Hawaii volcano Muana Lao, the world’s largest, erupts for the first time in 40 years

Although the lava remains contained for now, the USGS reported that the eruption could pose a threat should conditions change

Hawaii’s Mauna Loa, the largest active volcano in the world, has erupted for the first time in nearly 40 years, the U.S. authorities said, as emergency crews went on alert early Monday.

Flows of lava remained “contained” within the summit caldera of Mauna Loa, but the eruption could pose a threat to nearby residents should conditions change, the United States Geological Survey (USGS) reported at 11:45 pm local time Sunday (9:45 GMT Monday) some 15 minutes after the eruption inside Hawaii Volcanoes National Park.

“At this time, lava flows are contained within the summit area and are not threatening downslope communities,” the USGS said on its website, noting that residents of the area should review preparedness procedures.

While the eruption on the main island of the remote U.S. state in the Pacific remains confined within the basin at the top of the volcano, called the caldera, “if the eruptive vents migrate outside its walls, lava flows may move rapidly downslope,” according to the USGS.

Hours later on Monday morning the USGS volcano monitoring office tweeted: “Lava does seem to have flowed outside the caldera, but for now the eruptive vents remain confined to the caldera.”

The agency said the Hawaiian Volcano Observatory was in consultation with emergency management personnel and its staff would conduct an aerial reconnaissance over the 13,674-foot (4,168-meter) volcano as soon as possible.

Hawaii authorities said no evacuation orders have been given, although the summit area and several roads in the region were closed.