Mauna Loa is erupting for the first time since 1984, and Hawaii’s Big Island has been warned that ash may fall.

The world’s largest active volcano, Mauna Loa, is erupting for the first time in nearly 40 years, prompting an ashfall advisory until 10 a.m. Monday for Hawaii’s Big Island and surrounding waters (3 p.m. ET).

Monday morning, the Hawaii Tourism Authority tweeted that the eruption in Hawaii Volcanoes National Park poses no threat to downhill communities or flights to the island. The National Weather Service in Honolulu reported that a trace to less than a quarter-inch of ashfall could accumulate on parts of the island as winds may carry fine ash and volcanic gas downwind.

The Hawaii Volcano Observatory has received reports of lava overflowing into the southwest portion of the volcano’s caldera, or crater, the Hawaii Emergency Management Agency tweeted late Monday morning.

The agency tweeted that there is no evidence of a threat to nearby communities and no evacuation orders have been issued. Two shelters have opened as a precaution, despite the fact that “roughly half” of recorded Mauna Loa eruptions have remained in the summit area without threatening populated areas, according to a separate tweet from the same agency.

“People with respiratory illnesses should stay indoors to avoid inhaling ash particles, and anyone outside should cover their mouth and nose with a mask or cloth,” the office in Honolulu advised. Possible crop and animal damage. Minor equipment and infrastructure damage. decreased visibility Potentially extensive cleanup may be required.”

According to the weather service, ashfall can damage vehicles and buildings, contaminate water supplies, disrupt sewage and electrical systems, damage or kill vegetation, and abrasive volcanic ash can irritate the eyes and lungs.

Earlier, the observatory stated that lava flows pose no danger to downslope communities.

Hawaii, also known as the Big Island, is the largest island in the Hawaiian chain but has a population density of less than 50 people per square mile, according to the United States Census Bureau. The majority of the population resides in coastal cities and towns.

“Based on past events, the early stages of a Mauna Loa eruption can be quite dynamic, and the location and advance of lava flows can change rapidly,” the observatory said, adding, “If the eruption remains in Moku’weoweo, lava flows will likely remain within the caldera walls.”

However, lava flows may move rapidly downslope if the eruptive vents migrate outside the volcano’s walls.

Red hues from the eruption illuminated Monday’s predawn sky, as captured by Matthew Liano, a resident of Kailua-Kona on the west coast of the Big Island, at the Kailua Bay & Pier.

“I’ve lived in Kona my entire life, and I’ve never seen anything like it,” Liano told CNN.

Moku’weoweo, the summit caldera of Mauna Loa, began erupting at approximately 11:30 p.m. HST (4:30 a.m. ET) on Sunday, according to the observatory.

Near Kilauea, which erupted in 2018, is a volcano.

According to the US Geological Survey, Mauna Loa, which covers half of the Hawaiian island, has erupted 33 times since 1843, the first “well-documented historical eruption” of the volcano. The last eruption occurred in 1984, making this quiet period the longest in recorded history.

Mauna Loa’s summit crater is located approximately 21 miles west of Kilauea, a smaller volcano whose eruption in 2018 destroyed more than 700 homes and displaced residents in the Leilani Estates neighborhood.

According to the agency, Mauna Loa has been in a heightened state of unrest, citing elevated seismic activity and increased earthquake rates in a late-month update.

According to the US Geological Survey, the average number of daily earthquakes increased from five to ten in June 2022 to between ten and twenty in July and August. CNN reported that on September 23 and September 29, the daily occurrence of more than 100 earthquakes reached its peak.

The Hawaii Volcanoes National Park closed the Mauna Loa summit to all backcountry hikers in October due to increased activity, but the park’s main section remained open, according to the US National Park Service.

An earlier version of this story contained an error.