California’s Long Valley Caldera is one of the world’s largest calderas, measuring 20 miles long and 11 miles wide and up to 3,000 feet deep. Bishop tuff, a welded tuff that characterizes the area, was produced 760,000 years ago when a catastrophic eruption emitted hot ash that eventually cooled and turned into bishop tuff.
At eruption, the ash went up eight miles into the air, with deposits reaching as far east as Kansas.
Despite the potential for total disaster if Long Valley erupts, nothing has been written about it. Instead, the focus is on Yellowstone, a supervolcano located several hundred kilometers to the northeast.
However, Long Valley may be on the verge of exploding, according to the Science Channel.
The secrets of the underground
‘Secrets of the Underground’, a 2017 documentary, looked at the supervolcano and its recent activity.
“There are worrying signs of probable volcanic activity,” said Rob Nelson, a scientist and narrator of the show.
“And hints point to an impending eruption strewn across this valley – the site of North America’s second largest explosive volcanic eruption.”
Related article: Yellowstone eruption 630,000 years ago opens new geological mysteries
A possible threat
Although the recent eruption from Long Valley is not as large as in the past, it still poses an “existential threat” to the millions of people living nearby.
Science Channel surveyed part of the valley and discovered many clouds of smoke flowing down from the ground.
Using InSAR data that has been monitoring the region for the past 20 years, geophysicist Jared Peacock pointed to a worrying aspect of the caldera that could be indicative of problems.
InSAR is a remote sensing method that uses a laser to concentrate a beam of radiation on a target that bounces back to a sensor on an antenna and provides a comprehensive map of an area.
One of the most worrying places in InSAR was near Mammoth Lakes, a village in the highlands of the Sierra Nevada.
“Right here in the middle, you can see that there is a resurrected dome,” said Mr. Peacock and pointed to a map made from the data.
A burning hot red spot is depicted just below the Earth, indicating the presence of magma.
“Something below it pulls it higher,” Mr. continued. Peacock.
To study volcanic activities
Mr. Peacock and Mr. Nelson set up a pair of sensor tubes immediately above the site. The InSAR data revealed the resurrected dome and checked for signals of trouble deep down to see if the Long Valley caldera was coming to life again.
The tubes helped the two scientists detect changes in the Earth’s magnetic field so they could determine if there was any liquid underneath.
They observed enormous amounts of fluid below the surface of the domes during the experiments, indicating volcanic activity.
However, this activity was not centralized, giving cause for concern. Instead, it was scarce and scattered.
“We can state with certainty that there is no large magma chamber below,” Mr. Peacock, “but smaller satellite magma chambers surround the area.”
“The occurrence of huge amounts of melt in Long Valley’s magma reservoir remains unanswered despite 40 years of varied research,” the paper says.
The Long Valley Caldera Reservoir is expected to have “significant melting properties” with a volume of more than 240 cubic miles (1,000 cubic kilometers).
This melt can be hot enough to burn liquid rock in about 27% of cases.
Long Valley last erupted 100,000 years ago, according to the United States Geological Survey (USGS).
Also read: One of the world’s largest mass extinctions may have been triggered by volcanic winter
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