Acidic Gas, Not Rain, Affecting La Soufrière’s Slopes

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

Present La Soufrière Alert Level:ORANGEThere is a highly elevated level of seismic and/or fumarolic activity or other unusual activity. An eruption may begin with less than twenty-four hours' notice.

As the effusive eruption of the La Soufrière Volcano continues in St. Vincent, a new, but not abnormal, hazard has emerged. Burn spots, or areas where vegetation has been browned or burned, have appeared on the slopes of the La Soufrière.

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.

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.”

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)

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.

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.

Can this impact people?

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

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.

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. As the new dome fills the crater with new magma, it will push more gases over the crater rim and gases may reach further downslope.

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.

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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