After Kevin Fedarko wrote “The Emerald Mile: The Epic Story of the Fastest Ride in History through the Heart of the Grand Canyon” — a thought-provoking adventure story that takes place on the Colorado River — he intended to move on to other topics.

And then National Geographic offered him an assignment he couldn’t refuse. The magazine wanted Fedarko and award-winning photographer Pete McBride to take on another Grand Canyon story that involved the two friends traversing the length of the canyon on foot.

“The canyon gets into you and doesn’t let go,” Fedarko said. “I signed on thinking I knew everything about the canyon,” he said, as a river guide and author who spent 10 years researching and writing “The Emerald Mile.”

Fedarko, who lives in Flagstaff, Arizona, and McBride, of Basalt, Colorado, spent more than a year completing a series of sectional hikes across the canyon, a harrowing journey where water is scarce and there are no trails. They’d venture out for one to three weeks at a time before returning to Flagstaff to rest and replenish.

“We’d go back in to the same mile marker where we exited,” Fedarko said. “It opened up for me a landscape within the canyon I had not known about. There’s a world between the river and the rims where most people go. It contains all kinds of hidden treasures that people never see.”

Fedarko will talk about their experience, as well as threats facing Grand Canyon, during a presentation at Star Hall, 159 E. Center St., on Friday, Feb. 15 at 6 p.m. Admission is free.

The roughly 800-mile trek began at Lees Ferry in September of 2015 and ended at Grand Wash Cliffs at the canyon’s west end in November of 2016. The pair hiked during all four seasons, enduring temperatures ranging from minus 8 degrees to 111 degrees Fahrenheit. Their story appeared in the December 2016 issue of National Geographic.

The majority of the park is “brutal, austere, a vertical desert with no trails,” where few people go, Fedarko said. At times their journey involved walking across slick narrow ledges just inches away from steep drop-offs.

Fedarko, 53, didn’t quite know what he was getting into when he accepted the assignment, he said. He’s currently working on a book for Scribner about the adventure.

The purpose of the National Geographic project was not only to bear witness to the heart of the canyon’s hidden treasures, but also to shed light on various proposed projects threatening the Grand Canyon, including a proposal by Phoenix-area developers to build a cable-driven tramway from the canyon’s east rim down to the confluence of the Colorado and Little Colorado rivers. Another issue is noise pollution from a “tidal wave of unregulated air tours.”

The Star Hall presentation is a collaboration between the Grand County Public Library and Utah Humanities, a Salt Lake City-based nonprofit that helps bring programming to communities statewide.

The timing of Fedarko’s upcoming presentation ended up being a “lucky coincidence,” the library’s head of adult services Meg Flynn said. His appearance falls in the middle of a series of outdoor adventure presentations organized by the library through the month of February.

“Grand County Public Library is a model partnership, as Meg knows about the Moab community,” and what programming would be of interest, said Michael McLane, Utah Humanities’ director of the Utah Center for the Book.

Moab’s Back of Beyond Books will be at Star Hall selling copies of “The Emerald Mile” as well as the collaborative 2018 “The Grand Canyon: Between River and Rim” by McBride, Fedarko and Hampton Sides.

Learn about the canyon’s hidden gems at this outdoor adventure series presentation

“There’s a world between the river and the rims where most people go. It contains all kinds of hidden treasures that people never see.”

Grand Canyon” by Kevin Fedarko, author of “The Emerald Mile”

When: Friday, Feb. 15, at 6 p.m.

Where: Star Hall, 159 E. Center St.

Cost: Free

Information: 435-259-1111