The following two paragraphs are from an article in the recent National Geographic issue.The article featured two Mars rovers still functioning even more than a year after their predicted demise. I need your help with the boldfaced parts. What do they mean?

In Powell's day geologists puzzled over how water sculpted the pink-hued Colorado Plateau into a canyon maze; their counterparts today wonder about water's role in carving landforms on red-hued Mars. Just as Powell's ragtag company defied expectations in 1869 by surviving nearly a hundred days of savage rapids, the rovers, expected to conk out well before the end of last year, were going strong months later. Powell was a field geologist, cracking rocks and taking notes with his single arm. So too each rover uses its three-jointed arm to wield equipment including a camera and a tool for grinding into Mars rocks.

Rock-breaking brings up the essential reason to muse over these robots and old-timer Powell: ground truth. This is not a casual term among geologists. It evokes the dust-on-boots conclusions that arise from personally grabbing samples of rock, walking formations, and exposing fresh stone. Generations of geologists have placed their literal, bedrock faith in ground truth.

My guess on "dust-on-boots" is that it would mean 'coming from first-hand or hands-on experience (just as Powell trekked with boots on to hunt for his trophies). I have no clue to "walking formations." Who or what is walking? Or does it simply mean 'formations created by geologists walking'? Please enlighten me.

Best regards,
"Dust-on-boots conclusions" are conclusions that are made while actually studying out in the field. The implication is that for geologists to form accurate conclusions, they must go outdoors and study their subjects firsthand. In doing so, they are likely to dirty their boots, hence the expression.

"Walking formations" simply means to walk along various rock formations in an effort to study them. It's used as an example of field work.
Dear Komountain,

«Dust-on-boots conclusions» are perhaps «feet-on» experience, no? Emotion: smile

Kind regards,

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Thank you so much for your enlightening me, YoungCalifornian.

If there had been 'along' between 'walking' and 'formations,' I wouldn't have had trouble understanding the phrase.

By extension, the way the phrase is formed, I dare assume that 'walk the street' or 'walk the field' or 'walk the riverbank' may be a possible formation. But I would say no to my own assumption. What's your take on this?
Though not that common, you could indeed use or hear any of those examples. Have you ever heard the Johnny Cash song "I Walk the Line"?
Dear Komountain,

«To walk the streets» is to be a prostitute.

Kind regards, Emotion: smile

Students: We have free audio pronunciation exercises.
Thanks, guys.

Pleasure comes from a wide range of things. Learning is no doubt one of them.

Best regards.
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