Key point: The plan made sense, but the bombs likely weren't strong enough. However, the lava flow stopped eventually anyway.
Disaster seemed imminent: day by day, a glowing river of molten lava was creeping steadily towards Hilo, Hawaii. The town of 15,000 lay slightly over 30 miles northeast of Mauna Loa, known as the second-largest volcano on the planet.
The over 13,000-foot tall behemoth had erupted on Hawaii island on November 21. By December, Dr. Thomas Jaggar, a local volcanologist and founder of the Hawaii Volcano Observatory, estimated that one of the five streams of lava issuing from Mauna Loa was advancing at a mile per minute towards Hilo, threatening to first flood the Wailuku River feeding into it.
At first, Jaggar considered dispatching mule teams laden with explosive to Mauna Loa to collapse the lava tubes feeding the lava streams—but such a project seemed likely to take far too long to avert catastrophe.
Then his colleague Guido Giacometti proposed a faster solution: why not ask the Army Air Corps if it could blast the streams from the air with a little precision bombing?
On December 23, Jaggar contacted the G-2 intelligence staff officer of the Army Hawaiian Division, a young lieutenant colonel by the name of George S. Patton. He signed off on the idea and tapped the 23rd and 72nd Bomber Squadron for the job, both based at Luke Field on Ford/Oahu island.
At the time these units flew large, fabric-covered Keystone B-3A and LB-6 twin-engine biplane bombers. The obsolete aircraft had five-man crews armed with defensive machineguns, and Wright Cyclone engines nestled in the spars between their two sets of wings. Though highly similar, the older LB-6 was distinguished by its twin vertical tail fins compared to the single fin on the B-3A.
Jaggar briefed the pilots on the geological theory behind the raid, and on December 26 the Army Air Force bombers flew the 220-mile long journey from Luke Field in Pearl Harbor to a field in Hilo.
The following morning the aviators were visited by a native Hawaiian named Harry Keliihoomalu who warned them not to attack, lest they displease the Madam Pele, the Hawaiian goddess of volcanoes, and thus by implication the creator of the volcanic Hawaiian archipelago itself.
“Why don’t they leave Pele alone?” Keliihoomlu later told Hilo’s local newspaper. “They shouldn't interfere with the flow. If Pele decides to flow to Hilo, there's nothing that they can do to stop her.”
Pele, also known as She Who Devours the Earth, remains a popular local deity, and many Hawaiian natives believed it wrong to obstruct volcanos, seen as manifestations of her power.
Another citizen quoted in the paper said: “Pele should not be disturbed. This bombing is a folly. It will do more harm than good. If Pele makes up her mind to come to Hilo it is not for man to dissuade her by artificial methods. She cannot be stopped that way.”
Nonetheless, the Army pilots carried out their mission in two waves of five, the rickety open-cockpit aircraft approaching the volcano at an only 4,000 feet high due to their bombloads, and likely below their pokey maximum speed of 115 miles per hour. Jaggar observed the attack through his telescope from a perch neighboring on Mauna Kea, while a geologist named Harold Stearns accompanied the bomber crew for a first-hand view of the operation.
The first wave—two LB-6s and three B-3As—each carried two 300-pound practice bomb with black powder charges to test different approaches. In the following five-ship wave at noon, each aircraft carried two 600-pound Mark 1 bombs with fuses set to detonate a tenth of a second after impact.
Most of the bombs exploded ineffectually to either side of the stream—but five landed on target, their explosions creating craters that rapidly flooded with molten rock and causing lava to fountain hundreds of feet into the air. According to one article, flying volcanic sediment even burned holes in one of the bomber’s fabric-covered wings.
Six days after the raid on December 2, the lava stream abruptly ceased its advance. Jaggar was not shy about according to his bombing scheme credit for this fortuitous outcome.
“The experiment could not have been more successful; the results were exactly as anticipated,” he told the New York Times. He expounded:
This channel was broken up by the bombing and fresh streams poured over the side of the heap…. I have no question that this robbing of the source tunnel slowed down the movement of the front…. The average actual motion of the extreme front … for the five days after the bombing was approximately 1000 feet per day. For the seven days preceding the bombing the rate was one mile per day. How long would the flow have lasted without bombing it?
But Stearns, who witnessed the bombing up close concluded the opposite:
“The tube walls look 25 to 50 feet high and deep in the flow so that I think there would be no chance of breaking the walls. The lava liquid is low. The damming possibility looks effective but the target is too small.” Regarding the flow’s halt on December 2, he later wrote: “I’m sure it’s a coincidence.”
Most geological analysis of the bombing shared Stearn’s conclusion that the bombs simply weren’t powerful to meaningfully affect the lava flow.
Nonetheless, seven years later on May 1 or 2, 1942, the wartime Army Air Force again dispatched bombers to strike an active Mauna Loa, this time targeting her vents. The aircraft (most likely B-18 Bolo light bombers) again missed with most of their bombs and left behind several duds. A later study again judged the raid had been ineffectual. But three days later vents collapsed, likely due to natural causes.
Then from 1975–1976, the Air Force engaged in multiple tests using far more powerful 2,000-pound bombs on volcanic rock, producing 100-foot diameter craters. A detailed 1980 study by J.P. Lockwood and F.A. Torgerson judged that the attacks in 1935 and 1942 were unlikely to have had any affect, but estimated that larger weapons employed with greater precision could be effective. The idea continues to be proposed from time to time as possible solution for dealing with modern eruptions.
However, the idea of using bombers or other technologies to divert lava flows in Hawaii remains objectionable to many Hawaiians, who believe that respecting Pele means accepting her unpredictable bouts of fiery destruction—or risk suffering worse consequences.
Indeed, some hold Pele responsible for a fatal crash at Luke Field two months after the 1935 bombing which killed six aircrew who had participated in the raid.
Despite having possibly incurred the wrath of a goddess, the 23rd Bomber Squadron continues to sport a unit patch depicting bombs falling upon a volcano. In 2015 on the eightieth anniversary of the raid, the squadron dispatched two B-52 for a flyby of Mauna Loa to commemorate their shared history in a unique confrontation between man and nature.
Sébastien Roblin holds a Master’s Degree in Conflict Resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring. This first appeared in 2019.