Mauna Loa, the largest active volcano in the world, has begun to erupt in Hawaii, the U.S. Geological Survey and other authorities said.
The eruption started late Sunday night at about 11:30 p.m. HST in Moku'āweoweo, the summit caldera of Mauna Loa in Hawaii Volcanoes National Park, according to a USGS Hawaiian Volcano Observatory alert. The Observatory said it was working closely with emergency management partners.
As of early Monday, USGS Volcanoes and the Hawaii Emergency Management Agency said the lava was overflowing some from the caldera but that the eruption was not threatening nearby communities sitting downhill of Mauna Loa.
"Hawaii Volcano Observatory has received some reports of lava overflowing into the southwest portion on the Mauna Loa caldera, but at this point there are NO indications that it threatens populated areas. No evacuation orders are in place," the Hawaii Emergency Management Agency tweeted shortly after 9:20 a.m. EST (4:20 a.m. HST).
The agency added that shelters had been opened "as a precaution" in Kailua-Kona and Pahala, but noted that "roughly half of all recorded Mauna Loa eruptions have remained in the summit area without threatening populated areas."
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Still, USGS encouraged residents at risk from Mauna Loa lava flows to review their eruption preparations, noting that past events show lava flows can "change rapidly."
"If the eruption remains in Moku'āweoweo, lava flows will most likely be confined within the caldera walls. However, if the eruptive vents migrate outside its walls, lava flows may move rapidly downslope," the USGS Hawaiian Volcano Observatory wrote in its Sunday night alert.
Portions of the Big Island were also under an ashfall advisory Monday morning. The National Weather Service in Honolulu said up to a quarter-inch of ash could accumulate in some areas.
"People with breathing difficulties should stay indoors, and cover nose/mouth with cloth or a mask," the Hawaii Emergency Management Agency said.
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Due to a recent spike in earthquakes at the summit of Mauna Loa, scientists have been on alert for a potential eruption. With the Sunday night eruption, the volcano alert level for Mauna Loa has increased from "advisory" to "warning," with its aviation alert upgraded from "yellow" to "red."
Mauna Loa, which last erupted in 1984, rises 13,679 feet above sea level. It's among the five volcanoes that make up Hawaii's Big Island.
Mauna Loa sits immediately north of Kilauea volcano, which is also currently erupting - but with a "watch" volcano alert level and "orange" aviation alert, according to the USGS Hawaiian Volcano Observatory. A 2018 Kilauea eruption destroyed 700 homes and sent lava into the ocean.
Because Mauna Loa is taller than Kilauea, experts note that, if the lava significantly breaks out of the summit caldera, it could rush down its hillsides faster due to steeper slopes - possibly in a matter of hours.
Contributing: The Associated Press.
This article originally appeared on USA TODAY: Mauna Loa, the largest active volcano in the world, erupts in Hawaii