Hawaii volcanoes powered by ‘mind-blowing’ magma network

Hawaii volcanoes powered by ‘mind-blowing’ magma network

Hawaii volcanoes powered by ‘mind-blowing’ magma network

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When the sinuous structures first became visible on the computer screen, John Wilding’s jaw dropped. “I jumped across the office,” said the California Institute of Technology geophysics graduate student. “I thought it’s a part of the Earth where at this point I was the only person on the planet who knew these things were there.”

Scientists suspected that somewhere beneath Hawaii a secret was set in stone – something that plays a leading role in influencing the the famous volcanism of the island chain. Now, using nearly 200,000 earthquakes and a machine learning program, Wilding and his colleagues have finally unearthed it.

That’s according to a study published Thursday in the journal Science, the team has revealed a previously hidden collection of magma caches that could act as the beating heart of the volcanoes above. The discovery offers a possible solution to a long-standing mystery: how does magma travel from the deep mantle to the Hawaiian surface? The work gives scientists a valuable new look at the behavior of some of the most fickle and dangerous volcanoes on Earth.

Hawaii’s Mauna Loa volcano is erupting for the first time in 38 years

The shallow magma reservoirs that fuel Hawaii’s eruptions have been known for a while. This is partly due to seismic waves, which are closely monitored in Hawaii by an ever-expanding network of sensors. The waves act like an ultrasound for the Earth; changes in their speed and trajectory during their underground travels tell scientists what kind of matter they traveled through, and provide clues about its temperature, density and composition.

But to really understand what drives these volcanic powerhouses, scientists need to know what’s happening at the interface of the soft mantle and solid crust. That’s what the new study finally reveals in unexpected detail.

The giant feature described in the article consists of several elongated chambers called sills. When eruptions drain magma from the shallow reservoirs above, these deep-seated sills appear to respond. A cacophony of earthquakes signals when individual chambers begin to fill with molten rock at different times, somewhat like “blood flowing in a heart,” Wilding said.

“We were just looking at it, and it was just mind-blowing, really,” he said Zakaria Ross, a geophysicist at Caltech. “Since then I can’t get the image out of my head.”

–Ken Rubina volcanologist at the University of Hawaii who was not involved in the study said, “It’s a very elegant study and a hugely intriguing result.”

Like much of the planet, Hawaii wouldn’t exist without volcanism. Since time immemorial, a deep-seated fountain of superheated rock known as a mantle plume has set the underside of the Pacific tectonic plate on fire. As the plate has continued to drift, a succession of epic volcanoes has risen above the waves, creating the Hawaiian island chain.

Today, the chain is home to a small family of active volcanoes, including the Mercurial Long mountain and the hyperactive Kilauea on the Big Island, both of those stopped erupting at the same time this month.

A persistent seismic rumble from an area southwest of Kilauea and 20 miles underground had previously suggested that a collection of errors may exist there, creating pathways for magma to travel from the Hadean depths to surface reservoirs. And since the 1980s, special types of earthquakes that indicate drifting fluids have indicated that magma is churning in the region. But until recently, the true nature of this underground labyrinth was based more on speculation than scientific truth.

“It’s been this mysterious box in the mantle,” Wilding said. “We really have very little idea what’s going on.”

What scientists needed was a sustained spike in earthquakes emanating from that exact region, enough to greatly illuminate that shadowed zone. Things looked promising in 2015, as the region’s rumbling picked up somewhat.

But the team’s breakthrough came in 2018 when, after Kilauea had erupted more or less continuously for 35 years, a grand finale style blowout sequence started at the volcano. The event produced 320,000 Olympic pools of lava in just three months — and the rapid bleeding out of the volcano’s shallow magma reservoir caused the summit to collapse dramatically.

In a thrilling plot twist, geologists in 2019 recorded a shocking spike in deep seismic activity well below the town of Pāhala, which is about 25 miles southwest of Kilauea. Scientists thought that this could not be a coincidence.

While the Pāhala earthquake storm was an opportunity to excavate the island’s buried magmatic treasure, scientists alone wouldn’t be able to identify many of the individual quakes in that cacophony, especially the more mundane smaller ones that could be triggered by larger booms. be smothered.

Not wanting to miss a single beat of the geological drum, Caltech’s team fed the entire seismic storm recording into a machine learning program — a technique Ross and his colleagues had previously used to identify millions of hidden earthquakes in California. The program quickly taught itself what was a real earthquake and what was strange noise, then identified and characterized thousands of tremors that would have been missed by conventional seismic signal detection programs and their human analysts.

From November 2018 to April 2022, the system recorded about 192,000 quakes under Pāhala. Plotting these luminous points on a map, the team was stunned to discover a collection of pulsating magmatic structures – the throbbing volcanic heart of southern Hawaii.

Some earthquakes came from an area 28 to 52 miles deep: these long-lasting earthquakes are usually attributed to the vibrations created by the movement of fluids, including magma. Most of the seismicity came from an area 22 to 27 miles deep. These volcano-tectonic quakes — the kind that form when a fault line moves and breaks rocks in a volcanic area — outlined a number of near-horizontal plate-like structures, some four miles long and five miles wide.

At different times, the scientists detected spikes in seismic activity within individual sheets. The team suspected these slabs were sills, magma cavities whose own grumbling tracked the molten rock rushing up from the lower fluid-filled region close to the peak of the mantle plume.

Looking for a deeper connection

This new 3D map of a key segment of the Hawaiian circulatory system “is extraordinary,” he said Jackie Caplan-Auerbach, a volcano seismologist at Western Washington University who was not involved in the new study. It’s “terribly cool,” she said, that scientists can not only see this previously hidden heart, but also observe the convulsions of the ventricles within.

The Pāhala Sill complex, as the heart is technically called, appears to have several arteries branching off from it. An important path, marked by rock-breaking earthquakes, appears to lead directly to one of Kilauea’s shallow magma reservoirs. It is therefore no coincidence that the sill complex began to thunder relentlessly in 2019. During the 2018 eruption, Kilauea was stripped of a significant portion of its shallow magma pool, causing the pressure to drop. In response, magma was sucked into the sills to equalize the pressure. Similar events took place during Kilauea’s shorter eruption in 2020.

Further work could help resolve the controversial question of whether Kilauea and Mauna Loa, which are relatively close neighbors on the surface, somehow connected at great depths. To date, there is little concrete evidence for this hypothesis, and experts generally agree that the two volcanoes to be largely independent from each other.

The new study doesn’t overturn that consensus yet. It shows another major artery of the sill complex, marked again by rock-breaking earthquakes, shooting up toward Mauna Loa. But it stops short of a large horizontal fault and appears to fail to reach one of Mauna Loa’s shallow magma reservoirs.

Nor is it certain that magma moves through any of these paths. That would change if future work detects long-lasting earthquakes emanating from them — the kind that indicate the presence of fluids, probably magma.

“The results are amazing,” he said Diana Roman, a geophysicist at the Carnegie Institution for Science in DC who was not involved in the study. But “it is still unclear whether the magma intruding into Pāhala directly fuels the eruptions of Mauna Loa and Kilauea.”

Roman has also studied the earthquakes in Pāhala. Her co-written 2021 paper concluded that they were the result of magma intruding at depth and simultaneously causing turmoil at Mauna Loa and Kilauea by compressing both underlying conduit networks. The new study supports this idea of ​​an indirect connection. But even with this magmatic web mapped out, a more explicit link is still too early to name.

Still, much of the Hawaiian underworld remains unexplored, and more magmatic arteries could be located, Ross said.

“What else is in there that hasn’t been ripped off?” he said. Whenever Hawaii’s infernal subsurface shakes ferociously again, the team at Caltech is ready to shine a spotlight on it, hoping to reveal what remains hidden for now.





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