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

by Peter Brannen

Surprisingly, our ice age—which once hosted woolly mammoths and saber-toothed cats—isn’t over; it’s just on recess. Throughout the ice age of the past few million years, there have been dozens of so-called interglacials—brief windows of warmth, lasting only a few thousand years, when it gets warmer, the ice rapidly melts and retreats to the poles (where it is today), and the seas rise by hundreds of feet. We’re currently in one of these brief respites from the cold, but interglacials don’t usually last very long. This is all caused by the periodic wobble of the planet in space and the rhythmic changes to its orbit, which nudges the planet in and out of the sunlight, alternately locking much of the Northern Hemisphere in ice and then thawing it over and over again, like a geological metronome. The thaws often last fewer than 10,000 years before the great ice sheets at the poles begin to advance on the continents once more, sending the seas plummeting hundreds of feet.