Long Valley’s Hot Creek springs and pools have this year appeared to experience a resurgence in activity.
Visitors to the national park say the creek’s surface has bubbled and a new hot water feature has even emerged on the shore.
While many feared it was a sign the volcano was gearing up to explode, researchers at the California Volcano Observatory said the activity was more a result of dramatic winter snowfall than a resurgence in volcanic activity.
The caldera may be safe for now, but scientists have in the past warned that an eruption could well be around the corner.
Such an eruption would, they say, throw millions into a perilous path — endangering the lives of countless people and possibly shutting down an entire country.
Long Valley is situated next to Mammoth Mountain and is one of the world’s largest calderas, a huge, cauldron-like hole that forms after an eruption.
The caldera at Long Valley is huge, measuring a whopping 20 miles long and 11 miles wide.
It is up to 3,000 feet deep and was originally formed 760,000 years ago after a cataclysmic event shot hot ash into the air that cooled and formed the Bishop Tuff.
The ash is thought to have fallen as far east as Kansas, some 1,538 miles away.
As such, scientists like Rob Nelson warn that millions of people face utter devastation from a future eruption.
Speaking during the Science Channel’s 2017 documentary ‘Secrets of the Underground’, he 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.”
A modern-day event could be far smaller than previous events, but even then, Mr Nelson said it would still pose an “existential threat” to the millions who live around it.
The Science Channel conducted an investigation in part of the valley and discovered several instances of smoke rising from beneath the ground.
Geophysicist Jared Peacock also identified a worrying feature of the caldera. Using InSAR remote sensing technology — which creates a detailed map of a region — he found a “resurgent dome” near Mammoth Lakes, a town in the Sierra Nevada mountains.
Further tests confirmed that massive amounts of liquid beneath the dome’s surface were creating the resurgent dome — clear signs of volcanic activity — but it wasn’t centralised and so isn’t yet a cause for concern.
“We can say conclusively that there is no giant magma chamber below. But there are smaller satellite ones around the area,” said Mr Peacock.
The danger of an eruption is still a real threat, and in 2018, a study published in the science journal, GeoScience World, revealed evidence of ground deformation at Long Valley.
Researchers found evidence for an “ongoing uplift [which] suggests new magma may have intruded into the reservoir” since at least 1978.
The uplift could prove that molten rock has been moving below the ground, or that material deep within the chamber has been crystallising.
The study reads: “Despite 40 years of diverse investigations, the presence of large volumes of melt in Long Valley’s magma reservoir remains unresolved.”
