A new study by researchers at the California Institute of Technology (CIT) suggests so Long Valley Calderain eastern California, tosses and turns restlessly as its deep magma chamber cools for a long, deep sleep.
The last time the volcano erupted was About 100 thousand years ago. Long before that, enough ash was ejected to bury the modern city of Los Angeles under a kilometer of sediment.
Today, the Long Valley supervolcano is in a relatively slow process. But things are not calm on California’s eastern front. In the late 1970s, a swarm of earthquakes began emanating from the caldera – a depression located above the buried volcano.
Over the following decades, the volcano produced regular periods of “apparent disturbances” that caused the ground to swell and deflate.
Fortunately, this is not necessarily a sign of impending doom. CIT researchers have now found evidence that all this noisy activity is due to a cooling of the atmosphere A massive volcano that does not heat up.
“We don’t think the region is preparing for another massive volcanic eruption, but the cooling process could release enough gas and fluid to cause earthquakes and small explosions.” she says Geophysicist Zhongwen Zhan.
“For example, in May 1980, four magnitude 6 earthquakes occurred in the area alone.”
The team’s findings are based on data collected from a 100-kilometre-long fiber optic cable, using distributed acoustic sensing.
Over the course of a year and a half, Caltech researchers used this interconnected system—the equivalent of 10,000 individual seismometers—to catalog more than 2,000 seismic events, many of which could not have been felt by humans on Earth.
This data was then plugged into an algorithm Machine learningWhich converted the measurements into a high-resolution map of the caldera and the volcano beneath it.
This is the first time a network of deeply distributed acoustic sensors has revealed the Earth’s internal dynamics, says Ettore Biondi, a seismologist at Caltech and first author of the study.
the pictures produced The team says they have “exceptional lateral resolution” at depths of up to 8 kilometres. Even images of the deeper parts, up to 30 kilometers deep, were obtained with a “remarkable level of detail.”
The results show a definitive separation between the volcano’s large magma chamber, located 12 kilometers below the surface, and the shallow hydrothermal system above.
It appears that as the innermost chamber cools, gases and liquids flow toward the surface, potentially causing earthquakes and swelling of the Earth.
A diagram depicting the magma chamber below Long Valley Caldera. The plan was developed from tomographic images using seismic waves. (Biondi et al. Advancement of science2023)
This boiling effect can lead to “marked surface deformation and seismicity,” He writes Researchers.
This is different and much less dangerous than what happens during an active volcanic eruption, when magma in a volcanic chamber rises into the upper crust and emerges into the world.
The way seismic activity travels through these layers suggests that the top of the magma chamber contains a solidified cap of crystallized rock, which cools over time.
As the activity of the giant volcano declines, researchers They say Your “beating heart” gradually slows down.
The team plans to measure these last pulses at a depth of 20 km using a 200 km long cable of seismic sensors.
The study was published in Advancement of science.
Written by Carly Casella
Published on Science Alert