Hawaii’s Mauna Loa, the world’s largest active volcano, erupting for first time in almost 40 years

Hawaii’s Mauna Loa, the world’s largest active volcano, started erupting Sunday night and lava was flowing from its summit by Monday morning, the U.S. Geological Survey said. The lava wasn’t expected to threaten populated areas, officials said.

“Lava flows are not threatening any downslope communities and all indications are that the eruption will remain in the Northeast Rift Zone,” the USGS said in a statement.

Still, the agency warned all residents on Hawaii Island who are “at risk from Mauna Loa lava flows” to “review preparedness and refer to Hawai’i County Civil Defense information for further guidance.”

The early stages of an eruption can be dynamic, the agency warned, adding that “lava flows can change rapidly.”

Residents were also warned volcanic gas, ash and thin glass fibers known as Pele’s hair could be carried downwind.

The Hawaiian Volcano Observatory said it was “in close consultation with emergency management partners and will be monitoring the volcano closely to provide further updates on activity.”

A satellite captured images of Sunday’s eruption from space. The National Oceanic and Atmospheric Administration posted images of the heat signature and release of sulfur dioxide from the volcano.

Mauna Loa has erupted 33 times since 1843, according to the USGS. It last erupted in 1984, when lava spilled down its slopes and came within 4.5 miles of the island’s biggest town, Hilo.

Mauna Loa’s Hawaiian name means “long mountain,” which is fitting as the huge mountain extends roughly 74 miles from its edge along Hawaii Island’s southern coast, to the rim of its summit caldera, or crater, where the eruption began on Sunday evening.