La Soufrière de Guadeloupe volcano (Guadeloupe, France): seismic unrest continues
Sat, 5 Jan 2019, 11:1511:15 AM | BY: T
Weak volcanic unrest continues at the volcano. During 21-23 Dec 2018, another small seismic swarm took place under the volcano totaling 88 recorded earthquakes of very small magnitudes at shallow depths (less than 2.5 km beneath the summit of the lava dome).
Number of earthquakes under Soufrière volcano up to Nov 2018 (image: OVSG)
Here is an excerpt from the latest monthly summary (Nov 2018) of the volcano observatory (OVSG):
"Since the beginning of 2018, we have remarked a cyclic process of deep magmatic gas injection at the base of the hydrothermal system, at a depth between 2 and 3 km below the summit.
This generates a recurring process of heating and pressurisation of the hydrothermal system that results in:
1) disturbances in hydrothermal fluid circulation;
2) evolution in the activity of the summit fumaroles, one of which shows evidence of projections of hot and acid mud over a range of several metres;
3) an increase of seismic swarms of volcanic origins;
4) some volcanic earthquakes being felt by the surrounding population (four between February and April 2018) including the M4.1 on 27 April 2018, the strongest since 1976;
5) low- amplitude ground deformation limited to the La Soufrière dome, on the order of 3-7 mm / year, as well as the continued opening of summit fractures; 6) fluctuations in fumarolic gas flow rates emitted from an overpressured hydrothermal reservoir;
7) propagation of the ground thermal anomalies on the summit and dome of La Soufrière.
Though these phenomena incite the observatory to exert extra vigilance, they are currently not clearly accompanied by anomalies in other monitoring parameters related to a possible rise of magma. These could include, though not in every case the occurrence of increased deep and/or felt seismicity, large scale deformations, and sulphuric gas emissions at high temperature (> 150 °C).
On the basis of the observations recorded by the OVSG-IPGP during the month of November 2018 and summarised in this bulletin, and in accordance with the provisions laid down by the authorities, the current level of volcanic activity (see table in annex) remains : VIGILANCE (= YELLOW)
The short-term probability of eruptive activityremains low. However, an intensification of phenomena in the future. As a result, the OVSG-IPGP is in a state of increased vigilance.
The gaseous emissions in the vicinity and leeward of the main summit fumaroles (in particular Cratère Sud, Cratère Tarissan and Gouffre 1956) have, since 1998, proven risks of irritation and burns (eyes, skin, respiratory tract). Due to the presence of these toxic gases, the municipal by-law of the city of Saint-Claude No. 01-296 of October 29, 2001, amended on January 27, 2015, prohibits public access to certain areas of the summit.
Given the evolution described above and the other observations on the activity the OVSG- IPGP advises, as a precaution, to maintain a distance of 50 m radius from the main centers of fumarolic gas emissions (Cratère Sud Sud, Cratère Sud central, Cratère Sud Nord, Napoleon Nord, Napoleon Est, Gouffre 1956, Gouffre Tarissan)."
Links / Sources:
Links / Sources:
Tue, 11 Dec 2018, 09:44
The volcano has been showing weak signs of unrest since the beginning of 2018, in the form of increasing numbers of tiny earthquakes under the volcano. ... Read all