Robert Macfarlane’s ‘Underland’ explores the inscrutable world beneath our feet

“We know so little of the worlds beneath our feet,” writes Robert Macfarlane, in his wide-ranging but uneven new project, “Underland.” “Look up on a cloudless night,” he suggests, “and you might see the light from a star thousands of trillions of miles away, or pick out the craters left by asteroid strikes on the moon’s face.” Whenever we look down, Macfarlane argues, there’s an entirely different feeling: “I have rarely felt as far from the human realm as when only 10 yards below it.”

It’s a worthy project, going deep, making the space beneath us come alive, and it’s one Macfarlane seems uniquely suited to dispatch with aplomb. A fellow at Cambridge and the author of numerous much-lauded books, Macfarlane tries his best for hundreds of pages: from caves in Britain to the catacombs of Paris, from a raging subterranean river beneath the Italian-Slovenian border to the nuclear bunkers of Finland and Nevada to the wild underground on the frozen edges of Greenland, Finland and Norway.

There was so much potential, given his record of superlative studies, his ability to blend actual exploration with investigations rooted in history, literature and language: “The Wild Places” tracked with crackling and urgent prose Macfarlane’s effort to find the unruly, untrammeled corners of the United Kingdom. His follow-up, “The Old Ways: A Journey on Foot” — ranking as it did beside countless other books about walking — stood out as among the very best for its heart and erudition.

“Underland” starts strong, and any reader familiar with Macfarlane’s prose will find that precise and underloved stash of fabulous words. Glancing at one passage you might see “nubbing” and “stile” and the “swish” of a tail and the “twitch” of a head.

But a brittle format begins to emerge: A paragraph-long, scene-setting passage, all detail, few verbs. “Bees browsing drowsy over meadow grass. Gold of standing corn, green of fresh hay-rows, back of rooks on stubble fields.” It can be a gorgeous experience, to consider any one of them, but trouble lies in their accumulation.

Macfarlane has always excelled at considering not just the physical facts and peculiar logic of the world around — and now beneath — us but the way it connects to the longer legacy of human effort. In “Underland” the delicate balance between profundity and profligacy tests a reader. At one point, Macfarlane finds a man named Merlin Sheldrake, who, “as the oldest joke in mycology goes, is a fun guy to be around.” Then he proceeds to spend dozens of pages unraveling a tired and soggy metaphor, repeating it again and again: the “wood wide web,” about the interconnectedness of trees. Astonishingly, the previously stoic, ageless and gifted Macfarlane feels corny, too sure, unedited: Perhaps he was unchallenged, allowed to conclude just about any given episode or epiphany or joke is definitely worth sharing.

Too many times, dialogue exchanges go on too long. We feel trapped. There are additional jokes. Time in the Paris catacombs could have felt diamond-sharp and terrifying but instead run like a jaunty “Talk of the Town” permitted not 1,000 words but 100 pages. During a below-ground party, for instance, Macfarlane seems awkward when he notes a David Bowie song changing to “Underground” by Ben Folds Five. “Everyone cheers,” he reports, dully. At least three times, a writer previously reliable as reserved and wise documents people he meets telling him he’s good or cool or warm or smart.

Thankfully, toward the end of the book, Macfarlane returns to power; in the final 100, chilling pages, we’re in the spare territory of Greenland, in search of an elusive and enchanting frozen phenomenon called a moulin: the moment when a glacial melt reveals an ecstatic yawning portal to the underworld.

Here a steady Macfarlane obsesses over systems, logic and the way the world has always worked, rather than on himself, and he deploys epiphanies that can feel cut from stone. “Ice has a social life,” he writes, and shortly thereafter his team witnesses the massive cleaving of a significant chunk of an iceberg, a moment rarely seen. The wave produced is 40 feet tall. The deep black of the interior ice seems alien and frightening. “The air in this ice has been so compressed that cores brought up by deep drilling will fracture. … [I]f you were to put a piece of very old blue ice in a glass of water or whisky, it might shatter the glass.”

He might so easily have been tempted to sell, in these final pages, melting ice as metaphor or slogan. But Macfarlane ends on far grander and more wide-ranging footing. “The ice seems a ‘thing’ that is beyond our comprehension to know but within our capacity to destroy,” he writes. “What I thought would be my least human book has become, to my surprise, my most communal.”

Considering the book as a whole, you might say that Macfarlane is best when he’s honest, humble and specific, as when he’s plunging into the Timavo river, cut deep under the Carso Plateau where northeast Italy borders Slovenia. Standing on the edge of a tower, “One feels drawn to the edge,” he writes, and submerged in the river’s warm water, he experiences a “powerful longing to swim into the mouth on and on, until my air ran beautifully out.”

Poet Philip Larkin once suggested that what would survive us is love. “Wrong,” Macfarlane retorts. Having considered the vast universe of what appears not even to be, this unbelievably talented but imperfect writer offers a different kind of answer: “What will survive of us is plastic, swine bones and lead-207, the stable isotope at the end of the uranium-235 decay chain.”

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“Underland: A Deep Time Journey”

Robert Macfarlane

W.W. Norton, $27.95

Nathan Deuel is the author of “Friday Was the Bomb: Five Years in the Middle East.”