The Reykjanes peninsula in southwestern Iceland experienced what is likely its most powerful volcanic eruption yet, the fourth in a series of eruptions since December. This time, however, there was little warning—the Iceland Meteorological Office (IMO) registered warning signs only about 40 minutes before the eruption began around 8:30 p.m. Saturday, with a huge fissure opening near the town of Grindavík and the Svartsengi power plant. Grindavík had been evacuated several months earlier due to another eruption, but the nearby Blue Lagoon, a geothermal spa that is one of Iceland’s landmark tourist attractions, had about 700 guests to evacuate once the alarm was raised. The lava flow was streaming toward the power plant, the town, and a water distribution pipe around 1 a.m., which threatened to cut off the hot water supply to local residents. By Sunday morning, the lava had significantly slowed. The eruption marks the most powerful volcanic event in the Reykjanes region—which includes the nation’s capital, Reykjavik—since seismic activity resumed in 2021, ending 800 years of inactivity.