The Hazards Of La Soufrière’s Gases

Visible satellite imagery showing the La Soufrière Volcano’s new lava dome growing a considerable size within the crater and a large area of burnt vegetation (Image copyright: 2021 Planet Labs Inc.)

Present La Soufrière Alert Level:YELLOWThe La Soufrière Volcano is restless. Seismicity and/or fumarolic activity are above the historical level at the volcano, or other unusual activity has been observed. This unusual activity will be specified at the time that the alert level is raised. This is level two of four.

The new lava dome of the La Soufrière Volcano continues to grow in St. Vincent. This growth now has volcanic gases that have previously been contained to the crater, spilling over the volcano’s flanks. Burn spots, or areas where vegetation has been browned or burned, have appeared on the slopes of the La Soufrière as acidic gases of Soufrière interact with the forested land.

Before (left) and after (right) of the impact of the volcanic gases on  La Soufrière’s Leeward Slopes (Lennon Lampkin)

Much of the chemical burning have been confined to the North Leeward area, according to the UWI SRC as well as the top one-third of the crater ring.

The UWI SRC reported, “You can see the pre-existing small lake, the 1979 dome, and the new dome. There are multiple areas of steaming throughout, but most can be seen at the fumarole (steam vent) on the 1979 dome at the contact point between the old and new dome and on the top of the new dome. The radially circular pattern of dome growth creates large lenticular masses of rock that are visible over the top of the dome. You can see a black mass of burnt vegetation possibly caused by contact between the growing dome and abundant low lying shrubs in the crater that runs from the front of the growing dome on its western end outwards for about 100 meters. It is possible that this damage to the vegetation occurred on Saturday night (January 16th, 2021) and could be the cause of the incandescence or glowing reported by residents on the western side of the volcano.”

While local media reports in St. Vincent purported this to be the effects of acid rain, Professor and Geologist at the UWI SRC, Richard Robertson has clarified that it is actually gas mixing with moisture at the crater. Speaking with UWI SRC’s Education and Outreach Manager, Stacey Edwards, Robertson clarified, “It certainly has to do with the gases that are rich in sulfur and oxygen. When you mix with moisture, you have a dilute acid, which is essentially burning vegetation.”

The summit of the La Soufrière Volcano on 23rd January 2021 showing the growing dome and burnt vegetation. (Rommel De Freitas)

Acidic gases continue to affect the nearby vegetation, with extensive damage observed within the eastern, southern, and western parts of the inner crater walls. The damage reported previously occurring along the upper part of the southwestern crater rim has continued to extend downslope slowly.

Plume of steam and volcanic gases emanate from the new La Soufrière volcanic dome. (UWI SRC/Richard Robertson)
Plume of steam and volcanic gases emanate from the new La Soufrière volcanic dome. (UWI SRC/Richard Robertson)

Robertson explained that the burning effect is confined to where the gas plume is. “The plume that is coming out as the magma cool is letting off a lot of gases.

In addition, the UWI SRC further clarified that some plant species are directly affected by the exposure to the gas itself that dissolves in the water droplets from dew that remains on the plants’ leaves.

Gases from La Soufrière are rich in sulfur but other chemicals like hydrogen chloride and hydrogen fluoride can mix into the steam – all produced from the volcano. On January 14th, 2021, scientists detected elevated concentrations of carbon dioxide being emitted by Soufrière. Both sulfur dioxide and carbon dioxide can be fatal.

Can this impact people?

According to Robertson, yes, but it will be diluted enough that it won’t cause any harm at this time.

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Presently, the dilute mixture is not moving very far, creeping down the mountainside. Robertson explained that by the time it gets to occupied areas, meaning where people live, it would be dilute enough, so it doesn’t cause any great harm.

Robertson, speaking again with UWI SRC’s Education and Outreach Manager, Stacey Edwards, explained that the emission of gases would continue, and residents of St. Vincent will continue to see damage to the vegetation. As the dome grows, he also explained, “It might creep downslope a little bit as the [gas] plume becomes more pronounced. It is probably going to go further afield as the wind will take it.”

Residents in Leeward communities, meaning the western areas of the island, have already reported in the last month, smelling sulfur. However, with the emergence of increased concentrations of carbon dioxide, a new threat has emerged.

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“If you breathe too much of it, you [are] basically occupying the lungs with less oxygen and more of a gas you can’t make use of in your body. It is dangerous for you. It is odorless; you can’t smell it. While the sulfur you can smell, and you can move away from it, the carbon dioxide you can’t smell.”

Robertson also explained carbon dioxide, as it is denser than the surrounding air, “it collects in hollows, valleys, [and] in depressions like the crater so there might be pockets of it where it is very concentrated.”

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He warns, “If you are exposed to it for too long, you basically die from a lack of oxygen. It is quite dangerous at the crater and close to the areas where gas are emitted near and along the crater rim.”

This is why officials continue to stress that public access to the volcano is strictly prohibited.

Air Quality Monitoring To Occur

Burnt vegetation within the crater of the La Soufrière Volcano, St Vincent as acidic gases affect the area with the growing dome in the background. (UWI SRC/Richard Robertson)
Burnt vegetation within the crater of the La Soufrière Volcano, St Vincent as acidic gases affect the area with the growing dome in the background. (UWI SRC/Richard Robertson)

However, as the volcano continues to erupt, it is worth monitoring. Robertson warns, “The concentrations may get high so those who have asthma or respiratory problems may find some discomfort.”

He said that the UWI SRC has recommended to NEMO to start monitoring the environment to look at the concentrations of gases in the currently occupied areas. Although concentrations are normal at this time, with present monitoring, when levels do rise, NEMO can detect the changes and take appropriate action.

In the Georgetown Town Hall, Robertson explained, “Authorities are moving in that direction to monitor the quality of the air in the areas in the villages and the communities that surround the volcano. As a precursory measure to ensure that if there’s a chance that the gas gets into the areas and it gets above a certain quality a standard set by the World Health Organization, you can alert them and they could take action.”

“That said, one of the good things about the gases that probably could cause problems for people, that is, sulfur-rich gases, is that they’re very smelly. When you smell them, our instinct is to move away. In fact, the ones that you probably smell often are sulfur-rich, and you will tend to move out of the way. If you have respiratory problems and [the gas is] causing you problems, you will simply move. You should have that reaction long before it gets to the stage where it causes serious harm.

“It’s being monitored. It’s not a big problem we think currently. It’s something to be watched, but if you have particular problems and you’re particularly susceptible, you really need to think about, you know, moving a little bit further away if it becomes a problem.”

Volcanic Hazard Map for the La Soufrière Volcano, St. Vincent (UWI SRC/NEMO)
Volcanic Hazard Map for the La Soufrière Volcano, St. Vincent (UWI SRC/NEMO)

The National Emergency Management Organisation reminds the public that no evacuation order or notice has been issued. NEMO continues to appeal to the public to desist from visiting the La Soufrière Volcano until the scientists advise that it is safe.

Official information will originate from St. Vincent and the Grenadines National Emergency Management Organization and the University of the West Indies Seismic Research Center.

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