Hawaii volcanoes fueled by ‘mind-boggling’ magma network.

Hawaii volcanoes fueled by ‘mind-boggling’ magma network.


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

Scientists had suspected that somewhere below Hawaii, a secret was buried in the stone, something that plays a major role in influencing. the famous volcanism of the island chain. Now, with the help of nearly 200,000 earthquakes and a machine learning program, Wilding and his colleagues have finally figured it out.

In a study published Thursday in the journal science, the team has revealed a previously hidden collection of magma caches that can 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 window into the behavior of some of Earth’s most capricious and dangerous volcanoes.

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

The shallow magma reservoirs that feed Hawaii’s eruptions have long been known. This is partly due to seismic waves, which in Hawaii are closely monitored 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 journeys tell scientists what kind of matter they have been traveling through, providing 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 paper is made up of several elongated chambers called sills. When eruptions drain magma from the shallow reservoirs above, these deep sills appear to react. A cacophony of earthquakes signals when individual chambers begin to fill with molten rock at different times, a bit like “blood rushing to the heart,” Wilding said.

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

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

Like much of the planet, Hawaii would not exist without volcanism. Since time immemorial, a deep-seated source of superheated rock known as the mantle plume has ignited the underside of the Pacific tectonic plate. As the plate continued to drift, a succession of epic volcanoes rose above the waves, creating the Hawaiian island chain.

Today, the chain is home to a small family of active volcanoes, including Mercurial Long Mountain and the hyperactive Kilauea on the Big Island, both stopped exploding simultaneously this month

Persistent seismic noise from an area southwest of Kilauea and 20 miles underground had previously suggested that a collection of faults can exist there, creating pathways for magma to travel from Hadian depths to near-surface reservoirs. And since the 1980s, special types of earthquakes that suggest traveling fluids have hinted that magma has been produced 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 on the mantle,” Wilding said. “We really have very little idea what’s going on.”

What the scientists needed was a sustained increase in earthquakes from this exact region, enough to strongly illuminate this shadow area. Things looked promising in 2015, when the region’s buzz picked up a bit.

But the team’s luck came in 2018 when, after Kilauea had been erupting more or less continuously for 35 years, a grand finale style breakout sequence it started in the volcano. The event produced 320,000 Olympic-sized pools of lava in just three months, and the rapid exsanguination of the volcano’s shallow magma reservoir caused its summit to collapse dramatically.

In an exciting twist, geologists recorded a shocking increase in deep seismic activity in 2019 far below the town of Pāhala, which is about 25 miles southwest of Kilauea. Surely, the scientists thought, this cannot be a coincidence.

Although the Pāhala earthquake storm was an opportunity to unearth the island’s buried magmatic treasure, scientists alone would not be able to identify many of the individual earthquakes in this cacophony, especially the more common and more small ones that could be drowned out by larger blows.

Unwilling to miss a single beat of the geologic drum, the Caltech team fed the entire recording of the earthquake storm into a machine learning program, a technique that Ross and his colleagues had previously used. Identify millions of hidden earthquakes in California The program quickly taught what was a real earthquake and what was noise, then identified and characterized thousands of tremors that conventional seismic signal detection programs and their human analysts would have missed.

From November 2018 to April 2022, the system recorded about 192,000 earthquakes beneath Pāhala. Plotting these bright spots on a map, the team was surprised to discover a collection of pulsating magmatic structures: the volcanic heart of southern Hawaii.

Some of the earthquakes came from a region 28 to 32 miles deep: these long-period earthquakes are generally attributed to the vibrations made by the movement of fluids, including magma. Most of the seismicity comes from an area 22 to 27 miles deep. These volcanic tectonic earthquakes—the kind produced when a fault moves and rocks break apart within a volcanic region—delineated a series of nearly horizontal sheet-like structures, some of them four miles long and three miles across. wide

At different times, scientists detected increases in seismic activity within separate plates. The team hypothesized that these sheets were sills, pockets of magma whose own thicknesses tracked molten rock rising from the lower, fluid-filled region near the top of the mantle plume.

In search of 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 “really cool,” he said, that scientists can not only see this previously hidden heart, but also be able to sense the convulsions of the inner ventricles.

The Pāhala Sill complex, as the heart is technically known, appears to have several arteries branching off from it. A major pathway, marked by rock-shattering earthquakes, appears to lead directly to one of Kilauea’s shallow magma reservoirs. It may not be a coincidence, then, that the sill complex began rumbling nonstop in 2019. During the 2018 eruption, Kilauea was drained of a significant portion of its shallow magma supply, causing a fall of pressure In response, magma was drawn into the beds to equalize the pressure. Similar events happened during Kilauea shortest eruption of 2020.

Further work may help resolve the controversial question of whether Kilauea and Mauna Loa, which are relatively close neighbors on the surface, are in any way. online at great depths. So far, there is little concrete evidence for this hypothesis, and experts generally agree that the two volcanoes they are in large part independent of each other.

The new study still doesn’t overturn that consensus. It shows another major artery of the sill complex, again marked by rock-shattering earthquakes, that climbs up to Mauna Loa. But this one stops at a large horizontal fault and doesn’t seem to reach any of Mauna Loa’s shallow magma reservoirs.

Nor is it certain that magma moves through any of these pathways. That would change if future work detects long-period earthquakes coming from them, the kind that signify the presence of fluids, likely magma.

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

Roman has also studied the Pāhala earthquakes. His co-written in 2021 paper they concluded that they were the result of magma intrusion at depth, causing simultaneous upheaval in Mauna Loa and Kilauea by tightening both underlying plumbing networks. The new study supports this notion of an indirect connection. But even with this magmatic web mapped, a more explicit link is too early to call.

Still, much of the Hawaiian underworld remains unexplored, and more magmatic veins can still be located, Ross said.

“What else is still inside that hasn’t been lit?” he said Whenever Hawaii’s infernal underground shakes furiously again, the Caltech team will be ready to shine a spotlight on it, hoping to reveal what remains hidden for now.

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