Massive crater under Greenland's ice points to climate-altering impact in the time of humans
The 31-kilometer-wide Hiawatha crater may have formed as recently as 12,800 years ago when a 1.5-kilometer asteroid struck Earth
https://www.science.org/content/article/massive-crater-under-greenland-s-ice-points-climate-altering-impact-time-humans
The impact would have been a spectacle for anyone within 500 kilometers. A white fireball four times larger and three times brighter than the sun would have streaked across the sky. If the object struck an ice sheet, it would have tunneled through to the bedrock, vaporizing water and stone alike in a flash. The resulting explosion packed the energy of 700 1-megaton nuclear bombs, and even an observer hundreds of kilometers away would have experienced a buffeting shock wave, a monstrous thunder-clap, and hurricane-force winds. Later, rock debris might have rained down on North America and Europe, and the released steam, a greenhouse gas, could have locally warmed Greenland, melting even more ice.
The news of the impact discovery has reawakened an old debate among scientists who study ancient climate. A massive impact on the ice sheet would have sent meltwater pouring into the Atlantic Ocean—potentially disrupting the conveyor belt of ocean currents and causing temperatures to plunge, especially in the Northern Hemisphere. "What would it mean for species or life at the time? It's a huge open question," says Jennifer Marlon, a paleoclimatologist at Yale University.