Scientists suspected that a secret was buried in the rock below the Hawaiian Islands – which played a leading role in the impact. famous volcanism of the island chain. Now, with the help of almost 200,000 earthquakes and machine learning software, Wilding and his colleagues have finally discovered it.
In a study published Thursday in the journal Science, the team discovered a previously hidden collection of magma reservoirs that may 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 Hawaii’s surface? The work gives scientists a valuable new window into the behavior of some of the most capricious and dangerous volcanoes on Earth.
The shallow magma reservoirs that feed Hawaii’s eruptions have been known for some time. This is thanks in part to seismic waves closely monitored by an ever-expanding network of sensors in Hawaii. The waves act like ultrasound for the Earth; Changes in their speed and trajectory during their underground journey tell scientists what kind of material they are passing through, and give clues about its temperature, density, and composition.
But to really understand what’s driving these volcanic powerhouses, scientists need to know what’s happening at the interface of the squishy mantle and solid crust. Ultimately, that’s what a new study reveals in unexpected detail.
The giant feature described in the article consists of several elongated chambers called sills. These deep-seated sills react when eruptions drain magma from shallow reservoirs above. The cacophony of earthquakes signals when individual chambers begin to fill with molten rock at different times, a bit like “bleeding to the heart,” Wilding said.
“We were just looking at it and it was just mind blowing, it really was,” they said Zachary Ross, a geophysicist at Caltech. “I can’t get the image of him out of my head ever since.”
Ken Rubin“It’s a very elegant study and a very interesting result,” said the University of Hawaii volcanologist, who was not involved in the study.
Like most of the planet, Hawaii would not exist without volcanism. Since time immemorial, a deep-seated fountain of superheated rock known as the mantle plume has fueled the underside of the Pacific tectonic plate. As the plate continued to slide, a series of epic volcanoes rose above the waves, creating the Hawaiian island chain.
Today, the chain has a small family of active volcanoes, including Mercury Mauna Loa and hyperactive Kilauea On the big island, both at the same time it stopped erupting this month.
Persistent seismic rumblings from an area southwest of Kilauea and 20 miles underground have previously said set of defects may exist there, creating pathways for magma to move from the Hadis depths to near-surface reservoirs. Since the 1980s, specific types of earthquakes, suggestive of roaming fluids, have signaled that magma has been played in the region. But until recently, the true nature of this subterranean labyrinth was based more on speculation than scientific fact.
“It was the mysterious box on the mantle,” Wilding said. “We have very little idea what’s really going on.”
What the scientists needed was a steady increase in earthquakes from the precise region enough to strongly illuminate the shadow zone. Things looked promising in 2015 when the region’s buzz picked up a bit.
But the team’s lucky break came in 2018, after Kilauea had erupted more or less continuously for 35 years. a spectacular finale-type eruption sequence it started in a volcano. The event produced 320,000 Olympic-sized swimming pools worth of lava in just three months — and the volcano’s rapid depletion of its shallow magma reservoir caused its summit to collapse dramatically.
In an interesting twist, geologists recorded a shocking increase in seismic activity deep below the town of Pahala, about 25 miles southwest of Kilauea, in 2019. Of course, scientists thought it couldn’t happen.
While the Pahala earthquake storm is a chance to uncover the island’s buried igneous treasure, scientists may not be able to identify many individual earthquakes in the cacophony, especially the more common smaller earthquakes that can be drowned out by larger explosions.
Not wanting to miss a beat of the geologic drum, the Caltech team fed the entire record of the seismic storm into a machine learning program—a technique that Ross and his colleagues had used before. identify millions of hidden earthquakes in California. The program quickly taught itself what was a real earthquake and what was extraneous noise, then identified and characterized thousands of tremors that would be missed by conventional seismic signal detection programs and their human analysts.
Between November 2018 and April 2022, the system recorded approximately 192,000 earthquakes beneath Pahala. The team that mapped these bright spots was amazed to discover a collection of igneous structures with a beating volcanic heart south of Hawaii.
Some of the earthquakes came from a region 28 to 32 miles deep: these long-duration earthquakes usually vibration formed by the movement of fluids, including magma. The bulk of the seismicity came from an area between 22 and 27 miles deep. These volcano-tectonic earthquakes—the kind that occur when a fault moves within a volcanic region and rocks break—depicted a series of near-horizontal sheet-like structures, some four miles long and three miles wide.
At different times, scientists have detected an increase in seismic activity within separate layers. The team believed that these layers were pockets of magma with their own plumes following 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 major segment of Hawaii’s circulatory system is “extraordinary,” he said. Jackie Caplan-AuerbachA volcano seismologist at Western Washington University was not involved in the new study. “It’s amazing” that scientists can not only see the previously hidden heart, but also feel the contractions of the ventricles inside, he said.
The Pāhala Sill Complex, as the heart is technically known, has several arteries branching from it. One major path marked by rock-shattering earthquakes leads to one of Kilauea’s shallow magma reservoirs. So, perhaps it is no coincidence that in 2019 the threshold complex began to thunder non-stop. During the 2018 eruption, Kilauea released a significant portion of its shallow magma reservoir, causing a decrease in pressure. In response, magma was sucked into the sills to equalize the pressure. Similar events occurred during Kilauea’s time shorter 2020 eruption.
Further work may help resolve the controversial question of whether Kilauea and Mauna Loa, relatively close neighbors on the surface, are somehow present. related at great depths. To date, there is little concrete evidence for this hypothesis, and experts generally agree that there are two volcanoes there is wide independent From each other.
New research still doesn’t overturn that consensus. This shows another major artery of the sill complex, again marked by rock-splitting earthquakes, runs toward Mauna Loa. But it stops short of a major horizontal fault and doesn’t appear to reach one of Mauna Loa’s shallow magma reservoirs.
Nor is it certain that the magma moves in any of these ways. That will change if future work reveals long-duration earthquakes from them—the fate of which indicates the presence of fluids, presumably magma.
“The results are amazing,” they said Diana Roman, a geophysicist at the Carnegie Institution for Science in DC who was not involved in the research. But “it remains unclear whether the magma entering Pāhala directly fed the eruptions of Mauna Loa and Kilauea.”
Roman also studied the Pahala earthquakes. He co-wrote 2021 paper they concluded that the simultaneous upheavals were the result of magma penetrating deeply, squeezing both plumbing networks at Mauna Loa and Kilauea. New research supports this notion of an indirect link. But even with this mapped magmatic network, it’s still too early to call a more obvious connection.
Ross said there is still much of Hawaii’s underbelly unexplored and that more magmatic arteries may be located there.
“What is there that is still unlit?” I said that when Hawaii’s infernal subsurface shakes furiously again, the Caltech team will be ready to focus on it in hopes of uncovering what has been hidden until now.
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