Mauna Loa in Hawaii, the world’s largest active volcano, began spewing ash and debris from its summit, prompting civil defense officials to warn residents Monday to prepare in case the eruption sends pyroclastic flows into communities.
The eruption began late Sunday evening at the top of the volcano’s caldera on the Big Island after a series of relatively nearby and large earthquakes, said Ken Hoon, chief scientist at the Hawaii Volcano Observatory, during an early morning briefing. . Magma moved to the surface, although pyroclastic flows were contained in the summit area and did not threaten nearby communities.
Time-lapse video of the eruption overnight shows molten lava lighting up the caldera, moving across it like waves on an ocean.
Hoon said some images sent to the Hawaii Volcano Observatory indicate that the southern end of the caldera overflowed, causing a pyroclastic flow a few kilometers (miles) from the caldera.
In some previous eruptions, lava overflowed the caldera but did not bring it close to populated areas.
“Right now, we’re looking at the indicators, trying to determine whether this is an eruption that will stay within the Mauna Loa mountain range or move into one of the fault zones either to the south-west or northeast,” Hoon said. He said.
“We don’t want to second-guess the volcano,” Hoon said. “We have to let her show us what she’s going to do and then let people know what’s going on as quickly as possible.”
Officials said there are currently no indications of the eruption migrating into the fault zone. A rift zone is the area where a mountain splits and where rocks are fractured and relatively weak – facilitating the emergence of magma.
“Now is not the time to worry,” said Big Island mayor Mitch Roth.
There is no evacuation order.
Although there was no sign of lava moving through the crack, Hawaii County Civil Defense said it had opened shelters in Kailua-Kona and Pahala where it reported people were fleeing along the southern Kona coast.
Scientists will have to wait and see if this is still only a summit eruption or an eruption in the rift zone. Usually, the average Mauna Loa eruption is short, lasting two weeks, Hoon said.
“Usually, the biggest eruptions start on Mauna Loa first,” said Hoon. “After a few days, you start to calm down a bit.”
The US Geological Survey has warned residents threatened by pyroclastic flows from Mauna Loa to review their preparations for the eruption. Scientists have been on high alert due to the recent upsurge in earthquakes at the top of the volcano, which last erupted in 1984.
Parts of the Big Island were subject to an ashfall advisory issued by the National Weather Service in Honolulu, which said up to 0.25 inches (0.6 cm) of ash could accumulate in certain areas.
Mauna Loa is one of five volcanoes that together form the Big Island of Hawaii, the southernmost island of the Hawaiian archipelago.
Mauna Loa, which rises 4,169 meters above sea level, is the largest neighbor of the Kilauea volcano, which erupted in a residential area and destroyed 700 homes in 2018. Some of its slopes are steeper than Kilauea – so when it erupts lava can flow easier and faster.
During the 1950 eruption, lava traveled 24 kilometers from the mountain to the ocean in less than three hours.
Tourism is Hawaii’s economic driver, but Roth expected little trouble for vacationers while the volcano was erupting.
“If you enter one of the rift zones, it will affect a very small area of the island,” he said. “It would be great anywhere, but the chances of it really disrupting the visitor industry — very, very slim.”
For some, the eruption may reduce travel time, even if there is more smog 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,” said Roth. He said. “You can just look out the window at night and you can see Mauna Loa erupting.”
Associated Press writer Mark Thiessen in Anchorage, Alaska, contributed to this report.