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Guest Post: Remembering When Mauna Loa Last Awoke: The Last Resort (Part 3)

Rocky Planet iconRocky Planet
By Erik Klemetti
Mar 27, 2014 8:54 PMNov 20, 2019 12:33 AM


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And now, the exciting conclusion to Zahra Hirji's retrospective on the 1984 eruption of Hawaii's Mauna Loa. Be sure to check out Part 1 and Part 2 if you haven't! ---------- Remembering When Mauna Loa Last Awoke: The Last Resort (Part3)

Lava flows from the 1984 eruption of Mauna Loa, seen on March 25. Image: R.W. Decker / USGS. HVO’s head Bob Decker departed as conversations about thwarting the Hilo-bound lava flows, whether by barriers or bombs, reached a fevered pitch. A week into Mauna Loa’s 1984 eruption, the Big Island’s Mental Health Association director said, “The greatest cause of stress is the feeling that you have little or no control over a situation…and let’s face it; we have little or no control over Pele.” But that statement was not entirely true. There was always the controversial option of lava mitigation—in other words, stopping or diverting the lava in some way. One of the earliest known mitigation attempts dates back to Italy 1669. To protect against a menacing Mt. Etna volcano eruption, the town of Catania built a stone wall around the city. The barrier held for several days before one corner eventually caved. Geologists call these structures “earthen barriers” or “diversionary structures”; they are designed to obstruct a lava flow path while also cooling and solidifying the flow front, further disabling progress. This method is more successful when the barrier is positioned to redirect the flow of lava, rather than simply dam it. The most aggressive mitigation approach, cooked up in Hawaii in the 1930s, is pure cowboy—bombing lava flows. The theory goes that if a bomb is dropped on areas where lava collects within a flow, such as a lava cone, the explosion should temporarily disconnect the flow front from the lava source. This method was first tested on Mauna Loa lava headed towards Hilo back in 1935. Bombs were similarly used to thwart another Hilo-bound Mauna Loa flow in 1942. Both trials were inconclusive, as the eruptions stopped naturally before lava ever made it to the city. In the years leading up to Mauna Loa’s 1984 eruption, Hawaiian Volcano Observatory geologist Jack Lockwood made it his mission to verify that bombing a flow was a winning mitigation idea. His goal was to demonstrate that firepower could actually trigger the collapse of specific lava flow features—and he succeeded. In the late 1970s, Lockwood recruited the military to drop thirty-six bombs on historical Mauna Loa flows along the northern part of the mountain, within an Army training area. Lockwood assumed the strength of the hardened old flows was comparable to active flows, which often develop a solidified exterior mid-eruption. The result of the experiment was awesome demolition, where bombing pockmarked flows with mini craters. The largest craters formed in areas where the rock was less dense. It was proof enough that bombing could work. For any community contemplating mitigation, there are three main considerations: money, manpower, and time. But in Hawaii, the volcano goddess Pele provides an additional concern. According to Pele believers, “lava must flow.” This means that attempts to obstruct flows are considered culturally insensitive, even sacrilegious. In the past, especially before Hawaii became a state in 1959, the disaster management community largely ignored the native population’s opinions on mitigation. But by 1984, there was a greater general island awareness of the goddess. Consequently, mitigation was largely scorned in public discussions. On Tuesday, March 28, 1984, three days into Mauna Loa’s eruption, the Hawaii Tribune-Herald reported that Mayor Herbert Matayoshi and Governor George Ariyoshi had discussed and rejected the possibility of trying to divert the lava flows heading toward Hilo. But two weeks later, it was communicated that Matayoshi was reconsidering mitigation measures, although no details were released. Around this time, HVO’s leader Bob Decker officially stepped down and left the state. In an interview with a Hawaii newspaper, he explained that his reasons for leaving were family-related. “My 92-year-old mother is quite ill,” he said. He then added jokingly, “I’m not a rat deserting a sinking ship…I may be a rat but this is not a sinking ship.” Decker may have been confident about Hilo’s safety, but many were not, including those taking part in the mitigation discussions. Publicly, elected officials were opposed to lava mitigation, explained Lockwood. But behind closed doors, the governor’s office was creating a contingency plan and sought mitigation advice from the geologist. “And we weren’t talking about the grand-scheme bombing up here. They were talking about building diversionary structures to protect certain facilities,” said Lockwood. Bombing was avoided not because it couldn’t work, he said, but because it meant involving the military, a publicly unpopular move. Civil Defense director Harry Kim was against bombing but supported small-scale diversionary structures as a “last resort.” But diversionary structures opened up a legal can of worms, explained Lockwood. For example, imagine the government builds a protective wall around an agreed upon essential public building, such as the hospital. The barrier might successfully redirect flows on a new path toward previously safe private buildings. As of 1984, it was believed that if those private buildings burned down, owners would likely have the grounds to sue the government for damages. However, according to a little-known legal opinion published in 2004, under a natural disaster declaration the governor can authorize the construction of certain diversionary structures that then endanger surrounding buildings. While the government must provide monetary compensation for any damaged buildings, it is believed that people could not sue for additional damages. Despite the perceived liability issues, emergency managers and state officials were very likely going to approve a barrier in 1984. “There were basically plans afoot if lava diversion would have been necessary,” said Lockwood. “The governor certainly would have considered it.” Fortunately, mitigation was never necessary. On April 15, 1984, twenty-two days after Mauna Loa started adding a fresh lava coat to its rocky exterior, the eruption ended just as suddenly as it began. Lava flows stopped around 4.5 miles north of Hilo, sparing the city.

A view of Hawaii’s Mauna Loa volcano from the city of Hilo. Image: Hunter Bishop, flickr

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