The Implacable Power of Volcanic Lava

May 12, 2018

In 1935, lava from an eruption of the volcano Mauna Loa, on the Big Island of Hawai’i, started oozing toward the Wailuku River, main source of water for the city of Hilo. This danger to the more than 15,000 residents of Hilo was exactly the opportunity that Thomas Jaggar, founder of the Hawaiian Volcano Observatory, had been waiting for: to blow up a volcano.

This isn’t as crazy as it sounds. Actually, no, it was crazy. Jaggar thought, based on the state of the science, that explosives would collapse and plug the channels and underground tubes through which lava flows.

He approached the Army Air Corps, which had an airbase on the island of Oahu. There, a young lieutenant colonel named George Patton (yes, that Patton) planned a mission to deploy three Keystone B-3A bombers and two Keystone B-6As—biplanes!—to the slopes of Mauna Loa, where they’d drop 20 600-pound bombs on the lava.

Five dropped onto red-hot flows, splashing lava 200 feet into the air upon detonation (which then punched holes through one of the bombers’ wings). Most of the other bombs hit the solidified sides of the flows. A US Geological Survey geologist on board one of the planes, Harold Stearns, reported that most of the bombs merely impacted on the surface.

So did it work? Well, the lava diverted and stopped flowing before it reached the river. It remains … controversial as to whether the bombs or the cessation of the eruption did it. (Jaggar thought the explosions released enough pressure to stop the lava; no one else does.)

Volcanoes have a lot of ways to kill people—caustic ash, superheated hurricane-like pyroclastic flows, incandescent mudslides called lahars…and, of course, lava. As the world watches the ongoing eruption of the volcano Kilauea, Mauna Loa’s neighbor to the east, you can see why Jaggar would resort to explosives, and why people have been trying to build lava barriers, unsuccessfully, since 1881. Lava’s appearance is rarely a surprise—but where it flows and how fast remain unpredictable. And it is, as researchers say, binary. Wherever it goes, it incinerates or buries everything in its path. There’s not much anyone can do about it except watch.

“A lot of cultures around the world have come to the conclusion that it’s a bad idea to live too close to a volcano,” says Natalia Deligne, a volcanic hazard and risk modeler at GNS Science, the New Zealand equivalent of the USGS. That’s why lots of volcanoes are magically inside national parks. “If you look at indigenous traditions, often the vent area is a taboo area,” Deligne says. “That’s just another form of land use planning.”

Unlike the ostentatious, once-in-a-blew-moon eruptors like the stratovolcanoes of the Cascades and the Andes, Hawaiian volcanoes are “shield volcanoes,” slow and steady pumps of relatively runny, low-silica lava. Volcanoes in general aren’t as murderous as other natural disasters—since 1900 volcanoes have killed about 280,000 humans, but in that same time earthquakes have killed more than 2 million.

Lava comes in three types (highly viscous, deep “blocky” lava; chunky, fast-moving ‘a ‘a, and smooth pahoehoe), and it tends to move slow enough that it destroys property rather than kills people. So people continue to live on the slopes of the volcanoes. (Hawai’ian volcanoes also emit toxic, corrosive gas—sulfur dioxide turns into sulfuric acid on contact with the atmosphere, creating potentially deadly clouds called vog, short for “volcanic smog” [itself a contraction of “smoke” and “fog”].)

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