Hawaii’s Mauna Loa Volcano Gushes Lava, Threatening Major Highway

The world’s largest active volcano is erupting for the first time since 1984

Aerial photo showing lava flowing from Mauna Loa
An aerial photo taken at 7:15 a.m. Hawaii Standard Time on Monday shows the northeast rift zone eruption of Mauna Loa.  Natalie Deligne / USGS

The world’s largest active volcano, Hawaii’s Mauna Loa, is erupting for the first time since 1984.

Aerial footage has captured plumes of lava spouting from the volcano, reaching heights of nearly 150 feet. Now, lava flows are approaching a key road, threatening disruptions to residents’ lives. The Daniel K. Inouye Highway connects the east and west sides of Hawaii’s Big Island, where the volcano is located.

There is “a very high probability that this lava flow, if it continues, will definitely reach the road,” Ken Hon, scientist-in-charge at the Hawaiian Volcano Observatory, tells Jonathan Vigliotti and Analisa Novak of CBS News. “We're looking at about two days out.”

The eruption began late Sunday night local time, according to the United States Geological Survey (USGS). It started in the summit caldera, a large depression formed by past eruptions that sits atop the volcano, and migrated to cracks in the mountain that form a rift zone on the northeast side. But “all indications are that the eruption will remain in the Northeast Rift Zone,” the USGS tweeted on Monday.

On Wednesday, the Hawaii Emergency Management Agency tweeted that there is “still no immediate threat to populated areas.”

The Big Island was put under an ashfall advisory Monday until 10 a.m. Hawaii Standard Time (3 p.m. Eastern time), according to CNN’s Monica Garrett and Dakin Andone, because winds could potentially carry volcanic gas and fine ash from the eruption.

Up to a quarter of an inch of ash could collect on parts of the island, the National Weather Service in Honolulu said earlier this week, per the Washington Post’s Jonathan Edwards and Scott Dance. The ash could damage crops, harm livestock and cause respiratory problems in people, per the publication.

Officials haven’t issued any evacuation orders, but Hawaii County opened shelters in response to people self-evacuating along the South Kona coast, per Hawaii News Now’s Ben Gutierrez.

The location and advance of lava flows can quickly change during the early stages of an eruption, per the USGS. “Residents at risk from Mauna Loa lava flows should review preparedness and refer to Hawaii County Civil Defense information for further guidance,” the agency said in a statement.

Mauna Loa, which stretches more than 13,100 feet above sea level and extends over 55,000 feet from its base on the seafloor, takes up slightly more than half the island of Hawaii.

While the volcano hasn’t erupted in nearly 40 years, “this is a really active volcano,” Ed Venzke, a volcanologist with the Smithsonian’s Global Volcanism Program, tells Smithsonian magazine in an email. More than 90 percent of the mountain has been covered with lava from eruptions in the last 4,000 years, Venzke says.

Mauna Loa has erupted 33 times since 1843, according to the USGS. During its most recent eruption in 1984, the lava flow reached within 4.5 miles of Hilo, which is the island’s biggest town, per Tucker Reals and Alex Sundby of CBS News.

Residents had braced themselves for an eruption after the number of earthquakes at the volcano increased during the last several weeks, according to Hawaii News Now. The number of quakes rose from 10 to 20 per day in July and August to more than 100 on September 23 and 29, per CNN.