Warning as largest active volcano erupts
Waves of orange, glowing lava and smoky ash erupted yesterday from the world’s largest active volcano and people living on Hawaii’s Big Island were warned to be ready should debris threaten communities.
The US Geological Survey warned the roughly 200,000 people on the Big Island that an eruption of Mauna Loa “can be very dynamic, and the location and advance of lava flows can change rapidly”.
The eruption began on Monday following a series of fairly large earthquakes, said Ken Hon, the scientist-in-charge at the Hawaiian Volcano Observatory.
There’s been a surge of development on the Big Island in recent decades — its population has more than doubled, from 92,000 in 1980.
The biggest cities on the island are Kailua-Kona to the west of the volcano, which has about 23,000 people, and Hilo to the east, with about 45,000. Officials were most worried about several subdivisions about 50km to the south of the volcano, which are home to about 5000 people.
The US Geological Survey said the eruption had migrated to a rift zone on the volcano’s northeast flank. Rift zones are where the mountain rock is cracked and relatively weak — making it easier for magma to emerge.
An eruption from the northeast could send lava toward the county seat of Hilo or other towns in East Hawaii but it could take the lava weeks or months to reach populated areas. It’s possible the eruption may later shift to a rift zone on the southwest flank. Lava emerging from this area could reach nearby communities in hours or days.
“We don’t want to try and secondguess the volcano,” Hon said. “We have to let it actually show us what it’s going to do and then we inform people of what is happening Asap.”
Hawaii County Civil Defence announced it had opened shelters because it had reports of people evacuating from along the coast.
The average Mauna Loa eruption is not typically prolonged, lasting a couple of weeks, Hon said.
“Typically, Mauna Loa eruptions start off with the heaviest volume first,” Hon said. “After a few days, it starts to calm down a little bit.”
The USGS warned residents at risk from Mauna Loa lava flows to review their eruption preparations. Scientists had been on alert because of a spike in earthquakes at the summit of the volcano, which last erupted in 1984.
Portions of the Big Island were under an ashfall advisory issued by the National Weather Service in Honolulu, which said up to 6mm of ash could accumulate 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.
Mauna Loa, rising 4169m above sea level, is the much larger neighbour of Kilauea, which last erupted in 2018, destroying about 700 homes. Some of its slopes are much steeper than Kilauea’s, so lava can flow much faster when it erupts.