The lava tubes of the Mauna Loa Forest Reserve on the Island of Hawai‘i were created by lava flows carving out caves beneath hardened volcanic rock. Under most circumstances, they're safe to walk through, but what Kawika Singson saw on a recent hike there sent him in the opposite direction. As West Hawaii Today reports, the Kona resident discovered undetonated bombs lodged into the rock dating back as far as 1935.

Eighty-five years ago, a stream of lava from the active Mauna Loa volcano threatened to reach the nearby town of Hilo. Hawaiian Volcano Observatory founder Thomas A. Jaggar came up with a plan to protect the villagers that involved asking the U.S. Army to drop dozens of bombs near the molten rock.

While adding explosives to an already-volatile lava flow may sound misguided, his thinking was grounded in logic. The idea was that the bombs would push the lava stream off course and away from Hilo. When the bombs were dropped on December 27, 1935, they slowed the streams slightly and diverted them into the Hilo Forest Reserve. The re-routed flows eventually stopped altogether on January 2, 1936. There's still some debate over whether the bombs stopped the lava or whether the timing was a coincidence.

Similar bombings in the area were carried out for the same reasons in 1942, 1975, and 1976. Larger bombs were used in the 1970s, which means the artifacts discovered in February of this year must be from either 1935 or 1942.

Coming from a military background and knowing the history of the area, Singson immediately recognized the rusted objects embedded in the ceiling of the lava tube as bombs. After taking some photos, he retreated to safety and got in touch with the Department of Land and Natural Resources to share the exact location of the explosives. The department's Division of Conservation and Resources Enforcement and Division of Forestry and Wildlife are now working on a way to dispose of the devices safely, possibly with the military's help.

[h/t West Hawaii Today]