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Jessica Dufresne

Jessica Dufresne displays the Ice Age Floods National Geologic Trail sign.

The roar must have been deafening.

Somewhere close to 12,000 years ago, a massive ice dam that blocked the Clark Fork River near the Montana and Idaho borders came tumbling down. Measuring 2,000-feet-high and 35-miles-wide, the dam created what people now call Glacial Lake Missoula.

Its water stretched north into the Flathead and Blackfoot river valleys, east to Drummond and as far south as the Bitterroot Valley’s Lake Como.

When the dam failed, it sent a thundering torrent of water through the Northwest at speeds nearing 70 mph that forever changed the landscape across four states.

It’s a story that Daly Elementary librarian Jessie Dufresne is looking forward to helping teachers in the Bitterroot Valley and beyond share with their young students.

This past summer, Dufresne was offered a unique opportunity to learn about the geology of the Bitterroot Valley and Ice Age Floods National Geographic Trail through the National Park Service’s Teacher Ranger Teacher program.

The program offers teachers around the country professional development to learn about the resources and educational materials available through the National Park Service. The program’s emphasis is to link national park units — like the Ice Age Floods trail — to underserved student populations in both rural and urban settings.

When the Bitterroot Cultural Heritage Trust and Missoula’s Montana Natural History Center partnered to help sponsor the Teacher Ranger Teacher program in Ravalli County, Dufresne proved the perfect candidate for the job.

As the daughter of a longtime Bitterroot National Forest geologist, she already had the a good understanding of interesting geologic features of the valley and its surrounding mountains

“I grew up with geology,” said the Daly Elementary librarian. “I was around it all the time. I always thought it was super interesting, but this summer opened up a new world to my understanding to what we have here.”

Now, she’s anxious to create a curriculum that Bitterroot Valley teachers will be able to use to open the eyes of their own students to the interesting geologic story that’s told in scattered boulders, ancient lake edges carved into mountainsides and a landscape shaped by glaciers.

“The geology of this area is so cool,” Dufresne said. “Once we have the opportunity to share its story, I think students and people in general are going to get excited to learn more.”

That’s the hope of Montana Natural History Center executive director Thurston Elfstrom. The center has an exhibit that explains the origins of Glacial Lake Missoula and the interesting work by geologists who uncovered the first clues to its existence.

“We have a really interesting piece of natural history right here in our backyard,” Elfstrom said. “It’s something that we want to share with people.”

While there’s a lot more known about Glacial Lake Missoula in the Missoula and Plains areas, Elfstrom said it’s not quite as clear what occurred in the Bitterroot.

“It’s almost like it is a backwater when it comes to what occurred in Glacial Lake Missoula,” he said. “We know the surrounding valleys filled up with water. We think the dam broke 70 or more times. The water left glacial erratics across Washington and Oregon.”

A glacial erratic is rock that differs from the size and type of rock typically found in an area.

In the Bitterroot, people can see a glacial erratic in the front lawn of the Lone Rock School.

Dufresne’s mother, Lynn Dickman, said there are many others scattered throughout the Bitterroot Valley that were carried by ancient ice flows and dropped.

“A lot of those are now hidden from view on private lands in behind homes and garages,” Dickman said. “People can also certainly see the lake lines that run perfectly parallel along the mountains. Those lines are especially evident in the Sapphire Mountains. You can see them well in the Three Mile area and near Lake Como if you look south toward Darby.”

Kris Komar of the Bitterroot Cultural Heritage Trust said when Congress established the Ice Age Floods Geologic Trail in March 2009, it didn’t set aside any money to help spread the word.

The National Park Service’s Teacher Ranger Teacher program seemed a perfect way to begin educating Bitterroot Valley students about one of the three national trails that are found in their own backyard, Komar said.

The other two trails are the Lewis and Clark and Nez Perce.

Working alongside the Ravalli County Museum, Komar said the Trust wants to get the word out about the area’s interesting history.

Dufrense will focus her efforts on developing a curriculum that can be used by teachers in the fourth through eighth grades.

“People dig geology,” Komar said. “Once you begin to learn what it is you’re looking for, it opens up a whole new world for people. Our goal is to get people to learn how to see that. We want people to say ‘wow.' This place was once under 500 feet of water and that water went up and down 70 or 80 times.”

“A huge bit of science happened here,” she said. “We want to help people find out more about it.”

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Associate Editor

Reporter for The Ravalli Republic.