Why the volcano erupting in the Caribbean has such a deadly reputation

La Soufrière on the island of St. Vincent, which last erupted in 1979, has a long and tragic history of powerful but mercurial blasts.

Since December 2020, a strange and gloopy mass of lava has been oozing from the top of La Soufrière, a volcano on the northern side of the Caribbean island of St. Vincent. This eruption posed no real threat to the 110,000 or so people living on the island, but things took a turn for the worse at the end of March, when the volcano began shaking in a way that suggested something more violent was coming.

Sure enough, at 8:41 a.m. local time today, the first of several major explosions rocked the mountain, kicking off a more dangerous phase of the eruption. The situation on the island is extremely febrile: Anywhere from 20,000 to 30,000 people in the north needed evacuation, either off-island via boat, or to the island’s south via a single, jam-packed road. The process began the day before the blast and was still ongoing as the eruptions began.

The hazards for those still in the north include significant ashfall, falling volcanic blocks and bombs, and avalanches of superheated volcanic ash and gas that cannot be outrun. This volcano’s eruptions have killed thousands in the past, and it’s hoped that the evacuations have been successful enough already that the worst-case scenario has been avoided. So far, there have been no reports of deaths.

Today’s explosions are but a harbinger of things to come. If its past paroxysms are anything to go by, then La Soufrière is just getting started.

“We can’t be sure that because there’s been one explosion, that this is it,” says Jenni Barclay, a volcanologist at the University of East Anglia. “Many volcanic eruptions continue over weeks or even months, and they have different phases of activity associated with them.” La Soufrière is likely to be no different.

From toothpaste to terror

La Soufrière is the youngest volcano on St. Vincent, which is itself part of an archipelago of 32 islands and cays in the Caribbean. Its eruptions are known for their explosivity and lethality.

Before European colonists arrived in the early 1700s, the Indigenous population dwelled along the coast, away from the danger of any potential eruptions. But after becoming a British colony in the 1760s, the island’s enslaved population was forced to live and work in the volcano’s shadow. Many enslaved people died after an eruption in 1812, and many of their descendants perished when a 1902-03 eruption devastated a huge swath of the island.

Since its last eruption in 1979, the volcano has been relatively quiet. But in late December 2020, without much seismic fanfare beforehand, it began squeezing out gloopy lava that, over the following months, grew into a so-called lava coulee nearly 3,000 feet long. Paul Cole, a volcanologist at the University of Plymouth, says that this event could have been the entire eruption, and once it ran out of steam, the volcano could have gone quiet again.

But like many of the volcanoes in the region, La Soufrière has a reputation for being mercurial. Its magma type is known as a basaltic andesite, says Jazmin Scarlett, a social and historical volcanologist based in England. It is stickier than the stuff coming out of Kīlauea in Hawaii and in Iceland, which means the magma’s trapped gas has trouble escaping as it rises to the surface—a key feature that often leads to explosive eruptions as the gas finally breaks through and dramatically expands.

It isn’t clear why volcanoes like La Soufrière can suddenly switch between effusive and explosive eruption styles, says Scarlett. But it can happen at the drop of a hat, and that put volcanologists on high alert since December.

Something wicked this way comes

As the dome continued to grow, a number of earthquakes shook the volcano at the end of March. These were plenty energetic, but a second swarm of earthquakes on April 5 was more intense. These temblors, known as volcano-tectonic, or VT, earthquakes, are often associated with magma forcing its way through rock deep underneath.

“As soon as we saw these VT earthquake swarms, I think most people who were involved said that was really bad news,” says Cole.

In the past week, the dome cracked open, became noticeably more incandescent, and began blasting out a lot of noxious gases. Additional seismic activity linked to the shallow movement of magma was also detected. Although it’s too early to confirm, the most likely scenario is that all this behavior pointed toward a significant amount of gas-rich magma speedily rising toward the surface.

An explosion was on its way, and volcanologists were hoping an evacuation notice would be given. “But it’s very difficult when you can’t put your finger on a time and date and say, that’s when it’s going to get too dangerous to stay in your house,” says Barclay.

To many people’s relief, the Prime Minister of St. Vincent and the Grenadines, Ralph Gonsalves, ordered people in the northeast and northwest of the island to immediately evacuate during a televised address on April 8. Alerts were sent via the radio, as well as across social media channels. Police in the island’s north spread the word too.

A confluence of disasters

Early in the morning of April 9, a huge explosion took place at the summit, creating an ash plume six miles high. A second blast happened a few hours later.

The evacuation is still ongoing, and it’s no small feat, explains Scarlett. There were about 20,000 people in the so-called red zone, the area most threatened by any explosive eruption, with an additional 10,000 people in the orange zone a little further south. Some of Scarlett ‘s family live in Georgetown, which is in the red zone. At the time of writing, it’s not clear if everyone has left. “I’m just trying not to think about it, really,” she says.

“There is only one road that connects the northern end of the island to the south end,” says Scarlett. For many, this is the only passage to safety, and footage shared on social media has shown it at points to be choked with traffic.

Others are hoping to escape by sea, using anything from small fishing vessels to cruise ships. Surrounding island nations have offered to receive any refugees, but in 2021, it’s not simply a matter of cramming as many people onto those ships as possible. “This year, the framework of the pandemic makes things much more complicated,” says David Pyle, a volcanologist at the University of Oxford.

Evacuees are only allowed on boats if they can prove they have been vaccinated against COVID-19. Although the vaccination program on the island has been both widespread and rapid, says Scarlett, there is still a decent amount of vaccine hesitancy, partly due to antivax propaganda. That means unvaccinated people may still be stranded on the shores of the red zone.

“I’m absolutely certain there were still people in the red zone that were trying to get out” when the explosion happened, says Cole, though he hopes that many had already fled. As with previous volcanic eruptions, though, a small number of people in the dangerous zones will likely refuse to leave their homes behind.

But people still in the red zone are remain in harm’s way. The falling ash can cause breathing problems, especially for those with pre-existing respiratory conditions. It can block escape routes while adding a terrifying psychological layer to proceedings. “It’s a powerful and horrible form of darkness,” says Barclay.

Volcanic avalanches known as pyroclastic density currents, whose innards can be 1,300°F, may spill downslope and rush toward people at speeds exceeding 50 miles an hour. “They can flow over water, they have surmounted and flown uphill,” says Scarlett.

Huge blocks ejected by explosions can also kill people several miles away from the summit. And if it begins to rain, any old volcanic deposits may be mobilized into concrete-like slurries known as lahars that crush and suffocate anyone they impact.

Those that have managed to get to the island’s south also now present emergency managers with a huge logistical headache. Putting people into shelters, or, as is usually the case when disaster strikes the island, asking them to stay with friends and family, may inadvertently cause a jump in COVID-19 infection rates.

A worrying waiting game

Today’s activity is probably only the opening salvo. “I fully expect that there is likely to be further explosions,” says Cole. Historical eruptions have often featured prolonged successions of blasts, spread days, weeks, and even months apart. And these initial explosions may not be the biggest.

The island was well-prepared for the disaster though, which means the grimmest outcome may have been avoided.

For many years, explains Pyle, the University of the West Indies has led a volcano awareness week for the island. It’s held around Easter, during the anniversary of the 1979 eruption. The possibility of a future eruption has been kept in the minds of the populace thanks to this endeavor.

The National Emergency Management Organization also has been using seismic and volcanologic data to continuously update its warning and evacuation procedures long before this new eruption began. Scientists working at the Montserrat Volcano Observatory, another volcanic isle with a history of devastating eruptions, have been acting in a supportive capacity during the current eruption.

“This event is still showing us that nothing beats on-the-ground expertise, in terms of having scientists who have a sense of what the signals are telling you based on experiential knowledge,” says Pyle.

A profound sense of optimism, too, can be gained from a look at the island’s history, horrific though some of its chapters may be. Scarlett has looked at two centuries of volcanic paroxysms in the region.

“What I’ve found is that the Caribbean always comes together to help,” she says. The commonality these island nations have—cultural, religious, and historical, including the bonds they share as the descendants of enslaved people—mean that they, and the wider diaspora, help each other out in moments of crisis.

Already, offers of financial and logistical support have come in from around the region and the world. St. Vincent may be a small island. But, says Scarlett, “they’re not alone.”

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