Is California's supervolcano set to blow? Scientists identify more than 2,000 quakes at the Long Valley Caldera that they say 'are precursors for an eruption'

California's supervolcano that has the power to bury Los Angeles in more than 3,000 feet of ash is showing signs of activity.

Scientists at the California Institute of Technology (Caltech) identified over 2,000 earthquakes rumbling throughout the Long Valley Caldera in recent years.

The team conducted a new investigation to see if the seismic activity was a sign of impending doom or that the risk of a massive eruption was decreasing.

Caltech researchers created detailed underground images of the caldera, finding that the recent seismic activity results from fluids and gases released as the area cools off and settles down.

The study author Zhongwen Zhan said: 'We don't think the region is gearing up for another supervolcanic eruption, but the cooling process may release enough gas and liquid to cause earthquakes and small eruptions.

'For example, in May 1980, there were four magnitude 6 earthquakes in the region alone.'

A critical finding with the images revealed the volcano's magma chamber is covered by a hardened lid of crystallized rock, formed as the liquid magma cools down and solidifies.

The long-dormant volcano was the site of a super explosion 767,000 years ago, releasing 140 miles of volcanic material into the atmosphere and devastating the land. 

 Zhan and his team placed dozens of seismometers throughout the Eastern Sierra region to capture seismic measurements in a process called distributed acoustic sensing (DAS).

They covered 62 miles of the caldera with cables to capture underground snapshots.

Over a year and a half, the team used the cable to measure more than 2,000 seismic events, most too small to be felt by people.

A machine learning algorithm then processed those measurements and developed the resulting image, showing the locations of each quake.

Emily Montgomery-Brown, an expert on the Long Valley Caldera who was not involved in the study, told LA Times that the swarms of earthquakes started in 2011.

These quakes were then followed by a  ground deformation in which the land rose and the tremors dissipated in 2020, leaving the region quiet.

But she warns an eruption is still on the table.  

A study in 2018 found the Long Valley Caldera holds 240 cubic miles of magma underneath the surface.

'And so even if the Long Valley magma reservoir is moribund, there are other pockets of magma in the area,' Montgomery-Brown said. 

If the caldera were to erupt, it would eclipse the 1980 explosion of Mount St Helens, which belched out just 0.29 cubic miles of volcanic material into the atmosphere.

In fact, the valley's storage of 240 cubic miles of magma is enough to fill 400 million Olympic swimming pools.