Most of the residents of Heimaey, a small island south of Iceland, evacuated when the volcano erupted in 1973. But an international corps of volunteers stayed behind. Hoping to save the town’s harbor, they pumped frigid ocean water on the advancing lava. Five grueling months later, the eruption stopped. The mouth of the harbor was
half-blocked but still useable. Did human intervention affect the lava’s movement? That question is still being debated.