Mauna Loa USGS Update: Lava ‘Flow Fingers’ Now Spilling From Caldera

Lava “flow fingers” have been spotted emerging from Mauna Loa’s caldera as its current eruption continues.

The eruption of Mauna Loa in Hawaii—which is the biggest volcano on Earth, rising 13,000 feet above sea level—started at approximately 11:30 p.m. on November 27.

When the eruption began, it was confined to the volcano’s caldera summit and did not threaten any downslope communities. Caldera refers to the large depression formed when a volcano erupts and collapses.

This combined image shows lava at Mauna Loa. The USGS has said lava is now flowing from the volcano’s caldera. Jareb Ombao/USGS

Lava now “does seem to have flowed outside the caldera,” the United States Geological Survey (USGS) said in a tweet.

However, the volcano’s eruptive vents remain confined to the summit area.

The lava is currently flowing out of the caldera to the southwest, a not uncommon development the USGS said, as surface flows have been observed in past eruptions.

“It’s magma going into the rift zones that is the real concern, because that can develop into a serious situation much more rapidly,” the USGS tweeted.

The Hawaiian Volcano Observatory is monitoring the activity very closely and liaising with emergency management services.

The Volcano Alert Level and Aviation Color Code for Mauna Loa has been set to “Red” meaning “warning.”

Jessica Johnson, an Associate Professor in Solid Earth Geophysics at the School of Environmental Sciences at the University of East Anglia in the U.K., told Newsweek: “Eruptions from Mauna Loa have the capability of sending lava flows toward [the towns of] Hilo or Kona.

“If the vents [where the lava is coming out of the ground] should migrate to rift zones outside of the caldera, then voluminous lava flows could threaten towns on the island. These lava flows rarely present a risk to life, but they can be extremely destructive to infrastructure.”

Mauna Loa has erupted 33 times since historic records began, most recently in 1984, Johnson said.

“The 1984 eruption produced a lava flow that got within about 7 km of Hilo, the largest population center on Big Island,” she said.

Nobody was hurt then but lava flows blocked roads and there was significant damage to power lines.

Despite its huge size, Mauna Loa eruptions are not as dangerous as those of other Hawaii volcanoes, such as Kilauea, as they do not tend to be as explosive.

However, in a previous update the USGS said early stages of a Mauna Loa eruption can be “very dynamic,” meaning the “advance of lava flows can change rapidly.”

“If the eruption remains in Moku’āweoweo [the volcano’s summit caldera], lava flows will most likely be confined within the caldera walls,” the USGS said. “However, if the eruptive vents migrate outside its walls, lava flows may move rapidly downslope.”

Residents living near to the volcano previously told Newsweek that they were concerned about Mauna Loa’s recent heightened unrest.

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about volcanoes? Let us know via science@newsweek.com.