Director of the Montserrat Volcano Observatory (MVO) Dr Paul Cole said on local radio on Friday morning that it was a precautionary measure as they continued to monitor the volcano, which has been relatively quiet since early 2010.
By early afternoon the MVO released a statement noting that mild ash venting had begun and was emanating from the 11 February 2010 collapse scar.
“Following two volcano-tectonic (VT) swarms on the 22 and 23 March 2012 involving 49 and 54 events respectively, mild ash venting began at Soufriere Hills Volcano at around 8:00 am local time on 23 March. The venting was sourced from the floor of the 11 February 2010 collapse scar, immediately south of the old English’s crater wall and to the west of the long-lived hottest fumarole previously identified. Fumarolic activity on the volcano on the morning of 23 March increased markedly and a new steam fumarole was identified on the NW side of the dome immediately behind Gages Mountain,” the statement read.
“The ash venting was clearly pulsatory and sent ash to approximately 6,000 feet above sea level (3,000 feet above the volcano). At its peak, black jets of ash were seen rising a few hundred metres above the floor of the collapse scar. This type of activity is probably ‘phreatic’ in origin and is formed where superheated rock meets groundwater causing the rocks to fragment, generating ash.
“VT earthquakes are related to fracturing rocks probably as a result of increases in pressure. It is likely that these pressure increases and the resulting earthquakes are related to uprising magma below the volcano. Similar types of activity have occurred at Soufriere Hills Volcano up to several months prior to restarts in magma extrusion, for example in 2005 and 2008,” the MVO statement ended.
Zone C which comprises Cork Hill, Weekes, Foxes Bay, Richmond Hill, Delvins and extending 500 m out to sea is part of the Exclusion Zone. It was reopened in December 2011 after the hazard level was lowered from 3 to 2, which made daytime access possible in those areas. Cole says there are no plans to raise the hazard level but that the area would be closed off and the gates locked.
More information can be found on the MVO website at www.mvo.ms