HONOLULU– The world’s largest active volcano spewed some ash and lava Monday and officials said Mauna Loa is not threatening communities on Hawaii’s Big Island, but people should brace for worse.
The US Geological Survey warned the island’s 200,000 residents that an eruption “can be very dynamic, and the location and advance of lava flows can change rapidly.”
The eruption began late Sunday night in the Big Island volcano after a series of fairly large earthquakes, said Ken Hon, the lead scientist at the Hawaiian Volcano Observatory.
The Big Island has experienced rapid development in recent decades — the population has more than doubled from 92,000 in 1980 to 200,000 — and many newer residents were absent when Mauna Loa last erupted 38 years ago.
Most people on the island live in the city of Kailua-Kona west of the volcano with a population of about 23,000 and Hilo to the east with about 45,000. Officials were most concerned about several subdivisions about 30 miles south of the volcano, which are home to about 5,000 people.
Time-lapse video of the eruption overnight showed lava illuminating an area and moving above it like waves on the ocean.
The US Geological Survey said the eruption has moved into a rift zone — a place where the mountain rock is fractured and relatively weak — allowing magma to escape more easily.
An eruption from the zone could send lava toward the county seat of Hilo or other cities in eastern Hawaii, but it could take weeks or months for lava to reach populated areas.
“We don’t want to try and second-guess the volcano,” Hon said. “We have to actually let them show us what it’s going to do and then let people know what’s happening as soon as possible.”
The Hawaii County Civil Defense announced that it has opened shelters because of reports of people being evacuated along the coast on their own initiative.
The average Mauna Loa eruption is typically short-lived, lasting a few weeks, the Hon said.
“Typically, Mauna Loa eruptions start with the largest volume first,” Hon said. “It calms down a bit after a few days.”
The USGS warned residents at risk from Mauna Loa’s lava flows to review their eruption preparations. Scientists have been on alert for a recent earthquake spike at the volcano’s summit, which last erupted in 1984.
“At this point, it is not a time to be alarmed,” said Big Island Mayor Mitch Roth.
Parts of the Big Island were under an ash fall warning issued by the National Weather Service in Honolulu, which said ash could accumulate as much as 0.6 centimeters in some areas.
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.
Rising 4,169 feet above sea level, Mauna Loa is Kilauea’s much larger neighbor, which erupted in a residential area in 2018 and destroyed 700 homes. Some of its slopes are much steeper than Kilauea’s, allowing a lot of lava to flow faster when it erupts.
During an eruption in 1950, the mountain’s lava traveled 15 miles (24 kilometers) to the ocean in less than three hours.
Tourism is Hawaii’s economic engine, but Roth predicted few problems for vacationers during the outbreak.
“It’s going to be spectacular where it is, but the chances of it really disrupting the visitor industry — very, very slim,” he said.
For some, the eruption could cut travel time even if there’s more vog, or volcanic smog caused by higher sulfur dioxide emissions.
“But the good thing is that you no longer have to drive from Kona to Hawaii Volcanoes National Park to see an eruption,” Roth said. “You can just look out your window at night and see Mauna Loa erupting.”
Julia Neal, owner of Pahala Plantation Cottages, said the eruption brings some relief after many preparatory meetings and leaves many wondering what the volcano will do.
“It’s exciting,” she said. “It’s a kind of relief that it’s happening and we’re not waiting for it to happen.”
News that the eruption has moved from the summit to the northeast rift zone and that lava is not threatening communities on the slopes also brings relief, she said.
A couple of prospective guests from the US mainland called Neal and “asked me for a prediction, which I can’t do,” she said. “So I said just stand still.”
Associated Press writer Mark Thiessen of Anchorage, Alaska, contributed to this report.