To many people around the world, the all-but-certain prospect of a new volcanic eruption on Iceland’s Reykjanes Peninsula sounded ominous. But in March 2021, when lava rushed out of a fissure in a valley named Geldingadalur—a comfortable six miles away from the nearest town, Grindavík—those in Iceland were nothing but thrilled. The public was exhilarated to be able to see an eruption up close—one that posed little danger. Drone pilots flew their contraptions over rivers of molten rock like X-wing pilots. Scientists began forensically studying this once-per-millennium event, which is…