On January 23, 1973, Heimaey, a small island off the coast of Iceland, was shaken by an unexpected volcanic eruption. Lava poured down the slopes, threatening to seal off the island’s harbor—the lifeline of the local fishing economy. The destruction could have forced residents to abandon their homes and livelihoods. But the islanders didn’t run. Using massive water pumps, they blasted millions of tons of seawater onto the advancing lava. It sounds almost impossible, but it worked. The water cool