On March 30, Colombia’s Geological Service raised its alert level on the volcano from yellow to orange. They warn that the volcano could erupt with a strength unseen in the last 10 years within “weeks or days”.

President of Colombia Gustavo Petro on April 5 ordered the voluntary evacuation of about 2,500 families living near the volcano. Many locals have been unwilling to leave their belongings and livelihoods behind.

Geologists monitoring the volcano have recorded thousands of tremors every day – an unprecedented number.

Nevado del Ruiz, one of Colombia’s tallest peaks at 5,321 metres high, is located in a populated farming region. It is only 129 km west of the country’s capital city Bogotá.

In 1985, the volcano erupted with tragic consequences. It triggered mudslides that nearly completely buried the town of Armero. More than 23,000 of the town’s 30,000 residents were killed.

Despite humanity’s long history of living under the shadow of volcanoes and trying to understand them, geologists, seismologists and vulcanologists remain largely baffled by the lava-spewing behemoths.

The last time the threat level of Nevado del Ruiz was raised, for example, was in 2012. For over a month in April of that year, residents were under orange alert. This was increased to red alert for two days in June. But no major eruption occurred.

Recently, new methods for assessing the risk of volcanic eruption have been trialled from studying the chemical composition of the atmosphere above active volcanoes to utilising artificial intelligence to try and make sense of the pattern of eruptions.

University of Miami professor in marine geosciences Falk Amelung believes the threat should not be taken lightly.

“This is a high-risk and well-monitored volcano, and right now, all the ingredients for a new eruption are there,” Amelung says in a university press release on Newswise. “A significant seismic swarm occurred on March 30, and this [low-magnitude] earthquake sequence strongly suggests that magma is on the move.”

Like Mount St Helens in Washington state, US which famously erupted in 1980, killing 57 people, Nevado del Ruiz is a glacier-covered volcano. Amelung says that this places local residents under extra peril.

“Even a relatively small eruption would melt the glacier,” Amelung explains. “Volcanic ash combined with the meltwater would form mudflows, known as lahars, that can travel fast and for several miles.”

Amelung admits it is impossible to say with certainty what will happen.

“This increased period of activity could well die down and nothing happens,” he says.

Ironically, global warming over the last 38 years since the eruption which saw the inundation of Armero, means the glaciers that cover the volcano’s summit are smaller, lessening lahar hazards.

“But it is also bad news in terms of eruption hazards because there is less pressure from the overburden to keep the magma at depth,” Amelung adds.