“Why go low?” he asks. “It is a counterintuitive action, running against the grain of sense and the gradient of the spirit.” He notes the way that humans have long placed in the deep earth “that which we fear and wish to lose, and that which we love and wish to save.”

Image Robert Macfarlane Credit... Charlotte Hadden for The New York Times

What he sometimes finds on his explorations is, to his dismay, trash. He writes, in a typically crunchy sentence: “Philip Larkin famously proposed that what will survive of us is love. Wrong. What will survive of us is plastic, swine bones and lead-207, the stable isotope at the end of the uranium-235 decay chain.”

Macfarlane gets into some uncomfortable situations down there. He writes about claustrophobia and about his adrenaline spikes, his fatigue and his stomach flips. It can really wobble a person’s Weltanschauung, to borrow a line from the poet A.R. Ammons, to be way down in the shivering dark, a particulate in the earth’s lower intestines, your headlamps picking out the bats on the wall.

“For years I could only understand these pursuits of shadowed water, blind rivers and terrible depths as fierce versions of the death drive — fiercer even than what drove the most fearless mountaineers,” he writes.

“The language of extreme caving is often openly mortal and tacitly mythic: stretches of passageway ‘dead out,’ one reaches ‘terminal sumps’ and ‘chokes,’ the furthest-down regions are known as ‘the dead zone.’ But over time I saw that — as with extreme mountaineering — there was another aspect to the thanatos at work. Divers and cave divers often describe their experiences in terms of ecstasy and transcendence.”

Macfarlane’s writing can be humid. “For more than 15 years now I have been writing about the relationships between landscape and the human heart,” he writes, a line that made my own heart wrinkle its forehead. He describes “the flowing presence of otter.”

More often it is superb. He is so good at what he does, and has won so many awards for his books, that there has begun to be pushback in England, just to keep his career in perspective.