Daily Flight Stories
Historic Wings is pleased to present our daily story celebrating what happened today in aviation history.
Published on December 27, 2012
By Thomas Van Hare
The Mauna Loa volcano on Hawaii erupted on November 21, 1935. At first, the eruption was watched with concern, but then the lava flows stabilized. Some weeks passed before the situation grew acute when a dangerous lava flow began rapidly advancing toward the city of Hilo to the northeast. Hawaii’s leading volcanologist, Dr. Thomas A. Jaggar, PhD, Director of the Hawaiian Volcano Observatory, knew he had to take action.
In the past, he had experimented with TNT hauled by mules up the side of the volcano, with which he hoped to dynamite lava tubes to divert the flows. Even if his earlier experiments were inconclusive, with the threat looming to Hilo and its water supply, drastic action had to be taken. On reviewing the situation, Dr. Jaggar was able to estimate that the lava flow would wipe out Hilo on January 9, 1936 — unless it could somehow be stopped.
Dr. Jaggar placed a call to the US Army Air Corps in Hawaii and asked the radical question — could the Air Corps drop bombs on the lava? His theory was that the explosions would divert the lava flows and save the waterworks and the town itself.
Thus, it came to pass that, today in aviation history, the US Army Air Corps attempted one of the most bizarre bombing missions in history.
The Threat to Hilo
The situation changed dramatically when vented lava on the volcano’s north flank that had ponded between Mauna Loa and Mauna Kea for nearly a month broke through on December 22. The vast stream of lava, initially just 32 km from Hilo, burnt through the natural levees of stone and began a rapid flow directly toward the city. In the next four days, it traversed 8 km. Just 24 km remained to the city.
For Dr. Jaggar, a nearly 40 year veteran of the civil service as a volcanologist, the situation was clear. He had to do everything possible to divert the flow. His earlier work suggested that mule teams could take dynamite to the flows and, carefully placed, the charges could potentially collapse key lava tubes to divert the flows. Without time to prepare the mule trains, another volcanologist, Guido Giacometti, suggested instead using US Army Air Corps bombers to deliver precision explosions more rapidly on target.
On paper, the plan made perfect sense. Further, it appeared to be a lot more efficient than the manual labor of hauling explosives up the sides of the mountain by teams on foot. and by mule As time was of the essence, Dr. Jaggar placed a call to the nearest airfield, hoping to drum up support for his proposed mission.
The USAAC Mission
The US Army Air Corps approved the mission almost immediately. The day after Christmas, on December 26, 1935, six Keystone B-3A (or possibly B-5A) bombers were deployed out of Luke Field from the 23rd Bombardment Squadron to Hilo. As well another four LB-6 light bombers from the 72nd Bombardment Squadron (also from Luke Field), were sent forward. Immediately that afternoon, Dr. Jaggar briefed the newly arrived pilots and bombardiers at Hilo on the methods he had in mind to disrupt the flow. Later in the afternoon, he flew over the volcano himself on one of the airplanes to assess the flows and select the right points for bombing.
Thankfully, December 27, 1935, held the promise of beautiful weather. At 08:30 am, the first five bombers took off on their urgent bombing mission. A second flight of five aircraft was also planned for the afternoon. Each plane carried two 300 pound practice bombs to use in practice runs and sighting. Additionally, each would carry two 600 pound Mk I demolition bombs (of 355 pounds of TNT each) to be dropped for effect once the practice and sighting runs were completed. The bomb fuses were set to 0.1 second to ensure deep enough penetration for the lava tubes to collapse and disrupt of the flows. In all, this meant that twenty of the 600 pound bombs with full charges would be dropped onto the lava field.
In each of the two missions, a flight of three US Army Keystone B-3As bomber aircraft from the 23rd BS flew in a staggered V-formation. Additionally, two Keystone LB-6A light bombers from the 72nd BS trailed in line-a-step formation alongside. Together, the planes made their approach to Dr. Jaggar’s designated targets. The pilots flew as high as they could — just 12,500 feet with their full bomb loads, not far above the 8,500 foot altitude of the volcano.
As it was, five of the bombs were seen to strike directly into the molten lava flows, the explosions showering lava in all directions. These craters, however, were observed to immediately fill back in. The other fifteen bombs impacted along the channel margins — at least one was a dud (though this wasn’t realized at the time; only nearly 40 years later would the dud bomb be found embedded in volcanic rock and made safe by USAF ordinance officers).
One of the pilots flying the mission, William C. Capp, noted that the bombs caused a “sheet of red, molten rock” to be lofted upwards about 200 feet into the air. He also commented that higher flying flaming debris made small holes on the lower wings of his bomber. Luckily, none of the planes were lost and all returned to Hilo successfully.
Just one week after the bombing, the lava flow slowed and then stalled, well short of Hilo. After researching the matter, Dr. Jaggar would write in 1936 that the bombing had been entirely effective through the release of gases and destruction of the cycle of the “equilibrium of self-heating” — a terminology and understanding that modern science completely rejects. The Press ate it up. In newsreels, the USAAC was credited with saving Hilo and all of its waterworks.
To this date, the 23rd Bomb Squadron still officially takes credit for saving Hilo from destruction by lava.
In 1939, Dr. Jaggar would again write about the volcano bombing, this time making even stronger claim:
“The smashing of the tunnel had cooled the oncoming liquid so that it dammed itself. This confirmed the theory that the bombing solidified the tunnel lava back into the heart of the mountain. With twelve river hits out of sixteen, and liquid thrown up hundreds of feet, there can be no question whatever that the bombing stopped the flow.”
In retrospect, modern volcanologists are confident that Dr. Jaggar’s assessment of the effectiveness of the bombing was vastly overstated. Their more reasoned conclusion is instead that the lava flow stopped entirely by coincidence. In effect, the small Mk I bombs were a pointless and futile effort.
With that said, however, the volcanologists note that if ever Hilo is again threatened, the USAF might well have a role. Dr. Jaggar wasn’t entire wrong since some of the new, larger 2,000+ lb bombs and other precision-guided weapons would be powerful enough and accurate enough to create his imagined “diversion points” to manage, redirect or slow the lava flow. Ultimately, what was impossible in 1935 is today within reach.
Or at least that’s the theory.
By 1935, the USAAC’s Keystone B-3A bombers and Keystone LB-6A light bombers were obsolete types that the USAAC hoped to replace. That year, the new Boeing 299 (later B-17) was under development and a hotly reported effort within Air Corps circles. The growing challenge from Japan in the Pacific was becoming increasingly apparent. The Army was demanding a better bomber for its Air Corps. They got what they asked for. Indeed, their first Boeing B-17 Flying Fortresses were scheduled to arrive on the very morning of December 7, 1941 — right into the teeth of the Japanese air attack on Pearl Harbor.
Just five months later, in a bizarre twist, the Mauna Loa volcano again erupted, and again threatened Hilo. Once again, US Army Air Corps was called in for the job. Records are scant, but they probably flew the mission with B-18 bombers. Their bombs proved equally “effective” (in other words, once again rather pointless in the view of later scientists who have studied the matters closely).
What did US Army General George S. Patton have to do with the volcano bombings of 1935?