Hawaii Officials Warn Big Island Residents That Mauna Loa, World’s Largest Active Volcano, May Erupt Soon

by Suzanne Halliburton
Mario Tama/Getty Images

Scientists see the signs flashing green. It’s why they’re warning residents of Hawaii’s Big Island that Mauna Loa, the world’s largest volcano, could begin rumbling and burping fiery lava.

The Associated Press reported Thursday that scientists don’t believe an eruption of Mauna Loa is imminent. But it is coming. There are too many earthquakes occurring near the summit on a daily basis to ignore the signs. That’s why they say Mauna Loa is in a state of “heightened unrest.” The volcano kicked into that category last month. It hasn’t erupted since the 1980s during President Ronald Reagan’s first term.

“Not to panic everybody, but they have to be aware of that (if) you live on the slopes of Mauna Loa. There’s a potential for some kind of lava disaster,” Talmadge Magno, the administrator for Hawaii County Civil Defense, told the AP.

Here’s why signs are blinking towards eruption. On any given day, there may be 10 to 20 earthquakes near the top of the volcano. That number now is registering 40 to 50, according to the Hawaiian Volcano Observatory. The organization, which is part of the U.S. Geological Survey, said Mauna Loa hit the “heightened unrest” state in mid-September. Scientists think the number of earthquakes has increased because more magma is flowing into Mauna Loa’s summit reservoir system. It’s fueled from a hot spot under the earth’s surface.

The Hawaiian Islands are actually a chain of volcanoes that formed over the past one million years. Here’s how that happened. They’re a result of glacially slow movement within the Pacific Plate. This tectonic plate, ever so slowly, moves northwest over a hot spot of magma. You can’t see the magma because it’s far beneath the earth’s surface. The hot spot melts through an area underneath the plate. That sends magma to the ocean floor. Then it emerges from the ocean and voila, you have islands.

The Hawaiian Islands have six volcanoes, including Mauna Loa, that are considered active. And “active” is a broad definition. It means that the volcano has erupted within the last 10,000 years. Kilauea, another Hawaiian volcano, blew in 2018 and in late 2020 There are four active volcanoes on the Big Island — Kilauea, Mauna Loa, Mauna Kea and Hualalai. Another is on Maui: That’s Haleakala. Then Loihi is underwater, sitting to the south of Kilauea.

Overall, the United States has 169 volcanoes.

The Kilauea volcano erupted in 2018 and destroyed 700 homes on the Big Island. Mauna Loa, its neighbor, is much larger. (Don Smith/Getty Images)

Mauna Loa makes up 51 percent of the island’s land mass. It rises 13,679 feet above sea level. When Kilauea erupted in 2018, the lava destroyed 700 homes. Mauna Loa last blew in 1984. It’s erupted 33 times since 1843.

The state’s civil defense authorities are meeting with residents who live on the Big Island. They’re telling people to prep for a possible emergency. This involves putting together a to-go bag filled with food. And, they want residents to identify a safe place to stay if they’re forced to leave. Plus, they need to plan how they can reunite with family members if they’re separated. Residents do have time to prepare. Before an eruption in 1975, Mauna Loa showed increased earthquake activity for a year. In 1984, earthquakes zoomed in number for 18 months before lava started blowing.

Scientists at the Hawaiian Volcano Observatory noted that the earthquake numbers recently dipped. It’s current category for Mauna Loa is an “advisory” with no indication an eruption is looming. A “watch” means an eruption is imminent.