Futurology isn't what it used to be. The space operas that fill the future with intergalactic empires, or the Wellsian dystopias that depict a pre-technological regression, typically encompass barely more time than a geological blink. Jan Zalasiewicz suggests we get a little more perspective. A geologist at the University of Leicester, he gazes for a living into the giddy abyss of deep time, where millions of years pass like days.

The Earth After Us examines the possible legacy of humankind on this geological timescale; 99% of species thought ever to have existed (and we're guessing wildly here) are now extinct, possibly without trace. Why should we be any different? Evangelical optimists may forecast a kind of digitally enhanced immortality by the end of the century, but even some sober commentators speculate that this century is our last. While both sing the solipsistic refrain that we are living in unique times, rising global temperatures and sea levels, vanishing sea ice, soaring population and renewed nuclear proliferation do seem to load the dice in favour of the pessimists.

So suppose, whether through climate change, war or epidemic, we disappear. Forget lurid images of blackened or flooded cities, says Zalasiewicz, and fast-forward 100m years. The slate will have been wiped clean: wind, rain and the grinding of tectonic plates will remove all signs of humanity from the planet's surface. All the passions and follies of our race will be compressed into a geological stratum, in some places no thicker than a cigarette paper and in others literally atomised as the churning earth swallows its crust.

Our mortal remains then enter a geological lottery. The sluggish deep motions that power plate-tectonic shifts are too unpredictable to indicate how the continents will look this far ahead. Mountains may become oceans and vice versa, and we can't tell whether London, Lhasa or Las Vegas will be carried down to fiery hell or lightly pressed at shallow depths into sedimentary strata. The traces of some cities, enduring the milder fate, will await discovery by future Zalasiewiczes with geological hammers in their paws.

Before excavating these bones, the author considers the more common form of imprint that humans will leave: a layer perhaps a few millimetres thick in exposed rock strata. This supplies the book's most telling conclusion. Will future geologists even notice this compressed compendium of all human history? Oh, they will. The environmental changes we have now wrought, and to which we're already committed in the future, will make this stratum not just a slice of dark deeds sandwiched between ages of innocence, but a marker between one kind of planet and another. Mass extinctions, sea-level change, ocean acidification, coral destruction - all make the current short spell of human dominance, labelled the Anthropocene (firstly, but not now, half in jest), a transitional period to rival some of the great geological shifts of the past.

The future time span here is well chosen, providing analogies to the mysterious geological boundary 65m years ago when the dinosaurs vanished. In that case, a giant meteorite impact seems to have played a role, eliminating not only the great lizards but at least three quarters of all species on the planet. Geologically, Zalasiewicz explains, the impact of humans will be as instantaneous as that lump of space debris, and possibly as devastating.

This book grew out of a New Scientist article, and occasionally this shows in the hefty fleshing-out of background material. But it is refreshing to see attention given to the less glamorous niches of geology, such as the subsea mudslides called turbidites (the author is a specialist in mudrocks). And we learn just how intricately the cycles of the geo-, hydro-, atmo- and biospheres interlock on these immense time-scales, so that apparently insignificant effects can, like termites boring through trees, bring about dramatic change.

The framing conceit of the book (a team of intelligent, rodent-like palaeontologists gradually decoding the Anthropocene stratum) goes somewhat unexamined. These investigators are basically the author's colleagues in mouse-garb, sharing their preoccupations and assumptions. Imagining them otherwise could stray into sci-fi waffle, but one must bear in mind that the tales we reconstruct about even relatively recent history (the Roman Empire, say) are shaped by the present. This becomes particularly relevant when Zalasiewicz ponders what interpretations of human culture might be made from the evidence available. He cites Stonehenge to illustrate how function in an ancient structure can be unmistakable yet impossible to pin down. But here, as with the Lascaux cave paintings in France, or the great cathedrals, each interpretation tends to be a product of its times.

The strangely unexplored image that hangs over this study is that of Charlton Heston gazing in anguish at the head of the Statue of Liberty poking through a sandy beach in a world he had thought alien. That image, of course, echoed Shelley's Ozymandias, whose hubristic proclamation of power is empty millenniums later. This book offers a persuasive clarification of Shelley. “What lies at the heart of humanity” - our noblest achievements - “is probably not available for preservation,” says Zalasiewicz. Our temples and Titians will be crushed; Mozart and Goethe will leave no trace. But collectively we will have rewritten the geological record, and as the author concludes, “it would be immortality cruelly won”.

The Earth After Us by Jan Zalasiewicz

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