A Reader Asks: Why Not Divert Kilauea's Lava Flow?

Wednesday we wrote about Hawaii's Kilauea volcano, which is threatening homes and businesses on Hawaii’s Big Island and complicating tourism -- as well as daily life.

One of our Facebook commenters asked why officials aren’t “digging ditches to divert the lava away,” another thought that idea sounded “crazy.”

Dr. Charles W. Mandeville, program coordinator for the volcano hazards program at the U.S. Geological Survey, explains there's a history of lava control attempts, with varying degrees of success.

On the Icelandic island of Heimaey, lava flow from the eruption of Eldfell in 1973 was halted by pumping massive amounts of seawater onto the lava. In 1992, attempts to divert lava flow from Mount Etna in eastern Sicily were less successful.

For Etna, explosives were used to open a hole in the side of the lava trench (the channel through which the lava is flowing) and another trench was created for the lava to flow into. Unfortunately, there was a surge in the amount of magma and the lava returned to its old path.

Mandeville says the seawater approach would not be used for the Kilauea volcano as it’s too far from the coast to pump the requisite seawater. The key considerations for whether explosives or diversion trenches can be used are what the magma supply is, if the flow is narrow, and whether there is a spot to put all the diverted lava that won’t eventually be inundated itself.

Ultimately, Mandeville emphasizes, the choice of whether to (attempt) diverting lava flow is up to local officials, who have the best grasp of the economic and cultural effects of what is inevitably a costly undertaking.