How Do You Stop a Lava Flow?

Sicily’s Mount Etna has been spewing molten rock since last Sunday, when a series of earthquakes sparked the volcano’s first major eruption since 1992. Some villagers in the nearby town of Linguaglossa, located just a few miles from the crater, are making evacuation plans. Is there any way to stop a lava flow?

Not dead in its tracks, per se, but there are some viable tricks to slowing down the deadly stream. The Italians’ efforts to stymie Etna’s lava date back to 1668, when a retaining wall was built on the mountainside. (It didn’t work.) They’ve had more success in recent years, particularly 1983 and 1992, when hastily constructed earthen barriers managed to slow the flows, which typically sluice down Etna at a few dozen meters per hour. The lava eventually breached the barriers, but it was hindered enough that it atrophied before scorching inhabited land.

Some anti-lava folks put their stock in explosives. Back in 1935, a young George S. Patton Jr. (then a lieutenant colonel) led an aerial bombing strike against Hawaii’s Mauna Loa, hoping to divert the lava away from the city of Hilo; it didn’t work. But others have had success with dynamiting the narrow “lava tubes” through which the 1,800-degree rock travels. By widening the tubes, engineers force the lava to lose energy and dissipate higher up on the volcano. The Italians used this technique in 1992, too, with good results.

The most spectacular anti-lava effort in history occurred on the Icelandic island of Heimaey in 1973. Worried that the lava would flow into the harbor’s mouth, forever closing the vital port to ships, Icelanders came up with an ingenious plan. They sprayed the flow with 6 million cubic meters of water, hoping to cool the lava enough—by about 50 degrees Celsius—so that it would solidify. It took five months of nearly constant spraying, through fire hoses and pumps, to atrophy the lava, but the scheme succeeded. But most volcano fighters do not have the luxury of such time.

When all else fails, there is always the ancient Hawaiian method: sending a holy figure to the lava flow’s edge to make an appeal to Pele, the volcano goddess. Many Hawaiians credit the prayers of Princess Ruth Keelikolani with stopping an 1881 lava flow that threatened Hilo.

Next question?