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

by Peter Brannen

Animal life has been all but destroyed in sudden, planetwide exterminations five times in Earth’s history. These are the so-called Big Five mass extinctions, commonly defined as any event in which more than half of the earth’s species go extinct in fewer than a million years or so. We now know that many of these mass extinctions seem to have happened much more quickly. Thanks to fine-scale geochronology, we know that some of the most extreme die-offs in earth history lasted only a few thousand years, at the very most, and may have been much quicker.

In North America, fossils are found not only in the mythic Southwest and in exposed Arctic mountainsides but hidden under Walmart parking lots, in quarries, and in road cuts on the interstate. Underneath Cincinnati is an endless fossil bas-relief of tropical sea life in the early oceans of the Ordovician period, which ended half a billion years ago in the second worst extinction in Earth’s history.

“We think of mass extinctions as requiring an abiotic driver: an asteroid impact or a period of volcanism. But here there’s strong evidence that biological organisms that changed their environment drove the extinction of vast swaths of complex, eukaryotic life. I think it’s a powerful analogy for what we’re doing today.”

A sentiment exists—particularly among nonscientists—that the idea of humans seriously disrupting the planet on a geological scale is mere anthropocentric hubris. But this sentiment misunderstands the history of life. In the geological past, seemingly small innovations have reorganized the planet’s chemistry, hurling it into drastic phase changes. Surely humans might be as significant as the filter-feeding animals of the Cambrian Explosion.

“So I just think, here’s an example from the past when an ecological crisis happened because of ecosystem engineering,” said Darroch. “And we shouldn’t be too surprised or too staggered or too blown away by the fact that maybe it’s happening again. Biological organisms are an incredibly powerful geological force.”

To get to a mass extinction, you first need victims. Walking along the side of the highway outside Cincinnati (just past the Subway, Sprint, and Advance Auto Parts stores) is as good a place to start as any to meet this world eventually whisked away by the planet’s first global slaughter of animal life.

Before the Ordovician, they grew to only a couple of inches at most, but by now they included astonishing animals like Cameroceras, which was housed in a cone shell that stretched almost 20 feet long. Museum reconstructions of the animal look something like an octopus jammed into a bus-sized ice cream cone.

Here on the rugged and bare continents there were no droning insects, no footprints, no trees, no shrubs—nothing. Life on land was relegated to a few damp patches of liverwort hugging the shore. Farther inland was an endlessly bleak and dusty wasteland. This was so long ago that rivers didn’t even meander yet—the rooting plants that would have held back their banks would not exist for tens of millions of years. The day was 20 hours long and the night sky was filled with unfamiliar constellations.

There’s a reason why evolution was first discovered on islands—in the Galápagos by Charles Darwin, and independently in the Malay archipelago by Alfred Russel Wallace: islands drive biodiversity by separating populations, allowing them to pursue their own evolutionary stories and ultimately create new species.

but a 2008 Nature Geoscience paper argued that this Ordovician barrage from smaller rocks might have actually been a good thing, electrifying biodiversity by disrupting staid communities, clearing up ecospace, and just generally shaking things up.

The winter world is evident in the grooved lines, called striations, etched in the bedrock of the mountains of New Hampshire, where mile-thick grindstones of ice advanced and retreated, scraping bare the scenery behind them. Long Island, Block Island, Cape Cod, Martha’s Vineyard, and Nantucket are all essentially dump heaps of rocks and sand where the ice sheets pushed south, sputtered and spewed their guts out onto the tundra.

The greenhouse effect was first described in the 1820s by French physicist Joseph Fourier, who noted correctly that the planet would be uninhabitably cold if it weren’t for Earth’s blanket of insulating gases. In 1859, Irish physicist John Tyndall discovered carbon dioxide to be one such greenhouse gas, and in 1896 Swedish scientist Svante Arrhenius predicted that doubling CO2 in the atmosphere would warm the planet by about 4 degrees Celsius, a prediction that’s roughly in line with those of our most powerful modern supercomputers. Needless to say, discussion of this basic science by actors with baldly political motivations can be depressing beyond words.

everybody dies when adaptation is no longer possible.

The future of the town, the state decided, would be at the bottom of a lake. When New York City came to destroy the village to slake its thirst, it did so with a marked lack of bedside manner. While collecting oral history from the former town’s last surviving inhabitants, Wyckoff recalled the almost biblical exile that was imposed during dam construction. Residents came home to find ominous Xs scrawled on their doors, marking their homes for destruction. “[One resident] said that for the last load they went back to get her doll collection in her bedroom and the house was already leveled,” said Wyckoff. “They had burned it down. They didn’t give you a lot of notice.”

When renovations to the crumbling Gilboa Dam

“Did anybody bring any acid?” a geologist asked the group as we marched down the shoulder of I-68. “I did!” responded another. I would learn that this surprising question was customary among geologists. The acid is used, somewhat disappointingly, to take layers of grime off the rocks.

Some nautilus shells can command up to $200 on eBay, a bounty that proves irresistible to poor Philippine and Indonesian fishermen, and Ward has seen the animals disappear from atoll after atoll over the course of his diving career. “I mean, just anything that’s beautiful to humans is out of luck.”

Today the pH of the modern ocean is falling fast, already by a staggering 30 percent since the start of the Industrial Revolution. Even people unmoved by the galaxy of evidence for global warming have no rebuttal to ocean acidification. It’s simple chemistry.

“So that’s important to keep in mind too, right? Most of the extinctions we’ve observed in the last couple of millennia, most of those are due not to climate change but to direct human interaction—overfishing, overhunting, direct destruction of habitat, not due to climate change or ocean chemistry change.

“So when you form a supercontinent in our climate models, you end up with dry interiors,” Lee Kump told me. “And so they’re kind of a noncontributor to the global carbon cycle at that point because there’s no water to weather the rocks, and so, yeah, you could imagine that volcanic eruptions at a time of high continentality like Pangaea would break the regulator for CO2. Suddenly you have an unabated increase in carbon dioxide.”

It’s a simple fact of geometry that having a bunch of little continents gives you more coastline than having one big supercontinent. And more coastline gives you more shelf space to bury carbon in shallow sea life.

Sauropods like these were so monumental that their methane farts might have been partly responsible for making the Mesozoic so warm.

When a rocky envoy from outer space visited Chelyabinsk, Russia, in 2013, shattering windows and spawning dozens of dash-cam YouTube clips, the damage the meteorite caused took many by surprise.

Other evolutionary shadows of the Pleistocene live on in the produce aisle. Seeds in fruit are designed to be eaten and dispersed by animals, but for the avocado this makes little sense. Their billiard ball–sized cores, if swallowed whole, would at the very least make for an agonizing few days of digestive transit. But the fruit makes a little more sense in a land populated by tree-foraging giants, like the sometimes dinosaur-proportioned ground sloths, who swallowed the seeds and hardly noticed them. The ground sloths disappeared a geological moment ago, but their curious fruit, the avocado, remains.

Upon arriving in 1912, Norwegian explorer Roald Amundsen couldn’t believe his good fortune. “We live in a veritable Never-Never land,” he wrote about the new continent. “Seals come up to the ship and penguins to the tent, and allow themselves to be shot.” The unfamiliar animals hadn’t had time to develop what Darwin called a “salutary dread” of man.

“We’re not just warming, we’re not just pollution, we’re not just overexploitation, we’re piling it all on simultaneously. That’s why it’s really inaccurate to argue that because there’s been warming in the past that doesn’t count now, because it’s part of the perfect storm. I think that all mass extinctions work that way. I think it’s going to turn out that that’s how all the Big Five work—that lots of things go wrong.

The decisions we make as a civilization in the next several decades might influence the climate twice as far into the future as our species has existed in the past.

about this coming ice world after the brief greenhouse in his unsettling book The Life and Death of Planet Earth. “From the vantage point of a derelict and forgotten satellite orbiting far out in space, the reflection of our marbled home is as disquieting as it is dazzling: a reflective expanding white,”