study and compare these fragments to modern creatures that have similar features and body types and produce a series of reconstructions before landing on the best estimation of what the creatures may have looked like.

    • The term “Sea-Scorpion” is simply a nickname for the Pentecopterus decorahensis, because it looks relatively similar to modern-day scorpions. In reality, it does not share a close genetic relationship with them. It is actually an Eurypterid (yew-RIP-ter-id) – the scientific name for a group of extinct marine arthropods that feature segmented bodies, jointed limbs, and a flexible organic exoskeleton.  Pentecopterus decorahensis belongs to the same category as creatures like insects, shrimp, and lobsters, and is probably most genetically similar to a horseshoe crab.

    • The crater is often estimated to be around 465 million years old, but this is just a rough guess. Calculating a more exact age of the crater would require a dating process that involves analyzing little bits of sand called zircons– molecules that essentially had their atomic clocks reset by the impact.

    STAND ON THE ‘POINT OF IMPACT‘

    In Van Peenen Park in Decorah, there is now a large bronze medallion, set into a concrete base, that marks the scientific ‘point of impact’ from the meteor strike 465 million years ago. The Decorah Impact Crater sits many layers far below the current ground level (about 300 feet below the marker – one of the highest points in the crater circle, in fact!). It’s a short, pretty hike to the spot.

    Here’s how to get there: 

    • Park at the main entrance to Van Peenen Park off of Quarry Hill Road in Decorah• From the park informational kiosk, take the Higinn Trail loop (a 1.7 mile round-trip trek) to pass right by the impact marker. This off-road trail includes slight elevation changes. 

    • Dress for the weather and conditions, avoiding times of mud if possible.

    VISIT SCORPY!

    The current Pentecopterus decorahensis model lives in Valders Hall of Science at Luther College, and you can check it out and learn more about Scorpy! Here’s how:

    • Go to Luther College’s main entrance / 700 College Drive, Decorah

    • Stay left for Upper Campus.

    • Park in a visitor spot near the first building on the left, Sampson Hoffland Laboratories. 

     •  Enter SHL.

    • In the lobby of SHL, stay right to enter Valders Hall of Science.

    • See “Scorpy” on display in the hallway!

    Go to visitdecorah.com/decorah-impact-crater for more Impact Crater activities!

    Listen to a great Rhymes With Decorah Podcast interview with Birgitta Meade by Inspire(d)’s Benji Nichols at benjinichols.podbean.com/e/jyoungcrater

    Effigy Mounds Marching Bear Group / Photo courtesy NPS

    Summer Learning is Cool!

    Did you love learning about Scorpy? Well, get excited, ‘cause there’s always more to learn more about the natural world! Here’s a short list of some of our favorite educational places to visit in the Driftless – add them to your “to-explore” for this summer season!

    The Driftless Region is home to many great things – one being the only National Monument in the entire state of Iowa. Effigy Mounds National Monument, located on Hwy 76 north of Marquette, is the site of 200 plus American Indian effigy mounds, built between 800 and 2500 years ago. Effigy Mounds is open every day in the summer, 9 am to 4:30 pm, with daily guided tours and programs. Learn more and plan your visit at nps.gov/efmo

    Driftless Area Education & Visitor Center is well-worth a trip. Located on the banks of the Mississippi near Lansing, Iowa, the 10,000-square-foot center includes super cool cultural, recreational, natural, and historical exhibits. Check allamakeecountyconservation.org for workshops, special hikes, backwater paddling trips, and more! Open Monday-Friday, 8 am to 4:30 pm, Sat-Sun. 12-4 pm. More info at facebook.com/AllamakeeCountyConservation or
    563-538-0400.

    Clayton County’s Osborne Nature Center features a native wildlife exhibit, walking trails, open shelters, a welcome center, and more. Located five miles south of Elkader, Iowa, on Hwy 13,  folks can check out the outdoor nature playground, hike the trails, and fish along the Volga River as well. Clayton County Conservation also hosts fun Trail Runs, day camps, Heritage Days, and more. Summer hours: Mon-Sat 8 am-4 pm and Sun 12-4 pm. Learn more at claytoncountyconservation.org or 563-245-1516

    Driftless Area Wetland Centre’s mission is to connect people of all ages to the natural world and empower them to positively impact their local environments. We love that! The visitor center features wetlands, prairie, wildlife displays, and more. Located near Marquette, Iowa, it is open Tues-Sat, 11 am – 4 pm. Learn more (and check out the kids’ day camps!) at driftlessareawetlandcentre.com or by calling 563-873-3537.

    International Owl Center in Houston, Minnesota, works to make the world a better place for owls, and you can learn how to help at this neat education center! We suggest you visit for one of the three daily owl programs. There are usually live birds present each day, as well as fascinating owl displays. Summer hours: Friday – Monday, 10 am – 5 pm, with educational programs at 11 am, 1 pm, and 3 pm daily. Learn more (and see the 24/7 live owl cam) at internationalowlcenter.org or by calling 507-896-6957.

    Pin