When Hawaii’s Kilauea volcano spewed lava this spring and summer, destroying hundreds of homes and sending thousands fleeing, it was just a more dramatic episode of a long-running series: It’s been erupting nearly continuously for 35 years.
But that streak – the longest current run in the United States – may be at an end.
Kilauea has produced no lava on the surface of Hawaii’s Big Island for three months – neither at its summit, nor at its other vents, the lead scientist at US Geological Survey’s Hawaiian Volcano Observatory said Tuesday.
When volcanoes stop erupting magma for that long, the next eruption generally will happen in a different spot, marking a new eruptive event, said Tina Neal, the observatory’s scientist in charge.
“The long-running eruptive activity that began in 1983 appears to have ended,” Neal said in a phone interview.
“We’re taking this 90-day mark as a sign that it’s very unlikely at this point” that the same eruptions will resume, she said.
But don’t sleep on Kilauea’s potential – it’s still active. Magma still is moving underground and the volcano is emitting gas. It will erupt again; it’s just a matter of where and when, scientists say.
“We’re in a pause of some sort. We just don’t know whether the pause is going to end with what we had before, or whether it’s going be something different,” USGS research geologist Don Swanson said.
The 35-year streak
Kilauea’s eruptive history spans tens of thousands of years, and the volcano has long inspired fascination and anxiety, as a tourist-drawing pillar of Hawaii Volcanoes National Park and as a force that uprooted lives.
Kilauea’s most recent eruption streak started in January 1983, when lava broke out of fissures east of the summit; the lava fountains would eventually form a cone now called Puu Oo.
Between then and 2016, lava flows covered about 144 square kilometers, added more than 440 acres in the Big Island’s southeast, and destroyed 215 buildings, the USGS says.
Those eruptions came in more than 60 episodes, never with a three-month pause.
Kilauea’s summit itself began a nearly continuous eruption in 2008, eventually creating a lava lake that could sometimes be seen from public viewing areas.
Then came May’s eruption from fissures east of Puu Oo, destroying parts of the Leilani Estates community. By July, lava had covered more than 12 square miles and obliterated more than 700 homes.
But eruptions have stopped at all three sites. According to Neal:
• The Puu Oo vent hasn’t erupted since April.
• The summit’s lava lake drained away in early May.
• The fissures that erupted in May have been quiet since early September.
Why has it stopped erupting?
Neal cautions that eruptions could resume at any time. Even now, there are signs of magma refilling in Kilauea’s East Rift Zone, though not near this year’s vents.
Just two months ago, the USGS ranked Kilauea as the most threatening of the United States’ 161 active and potentially active volcanoes. The ranking took historic activity into account as well as how exposed people and property would be to eruptions.
Even without eruptions, the volcano poses hazards. Ground is unstable at the site of recent lava outbursts, and the thickest lava flows will remain hot for weeks or even years, Neal said.
The USGS on Tuesday morning still had Kilauea at an advisory, or “yellow,” alert level, which indicates either that the volcano is showing signs of elevated unrest, or volcanic activity has decreased significantly but is being closely monitored.
But why has Kilauea stopped erupting now?
“At its simplest, it just means there is not enough pressure in the system to push magma up and out,” Neal said.
“That could be caused by reduction in supply from the source.”
Or, she said, so much magma was evacuated this year that “there’s just a lot of room in the volcano to refill before it erupts again.”
Swanson, 80, has been studying Kilauea off and on since 1968, and has been working in Hawaii for the last 22 years.
In a November 29 essay on the observatory’s “Volcano Watch” site, the research geologist wrote, “This is, without a doubt, the most intellectually exciting time to be a volcanologist at the USGS Hawaiian Volcano Observatory.”
“The current inactivity at Kilauea has so many possible outcomes that it is a real challenge to figure out what might happen next,” he wrote.
“That, to research scientists, is a very stimulating and exciting thing to do – to think carefully,” he added by phone Tuesday.
Michael Garcia, a geology professor at the University of Hawaii at Manoa, said Kilaeua’s eruptions have given scientists a virtual gold mine of data. Lava composition shows scientists what has been melted in the Earth’s mantle, and over the last 35 years, the composition changed often.
“A pause is actually a good thing. It gives us time to figure out what’s happened,” Garcia said.
Swanson said there are many possibilities, including a return to what had been happening, or a step toward a vast change, like a shift toward fewer effusive eruptions and more explosive ones.
“This has happened in the past. If it returns to an explosive period,” it wouldn’t be unexpected, he said.