Geoscientist addresses questions about volcano's eruption

Geoscientist addresses questions about volcano's eruption

Satellite image captured after an eruption of La Soufrière volcano in the Caribbean island of St. Vincent on April 9.

Credit: Planet Labs

By Diana Udel

Satellite image captured after an eruption of La Soufrière volcano in the Caribbean island of St. Vincent on April 9.

Credit: Planet Labs

Geoscientist addresses questions about volcano's eruption

By Diana Udel
Falk Amelung, professor with the Rosenstiel School's Department of Marine Geosciences, provides answers about the La Soufrière volcano in St. Vincent in the Caribbean. An effusive eruption began as early as December 2020, and explosive eruptions were recorded as recently as April 12.

What do we know about the La Soufrière volcano eruption?

St. Vincent is a volcanic island part of the  Lesser Antilles volcanic arc which is the result of the westward subduction of the North American tectonic plate under the Caribbean tectonic plate.

What prompted the eruption?

The eruption started on December 27, 2020, with the appearance of a lava dome at the surface that has since grown to more than 100 meters elevation (~15 million m^3 volume). Some of the recent explosive activity are lava dome collapse events. The dome (a pile of newly extruded volcanic material) has grown so big that it has become unstable. When it collapses, it sends pyroclastic flows down the valleys, and then resumes growing.  Normally both things happen: explosive activity triggers dome collapse and dome collapse triggers new explosive activity.  Lava dome eruptions are typical for the Lesser Antilles volcanoes. It is a good thing in terms of hazards because pressure is relieved gradually, making a very large eruption unlikely.

When was the last time this volcano erupted and what is its projected length of activity?

The volcano had 6 eruptions in the past 300 years with the last ones in 1902, 1971-72 and 1979. Previous eruptions took a couple of months. This gives some hope that the eruption will not last very long.  On the other hand the most recent eruption in the Lesser Antilles further north on Montserrat, a British overseas territory,  lasted for 18 years from 1995 to 2013. 

What else should we, and the people of St. Vincent know ?

The lightly populated northern part of  the island which is a designated hazard zone will be heavily impacted by this eruption. The main hazards are hot pyroclastic flows that destroy everything along their path. However, the densely populated southern part of the island including the capital of Kingstown will not receive any pyroclastic flows. The impacts are occasional ash falls.  For now there is nothing  indicating that this will change.  

There is a GPS station which is part of a network funded by the U.S. National Science Foundation at 10 km distance from the volcano.  It has data until April 3rd.   This station does not show any vertical uplift, suggesting that no egregious amounts of magma accumulated at shallow levels, something that hopefully satellite observations will confirm in the following weeks.

Although this eruption is disruptive, there is a silver lining. The island of St. Vincent has been growing by eruptions like this one for millions of years.  In Miami where we don’t have any volcanoes,  we will be swallowed by the rising seas in 200 years or so.

Live Stream St Vincent Volcano Webcam https://youtu.be/tTzzb6nb9k0
Via TheRealPax