HONOLULU (AP) — The world’s largest active volcano erupted Monday and was not an immediate threat to communities on Hawaii’s Big Island, but officials warned residents to be prepared for worse.
Many current residents were not living there when Mauna Loa last erupted 38 years ago. The U.S. Geological Survey warned the Big Island’s population of about 200,000 that an eruption “can be very dynamic and the location and progression of lava flows can change rapidly.”
The eruption began late Sunday evening after a series of fairly large earthquakes, said Ken Hon, the scientist in charge at the Hawaiian Volcano Observatory.
There has been a surge of development on the Big Island in recent decades – the population has more than doubled, from 92,000 in 1980.
Most people on the island live in the town of Kailua-Kona west of the volcano, home to about 23,000 people, and in 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.
A timelapse video of the night’s eruption showed lava illuminating an area and moving over it like waves on the ocean.
The U.S. Geological Survey said the eruption had migrated to a rift zone — a place where the mountain rock is cracked and relatively weak — making it easier for magma to emerge.
An eruption from the zone could send lava to the county seat of Hilo or other cities in eastern Hawaii, but it could take weeks or months for the lava to reach populated areas.
“We don’t want to try to put the volcano second,” Hon said. “We need to show it to us what it’s going to do and then we’ll inform people about what’s happening as soon as possible.”
Hawaii County Civil Defense announced it had opened shelters as it had reports of people evacuating on their own initiative along the coast.
Mauna Loa’s average eruption typically doesn’t last long, lasting a few weeks, Hon said.
“Usually Mauna Loa eruptions start with heaviest volume first,” Hon said. “After a few days things start to calm down a bit.”
The USGS warned residents at risk from Mauna Loa lava flows to review their eruption preparations. Scientists were alert due to a recent spike in earthquakes at the volcano’s summit, which last erupted in 1984.
Parts of the Big Island were under an ash advisory from the National Weather Service in Honolulu, which said up to a quarter of an inch (0.6 centimeters) of ash could accumulate in some areas.
Mauna Loa is one of five volcanoes that make up the Big Island of Hawaii, the southernmost island of the Hawaiian archipelago.
Rising 4,169 feet above sea level, Mauna Loa is Kilauea’s much larger neighbor, which erupted into a residential area in 2018, destroying 700 homes. Some slopes are much steeper than Kilauea’s, so lava can flow much faster when it erupts.
During an eruption in 1950, lava from the mountain traveled 15 miles to the ocean in less than three hours.
Tourism is Hawaii’s economic engine, but Roth predicted few problems for vacationers during the eruption.
“It will be spectacular where it is, but the chances of it actually disrupting the visitor industry are very, very slim,” he said.
For some, the eruption may shorten travel time, even though more volcanic smog has been 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 just look out your window at night and you’ll be able to see Mauna Loa erupt.”
Julia Neal, owner of Pahala Plantation Cottages, said the eruption brings some relief after many preparation meetings and many questions about what the volcano will do.
“It’s exciting,” she said. “It’s kind of a relief that it’s happening and we’re not waiting for it to happen.”
Some future guests from the mainland US called Neal “to ask me to make a prediction, which I can’t do,” she said. “So I said, just stand.”
Associated Press writers Jennifer Kelleher in Honolulu and Mark Thiessen in Anchorage, Alaska contributed to this report.