HONOLULU (KHON) — Mauna Loa remains in a yellow advisory with dozens of small daily earthquakes, a sign that the large volcano could be headed toward eruption. The unrest began back in July and peaked in September with 40 to 50 small earthquakes a day. Recently, there have been about 10 to 20.
While an eruption is not imminent, officials say there are other signs of unrest. “We’re continuing to see the same levels of increased rates of inflation at the summit, which is indicative of magma moving into that shallow reservoir of Mauna Loa,” Hawaiian Volcano Observatory geophysicist Andria Ellis said.
Mauna Loa is one of five volcanoes that together make up the Big Island of Hawaii, which is the southernmost island in the Hawaiian archipelago. It’s not the tallest (that title goes to Mauna Kea) but it’s the largest and makes up about half of the island’s land mass.
Mauna Loa last erupted 38 years ago. In written history, dating to 1843, it’s erupted 33 times. Its height gives it steeper slopes, which allow lava to rush down its hillsides quickly.
It’s a tough challenge for Hawaii County Civil Defense to coordinate what an eruption would do. Each eruption since 1843 started at the summit. Half the time, the volcano also began erupting from vents at lower elevations. The other half of the time it only erupted in the summit caldera.
Hawaii volcanoes like Mauna Loa tend not to have explosion eruptions like Mount St. Helens, for example. Still, lava covering one of the island’s many two-lane highways would be tough on residents and first responders.
“Shutting down the main arteries will disrupt life,” Hawaii County Civil Defense administrator Talmadge Magno said. “I went down to lower Puna a couple of weeks ago and roads are still out. They are planned to be reconstructed, but life is returning. So that’s living on an active volcano. These are dynamic, and we have to face this.”
With that, it’s up to residents to have a plan. “We need to be prepared for that volcano if it does go off and affects communities. But what about the prior stuff? What about the earthquakes?” Big Island resident Marni Renner asked. “If there’s any earthquake, are people even prepared for that? Simple things like gas in your car, propane tanks, having an emergency kit or backpack packed for each person in your household.”
There could also be situations where families are separated. “They need to recognize what their situation is where they’re living, where they’re working with their families to have their activities, especially when they’re, you know, about their daily activities and separated. They need to know how to communicate to the point where, you know, they even have a family plan, maybe a rally site,” Magno said.
During an eruption, civil defense can rely on HVO maps to pinpoint where flows would go to keep people out of harm’s way and avoid evacuating random large communities if it’s not necessary. The Hawaiian Volcano Observatory has more than 60 GPS stations on Mauna Loa taking measurements to estimate the location and the amount of magma accumulating beneath the surface.
Scientists use tiltmeters to track long-term changes in the tilting of the ground, helping them identify when the ground is swelling or deflating. A rapid change in tilt can indicate when an eruption will occur. There’s also a thermal webcam at Mauna Loa’s summit that will identify the presence of heat. And satellite radar can keep track of ground swelling and deflation.
The Associated Press contributed to this report.