Hawaii's Mauna Loa volcano, the largest active volcano in the world, has erupted for the first time in 38 years, prompting officials to issue an ashfall advisory.
The volcano, on Hawaii's Big Island, erupted at 11.30pm on Sunday at the Moku‘aweoweo summit caldera, the US Geological Survey said.
“If the eruption remains in Moku‘aweoweo, lava flows will most likely be confined within the caldera walls,” the agency said.
“However, if the eruptive vents migrate outside its walls, lava flows may move rapidly downslope.”
Lava flows remained restricted to the summit area and nearby communities were not immediately threatened. As of Monday, no evacuation orders were in place.
“However, lava flows in the summit region are visible from Kona,” the Hawaiian Volcano Observatory said in a Monday status report.
“There is currently no indication of any migration of the eruption into a rift zone.”
The rift zone is where the mountain splits apart and the weakening of the rock makes it easier for magma to flow out.
Hawaii's Emergency Management Agency said shelters in Pahala and in Kailua-Kona had been opened as a precaution.
Up to 0.6cm of ash could accumulate in some areas on the Big Island, the National Weather Service in Honolulu said.
Mauna Loa is one of five volcanoes that make up the Big Island, Hawaii's southernmost island.
Mauna Loa rises 4,169 metres above sea level, making it much larger than the neighbouring Kilauea volcano, which destroyed 700 homes when it erupted in 2018.
During a 1950 eruption, Mauna Loa's lava travelled 34km to the ocean in less than three hours. The volcano last erupted in 1984.
The Associated Press contributed to this report