The year was 1935. Setting: The Big Island of Hawaii. Backdrop: Mauna Loa. For two months prior to November 21st, the island experienced swarms of earthquakes – an imminent sign to the locals that something was afoot beneath the ground they walked upon. On the morning of November 21st a large earthquake occurred, shaking the entire island. The earthquake was large enough to be felt as far away as Oahu. In the evening of the same day, a volcanic eruption took place.
Mauna Loa, or “Long Mountain,” began erupting at 6:20 p.m. on November 21st, 1935. Fountains of lava issued forth within the summit caldera. During the six days of the main event, fissures opened up along the northeast rift zone of the mountain, ejecting lava 200-300 ft. into the air. On November 26, the summit eruption died and the northeast rift activity was reduced to a single vent at the 11,400 ft. elevation. A small vent also opened up further below on the north flank of the mountain at the 8,600 ft. elevation. The spewing of Lava from Mauna Loa lasted till January 2, 1936. It was during this time frame that things “got interesting.”
Lava flows from Mauna Loa were generally fast-moving and voluminous. Lava pooled up between Mauna Kea and Mauna Loa where is now located “Saddle Road,” an east-west cross-island highway. The ponded lava eventually began to follow the lay of the land, a natural drainage, which put the city of Hilo in it’s cross-hairs. This was a big fear.
Hilo, the rainiest city/town in America is home to many. To Hilo, Mauna Loa was and still is a threat to the Islands’ economy, tourism, distribution of goods, local government, etc. Hilo overlooks Hilo Bay, a natural bay that is home to the islands’ main shipping port. The fear is that in the event of an eruption from Mauna Loa, lava flows could potentially disrupt the main operating infrastructure of the island. Watersheds would be destroyed, the local economy would come to a halt, and Hilo Bay would be filled in – destroying any means to bring in any goods or aid by sea. Hilo International Airport could also be lost. This fear was realized in 1935. A fast-moving flow advanced towards Hilo. What to do?
Enter Dr. Thomas A. Jaggar, Jr.
“Thomas Augustus Jaggar, Jr. (January 24, 1871 – January 17, 1953) was an American volcanologist. He founded the Hawaiian Volcano Observatory and directed it from 1912 to 1940 – (http://en.wikipedia.org/wiki/Thomas_Jaggar).” He knew that something must be done to divert the rapidly advancing lava flow away from Hilo. He suggested collapsing lava tubes near the source of the flow in order to stop or divert it, using dynamite. The novel idea of using explosives to stop lava flows goes as far back as 1881. However, Dr. Jaggar’s plan of mule teams hiking the explosives up the mountain would take far too long. The lava flows were moving a mile a day. At that rate, Dr. Jaggar estimated that the flow would reach Hilo by January 9 of 1936. A friend of Dr. Jaggar, Guido Giacometti, had suggested using US Army Air Corps bombers to precisely deliver explosives. Dr. Jaggar, acknowledged this notion as a brilliant idea and in no time, the call was made.
The U.S. Army Air Corps approved the mission and plans to strategically bomb Mauna Loa were set into motion. Lieutenant Colonel George S. Patton was called on to oversee a U.S. Army operation, in which military planes would drop bombs near the eruptive vent to disrupt or divert the flow. Yes, the same George S. Patton that would go on to WWII fame.
On December 26, 1935, from Luke Field, Ford Island, was deployed, six Keystone B-3A bombers of the 23d Bomb Squadron and four Keystone LB-6A light bombers from the 72d Bomb Squadron, to Hilo. Upon arrival, Dr. Jaggar briefed the pilots and bombardiers on the methods he had in mind to divert the lava flow. He then flew over the volcano to assess the flows and select the right points for bombing.
The morning of December 27, 1935, saw the takeoff of the first five bombers at 8:30 a.m. A second bombing run was planned for later the same day. Each plane carried two 300 pound practice bombs (to use for practice runs and sighting) and two 600 pound Mk I demolition bombs (355 pounds of TNT each). The fuses were set to 0.1 second. This was done to ensure the right timing for lava tube collapse and disruption of the flows. Twenty of the 600 pound bombs would be dropped onto the lava tubes. Each mission consisted of a flight of three staggered V-formation US Army Keystone B-3As bomber aircraft and two Keystone LB-6A light bombers in line-a-step formation alongside the B-3As. They approached Dr. Jaggar’s designated targets. They released their payloads at about 12,500 ft., not that far above the 8,500 foot altitude of the volcano’s flows. Five of the bombs directly hit the “fire rivers,” or molten lava flows. The other fifteen bombs were released along the channel margins. One of the fifteen bombs turned out a dud, only to be found intact and made safe years later by USAF ordinance officers. “Colonel William C. Capp (USAF, ret.), a pilot who bombed the lower target, reported direct hits on the channel, observing a sheet of red, molten rock that was thrown up to about 200′ elevation and that flying debris made small holes in his lower wing. Bombs that impacted on solidified, vesicular pahoehoe along the flow margin produced craters averaging 6.7 m diameters and 2.0 m depth. . . .”
To see actual video footage of Mauna Loa bombing run, click here: http://www.criticalpast.com/video/65675069574_bomb-Mauna-Loa_divert-lava_Keystone-B-3A_Keystone-LB-6A_United-States-fliers
A week after the bombings, the lava flow stalled, 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.” Later in 1939, Dr. Jaggar would write: “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.”
In the case of another eruption from Mauna Loa, should lava flows threaten Hilo, bombing to divert flows, is still an option on the table according to J. P. Lockwood and F. A. Torgerson.
“Because ordnance, tactics, and aircraft delivery systems have changed dramatically since 1942, the U.S. Air Force conducted extensive testing of large aerial bombs (to 900 kg) on prehistoric Mauna Loa lavas in 1975 and 1976, to evaluate applicability of the new systems to lava diversion. Thirty-six bombs were dropped on lava tubes, channels, and a spatter cone in the tests, and it was verified that spatter cones are especially fragile. Bomb crater size (to 30 m diameter) was found to be inversely related to target rock density, with the largest craters produced in the least dense, weakest rock. Bomb fuze time delays of 0.05 sec caused maximum disruption effects for the high impact velocities employed (250 to 275 m/sec).
Modern aerial bombing has a substantial probability of success for diversion of lava from most expected types of eruptions on Mauna Loa’s Northeast Rift Zone, if Hilo is threatened and if Air Force assistance is requested… (Bulletin Volcanologique 1980, Volume 43, Issue 4, pp 727-741).”
I live on the Big Island of Hawaii. Mauna Loa is one of the several volcanoes that are in my “backyard.” Let us hope that the theory of bombing Mauna Loa to divert lava flows is never needed. 😀