La Soufriere could erupt sideways

A bird’s eye view of the La Soufriere volcano. Photo: NEMO.

Kingstown, St. Vincent (ONE NEWS SVG) – The La Soufriere volcano could erupt in a lateral blast.

According to the National Geophysical Data Center a Lateral Blast is a “relatively rare explosion of hot, low-density mixture of rock debris, ash, and gases that moves at high speed out the side of the vent (laterally) rather than up from the vent (vertically).”

A lateral (sideways) blast of Mount St. Helens in the U.S, captured by an eyewitness. Photo: Mount St. Helens Science and Learning Center.

The head of the Seismic Research Center at the University of the West Indies, St. Augustine campus, Professor Richard Robertson said on VC3’s Round Table Talk aired on Wednesday, that a lateral blast eruption could happen at La Soufriere.

Responding to a question asked of him, Professor Robertson said that “because of the obstruction of the 1979 dome, the vent is now southwest”.

The growth of the new dome (2020/2021) which came up through the crater floor and which now lays beside the southwestern crater wall of the La Soufriere volcano could compromise the crater wall.

“Yes, there is a possibility that it could compromise the crater wall and you could have potential things like lateral blasts and preferential movement in that direction,” he said.

“People would have heard us speak about the fact that we would have put in a set of reflectors on the south-western wall (of the volcano) to look for potential failure of that wall, now, our concern was twofold,” Professor Robertson said.

He said the two reasons for the installation of the reflectors was “to look at whether the weight of the dome itself, the size of that mass of rock that was not resting on the crater wall, whether that rock weight could somehow cause the crater wall to fail and if the crater wall then fails, you have that potential for that hot material that is in the crater getting outside the crater. So, we were concerned about that, so we put a reflector there.” Professor Robertson said.

“But the other thing was really generally to monitor the stability of the southwestern crater wall, both because of that type of event but also because of the potential for other things,” Professor Robertson added.

He said that if there are explosions from the southwestern part of the crater, “there is a potential that the explosions could result in some sort of collapse from that direction”.

“But we would hope that by then, we would have alerted people insufficient time, so nobody would be in harm’s way,” he said.

He said if such a collapse was to occur, it could potentially cause a lot of damage, destroying a lot of property in the area, adding that “it shouldn’t harm lives because people would be long gone out of the way before it reaches that stage”.

He said “we might get an indication that we are headed in that direction before and certainly, people should be out of harm’s way”.

According to the US Geological Survey, the May 18, 1980 eruption of Mount. St. Helens in the US involved a lateral blast.


  1. Please note that a lateral blast from La Soufriere is low on the realm of possibilities from the volcano. More likely is simply for dome growth to continue either at the same rate or at a faster or slower rate. Also possible is for the eruption to end with or without it going to an explosive stage. If it does go explosive the most likely way for it to erupt would be simply through vertical explosions from the present source of effusive activity located in the SW part of the crater i.e. NOT a lateral blast.


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