A volcanic eruption in Southwestern Iceland forced the evacuation of a nearby town and the world-famous Blue Lagoon geothermal spa on Wednesday, July 16. Media images captured huge plumes of smoke and glowing lava flows spewing from an enormous crack in Earth’s surface roughly 30 miles (18.6 miles) southwest of Reykjavík.

The concept isn’t hypothetical. Tephra layers in Icelandic peat cores show that eruptions soared six-fold between 12,000 and 10,000 years ago —exactly when