|Present La Soufrière Alert Level:||YELLOW||The 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.|
Research into La Soufrière‘s evolution is still incomplete. According to the Volcanic Hazard Atlas of the Lesser Antilles, during the past 4000 years, the volcano has had an average of one explosive eruption every 100 years.
More recently (during the past 250 years) the Soufrière Volcano has displayed two distinct types of eruptions.
Type 1: Explosive Eruptions
These are the typical “St. Vincent style” eruptions. They are highly explosive eruptions usually preceded by frequent, strong earthquakes. Rapid rates of magma production result in the ejection of large volumes of new material. This type of activity is exemplified by the 1902-03 and 1979 eruptions.
Type 2: Non-explosive or Effusive Eruptions
This type of eruption is effusive and may be unaccompanied by earthquakes. Effusive eruptions occur when molten rock (lava) reaches the Earth’s surface and erupts passively. The products of these eruptions are lava flows and lava domes. They generally occur when the gas content of the magma is low. This type of eruption is exemplified by the 1971-1972 eruption.
A cyclical pattern of eruptive activity during the past 250 years with alternating eruptions of Type 1 and Type 2 has been observed at the volcano
Summary of La Soufrière’s Eruptive History
|Date||Summary of activity|
|1718||Explosive volcanic eruption preceded by one month of earthquake activity; possibly started on May 26 and continued until May 29. Ash fell on Martinique, St. Kitts, Barbados, and Hispaniola, and the noise of the eruption was heard as far as Trinidad and Antigua. This eruption was estimated to have been the most violent of the historical period based on research from Anderson and Flett (1903).|
|1780||Increased fumarolic activity, possibly accompanied by lava emissions.|
|1812||Explosive volcanic eruption preceded by >200 earthquakes during the previous year. The eruption started on April 27 and continued up to June 9. Pyroclastic flows, mudflows and ash falls affected the areas of Wallibou to Baleine and Grand Sable to Tourama. Fifty-six people died; a new crater was formed. The eruption is estimated to have been of a lower magnitude than the 1902 eruption.|
|1814||A small eruption of January 9; rocks were thrown 0.5 km from the crater.|
|1880||The lake temperature increased accompanied by a major rise in the water level. Increased fumarolic activity with possible development of lava dome.|
|1902-1903||Explosive volcanic eruption preceded by approximately 12 months of earthquake activity. The eruption began on May 6, 1902, and continued up to March 30, 1903. Pyroclastic flows, mudflows, and ash falls affected areas to the northeast, east, and west of the volcano. Over 1500 people died and extensive damage was caused to agriculture in the areas around the volcano.|
|1948-1954||The 1946 mean temperature of the Crater Lake was 4C above ambient air temperature (~23C). The annual mean temperature of the Crater Lake increased to ~28C during the period 1948-1949 but returned to the 1946 value by 1954. This was attributed to fumarolic activity on the lake bottom based on research done by Tomblin (1970).|
|1971-1972||An aseismic effusive eruption occurred resulting in the discharge of 80 million cubic meters of lava into the crater and an increase of 30 meters in the level of the crater lake. The eruption started between September 28 and October 10 and lava extrusion continued up to 1972. A dark grey basaltic andesite with 54% SiO2 was emitted. The vegetation was destroyed in a 30-meter zone above the lake level. A spontaneous evacuation of people from the area started in November but the official evacuation of the population from areas north of the Rabacca River only began on December 7.|
|1978||Local earthquake swarm.|
|1979||An explosive eruption occurred accompanied by effusive activity. The eruption was preceded by increased numbers of earthquakes, an increase in the temperature of the crater lake, and a slight inflation of the volcano flanks. The eruption started on April 3 with dome building continuing up to 1983. There were no fatalities, but there was a loss of crops and livestock. The final cost of the eruption to the economy was estimated at EC$13,784,797. Over 14,000 people were evacuated from areas located north of Union Village (east) and Belleisle Hill (west); explosions continued for two weeks followed by six months of non-explosive emission of lava.|
|1983-2019||Weak and infrequent earthquakes.|
|2020-2021||(Ongoing) - An effusive eruption begun on the afternoon of December 29th.|
This table was taken from the Volcanic Hazard Atlas of the Lesser Antilles (UWI SRC) and Professor Richard Robertson’s (1992) “Volcanic Hazard and Risk Assessment of the Soufrière Volcano.”
According to Professor Richard Robertson, La Soufrière has had explosive eruptions in 1718, 1812, 1902 and 1979. Robertson explained that the dome took various forms over time.
Following the explosion of 1902, there was significant damage to the surrounding area. By the 1930’s, a crater lake had reformed within La Soufrière’s crater.
From the 1930s to the 1970s, the crater lake persisted with little to no volcanic activity taking place in La Soufrière.
In 1971, the effusive eruption began, creating a small island within the lake and persisting into 1972.
This new dome gradually boiled the lake (not in its entirety) and persisted for about a year.
The 1971-1972 dome gradually grew until 1979 when an explosive eruption occurred.
In 1979, another dome grew following the explosive eruption.
Effusive eruptions, or eruptions that created domes, occurred in 1780, 1880, 1971-1972 and now, 2020-2021. Explosive eruptions occurred in 1718, 1812, 1902 and 1979.
Prior to the 2020-2021 activity, the current crater consisted of a small crater lake (which has now been entirely boiled off), the 1979 lava dome and the crater walls. The new dome has formed in the west-southwestern area of the crater and has been growing laterally to the north and south.
The U.W.I. Seismic Research Centre is the official source of information for earthquakes and volcanoes in the English-speaking Eastern Caribbean. The SRC is the scientific monitoring agency that supports various local disaster management agencies of the Eastern Caribbean. This includes the monitoring of the La Soufrière Volcano.
The Seismic Research Centre (SRC) updates the National Emergency Management Organization (NEMO) of St. Vincent and the Grenadines which is then responsible for adjusting the alert level of La Soufrière based on the SRC’s information. NEMO is then responsible for coordinating evacuations across the hazard zones based on the alert level and volcanic hazard.