Thousands of awestruck viewers have been drawn to Mauna Loa, the world’s largest active volcano, which has been sending volcanic ash and debris down from the sky and oozing hot lava since it erupted over the weekend.

Anne Andersen was among the many people who jammed a highway near Volcanoes National Park – an impromptu viewing point – to catch a glimpse of the eruption.

She said she left her overnight shift as a nurse to see the spectacle on Wednesday, afraid that the road would soon be closed.

“It’s Mother Nature showing us her face,” Andersen said, as Mauna Loa belched gas on the horizon. “It’s pretty exciting.”

Another observer, Gordon Brown, said he travelled over from Loomis, California, with his wife in hopes of getting “as close as [they] could get” to the volcano. “And it is so bright, it just blows my mind,” he said.

Mauna Loa began erupting on Sunday for the first time since 1984, ending its longest dormant period in recorded history.

The night sky above Hawaii’s largest island glowed a hellish red as bright, hot lava sprang forth at the volcano’s summit. The lava is contained within the summit and does not threaten Hawaiians living downslope, for now, the US Geological Survey said.

The service warned residents on Monday that volcanic gases and fine ash may drift their way.

On Wednesday, the lava was tumbling slowly down the slope and was about 10km (6 miles) from the highway known as Saddle Road. It was not clear when, or if, it would cover the road, which runs through old lava flows and connects the cities of Hilo and Kailua-Kona.

Mauna Loa rises 4,169m (13,678 feet) above the Pacific Ocean, part of the chain of volcanoes that formed the islands of Hawaii. It last erupted in March and April of 1984, sending a flow of lava within 8km (5 miles) of Hilo, the island’s largest city.

Hawaii’s Emergency Management Agency said it had opened two shelters on the island as a precaution, but also emphasised that there are no signs that lava will threaten populated areas and that it had not issued any evacuation orders.

About half of all recorded eruptions of Mauna Loa were confined to the summit, the agency said.