The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions

by Peter Brannen

and with the PETM, we’ve verified that theory. It does take 100,000 years to restore ocean chemistry.”

We now hurl ourselves deep into the far future. As in the footstep analogy of the first chapter—where all of human history takes only a few dozen steps to traverse—we’ve begun to trudge again for hundreds of miles—that is, hundreds of millions of years—forward in time. It’s a planet where the climate tantrums of humans, the whiz-bang ingenuity of our machines, and the projects of our civilization are irrelevant. The continents have been rearranged, entire oceans have been consumed and created, and the constellations have been jumbled and scattered across the sky. Only a handful of spots on earth will count themselves lucky enough to get covered in sediment and then subside into the earth, where they’ll remain shielded from erosion and endure the ages unmolested by plate tectonics. These are the fragments of our modern world that have even the slightest chance of leaving any trace in the rocks in the far, far future of geological time. It’s heartening to know that, though its prospects for short-term survival are grim, New Orleans—sitting as it does on the business end of a subsiding sedimentary basin—has perhaps the world’s greatest potential for long-term preservation. If, in 100 million years, a geologist from somewhere on the tree of life discovers the flattened strata of the Crescent City in the side of a canyon, I can think of worse ways to be represented in the fossil record than by this one data point about humanity. But while the French Quarter’s Preservation Hall ...

This will lead to a strange world, one that’s both hot and without much CO2. As a result, there won’t be much plant life anywhere, or animal life for that matter, since both depend on the stuff. Already, as carbon dioxide has dropped since dinosaur times, plants have evolved new photosynthetic pathways to adapt to this new low-CO2 regime. These are the so-called C4 plants, plants like grasses and shrubs and cacti. Over the next few hundred million years, these plants will slowly come to dominate this hot, humid, and generally unpleasant world, while many trees and forests, unable to photosynthesize in the carbon-poor atmosphere, will disappear.

In 1.6 billion years, in the face of a pitilessly hostile and temperamental star, conditions on the planet will become so inimical to life, even deep underground, that bacteria will be extinguished. On the other side of this last mass extinction is eternity. Peter Ward and Donald Brownlee have noted the poetic symmetry to this story of life on earth, where multicellular life, eukaryotes, and prokaryotes will take a bow in the reverse order that they first appeared onstage.