‘Mouth of Hell’ volcano is waking up: Scientists warn magma is building beneath one of Earth’s most dangerous craters

The ‘Mouth of Hell’ volcano may be waking up, scientists have warned.

Researchers have discovered evidence of two magma chambers filling up beneath the active Masaya volcano.  

It is located just 13 miles (20km) from the two million residents of Managua, the capital of Nicaragua. 

Meanwhile, thousands of tourists flock each year to see the lava-filled Santiago crater that gives this imposing volcano its ominous name.

This makes the threat of eruption a constant concern – and a new study has just found troubling signs of activity hidden beneath the ground.

While their study didn’t identify any immediate dangers, this suggests that the Mouth of Hell’s ‘plumbing’ is more complex than they had previously thought.

Understanding that system of magma tubes and reservoirs is key to spotting the changes that could hint at an impending eruption.

Lead author Lizzie Johnson, from Penn State University, said: ‘Having a thorough understanding of Masaya’s volcanic activity and its related hazards is critical.’

The Mouth of Hell is an exceptionally complex volcano, made up of nested craters and sinkholes formed by empty magma chambers.

Due to this complexity, the network of tunnels and chambers beneath the surface is poorly understood.

That makes it hard to read the subtle signs that might indicate whether an eruption is impending, a serious hazard for a major tourist attraction so close to the city.

‘Although Masaya last produced a major lava flow in 1772, its persistent degassing often produces dangerously high concentrations of sulphur dioxide volcanic gas,’ says Ms Johnson.

The volcano has also produced several explosions over the last 50 years – and while these haven’t caused any injuries so far, researchers don’t want to take any risks.

In their new paper, published in the journal Geophysical Research Letters, the researchers looked at data collected by the Sentinel-1 satellite.

This satellite passes over the site once every 12 days, building up a detailed picture of how the ground rises and falls with the movement of magma beneath the surface.

Ms Johnson says: ‘When it’s subsiding, that means that there’s probably magma draining away from the volcano – but once the ground starts uplifting again, that can mean that there’s potentially new magma moving in.’

Between 2018 and mid-2022, the researchers saw that the area around the Masaya Central Reservoir, just north of the famous Santiago crater, had sunk by about 1.2in (3cm).

This suggests that some of the magma had moved away from the reservoir hidden beneath the surface, causing deflation.

However, from 2022 to 2024, the ground started to rise once more, suggesting that the reservoir was once again filling with magma.

Strangely, the area directly around the Santiago crater and its lava lake deflated over the whole six-year period.

According to the researchers, this may mean there is a second, shallow reservoir buried about 656ft (200m) below the surface that is also active.

‘This indicates that the plumbing system is more complex and could be due to decreasing magma in a second, shallower reservoir,’ adds Ms Johnson.

In the future, the researchers hope that more measurements like these will build up a better picture of the volcano’s behaviour and improve eruption forecasting.

Co-author Dr Young Cheol Kim, of Penn State University, says: ‘Doing continuous monitoring allows us to understand the baseline activity and identify if things are changing.

‘And then if there is a need to warn people, we can do that in a timely manner.’