Sarah Marquis documents extreme journey in new book

Growing up in Switzerland, Sarah Marquis had never heard of solo extreme walking, but by age 17, she was walking across continents by herself.

Now 42, she's an explorer for National Geographic. Her new book, "Wild by Nature" is about one of her most extreme journeys, from Siberia all the way to Australia, reports "CBS This Morning: Saturday" co-host Vinita Nair.

When Marquis took her first steps of the journey near Russia's border with Mongolia, she knew from past travel she would be unprepared. It takes her six months of walking to physically adapt. That's also how long it takes to declutter her mind.

"You've got still the voice of your family going through, your friends, and then you got this amazing moment where one morning, you wake up and all that is gone," Marquis said.

But once she has tuned out the voices, Marquis said she is "in the moment."

"...And it is sharp, it's clear. Things are really, really focused and you just feel alive from the core of it and you feel this belonging with the planet," Marquis said.

Marquis's initial idea -- to walk from Siberia through the Gobi desert to China, then to Laos and on to Thailand, before taking a cargo boat to Brisbane, Australia, to walk across that continent - came to her while she was walking home from the grocery store.

"I turned around and behind me was this little travel shop and in the window was this massive great picture that was in Mongolia. And you could feel the picture was taking you in," Marquis said. "And so then I came back home, didn't think much about it, and this idea, this picture actually grew in me."

The first person to hear her idea, as always, was her mom.

"And I said to her, 'Imagine it's a line, I'm going to cross the world!'" Marquis said.

To prepare for her trip across the world, Marquis ensured nothing would be a mystery. She spent two years walking and she meticulously studied all of the terrain and researched what equipment she would need. She also modified her diet to gain weight.

"So you can plan as much as you can, but then you have to let it go," Marquis said. "This is two different worlds where you plan everything, but then when you do the first step, you have to let it go and be ready for the unknown."

Marquis documented the trip on camera. You get a sense of how isolated she was, how self-reliant she had to be and how connected she was with the nature.

"I'm going from one world to another, from the human world to the nature world and cross this little bridge and come back here and say, 'Hey guys, we are capable of so much but we do not experience the strengths we've got in us most of the time.'"

"Where do you think the majority of people misplace their focus?" Nair asked.

"We don't really understand how the surviving starts with our mind. Life is short, we don't always know when it's going to end. So we need to eat every minute. We need to go for it, we need to actually enjoy every second of it."

Long before she started her journey, Marquis picked a tree as her stopping point, which she first met 10 years ago.

"I camped there and I said to him, 'Darling, I will be back.' So I kept my promise," she said. "I knew it was that tree. It was kind of magical to actually walk three years to get to that tree. This is my connection with the land."

About two years after finishing her journey, Marquis was on to her next adventure, this time in Western Australia. Each trip allows her to see the world and explore what she is made of.

"It's really a humbling road, it's a long process. It's a painful process most of the time but the reward from that journey, from every journey, it's so deep and so amazing," Marquis said. "Coming back here, being alone for so long, I actually understand people better because I know myself now."