'Underland' is full of fascinating stories, sprinkled like Hansel and Gretel-esque breadcrumbs
Hamish Hamilton, hardback, 425 pages, €22
For most people, the thought of caving fills us with premonitory dread. It's to Robert Macfarlane's credit as a writer of expressive power (though more nervous readers won't thank him) that his account of speleological exploration in the Mendips Hills in Somerset, England - the opening chapter of this book - is almost viscerally felt.
I squirmed as he describes navigating piles of subterranean boulders, squeezing through gaps too small to turn back about, ever-cognisant of the threat of rising water, subsidence or injurious bad luck.
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Not in a million years, in short, would I descend into that damp blackness: an appropriate turn of phrase, actually, because Underland in part deals in million-year epochs, in billions. Macfarlane has previously written groundbreaking works on landscape, especially mountaineering. Here he reverses direction and looks far beneath the surface, literally and figuratively.
Underland is subtitled 'A Deep Time Journey', which gives a clue as to how this book exists on - again, appropriate enough - different strata. First off it's his travelogue of the wildly diverse underground places where humans have built, dug, bored, mined, journeyed, buried, made art, spoke to God, hidden, lived and died: Macfarlane goes forth with the intrepid heart of a Victorian adventurer, the observational powers of a reporter, and the acuity and flair of a poet.
On another level, it's a psychological study of what compels people to go into caves or other underground lairs, "driven into the depths by complex longings". This is an old and obviously fundamental aspect of our subconscious: back to ancient times, literary epics such as the Epic of Gilgamesh were narrating a hero's journey into the underworld to earn power, knowledge or redemption.
Underland is also a history of humanity's engagement with the subterranean: everything from Parisian catacombs, undersea potash mining and tales of caving tragedy and triumph, to Bronze Age burial grounds, toxic-waste disposal and a decades-long multinational project to chart the flow of an underground river from Slovenia to Italy.
And on its deepest level, Underland is natural history which, returning to that concept of deep time, reminds us that the world is incomprehensibly old, and human history is close to an eye-blink in its lifetime. Some rocks are billions of years old; civilisation, as we know it, just 10,000 years.
On a trip to Greenland, he sees icebergs calving off a glacier: the end-product of a process which began countless thousands of years before. He traverses cave systems and sea-beds formed before the dinosaurs. Even seemingly ancient treasures and delights - cave-paintings off the Norwegian coast, Roman coins lying under the soil for millennia - mean almost nothing when measured by the profoundly slow tick of that geological clock.
Yet, this is the Anthropocene age, defined by the changes we're wreaking on the planet. So Macfarlane also looks to the distant future, wondering if we will prove ourselves "good ancestors" to our descendants, or some unrecognisable evolutionary iteration.
Some uranium by-products have a half-life of 4.5 billion years; in effect, the remainder of Earth's existence. How, then, to warn future beings not to approach the nuclear-waste dumps currently being built, deep underground, at sites around the world? Here be monsters, not buried treasure. It's an unsettling, and somehow shameful, thought.
In the meantime, at least, we have this time to use productively, and this incredibly beautiful and varied world to learn about. Underland is full of fascinating stories, Macfarlane's own and others', sprinkled like Hansel and Gretel-esque breadcrumbs.
I laughed at his adventures, and misadventures, tiptoeing around underneath Paris and London. I laughed queasily at the underground cemetery which burst its banks into the basement of an adjoining house.
The mind boggled at the scale of those potash mines - 600km of tunnels, a mile undersea, so deeply penetrating that when digging equipment wears out, it's just abandoned, to be absorbed eventually by the rock-salt walls. Good luck interpreting that one, geologists of the future.
Oddly, the most captivating, and affecting, story for me didn't involve people at all. In one chapter, Macfarlane explores the "worldwide wood": a scarcely believable natural phenomenon, whereby above-ground plants communicate with each other through a subterranean network of fungi.
It's symbiotic, mutually supportive, super-efficient, the very definition of an elegant solution. And it asks intriguing questions. Are plants and fungi sentient? Where does one organism end and the larger collective begin? Is nature viciously Darwinian or a gentler, more altruistic system? And could we learn something from these clever little mushrooms? It seems glib, too simplistic - but then you remember the deep time nightmare of uranium-235 and wonder, has our cleverness always served us well?