For many runners, completing a marathon is a transcendent achievement, a sense of accomplishment so pure it can become almost addictive.

For those looking for something tougher, there are ultramarathons, even longer and more grueling than the shorter, amore commonplace runs.

For those looking for something even tougher, there’s the Atacama Crossing.

The Atacama Desert is a plateau in South America covering a 600-mile strip of land on the Pacific Coast, west of the Andes Mountains. It is reportedly the driest place on the planet, the only “true desert” to receive less precipitation than the so-called polar deserts.

Basically it’s dry, real dry. And hot. It’s really, really hot, too.

It is also home to the namesake seven-day, six-stage 155-mile annual ultramarathon, which this year saw the father-son team of Mike and Greg Nance, of Bainbridge Island, among the obsessive athletes seeking to conquer the desert.

“It was an awesome adventure,” Greg Nance, a 2007 Bainbridge High School grad, said. “We battled towering sand dunes, treacherous salt flats and river crossings, 10,000-plus-foot elevation, and scorching 116 [degree] heat.”

More than 100 runners from 36 different countries participated this year, though the boys from Bainbridge still managed to stand out.

“I finished 15th overall and was the top American in the field, while my dad, at 65, was the second-oldest finisher,” Greg said. “It was a huge challenge and to be able to do it with my dad made it all the more special.”

The Atacama Crossing’s official course description does its best to make the route sound scenic — and it is, both Nances said, almost impossibly beautiful country — but the torturous details sneak through regardless.

“The course of the Atacama Crossing takes competitors across a wide variety of terrain and includes approximately … 5,521 feet of ascents and … 8,228 feet of descents over the seven-day race.

“Competitors will go through magnificent salt flats stretching as far as the eye can see, run down huge sand dunes which will literally take your breath away, go through canyons where you can touch the walls on both sides and sleep under glittering night skies in the driest place on earth.

“[Runners] will tackle sand dunes, river crossings, gravel, loose rocks, hard-packed earth and even waist-high grass. This is in addition to the infamous salt flats … that will challenge even the most dexterous of runners to cross at full-speed.”

The run more than delivered on its promise of a challenge.

“It was a huge adventure,” Mike Nance said. “Normally I just read about things like this, but this was actually an opportunity to do it and to experience it firsthand.

“[It was] a really very physically challenging, physically exhausting thing, but really spiritually uplifting,” he added. “Just a great experience to run and move through this extremely harsh, forbidding terrain — beautiful, but very forbidding — and to do it for long hours at a time and then reunite each evening with my son and with new friends that we met and made.”

Mike was previously a more active runner, and a longtime figure in the island rowing community, who has recently returned to the road — and the trail, and the desert — in recent years. It was after hearing of his son’s experiences during his first ultramarathon, several years ago in the Gobi Desert, that Mike’s own interest was piqued, and when Greg suggested they tackle the Atacama Desert together, dear old dad didn’t need much convincing.

“I could wax on about how it felt, but it was really a test of personal limits,” Mike said. “And it is true, it’s both a physical and mental thing; it’s largely mental, just persuading yourself that you really can do this.

“It all comes down to a step at a time. You can always take the next step no matter how tired you think you are.”

Still, being 65, he got some looks.

“The most common response I got from other people, telling them that I was doing this was sort of a puzzlement,” he said. “Age, I’m sure, was a limiting factor, but it was what it was; I did the best I could do.”

And he did amazingly well, and was, in fact, beaten by just one other senior runner, from France.

“This would have been great if I was 30 years younger. It would have been a little smoother, a little easier to do,” Mike said. “But once you’re out there it’s you and largely the elements, whether you’re an Olympic athlete in prime shape or you’re anyone else, you just have to adapt to your immediate circumstances and deal with it.”

Greg too turned some heads with his impressive finish, though he’s already no stranger to the spotlight. Last year he grabbed international headlines when, while living in Shanghai, he was chosen to star in a special Seahawks-themed Delta Airlines TV commercial (“The Flight of the 12s Ambassador”).

“I’m a strange guy,” Greg said. “In order to train for these ultramarathons, one of my rituals [is] I’ll run to a local sports bar here in Shanghai that’s on the other side of town, so it’s about 30 miles round trip, and wear my Seahawks gear out there.”

He still lives in China, where he works as the CEO of Dyad.com, a mentorship platform that has helped students earn over $25 million in scholarships, and also the chairman of Moneythink, a nonprofit providing about 15,000 low-income teens in 30 communities with financial planning mentorship. His work has reportedly been recognized by President Barack Obama, the Harvard Business Review and the World Economic Forum.

Running, he said, is both a challenge and a treat — a stress reliever and even a kind of mediation — in his life.

“My daily life is absolutely richer for running,” he said. “It benefits me literally every day.”

Even for him, though, Atacama was a list-topping challenge.

“You’re running on, it feels like glass shards and sharp barnacles and giant sand dunes. It’s otherworldly,” he said. “It is so beautiful, but you’re in pain, you’re overheating, you’re dehydrated — it’s really tough.”

Seeing runners from all over the world come together and put political and cultural differences temporarily aside was a reassuring experience, Greg, a former BHS track team member and summertime Kiwanis All-Comers Meet regular, said, given the divisive nature of our time.

“One of the nicest parts about all this is a lot of those differences melt away and folks that might traditionally have adversarial tension, they’re struggling with the same challenges and they rally together,” he said. “Looking out and seeing a Japanese, a Korean and a Chinese runner assisting each other with their blisters, or watching a French and a German fellow exchanging chocolate bars out on the course … I think the ultramarathon, given how challenging it really is and how much every one of us is struggling, there’s a certain beauty in connecting people through that adversity.”

For his next challenge, Greg has set his sights on something even more challenging (if you can believe such a thing exists) than the Atacama Crossing.

“In [January] I’m beginning what’s called the World Marathon Challenge,” he said. “It’s running seven marathons in seven days on seven continents.”

Greg will be running to raise funds for Moneythink, which lets aspiring college students in need of financial help connect with financial advisors and budgeting tools.

“I’ve been working on it with actually several [Bainbridge] Islanders,” he said. “Inner city students get shut out of college way too frequently because they don’t think they can afford it. But if they’re able to fill out the [Federal Student Aid form], in the vast majority of cases they can actually get the needs-based funding to actually cover the vast majority of college expenses.”

Visit www.gofundme.com/GregRunsFar to learn more or to donate.