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.

The most dependable and frequent administrators of global catastrophe, it turns out, are dramatic changes to the climate and the ocean, driven by the forces of geology itself. The three biggest mass extinctions in the past 300 million years are all associated with giant floods of lava on a continental scale—the sorts of eruptions that beggar the imagination.

Today much of the discussion about carbon dioxide’s role in driving climate change makes it seem as though the link exists only in theory, or in computer models. But our current experiment—quickly injecting huge amounts of carbon dioxide into the atmosphere—has in fact been run many times before in the geological past, and it never ends well.

And thankfully, we still have time. Though we’ve proven to be a destructive species, we have not produced anything even close to the levels of wanton destruction and carnage seen in previous planetary cataclysms. These are absolute worst-case scenarios. The epitaph for humanity does not yet have to include the tragic indictment of having engineered the sixth major mass extinction in earth history. In a world sometimes short on it, this is good news.

Our conception of history tends to stretch back only a few thousand years at most, and typically only a few hundred. This is a scandalously shortsighted appreciation of what came before—like reading only the last sentence of a book and claiming to understand what’s in the rest of the library. That the planet has nearly died five times over the past 500 million years is a remarkable fact, and as we, as a civilization, push the chemistry and temperature of the climate-ocean system into territory not seen for tens of millions of years, we should be curious about where the hard limits are.

The lesson of geology is that we inherit this world—this “antique planet with a brand new civilization,” as Carl Sagan put it—from countless vanished ages. To see the world through the lens of geology is to see the world for the first time.

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.