People living on the slopes of the Mauna Loa volcano on Hawaii’s Big Island have been told to prepare for a worst-case scenario as it continues to erupt and belch volcanic ash into the air. 

Waves of orange, glowing lava are flowing from the world’s largest active volcano in its first eruption in 38 years and officials told residents to be ready to evacuate if lava flows start heading toward populated areas.

While the eruption of Mauna Loa isn’t immediately endangering towns, the US Geological Survey has warned the roughly 200,000 people on the Big Island that an eruption “can be very dynamic, and the location and advance of lava flows can change rapidly”.

Governor David Ige said: “Lava flows are not threatening any downslope communities at this time and all indications are that the eruption will remain in the northeast rift zone.

“Volcanic ash and possibly fine ash and Pele’s hair may be carried downwind. So, certainly we would ask that those with respiratory sensitivities to take precautions to minimise exposure.”

Pele’s hair is the name given for volcanic glass fibres.

The eruption began late on Sunday night following a series of fairly large earthquakes, said Ken Hon, scientist-in-charge at the Hawaiian Volcano Observatory (HVO).

The areas where lava is emerging – the volcano’s summit crater and vents along the volcano’s northeast flank – are both far from homes and communities.

Officials urged the public to stay away from them, given the dangers posed by lava, which is shooting 100 to 200 feet (30 to 60m) into the air out of three separate fissures roughly estimated to be 1 to 2 miles (1.6 to 3.2km) long.

Air quality on the Big Island more generally is good right now but officials are monitoring it carefully, said Dr Libby Char, the director of the state Department of Health.

The HVO has also increased the aviation threat level from “yellow” to “red” to reflect the presence of airborne gases and ash particles.

More on Mauna Loa

Mauna Loa is one of five volcanoes that together make up the Big Island of Hawaii, the southernmost island in the Hawaiian archipelago.

Mauna Loa, rising 13,679 feet (4,169 meters) above sea level, is the much larger neighbor of Kilauea, which erupted in a residential neighborhood and destroyed 700 homes in 2018.

Some of Mauna Loa’s slopes are much steeper than Kilauea’s, so lava can flow much faster when it erupts.

During a 1950 eruption, the mountain’s lava travelled 15 miles (24km) to the ocean in under three hours.

El Salvador also on alert

Authorities in El Salvador have warned residents near the Chaparrastique volcano in the country’s east to be alert after it began to erupt on Sunday.

The Environmental Ministry’s observatory reported explosions in the central crater of the volcano located about 83 miles (135km) east of the capital. It said the eruption’s intensity was a 1 on a scale from 0 to 8.

The eruption began when the volcano launched rock and ash to areas surrounding the crater. There were no reported injuries.