Activity at the Soufrière Hills Volcano is low, although there was a slight increase between 3 and 6 February. This involved VT earthquakes, an elevated gas flux and possibly light venting of ash. This type of activity has been observed on several occasions since the end of extrusion on 11 February 2010 and this week’s was the most intense since the ash-venting episode on 23-25 March 2012.
The seismic network recorded one rockfall, 25 volcano-tectonic earthquakes and two hybrid events this week. The VT earthquakes occurred mainly in four brief swarms, at 10:20 pm on 3 February, at 9:15 am and 9:50 pm on 4 February and at 6:20 am on 5 February (all local time). The second swarm was the most intense. One of the hybrid events occurred at the end of the second swarm and the other was an isolated event.
Sulphur dioxide measurements for the week gave an average flux of 929 tonnes/day with a maximum of 2381 and a minimum of 273 tonnes/day. The flux was not steady, with peaks of 962, 1266 and 2381 on 1, 4 and 6 February respectively. The last of these is the highest daily value since the ash-venting episode on 23-25 March 2012.
After the second, largest, VT swarm on 4 February, there were increases in the temperatures of several fumaroles inside the 11 February 2010 collapse scar, as observed using a handheld thermal infra-red camera at MVO, 5.7 km away. There was a further increase, as well as some loud roaring sounds, around the time of the third swarm. It is likely that the activity included minor ash venting from a large fumarole in the floor of the collapse scar as fresh ash deposits were observed adjacent to this fumarole on the morning of 5 February. All fumaroles had returned to background levels of activity and temperature by later that day.
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 are frequently 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 2. There is no access to Plymouth or Zone V. There is daytime access to Zone C: 8 am to 4 pm, Monday to Saturday. Maritime zone W remains daytime transit only (boats may sail through the zone but must not stop).