Thousands Flee a Volcano in the Philippines Fearing a Possible Violent Eruption

Hot, ground-hugging flows of volcanic ash and debris began cascading down the slopes of Mayon Volcano, a 1.5 mile-high volcano—the most active one in the Philippines—in a peninsular region around 202 miles southeast of the Manila capital, last week. Volcanic activity increased in the following days, with Mayon spewing incandescent lava at night and causing tremors to neighboring villages. By Wednesday, June 14, some 17,000 people were evacuated, including those within its six-kilometer dangerous perimeter. National volcanologists have predicted that hazardous, eruptive activity could be imminent in weeks or days.

The Philippines is no stranger to volcanic activity in the seismologically-active Pacific “Ring of Fire.” In 1991, the violent eruption of Mount Pinatubo in Zambales killed some 700 people—outnumbering casualties from Mount St. Helens’ eruption in Washington State in 1985. And in 2020, just as most of the world scrambled to find masks for COVID-19, Taal Volcano ejected tall columns of volcanic ash that reached as far as the country’s capital, forcing its airports to close and exposing residents to harmful particulates.

But compared to these precedents, Mayon recently has shown some peculiar activity that may signal a gentler eruption, says Ma. Antonia Bornas, the chief of the volcanology institute’s monitoring and eruption prediction division: Levels of sulfur dioxide, which is typically released when magma is near the surface, is currently in the hundreds of tons, and volcanoes usually release at least thousands of tons of the gas before an explosive eruption. “We’re not seeing any volcanic activity,” Bornas tells TIME. “If you look at the seismic energy of the volcano—the way it charts—since a few months ago until now, it’s practically the same.”

Still, that’s no reason to be complacent. “For today, the chances of an explosive eruption are quite low,” she says. “But tomorrow might be a different story.”

Has Mayon erupted violently in the past?

Mayon, located in the Albay province, is a stratovolcano—steep volcanoes built up by eruptions of volcanic material over the course of thousands of years.

Data from the Philippines’ volcanology institute show the earliest recorded eruption of Mayon in 1616. Its eruptions range from phreatic (steam-driven) to Plinian—extremely explosive eruptions that can send volcanic debris tens of miles into the Earth’s atmosphere.

The last Plinian eruption of Mayon was in February 1814, which reportedly killed at least 1,200 people. Five foreign climbers were killed by falling rocks from a smaller eruption in 2013. From January 13 to March 18, 2018, volcanic activity in Mayon increased, spewing ash columns and lava and forcing thousands to evacuate, but there were no direct casualties.

What’s the current alert level for Mayon?

In a five-tier scale, Mayon’s activity as of Thursday was classified under Alert Level 3, which Bornas says indicates an effusive eruption from the crater.

The latest alert level can be found on the volcanology institute’s daily bulletin.

Despite the unrest, some volcano-watchers have flocked to see Mayon, which has become a popular tourist sight thanks to its majestic cone shape, prompting government officials to designate safe viewing zones, reports Philippine news site Rappler.

What are the potential effects of such an eruption?

Volcanic eruptions can lead to various health threats, such as the contamination of drinking water, wildfires, and the spread of infectious and respiratory diseases, according to the Centers for Disease Control and Prevention. “There is a concomitant health risk for being close to the eruption because of inhaling sulfur dioxide gas or the particulate matter from the ashfall,” said Philippine health secretary Teodoro Herbosa in a press briefing on June 11.

Should Mayon erupt explosively, Bornas from the volcanology institute says the effect won’t span the planet—only likely reaching the Visayas island group to its south and the rest of the main island of Luzon to its north. But the elevation of the volcano alone can cause serious damage to the surrounding communities due to the high potential energy, even possibly extending beyond the six-kilometer danger zone. Agriculture officials also estimate more than 5,700 hectares worth of crops will be affected in the event of a massive eruption.

On Wednesday, Philippine officials also warned that Mayon Volcano’s activity could possibly last for months, which would mean that some evacuees may find themselves displaced longer than expected as they are barred from returning to their homes within risky zones.

When Mayon erupted in 2018, more than 66,000 people stayed inside evacuation centers, and the damage to local agriculture cost an estimated 185 million Philippine pesos ($3.5 million).

How, if at all, are volcanoes related to climate change?

The U.S. Geological Survey (USGS) says major explosive eruptions can launch large amounts of volcanic material into the atmosphere—of which some can affect the global climate. Gases like sulfur dioxide can cause global cooling, while greenhouse gases like carbon dioxide can cause global warming.

Mount Pinatubo’s 1991 eruption ejected 20 million metric tons of sulfur dioxide into the Earth’s stratosphere at an altitude of more than 20 miles, cooling the planet by at most 1.3°F at peak impact, according to USGS.

Conversely, shifts in climate can also influence volcanic eruptions. A 2017 study published in the Geology journal found that eruptions were less frequent in cooler global temperatures, suggesting that a warming Earth may increase them. A 2021 study from the University of Cambridge also found that as the planet warms, the smoke and fumes from eruptions can rise higher and allow them to travel farther.

Patrick Whelley, a geologist at NASA who previously studied the frequency of explosive eruptions in Southeast Asia, tells TIME via email that most explosive eruptions from Mayon Volcano are “small” and “don’t pose a risk to anyone outside the summit region.” However, Southeast Asia has had several volcanoes whose eruptions affected the global climate. Says Whelley: “They occur in Southeast Asia on the order of 1 per thousand years.”