The activity at the Soufriere Hills volcano during the night was much higher than that observed during the past several days.
There was significant small volcano-tectonic earthquake occurrence throughout the whole period , with a concentrated burst between 18:00 and 20:00 on 20 July. Locations calculated for some of these events indicate that they occurred at very shallow depths in the northeastern part of the crater. Signals indicative of small- to moderate-sized rockfalls from the growing lava dome were, as usual, quite common. A rockfall at 16:04 on 20 July resulted in a moderately thick ash cloud which could be seen drifting in a westerly direction over the Upper Gages, Amersham and Plymouth areas. A relatively large signal recorded on all the stations at about 20:17 on 20 July and which lasted for about 10 minutes and had a waveform similar to those of rockfalls may have been generated by a debris flow in the Tar River valley area. This does not seem to have been associated with any major ash production since none of the communities to the west and northwest of the volcano were affected. Episodes of low- to moderate-amplitude broadband tremor at the closest seismic stations continued at a slightly higher level than before although there has been a decrease in the early part of this morning. A regional earthquake of magnitude greater than 4.0 occurred at 05:40 this morning about 160 km from Montserrat.
The low cloud cover prevented any views of the dome during the early morning period.
Dome growth is continuing and therefore the threats posed by the Soufriere Hills Volcano continue at the same or a greater level as over the past several months. The Tar River and Long Ground areas to the east and the upper Fort Ghaut, Gages Village and Upper Amersham areas to the west are still extremely hazardous. People should not enter these areas under any circumstances because they put themselves and others at direct risk of very serious injury or death. People are urged to keep visits to the evacuated zone to a minimum.