Daily Flight Stories
Historic Wings is pleased to present our daily story celebrating what happened today in aviation history.
Published on December 27, 2012
The Mauna Loa volcano on Hawaii erupted on November 21, 1935. At first, the eruption was watched with concern, but then on the northeast and within hours a dangerous lava flow was rapidly advancing toward the city of Hilo. Hawaii’s leading vulcanologist, Dr. Thomas A. Jaggar, PhD, Director of the Hawaiian Volcano Observatory, had been experimenting with using TNT hauled by mules up the side of the volcano to dynamite lava tubes and divert the flows — yet with the threat looming to Hilo and its water supply, there wasn’t time. In fact, Dr. Jaggar was able to estimate that the lava flow would wipe out Hilo on January 9, 1936, unless it could somehow be stopped.
He 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 to divert it and save the waterworks? The year was 1935 and today in aviation history, the USAAC attempted one of the most bizarre bombing missions in history.
The Threat to Hilo
The eruption of November 21, 1935, was not a great concern initially. However, just six days later, a new vent opened on the volcano’s north flank and this began spewing lava. This molten rock ponded between Mauna Loa and Mauna Kea, holding there for a time. Dr. Jaggar at the Hawaiian Volcano Observatory concluded that the threat to Hilo was limited. Nearly a month later, however, the situation dramatically changed. On December 22, the ponded lava, located 32 km from Hilo, broke through the natural levees of stone and began a rapid flow directly toward the city. In the next four days, it traversed 8 km and that left just 24 km remained to the city.
For Dr. Jaggar, a nearly 40 year veteran of the civil service as a vulcanologist, 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 he could attempt to collapse lava tubes and thereby divert the flows. However, another vulcanologist, Guido Giacometti, suggested using US Army Air Corps bombers to deliver precision explosions more rapidly. 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. As time was of the essence, a call was placed without delay.
The USAAC Mission
The US Army Air Corps approved the mission almost immediately. 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 as four LB-6 light bombers from the 72nd Bombardment Squadron (also from Luke Field). 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 to assess the flows and select the right points for bombing.
Thankfully, December 27, 1935 — today in aviation history — held the promise of beautiful weather. That morning at 08:30, the first five bombers departed on the urgent bombing mission. A second flight of five aircraft was planned for the afternoon. Each plane carried two 300 pound practice bombs to use practice runs and sighting. Additionally, each would carry two 600 pound Mk I demolition bombs (355 pounds of TNT each) to be dropped for effect. The fuses were set to 0.1 second to ensure the right timing for lava tube collapse and disruption of the flows. In all, this meant that twenty of the 600 pound bombs with full charges would be dropped onto the lava tubes.
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 while two Keystone LB-6A light bombers from the 72nd BS trailed in line-a-step formation alongside as they 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 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 of 200 feet into the air. He also commented that higher flying flaming debris made small holes on his lower wings. 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, still well short of Hilo. After researching the matter, the vulcanologist, Dr. Jaggar would write in 1936 that the bombing had been entirely effective through the release of gases and destruction of cycle of the “equilibrium of self-heating” — a terminology and understanding that modern science completely rejects. In the resulting news reels, the USAAC was credited with saving Hilo and 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 vulcanologists are confident that Dr. Jaggar’s assessment of the effectiveness of the bombing was vastly overstated. The 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 vulcanologists note that if ever Hilo is again threatened, the USAF might well have a role — some of the larger 2,000 lb bombs and other precision-guided weapons would be powerful enough to create diversion points to manage and redirect or slow the lava flow. Ultimately, what was impossible in 1935 is today within reach.
Or at least that’s the theory.
The USAAC’s Keystone B-3A bombers and Keystone LB-6A light bombers were obsolete types that the USAAC hoped to replace. Even in mid-1935, 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 increasingly apparent and the Army was demanding a better bomber. They got what they asked for — and 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, threatening Hilo. Once again, US Army aviation assets were called in for the job — probably in B-18s. 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?