Midwest Traveler: Fossil hunting at Iowa's Devonian Gorge and five more regional sites

Our next Iowa destination started as so many do. Grumbles. Eye rolls. Dramatic groans.

Anything remotely field-trippy is like offering teens a starlight mint you found under the car seat instead of a jumbo bag of  Takis. Admittedly, "Devonian Fossil Gorge" lacks the spark of "trampoline park."

Fortunately, I had instinct on my side. My kids like caves and cool rocks. A trip to South Dakota's Mammoth Site and a dinosaur dig in Thermopolis, Wyo., rank among our best family adventures. No way would I miss checking out this intriguing, scientific and free attraction.

The Devonian Fossil Gorge sits near a recreation area and campgrounds on the south side of Coralville Lake, created after the U.S. Army Corps of Engineers dammed the Iowa River five miles north of Iowa City and Coralville. Devastating floods in 1993 created the gorge when the river rose more than 4½ feet above the dam's spillway and tore away everything in its path, revealing the fossils once water receded.

"I found one! Come look!" came the excited, rapid-fire commentary from two 14-year-olds who wouldn't get out of the minivan at the visitor center. Even our untrained eyes could find treasures in this game of prehistoric "I Spy." We studied intricate hexagonal patterns left by colonial coral, tubular stems of crinoids ("sea lilies"), spirals of horn corals, and scallop-like ridges of brachiopods embedded in light-gray limestone and short walls.

The fossils had gotten harder to see until a second flood in 2008 sent water over the spillway again, scouring old fossils and exposing new ones, said Nicholas Thorson, a natural resource specialist at the dam.

The fossils help reconstruct life on Earth during the Devonian "Age of Fish" more than 375 million years ago — long before land mammals or dinosaurs. The planet had only two supercontinents, the Appalachian Mountains were just forming and "Iowa was a shallow, warm sea," Thorson said.

He estimated the sea depth at eight to 13 feet — shallow enough for plankton-filtering "sea lilies" and plants to grow up and out of the water as if in a vast wetland, but deep enough for armor-plated fish known as placoderms.

The Coralville Dam Visitor Center exhibits the gorge's most dramatic specimens, including a sink-sized ammonite, trilobites, cephalopods (shelled relatives of squid) and a section of skull from a Dunkleosteus, nicknamed "terrible fish."

"It was probably as long as a school bus," Thorson said of the armored fish. "It ruled the ocean."

To visit the gorge and see the fossils, consider going on a weekday when the Coralville Lake area and the popular campgrounds (1-877-444-6777; recreation.gov) are less crowded. For more information, call 1-319-338-3543 or go to www.mvr.usace.army.mil/Missions/Recreation/Coralville-Lake/Recreation/Devonian-Fossil-Gorge.

Here are some other noteworthy places to inspire prehistoric road trips and sneak in a science lesson that fuels imaginations:

In 2010, a 7-year-old girl found a saber-tooth cat fossil, renewing interest in the Badlands' geology. While there are no active dig sites for the public to observe, visitors can watch fossils being prepped in the paleontology lab in the Visitor Center from mid-June through early fall. Exhibits and images from the Oligocene Epoch more than 24 million years ago show relatives to camels and rhinoceroses, land turtles and three-toed horses, which once roamed the area. Rangers give talks on the Badlands' fossil exhibit trail twice daily and daily geology walks on the White River Badlands, which have been a source of fossil discoveries since the mid-1800s (nps.gov/badl).

Expect a hush of awe when entering this enormous active dig site where more than 60 mammoths died in a sinkhole on the southern edge of the Black Hills. It ranks as both the world's highest concentration of mammoths (mostly Columbian and a few woolly) and one of its most impressive paleo finds. In the museum built around the excavation that started in 1974, kids' paleontology programs let them excavate, identify, map and jacket fiberglass replicas of mammoth bones. The museum also has a hands-on component for younger kids and uses exhibits to reveal more animals from 26,000 years ago, including a short-faced bear (mammothsite.org).

Two hours south of the Mammoth Site and tucked into the Niobrara River Valley, a visitor center re-creates the Miocene Epoch. Meat-eating Dinohyus or "terrible pig," Daemonelix dryland beavers with corkscrew burrows and moropus, an 8-foot-tall clawed horse- or tapir-like creature, were among the mammals roaming this grassland 5 to 23 million years ago. Trails wind through hills and quarries where the fossils were found in the mid-1880s (nps.gov/agfo).

About 12 million years ago, an Idaho volcano blew a layer of ash across what's now northeast Nebraska's Verdigre Creek Valley. Rhinoceroses, three-toed horses, giraffe-like camels, raccoon dogs, saber-toothed deer, cranes and giant tortoises came to the watering hole and died after inhaling powdered volcanic glass. A visitor center about 6 ½ hours from Minneapolis tells that story and sets the stage for touring the Hubbard Rhino Barn, where visitors can watch the excavation that began in 1991 (ashfall.unl.edu).

Less than an hour northwest of the Minnesota-North Dakota border, this Manitoba community claims Canada's largest collection of marine reptile fossils. "Bruce," a toothy 43-foot-long Tylosaurus (from a group of Mosasaurs), serves as the mascot of sorts for the Discovery Centre, which showcases the Cretaceous Period 80 million years ago when an interior seaway stretched from the Arctic to the Gulf of Mexico. The center hosts half- to full-day fossil dig adventures, as well as two- to five-day digs at 30 sites northwest of Morden (discoverfossils.com).

St. Cloud-based Lisa Meyers McClintick (lisamcclintick.com) wrote "Day Trips From the Twin Cities" and "The Dakotas Off the Beaten Path."