HONOLULU (AP) – The world’s largest active volcano erupted Monday and did not immediately threaten communities on Hawaii’s Big Island, but officials warned residents to be prepared for the worst.
Many current residents were not living there when Mauna Loa last erupted 38 years ago. The US Geological Survey warned the roughly 200,000 people on the Big Island that an eruption “can be very dynamic and the location and advance of lava flows can change rapidly.”
The eruption began Sunday night after a series of fairly large earthquakes, said Ken Hon, the scientist in charge of the Hawaii Volcano Observatory.
There has been an increase in development on the Big Island in recent decades: its population has more than doubled from 92,000 in 1980.
Most of the island’s population lives in the city of Kailua-Kona, west of the volcano, which has about 23,000 people, and Hilo to the east, which has about 45,000. Officials were more concerned about several subdivisions about 30 miles south of the volcano, which are home to about 5,000 people.
A time-lapse video of the eruption overnight showed lava lighting up an area, moving across it like waves in the ocean.
The US Geological Survey said the eruption had migrated into a rift zone, a place where the mountain’s rock is cracked and relatively weak, making it easier for magma to emerge.
An eruption from the area could send lava toward the county seat of Hilo or other cities in East Hawaii, but it could take weeks or months for the lava to reach populated areas.
“We don’t want to try to second-guess the volcano,” said Hon. “We have to let him really show us what he’s going to do and then let people know what’s going on as soon as possible.”
Hawaii County Civil Defense announced that it had opened shelters because it had reports of people evacuating from the coast on their own initiative.
The average eruption of Mauna Loa does not usually last for a couple of weeks, said Hon.
“Usually, Mauna Loa eruptions start with the largest volume first,” said Hon. “After a few days, it starts to calm down a bit.”
The USGS warned residents at risk of Mauna Loa lava flows to review their eruption preparations. Scientists had been on alert because of a recent increase in earthquakes at the summit of the volcano, which last erupted in 1984.
Parts of the Big Island were under an ash fall warning issued by the National Weather Service in Honolulu, which said up to a quarter inch (0.6 centimeters) of ash could accumulate in some areas.
Mauna Loa is one of the five volcanoes that together form the Big Island of Hawaii, which is the southernmost island of the Hawaiian archipelago.
Mauna Loa, which rises 13,679 feet (4,169 meters) above sea level, is Kilauea’s much larger neighbor, which erupted in a residential neighborhood and destroyed 700 homes in 2018. Some of its slopes are much higher steeper than Kilauea’s, so the lava can flow a lot. faster when it explodes.
During a 1950 eruption, lava from the mountain 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 those vacationing during the eruption.
“It will be spectacular wherever it is, but the chances of it actually disrupting the visitor industry are very, very slim,” he said.
For some, the eruption could cut travel time, even if there is more volcanic smog caused by higher sulfur dioxide emissions.
“But the great thing is that you no longer have to drive from Kona to Hawaii Volcanoes National Park to see an eruption,” Roth said. “You can look out the window at night and you can see Mauna Loa erupting.”
Julia Neal, owner of Pahala Plantation Cottages, said the eruption brings some relief after many preparation meetings and much wondering about what the volcano will do next.
“It’s exciting,” he said. “It’s kind of a relief that it’s happening and we’re not waiting for it to happen.”
A few prospective guests from the continental United States called Neal “asking me to make a prediction, which I can’t,” he said. “So I told him, stay tuned.”
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Associated Press writers Jennifer Kelleher in Honolulu and Mark Thiessen in Anchorage, Alaska contributed to this report.