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Source: Universal Science (ID: huanqiukexue)
Author: Global Sciences
Located in the laguna del Mole volcano region in central Chile, the rhyolite formed by the eruption of the volcano creates layers of circular structures on the ground that extend outward. (Image source: U.S. Geological Survey)
Recently, the eruption of a volcano in Tonga has revived human fear of volcanoes. However, in the face of a real "supervolcano", whether it is the eruption of Tonga Volcano, the eruption of Mount Pinatubo in the Philippines in 1991, or the eruption of Mount Tambora in Indonesia in 1815, which brought about a "summerless year", it can only be regarded as an "ordinary" volcanic eruption event.
Supervolcanoes store enormous destructive power, erupting large enough to reshape continents, and humans have never seen such eruptions. In Laguna del Mole, high up in the Andes, a supervolcano system is brewing that could accumulate to a very large scale in our lifetime.
Written by | Shannon Hall
Translate | Wei Xiaojie
An Airbus helicopter jolted violently over hundreds of meters over Chile's Andes. Brad Singer sat in the cabin, and even though he was firmly tied to the cabin seat, the bumps and clearly visible pavement made Singer insecure.
But the distant scenery instantly alleviated Singh's anxiety, a historic landmark left behind by a massive volcanic eruption. In the Laguna del Maule volcanic region, there are about 50 lava flows and 70 volcanic ash deposits, surrounded by an ice-blue lake with an area of about 54 square kilometers. Singh has been doing research here for more than 20 years. He said that only by looking down on this land can you understand how huge the volcano really is, and you can realize how powerful the last eruption of Laguna Del mole volcano was, which is simply the largest volcanic eruption in the world.
Geologists speculate that the fluids and sediments formed over the past 20,000 years and may have come from 25 to 30 surrounding volcanoes. Such a record is as strange as California's Long Valley. In Canggu, in addition to this "cascade" of volcanic eruptions, there is another feature: about 765,000 years ago, a huge volcano blew up a 500-square-kilometer deep crater on this land. Combined with the anomalous ground uplift of Laguna Delmore Volcano in about 10 years, they concluded that Laguna Del mole Volcano is likely to be home to the next supervolcano eruption worldwide.
Supervolcanoes are one of the most destructive forces on Earth. Once it erupts, it will cause at least 1,000 cubic kilometers of rock and ashes to rush out of the earth. This volume is basically 2500 times the amount of the devastating eruption of Mount St. Helen in 1980. The latest underground data from the magma chamber of The Laguna Del mole Volcano show that the volume of the magma chamber is large enough to have the energy to erupt all the material into the air at once.
Recently, Singer and colleagues have spotted some interesting signs: Bubbles generated from the hot region below may flow upwards, suddenly hitting cooling magmatic rocks. Not only that, but scientists have found evidence in other volcanoes that bubbles erupting from deep, high-temperature magma chambers can flow upwards, impacting low-temperature solid magma chambers. The researchers tried to piece together these clues through real-time observations of Laguna Delmol Volcano.
Brewing supervolcanoes
Historically, the power unleashed by supervolcano eruptions has been staggering. For example, a volcanic eruption in Yellowstone National Park in the United States, about 631,000 years ago, released a deadly heat wave, volcanic ash and poisonous mist that swept across the landscape. Until now, these volcanic eruptions can still reach a thickness of 200 meters. After the eruption, the sky was pitch black, and large amounts of volcanic ash fell into large areas of North America, leaving a layer of rubble and dust.
In recorded modern history, there has been no figure of a supervolcano eruption. In 2013, Singer launched a 5-year project in which they sought to study the past and present of the supervolcano system. He and his colleagues worked with Chile's National Geology and Mining Service to deploy about 50 sensors on the ground. In addition, they flew helicopters above the lake, scanning the surface with portable instruments.
Geologists place probes near lakes to detect the extent of ground uplift. (Image: Brad S. Singer University of Wisconsin-Madison)
All the data suggests that a supervolcano is brewing beneath the surface. Judith Fierstein, a geologist at the U.S. Geological Survey, said: "I don't want to be alarmist, but it does show that below Mount Laguna Del Mole, a magma chamber is converging, and getting bigger and bigger." Scientists did find that the area is located in the upper part of a magma reservoir with a capacity of up to 450 cubic kilometers and contains a huge amount of explosively reticulated magma. If the volcano erupts in its entirety, Singh said, the magma would be converted into 1,000 cubic kilometers of ash, rock and lava, a level that has reached the scale of a supervolcano.
Usually, magma does not erupt in its entirety instantaneously. But for the magma mass of Laguna Delmole Volcano, just 10% of the magma eruption would have caused about twice the size of the 1883 Eruption of Krakatoa in Indonesia. Although not classified as a supervolcano, the eruption claimed the lives of 36,000 people in 1883.
Low-temperature solid magma?
There are also many scientists who are more concerned about the temperature of Laguna Del mole. According to traditional views, the magma beneath the active volcano is a boiling liquid mass that rises to the top of the earth's crust like a bead of water inside a lava lamp. But in 2014, a discovery by Adam Kent of Oregon State University and Kari Cooper of the University of California, Davis, led scientists to recognize that some volcanoes may really be cold.
Among the rocks left behind by the eruption of Mount Hood in Oregon, Kent and Cooper examined tiny crystals in the volcanic rock. Before eruption, these crystals developed in the magma chamber below, accumulating layer by layer. Like the annual rings of trees, this process records and preserves the chemical reactions of magma evolution, including changes in information such as composition, pressure, and temperature. Crystals of Hood's volcanic rocks indicate that magma is in a state of temperature that is supercooled and unable to erupt 99% of the time. In this state, magma is not a typical liquid state, but a paste: there is some fluid present between a system of large numbers of crystals.
Some scientists have begun to explore whether this process is also suitable for other volcanoes. In late 2017, Singer and colleagues analyzed volcanic remnants in California's Long Valley region, and they saw similar solid records. Similarly, the magma chambers of Yellowstone National Park also appear in a colder, mushy crystalline state.
Although Kent and Cooper have found that magma may be present in slightly warmer regions in older eruptions in North and South America. But it's clear that supervolcanoes tend to exhibit magma chambers as solid. The supervolcano remained in this cool state until the eruption, which also meant that the magma changed from a near-solid state to a hot liquid, occurring rapidly in the short time before the eruption. Cooper's work on Taupo shows that the supervolcano system only began to liquefy 40 years before the eruption. In Canggu, liquefaction occurs between decades and centuries before eruption. At Yellowstone, the process also takes decades.
So what about Laguna Del Mole? Similarly, the massive magma looks like a crystalline paste. Singer and his colleagues believe that the volcanic system is made up of crystals and only 5% is molten liquid magma. The temperature of this paste is relatively low, around 800 ° C. By comparison, the temperature of lava pouring down the slopes of Kirayoua, Hawaii, in the summer of 2018 was about 1200°C. These findings may once again illustrate that cooler magma needs to "wake up" quickly before the supervolcano erupts.
Satellite imagery of the Laguna Delmol volcano area, including vegetation (vegetation) and snow-covered peaks (Credit: NASA/GSFC/METI/ERSDAC/JAROS and U.S./Japan ASTER Science Team)
Two mechanisms
But this theory also comes with a difficult question to solve: How do systems that are close to solids melt and move rapidly? Christy Till, a geologist at Arizona State University, believes that the most recent super-eruption in Yellowstone National Park occurred when liquid magma climbed upward from the Earth's interior and hit the upper solid rock formations. The rising liquid mixed with a solid substance, melting the crystals and heating the entire chamber. During the formation of the liquid, the pressure in the cavity is also increased, causing the magma to gush to the surface.
However, the situation in Chile may not be the same. Yellowstone sits on a hot mantle pillar, while Laguna Del Mole and Canggu are neither. At these sites, the crust of one plate is subducting beneath another, and during the dive, the rock inserted deep into the depths melts and forms a magma spurt upward.
Nathan Andersen, a geologist at the University of Oregon, analyzed the crystals from past eruptions of Mount Laguna Del mole and found that basalt magma originating deep in the Earth did not fully penetrate the volcanic system. These magmas remain at the bottom of the Laguna delMore-type volcanic reservoir. The two rocks have never been mixed. Basalt cools down when flow stagnates, releasing heat to the material above and releasing volatile water vapor in the form of bubbles. When heat and bubbles begin to rise, the surrounding crystals melt, forming a floating, bubble-filled plume that penetrates upwards to the top of the reservoir and exerts such pressure on the crust that it erupts.
Such thoughts worried Singer. If the current unstable bubbles are rising beneath the Laguna Del mole volcano, it will be difficult for local residents to escape. There are no hydrothermal features, such as vents, hot springs, or vents near mountain lakes. "In my opinion, this makes Laguna Del Mole more dangerous than other supervolcanoes," Singh said. If the gas is able to leak to the surface, the growth rate of the reservoir may slow down. "But if there's a reservoir that's completely enclosed in the ground, and it's trapped there, it's going to gradually gather all the magma and bubbles to build up a massive volcanic system." Moreover, once such an eruption occurs, the earth will be reshaped, which will be a volcanic eruption never seen in human history.
So while the reservoir beneath the current Laguna Del Mole volcano is only barely reaching the size of a supervolcano, it is likely to become larger in the coming centuries. Of course, Singh's current concerns are only predictive, and the mechanism of the eruption is only an inference. For example, rising melts (rich in bubbles) may not themselves generate enough pressure to trigger giant eruptions, and earthquakes are needed as an additional trigger mechanism. Singh's team is currently trying to identify potential, hidden trigger mechanisms, as well as associated signals.
Even if Laguna Del Mole had produced only a series of smaller eruptions (ash and lava records on the surface indicate that it did have had successive small eruptions in the past), ash could still render aircraft impassable in the region and could disrupt agricultural production in Argentina. Previously, Singer's team had removed the detection instrument from the site, but scientists from Chile and Argentina had picked up batons and installed new monitors to assist in observing the lake. Perhaps with a deeper understanding of supervolcanoes, scientists can do a better job of predicting the timing of eruptions. (This article is from the 2021 human crisis special issue of Global Science)
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