The last time Mauna Loa, the world’s largest volcano, produced enough lava to cause any major concern to residents of Hilo was in 1942 when it came within 11 miles of the coastal city.
At that time, military officials bombed the flow in an attempt to divert it from Hilo, located 40 miles north of the summit.
But the tactic won’t be used for the current eruption.
"Bombing is out of the question because it would not be effective," said Jim Corey, vice director of state civil defense.
"There are two kinds of eruptions — one involving a cinder cone and the other is a slash in the ground like a bleeding wound," he said.
"The current eruption is like a bleeding wound and bombing it won’t be effective. Bombing would be effective only if you had a cinder cone."
The cinder cone has an open end, like a horseshoe, with the lava coming out from that end. Bombing would break down another side of the cinder cone, forcing the lava to run out in two directions.
"That would relieve the pressure from the other end, slowing down and possibly diverting the lava flow," Corey said. …
The first time bombing was used to prevent Hilo — located 40 miles away from the summit of Mauna Loa — from being engulfed by lava flows was in 1935. Then a 800-foot-wide stream of molten rock came within 15 miles of the center of the coastal town. Ten bombers of the U.S. Army Air Corps, the forerunner of the U.S. Air Force, dropped 20 bombs, each weighing 600 pounds, along a rift in the volcano, slowing the flow of the lava.
Six hours later the eruption ended. …
The 1942 Mauna Loa eruption was not made public until a long time after the volcanic activity ended.
The 13-day outbreak began April 26, four months after the Japanese attack on Pearl Harbor.
Army efforts to keep the eruption secret were to no avail, because the glow could be seen in the sky from 200 miles away, according to the 1960 edition of the fact book "All About Hawaii."
The Japanese learned of the eruption almost immediately. On April 27, Tokyo Rose congratulated Hawaii over Japanese radio for its spectacular Mauna Loa eruption.
