Leila Battison

Every so often, I come across a story in geology that reminds me how much of Earth we still don’t fully understand. Take the Younger Dryas: a sudden, sharp return to ice-age cold about 13,000 years ago. It coincided with the disappearance of mammoths, and with the vanishing of the Clovis people in North America. For decades, scientists have argued over what caused this dramatic cold snap. Was it ocean currents, volcanoes, or something more dramatic like an asteroid impact?

That last idea got a huge boost in the 2010s, when radar surveys of Greenland revealed a vast, circular hole beneath the Hiawatha Glacier. Thirty kilometers wide and 300 meters deep, it looked an awful lot like an impact crater. If it were tied to the Younger Dryas, it might have been the “smoking gun” explaining why the planet suddenly chilled.

To test the idea, scientists turned to quartz, the humble, six-sided mineral that shows up in everything from granite to jewelry to glass. Under a microscope, quartz crystals sometimes record the scars of catastrophic events. Shocked quartz, marked with telltale internal fractures, only forms under extreme pressures like those from asteroid impacts or nuclear explosions.

Sure enough, the sand draining from under the glacier contained shocked quartz. It confirmed the hole was a true crater, blasted out by a meteorite perhaps 1.5 kilometers across, striking with the energy of 700 nuclear bombs. For a moment, the case seemed closed.

But science rarely works in straight lines. When researchers dated the shocked quartz, they discovered the impact wasn’t 12,000 years old at all. It was 58 million years old. At the time, Greenland wasn’t icy tundra, but a forest of conifers, small mammals, and birds. The Hiawatha impact was spectacular, but it happened long before humans existed. Which meant it couldn’t explain the Younger Dryas after all.

And yet—the quartz still whispers of catastrophe. Across sites in North America, scientists have found “lightly shocked” quartz grains in sediments just before the Younger Dryas began. These point not to a crater-forming collision, but to a comet that fragmented in the atmosphere and exploded in fiery airbursts. Such blasts could have blackened skies, scorched landscapes, and tipped the climate into chaos.

So the Younger Dryas mystery remains, balanced between competing hypotheses. But thanks to quartz—ordinary, abundant quartz—we’re at least narrowing in on the truth. It’s humbling to think that the fate of entire ecosystems and cultures can be written in the microscopic scars of a mineral.

Watch the full video I wrote for SciShow here: