MVO Weekly Report for the Period 15 to 22 September 2023

Activity at the Soufrière Hills Volcano remains low.

The seismic network recorded 16 volcano-tectonic earthquakes this week. 12 of these occurred in two very brief swarms on 18 September.

Measurements of the SO2 flux were taken by helicopter on 20 September. There were nine traverses with an average flux of 133 tonnes per day.

Due to the large size of the lava dome, pyroclastic flows can occur at any time without warning on any side of the volcano, including Gages from where they can travel rapidly into Plymouth. Tracks across the Belham Valley can be destroyed or heavily modified by flash flooding or lahars, and caution should be exercised crossing the valley during and after rainfall.

The Hazard Level is 1. There is no public access to Zone V, including Plymouth. Maritime Zones E and W are daytime transit only between sunrise and sunset (boats may sail through the zone but must not stop). Anyone who ignores these restrictions is liable to be prosecuted.

This report along with additional information on the Soufrière Hills Volcano and the Hazard Level System can be found at the MVO website: Old weekly reports can be downloaded from You can also follow @mvoms on both Facebook, Instagram, and Twitter.

Graham A. Ryan