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

by Peter Brannen

“The Devonian research community is a little anemic, frankly,” said Thomas Algeo. “It’s hard to get enough people together for meetings. We tried to do a special issue on the Devonian and didn’t get enough papers to make it fly. There aren’t enough people actively working on it.” Depressingly, while research on the pivotal Devonian period languishes, only a few miles from Algeo’s office is the Creation Museum, a bizarre evangelical funhouse where glassy-eyed schoolchildren are told that the Earth isn’t much older than the pyramids and shown dioramas of tyrannosaurs boarding Noah’s Ark. Awash in donor money—and even state tax breaks—the Creation Museum is expanding.

Though plant and animal life on land might strike us as the default setting for Earth, it was revolutionary for a planet whose continents had been barren for more than 4,000 million years. The fish that had been timidly crawling onto land in the Devonian had made it by now and had split into two reptile lineages: one that would remain reptiles (and eventually give rise to crocodiles, snakes, turtles, lizards, dinosaurs, and the dinosaurs’ popular spin-off, the birds) and another group that would eventually become the mammals.*

At the end of the Permian, Siberia would turn inside out, burbling lava over millions of square miles and swamping the atmosphere with volcanic gases. One gas in particular stands out as the primary killer in what would become the greatest mass death in earth history. Researchers don’t study the worst catastrophe ever purely out of academic, or even morbid, curiosity. The End-Permian mass extinction is the absolute end-member—the worst-case scenario—for what happens when you jam too much carbon dioxide into the atmosphere.

Over millions of years, as plankton snowed through the oceans and accumulated on the seafloor—millimeter by millennium—some of it became solid rock, called chert, made of billions of single-celled critters. After the End-Permian mass extinction, there’s a “chert gap” in the fossil record as this rock of life all but vanishes. The gap illuminates the truth that life and geology are two descriptions for the same reservoir of raw material. Pull the lever on one and there’s a response in the other, and vice versa.

Along with the chert gap in the seas, there’s also a “coal gap” on land, as trees disappear from the fossil record for 10 million years after the extinction.

Unnervingly, at the same time that plants all but disappear, a brief spike in fungus suddenly appears in the rock layers of the mass extinction, possibly from dead things rotting all over the world.

The cause, then, of the End-Permian mass extinction and our own looming modern catastrophe might have been one and the same. The Siberian Traps intruded through, and cooked, huge stores of coal, oil, and gas that had built up over hundreds of millions of years during the Paleozoic. The magma had no economic motive, but the effect was broadly familiar: it burned through huge reserves of fossil fuel in a few thousand years as surely as fossil fuels ignited in pistons and in power plants.

nadir

“In the latest Triassic, reefs do really well, and the classic case is the Austrian and German Alps,” says Martindale. Martindale did her PhD work in these fairy-tale mountains, which are largely constructed from coral reefs that formed in the days when Europe huddled around the tropical Tethys Sea on the east coast of Pangaea. The hills surrounding Salzburg might be alive with the sound of music, but they’re also dead with the eventual victims of the End-Triassic mass extinction. “You hit the Triassic-Jurassic boundary, and for about 300,000 years there’s no reefs and no corals in the rock record whatsoever,” said Martindale. Though it was 200 million years ago, the obliteration of reefs at the end of the Triassic is grimly resonant for the twenty-first century. “The cool thing about the Triassic-Jurassic event is that it’s the biggest hit ever to modern corals,” Martindale said. “So that’s why it’s a big deal.”

To understand what happened in the oceans at the end of the Triassic, it’s useful to look at modern coral reef systems, which have shrunk by perhaps 30 percent since the early 1980s (an appalling, geologically instantaneous lightning strike). Coral growth rates have slowed by 20 percent in the past two decades, and devastating bleaching events—what happens when warmer water forces corals to lose the microorganisms upon which they rely for food—have become common. Humans are currently increasing the carbon dioxide concentration in the atmosphere at a rate of 2 parts per million every year; if this trend continues and the oceans continue to acidify, coral reefs worldwide “will become rapidly eroding rubble banks” by midcentury, according to one landmark study. Reef diving after the End-Triassic mass extinction would bring a snorkeler back to this future, face-to-face with a world of broken slimy husks of coral that once billowed with Technicolor clouds of life.

Additionally, corals are exquisitely sensitive to temperature changes: many species cannot live in the cold, but they are also subject to life-threatening episodes of bleaching when the water gets too warm. Microorganisms called zooxanthellae live on reef-building corals (the corals first recruited these symbionts in the Triassic), and the corals rely on them to photosynthesize their food. When episodes of unusually warm water hit, zooxanthellae literally start poisoning this relationship and the corals, it’s thought, expel them out of desperation. This is called “bleaching” for a good reason: to visit a reef after a bleaching event is to visit a panorama of calcium carbonate as white as desert bone. Bleaching is a medical emergency for corals, and the rare colony that does survive a bleaching event is often left an exhausted shade of its former splendor and even more vulnerable to future crises. Cores of centuries-old coral colonies show that the waves of global bleaching events that have wiped out corals in the past few decades—like the horrific bleaching that pummeled the Florida Reef and the Hawaiian Islands in 2015—are unprecedented for at least the past several thousand years.

Though it might take only a few decades for us to wipe out coral reefs, if the End-Triassic mass extinction is any guide, these ecosystems will take not decades, centuries, or even millennia, but millions of years to restore.

Today in western India, 11,500-foot-tall bar-coded mountains, like the jagged, banded basalt peaks of Mahabaleshwar, have been carved from this surfeit of molten rock. Ancient

lava from the Deccan Traps is even found spilling over off the other side of the subcontinent, into the Bay of Bengal, transported there by “the most extensive and voluminous lava flows known on Earth.” These molten rivers carried about 2,400 cubic miles of lava over a distance of perhaps almost 1,000 miles, or roughly the distance between Chicago and Boston. And just as the Mayans unwittingly alighted on the dinosaur-killing crater in Mexico—relying on it for freshwater—on the other side of the world Buddhist monks also found the geology of the End-Cretaceous mass extinction agreeable. Beginning twenty-two centuries ago in the jungles of the Western Ghats, Buddhists carved some two dozen monasteries and five temples into the cliffs of this Deccan basalt. These are the stunning Ajanta Caves, which, like the Ring of Cenotes, are a UNESCO World Heritage Site. Thousands of years ago, monks sat in silent meditation deep inside the rock that might have destroyed the world, a fitting place to contemplate that foundational Buddhist concept

anicca—the impermanence of ...

Richards suddenly recalled the work of his UC Berkeley colleague Michael Manga, who had worked on the hypothesis that earthquakes could trigger distant volcanoes. It wasn’t exactly a new idea, but it was one that was beginning to gain the force of statistical validation. In 1960 the largest earthquake in recorded history struck Chile. Thirty-eight hours later, the Cordón Caulle volcano blew its top 150 miles away. More than a century earlier, Charles Darwin experienced a similar earthquake in Valdivia, Chile, and within a day came the eruptions of Minchinmávida and Cerro Yanteles. Darwin sensibly imputed a causal connection between the phenomena, but struggled to come up with a convincing mechanism. For many years, this suggestive evidence for the intuitive link between earthquakes and volcanoes was only anecdotal. But recently the application of statistics has revealed it to be a real phenomenon. It seems there is a relationship between the magnitude of an earthquake and the distance at which it can trigger volcanoes. It was this relationship that Richards’s colleague Manga was sketching out. Scaling up to a preposterous magnitude 11 earthquake, of the sort caused by Chicxulub, Manga calculated that the triggering distance is effectively global. That is, a magnitude 11 earthquake should be capable of setting off volcanoes all around the world. An earthquake of the size induced by the Chicxulub impact—Richards realized in his witching-hour revelation—could have turned the ...

“It may be that Chicxulub was the gun and the Deccan Traps were the bullet,” he said. So what would it take to wipe out the dinosaurs, the most dominant animal group on land in the history of the planet and one that ruled the earth for 136 million years? Well, this might do: a climate that was deteriorating at the end of the Cretaceous, with greenhouse heat waves punctuated by brief and bitter winters . . . interrupted by an asteroid the size of San Francisco plowing through the atmosphere in a second, creating Mordor in Mexico, incinerating everything around, sending tsunamis hundreds of miles inland over distant shores, collapsing the eastern seaboard, bringing an age of darkness, failing plankton blooms, foundering food webs, and acid rain, and then . . . on the other side of the world, while the midocean ridges grumbled at the bottom of the ocean, the earth opened up, as it has in only a few catastrophic chapters previously in its history, drowning western India in fire, acidifying the oceans, and bringing punishing warmth to the world for thousands of years. Of course, this remains a speculative sketch. The fact is, we still have no idea what the last days of the dinosaurs were like. The only thing we know is that they were unspeakably awful.

It seems reasonable to ask how dinosaurs could have been dealt such an improbably terrible hand. The sheer overdetermination of kill mechanisms in their death seems almost to hint at some vengeful, dinosaur-hating destroyer god.

More likely, it was an unfortunate consequence of being so successful. Dinosaurs absolutely dominated the planet for a functional eternity. The longer you’re around, the more likely you are to see some very, very rare, very, very bad stuff. Humans have been around for far less than a million years, but if we can hold on for...

These New Mexican badlands were chock-full of turtle shells, gator bones, and mammal teeth. Familiar enough, but most of these mammals were barren lineages with no descendants in the modern world. Elsewhere, the earth was running truly strange experiments, straining to fill the ecological chasm left by the dinosaurs’ disappearance. In South America, there was titanoboa, a 2,500-pound snake stretching almost 50 feet. The monster snake would be matched in fearsomeness by the continent’s “terror birds,” which first evolved in the Paleocene but would later grow heads the size of horses, dinosaurian feet, and giant hooked beaks, with which they terrorized the countryside, carrying on the family business of their dead cousins.

When India crashed into Asia around 45 million years ago, this CO2 factory—in operation for tens of millions of years—shuttered its doors and the volcanoes went quiet. As the collision pushed the Himalayas into the sky, these volcanic rocks and this newborn mountain range began to weather, drawing down CO2 even further. As with the creation of the Appalachians and the Ordovician ice age 400 million years prior, when the uplift and weathering of the Himalayas began, the long, slow decline to the modern ice age was set in motion.

Eventually Antarctica, long a lush, forested preserve, began to separate from Australia, bringing an end to the last vestige of the supercontinent Gondwana. As the southernmost continent began to grow an ice cap and cooler and dryer climates spread across the globe, the Eocene ended with a chill 34 million years ago. This transition, from the long-standing greenhouse climate to a more modern climate with ice at the poles, caused a major turnover in animal life.

Then, a mere 3 million years ago, as carbon dioxide continued its faltering ebb and North and South America joined hands at Panama—a marriage that rerouted global ocean circulation—the top of the planet began to freeze over as well. The North Pole has probably remained mostly frozen ever since—that is, until our own time, when it’s expected to melt away in the summers of the coming decades.

When the earth had cooled enough, about 2.6 million years ago, the wobble of the planet began to dominate the climate, tilting the earth in and out of the sunshine and thrusting the entire planet in and out of great ages of ice. When these periodic wobbles tilted the earth away from the sun in the summer, the ice could march across the continents in colossal sheets more than a mile thick. Winter came to the earth, clasping it in an icy embrace for tens of thousands of years. Over the past few million years, these wobbles in space and the regular changes to Earth’s orbit have thrust the planet in and out of perhaps more than fifty cycles of advancing and retreating ice.

Which brings us to today. We find ourselves sandwiched between great ice ages, in a brief interglacial of warmth for a few thousand tenuous years, like the dozens of warm respites that have come and gone before. We should not expect this pleasant vacation to last much longer than it already has. In a geological moment, we should expect to be cast back into a great glacial age, during which New York City will look like the edge of Antarctica, with the Empire State Building an insignificant speck beside the icy face of the continental ice sheets. If the ice age returns, the seas will plummet 400 feet, pushing our familiar coastlines hundreds of miles off...

Curiously, the wild climate swings of the past few million years—in and out of punishing ice ages—have caused precious few extinctions. Unlike Isotelus rex or Dunkleosteus, which perished in earlier glaciations in earth history, woolly mammoths, giant ground sloths, enormous marsupials, and armadillos the size of cars seem to have survived the many swings between ice ages and warm interglacials...

Then, a geological moment ago, the world lost half its enormous land mammals. These are known as the “near-time” extinctions because, to geologists, events that happened only a few thousand years ago might as well have happened yesterday. These near-time extinctions, which represent the biggest hit to large land vertebrates since the biblical chaos at the end of the Cretaceous, follow a pattern unlike any other: avoiding the mari...

After millions of years of relative stability, even through countless punishing climate swings, a strange wave of extinctions suddenly swept across the planet, eerily shadowing the heroic migrations of the recently evolved African primate species Homo sapiens. Starting only a few tens of thousands of years ago, the extinctions jumped from continent to continent, then to remote islands, and they continue unchecked to the modern day. The idea of man-made extinctions evokes images of gasoline-chugging chainsaws melting through old-growth timber, or industrial fishing trawlers sterilizing the seabed with rusty submarine plowshares, but in fact, humanity’s gain has been biodiversity’s loss since birth. Sometime between 40,000 and 50,000 years ago, Australia lost its marsupial lions and its giant kangaroos, which were far larger (and slower) than those now living. It lost its diprotodons, giant lumbering herbivores the size of rhinoceroses—the largest marsupials to ever live. It lost its giant flightless birds, more than 6 feet tall. It lost a giant python, two species of terrestrial crocodiles, and an enormous monitor lizard called megalania, which, stretching some 15 feet, looke...

The extinction of woolly mammoths, viewed hazily by the public as sometime back there with dinosaurs, is so recent that it’s possible to eat woolly mammoth meat retrieved from the snow, as science writer Richard Stone witnessed one Russian comrade do on a trip to Siberia. “Even after a few shots of vodka, he said, ‘It was awful. It tasted like meat left too long in the freezer.’” Spread across eastern Europe and Russia are the scattered remains of settlements featuring houses constructed entirely from mammoth bones, including the Ukraine’s stunning Mezhyrich site, which includes the bones from some 150 animals.

Around 12,000 years ago, humans arrived in North America. At the same time, after millions of years of relative stability—again, even through wild shifts in climate—North America lost a staggering array of megafauna. The continent was home to a suite of animals far surpassing in grandeur that found on any modern African savanna. It lost its four species of mammoths, its elephant-like gomphotheres, and its giant ground sloths—some towering 15 feet tall on their hind legs. It lost its giant armadillos weighing more than a ton; beavers the size of bears; bears, like arctodus, that were far larger than any now living; and giant peccaries, tapirs, stag moose, capybaras, wild dogs, dwarf antelopes, brush oxen, woodland musk oxen, and mastodons.

Spores of a fungus that lived and relied on mastodon dung hint that this extinction wasn’t due to natural forces like a shift in vegetation or climate change. The spores plummeted—indicating the disappearance of the mastodons and other megafauna they depended on—even as the animals’ preferred spruce forests were spreading. Native American kill sites, as well as computer models simulating the relative ease of overhunting the megafauna to extinction in only a few generations, point to another culprit. North America also lost its many camels, which originated and evolved on the continent, only later spreading out into Asia and Africa. When camels were experimentally employed in military convoys across the Southwest in the 1850s, Lieutenant Edward Beale—unaware of the animals’ ancestral connection to the land—was pleasantly surprised by their uncommo...

North America lost its American zebras as well as its horses. The story of horses in North America is a curious one. Horses evolved on the continent over millions of years, then suddenly went extinct around 12,000 years ago, only to be reintroduced a few thousand years later by Spanish colonists. If they persist on the continent for millions of years from...

Unable to scavenge the previously plentiful carcasses of North American megafauna, the continent lost its teratorns—among the largest birds ever to fly—along with many of its condors. It lost its dire wolves and its saber-toothed cats. It lost an American cheetah, as well as one of the largest cats ever, the American lion—bigger even than its African cousin. You can find the remains of many of these animals where they died; in downtown Los Angeles, for instance, the...

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.

Finally, there existed control groups to test Martin’s theories. On islands and landmasses that remained undiscovered by humans for thousands of years, megafauna survived the climate changes at the end of the Pleistocene, as they had many times before, only to be destroyed when humans eventually arrived on their shores. The last ground sloths might have vanished from mainland North America 10,000 years ago, but in 2005 Martin’s former student, University of Florida paleontologist David Steadman, found fossils of a species that lingered on in Hispaniola and Cuba for an additional 5,000 years. When the West Indies were first settled by humans, these ground sloths of the Caribbean quickly disappeared as well.

In New Zealand, the fossil record for outlandish flightless birds called moas shows the colossal birds—some taller than a basketball hoop—handling the finicky climate of the Pleistocene sanguinely, marching up and down the island as the earth wobbled in and out of the sunshine. But 500 years ago, the Maori arrived in New Zealand and the moas disappeared. The extinction puzzled UCLA ornithologist and geographer Jared Diamond, also the author of Guns, Germs, and Steel. He thought the idea that human artifice alone could cause the extinctions was ridiculous on its face. He shed his skepticism while working in the remote and inaccessible Gauttier Mountains of New Guinea, where he encountered an utterly fearless tree kangaroo. Until I had worked in the Gauttiers, I was mystified to understand how the few Maoris in the vastness of New Zealand’s South Island could have killed all the moas, and how anyone could take seriously the Mosimann-Martin hypothesis of Clovis hunters eliminating most large mammals from North and South America in a millennium or so. I no longer find this at all surprising when I recall the large kangaroo Dendrolagus matschiei remaining on a tree trunk at a height of 2 meters, watching my field assistant and me as we talked nearby in full sight. It is this naïveté about humans that may account for many of the extinctions. Besides, how could any animal have any idea that this strange, bipedal mammal, smaller than some deer and lacking fearsome claws or teeth, ...

That said, the relative intactness of African megafauna, which spent the most time in the company of humans, has been cited as evidence against the overkill hypothesis. But it might be the exception that proves the rule. Slowly coevolving with people over 2 million years as hominids became ever more adept at wielding technology and strategy in pursuit of prey, these animals, alone among their global counterparts, had the requisite evolutionary time and harrowing experience to learn their “salutary dread of man.” Still, even Africa lost 21 percent of its megafauna, with larger animals getting hit the hardest.

British geologist Anthony Hallam (with a somewhat unseemly triumphalism) cites this record of precolonial ecological ruin to “dispel once and for all the romantic idea of the superior ecological wisdom of non-western and pre-colonial societies. The notion of the noble savage living in harmony with Nature should be dispatched to the realm of mythology where it belongs. Human beings have never lived in harmony with nature.” That the human project since its birth, and human flourishing in general, s...

But the carbon cycle is not the only earth system getting short-circuited thanks to human ingenuity. We’re also living through the largest disruption to the earth’s nitrogen cycle in 2.5 billion years. This might sound like arcane geochemistry, but the ramifications are extraordinary. Plants need nitrogen to live. It’s what Miracle-Gro is made of. Until the twentieth century, almost all biologically available nitrogen was fixed by microbes in the roots of legumes. Now humans synthesize this fertilizer from fossil fuels, fixing twice as much nitrogen as the natural world does every year. Before the twentieth century, the human population was limited in size by the number of crops it could grow, which was limited by the amount of nitrogen fertilizer available in nature from sources like manure. In 1909 the German chemist Fritz Haber invented the process of artificial nitrogen fixation and destroyed these natural limits. The subsequent explosion in agriculture is directly responsible for the existence of the billions of people alive today who would otherwise not be here, most likely including myself.

It stands to reason that, until very recently, all vertebrate life on the planet was wildlife. But astoundingly, today wildlife accounts for only 3 percent of earth’s land animals; human beings, our livestock, and our pets take up the remaining 97 percent of the biomass.

almost half of the earth’s land has been converted to farmland.

What these trawlers have to show for all this destruction is the removal of up to 90 percent of all large ocean predators since 1950, including familiar staples of the dinner plate like cod, halibut, grouper, tuna, swordfish, marlin, and sharks.

the victims in the animal world include scary apex predators that pose obvious threats to humans, like lions, whose numbers have dropped from 1 million at the time of Jesus to 450,000 in the 1940s to 20,000 today—a decline of 98 percent.

Fish might have been decimated by industrial-scale fishing in the past few decades, but very few have gone extinct: each year sperm whales eat as much seafood as we do—though a fraction of their historic population—there are still hundreds of thousands of sperm whales.

“The headlines are not just inaccurate,” writes futurist Stewart Brand on the premature obituary for the planet that has become de rigueur in some circles. “As they accumulate, they frame our whole relationship with nature as one of unremitting tragedy. The core of tragedy is that it cannot be fixed, and that is a formula for hopelessness and inaction. Lazy romanticism about impending doom becomes the default view.”

Plankton has gotten bulkier and heavier over time—with huge implications for the ocean and for life on earth. Today’s single-celled, armored drifters—creatures like foraminifera, and the more plant-like diatoms, and coccolithophores—are microscopic to our eyes but are still enormous compared to the single-celled plankton of the Paleozoic, a suite that was dominated by bacteria and green algae. This sort of modern plankton is also freighted with mineral ballast, an extra load that, combined with its size, allows it to sink much further into the deep ocean before being consumed again by life. This has huge consequences, as consumption of this biological snowfall in the oceans uses up oxygen. If plankton can sink deeper into the ocean before being consumed, then so too will the ocean’s Oxygen Minimum Zone (OMZ), the layer at which dissolved oxygen in the ocean is at its lowest. Today the OMZ is at about 600 meters down. But in the earth’s past—when plankton particles were tinier and sank more slowly—the OMZ might have been much, much shallower, with devastating consequences for life.

vitiated

“If you focus completely on the climate stuff and ignore super-intelligence, we might find that yeah, the Paper Clipper gets us first.” The Paper Clipper? “My idea with the Paper Clipper is, you have this artificial intelligence and you give it the goal of making paper clips. So it tries to do the actions that maximize the number of paper clips, and it figures out how to make itself smarter, because if it’s smarter, it’s better at making paper clips. So it makes itself really smart, and it comes up with a foolproof plan to convert Earth into paper clips, and it implements that plan. That’s very bad news for us. The problem here is, of course, if I tried to pull the plug on it, it’s smart enough that it’s figured out a way of stopping me, because if I pull the plug, there will be fewer paper clips in the world and that’s bad. So it must overcome any attempt at stopping it or changing its mind. It might even be that the universe has something like Kantian ethics, so a sufficiently smart mind will recognize that it’s a moral truth that it shouldn’t turn people into paper clips. Unfortunately, if the architecture of AI is such that it just maximizes its utility, and utility is defined by paper clips, it’s going to think, ‘Hmm, being moral or paper clips? Paper clips!’”

axiology,

Today our orbit is similar to that of 400,000 years ago, when a more circular orbit enabled a warm interglacial lasting 50,000 years.