Long Valley supervolcano: Geologists wonder if it's 'waking up'
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The caldera is located in eastern California and sits next to Mammoth Mountain. One of the planet’s largest depressions, it is a huge, cauldron-like hollow that forms after an eruption. Measuring a staggering 20 miles long and 11 miles long, it is up to 3,000 feet deep.
It originally formed 760,000 years ago when a devastating eruption released plumes of hot ash that later cooled and formed what is known today as the Bishop Tuff — a welded rock formation that characterises the region.
The event saw ash shoot eight miles into the sky, with deposits thought to have fallen as Far East as Kansas — around 1,538 miles away.
If Long Valley were to erupt again, the consequences would be devastating.
Yet, little is said of it compared to other volcanic sites like Yellowstone.
According to the Science Channel, Long Valley could be on its way to erupting, its recent volcanic activity explored during the channel’s 2017 documentary ‘Secrets of the Underground’.
Rob Nelson, a scientist and the show’s narrator, said: “There are alarming signs of possible volcanic activity.
“And there are clues pointing towards an imminent eruption scattered throughout this valley — the site of the second largest explosive volcanic eruption in North America.”
Even if a modern-day eruption was not on the same scale as events previously seen, it still poses an “existential threat” to the millions who live around it, according to Mr Nelson.
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An investigation carried out by the Science Channel in part of the valley found several instances of smoke billowing out from beneath the ground.
Jared Peacock, a geophysicist, also pointed out an alarming feature of the caldera that could spell trouble using InSAR data that has monitored the region for the last 20 years.
InSAR is a remote sensing technology which focuses a beam of radiation on a target, which then bounces back to a sensor on an antenna, creating a detailed map of a region.
One of the most troubling areas the data pinpointed happened to be within close proximity to Mammoth Lakes, a town in the Sierra Nevada mountains.
Pointing to a map created from the data, Mr Peacock said: “Right here in the middle, you see there’s a resurgent dome.”
An intense red blob is seen pictured on the screen directly beneath the ground, where magma is likely deposited.
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Mr Peacock said: “Something underneath it is pushing it upwards.”
To determine whether the volcano was coming back to life, the two assembled a pair of sensors and installed them directly above the resurgent dome, the pipes helping to detect any changes in the Earth’s magnetic field.
This in turn enabled the scientists to determine whether any liquid — hot magma — was bubbling away underground.
The tests confirmed that there were massive amounts of liquid beneath the domes’ surface — clear signs of volcanic activity.
But, because the activity was not centralised, it was not a cause for concern.
Mr Peacock said: “We can say conclusively that there is no giant magma chamber below. But there are smaller satellite ones around the area.”
However, the danger of an eruption has not been completely ruled out.
A year later, in 2018, a study published in the science journal, GeoScience World, revealed evidence of ground deformation at Long Valley.
Geologists who led the study found “ongoing uplift suggests new magma may have intruded into the reservoir” since at least 1978.
The uplift could be evidence of moving molten rock or the crystallisation of material deep beneath the ground.
The study reads: “Despite 40 years of diverse investigations, the presence of large volumes of melt in Long Valley’s magma reservoir remain unresolved.”
The scientists estimated the Long Valley Caldera reservoir contains “considerable qualities of melt”, likely greater than 240 cubic miles (1,000 cubic kilometres).
About 27 percent of this melt could be hot enough to be scorching liquid rock.
According to the United States Geological Survey (USGS), Long Valley last erupted about 100,000 years ago.
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