1935 Lava Bombing Mission: US drops 40 bombs on Mauna Loa flow

On December 27, 1935, US military aircraft dropped 40 bombs on Mauna Loa's lava flow to divert it from Hilo, in a controversial attempt to influence volcanic activity. The eruption, which began on November 21, 1935, within Mauna Loa's summit caldera, had shifted to the Northeast Rift Zone by November 27, with lava flowing toward Hilo at roughly one mile per day, threatening the Wailuku River and the town's water supply.

Thomas A. Jaggar, founder of the Hawaiian Volcano Observatory, and volcanologist Ruy Finch proposed bombing the lava channels to break the insulated tubes allowing the lava to travel long distances. The goal was not to stop the eruption but to make the lava spread out and slow down.

Overseeing the operation was Lieutenant Colonel George S. Patton. Twenty 600-pound demolition bombs and 20 marker bombs were dropped near the lava channels on Mauna Loa's northern flank. Of the demolition bombs, 16 reached the target area, with 12 hitting the lava tunnel. Jaggar deemed the operation a success, observing the lava flow slow down and stop by January 2, 1936.

However, not all were convinced of the bombing's effectiveness. Howard Stearns, a USGS geologist, suggested the lava's natural fading around the same time made the bombing's impact unclear. The USGS describes the effectiveness of such methods as unresolved, with a 1942 attempt also yielding inconclusive results.

Despite the debate, the 1935 mission represents one of the earliest organized attempts to divert lava flow, showcasing human efforts to influence volcanic activity with limited understanding at the time.