La Soufrière’s Steaming Domes

Steam emanating from the 2020-2021 and 1979 La Soufrière Dome (NEMO)

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 La Soufrière Volcano crater has historically been a water-abundant area outside of eruptive activity. The crater has housed crater lakes of varying sizes in the last 100 years, with ever-present groundwater being located in a tropical climate.

When hot rock from deep within the earth breaks through the surface, water at and below the surface quickly reaches its boiling point and converts into steam.

Image of the La Soufrière Volcano crater prior to the 2020 eruption of the new lava dome, which occurred west-southwest of the 1979 lava dome. (UWI SRC)
Image of the La Soufrière Volcano crater prior to the 2020 eruption of the new lava dome, which occurred west-southwest of the 1979 lava dome. (UWI SRC)

The University of the West Indies Seismic Research Centre (UWI SRC) offers the same explanation. “There is a large amount of hot rock present and when it combines with the high volume of groundwater in the crater, the heat causes the water to boil – think a boiling kettle.”

The steaming is most prominent where there are cracks and fissures in the ground – providing a pathway for steam to escape into the atmosphere. “The steaming is most prominent at the top of the new dome and the interface between the old dome and the new because there are now more gaps through which the steam can come through.”

These pathways are sometimes called fumaroles, an opening in a planet’s crust that emits steam and gases such as carbon dioxide, sulfur dioxide, hydrogen chloride, and hydrogen sulfide. The UWI SRC indicates, “The fumarolic activity along the old dome will also steam more due to the increased activity within the crater.”

As the dome grows, there are now multiple contact points with the 2020-2021 dome and the 1979 lava dome. According to the SRC, “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.”

In an interview with the UWI SRC’s Education and Outreach Manager Stacey Edwards, Dr. Thomas Christopher offered two possibilities for why steaming has increased in the 1979 fumarole. “Either that it’s driving steam off from the groundwater and putting more steam into the actual emissions of the old dome or [it] is actually interacting with the old dome.”

He explained that more data and measurements would be required to test his hypotheses. “For me to answer that question, I need to take a gas measurement from the old dome and see what the gas composition is and see if it’s different to the dome. I can’t say if it’s one or both, but there’s definitely a lot more steaming coming from it.”

Dr. Christopher also offers another explanation for the increased steaming at certain points of contact between the old and new domes.

“What we notice is that they’re steaming along the contact with the two domes. What I think is causing that is that there was a lot of vegetation on the old dome, and I think that vegetation is being burnt off by the heat generated by the new dome.”

New cracks have also developed on the crater floor, causing more pathways for superheated water to escape as steam. However, recent changes in the gas composition indicate that the groundwater is drying up.

The alert level remains at Orange. The volcano continues to exude magma on the surface and steam can still be observed from the Belmont Observatory. Persons living in areas close to the volcano should expect strong sulfur smells for several days to weeks, depending on changes in wind direction.

The NEMO is reminding 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 and especially going into the crater since doing so is extremely dangerous.

The @uwiseismic and NEMO continue to advise access to the #LaSoufriere Volcano is strictly prohibited at this time….

Posted by Trinidad and Tobago Weather Center on Thursday, January 14, 2021

According to the SRC, the new volcanic dome is extremely dangerous for those in close proximity as it can explode at any time without warning. People have been killed in this way. This warning comes as images from a birthday photoshoot surfaced on social media.

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)

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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