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Soufriere Hills volcano (Montserrat): phreatic explosions suggest rising magma

Fri, 23 Mar 2012, 22:29 | BY: T
Ash venting at Soufriere Hills volcano on 23 March (Photo: MVO)
Ash venting at Soufriere Hills volcano on 23 March (Photo: MVO)
New ash eruptions have occurred at Soufriere Hills volcano on Montserrat. The activity is probably phreatic in origin and caused by rising magma under the volcano.
The ash emissions began at around 8 am local time on 23 March, following 2 volcanic earthquake swarms on 22 and 23 March, the Montserrat Volcano Observatory (MVO) reports.

The vents of the new activity are on 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 increased markedly and a new steam fumarole was discovered on the NW side of the dome immediately behind Gages Mountain.
The ash venting was pulsating and produced ash clouds reaching approx. 6000 feet above sea level (3000 feet above the volcano). At its peak, black jets of ash were seen rising a few hundred meters above the floor of the collapse scar. This type of activity is probably "phreatic" in origin, caused when superheated rock meets groundwater, which evaporates explosively and fragments rock into ash.

The volcano-tectonic earthquakes are related to fracturing rocks underneath, probably as a result of increases in pressure. It is likely that these pressure increases and the resulting earthquakes, along with the rising temperature driving the phreatic activity, 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.

Previous news

Wed, 21 Mar 2012, 06:00

Soufriere Hills volcano (Montserrat) - Smithsonian / USGS Weekly Volcanic Activity Report for 21 March-27 March 2012 (New Activity / Unrest)

MVO reported that during 16-23 March activity at the Soufrière Hills lava dome was at a low level, although seismicity increased. Two swarms of volcano-tectonic earthquakes occurred, the first between 1604 and 1651 on 22 March (49 events) and the second between 0310 and 0527 on 23 March (54 events). Earthquakes in the second swarm were markedly larger than those in the first. ... Read all
Wed, 14 Mar 2012, 11:52

Soufrière Hills volcano (Montserrat): small pyroclastic flow from dome with no warning

A small pyroclastic flow occurred from Montserrat's Soufrière Hills volcano on 9 March, MVO reports. The flow was small, but happened with no warning at around 5:20 pm (local time) from the western flanks of Soufriere Hills Volcano down into Spring Ghaut. ... Read all
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Soufriére Hills volcano dome satellite image by (c) Google Earth View
Soufriére Hills volcano dome satellite image by (c) Google Earth View
Stratovolcano, lava dome 915 m / 3002 ft (changing!)
Montserrat, West Indies (UK), 16.72°N / -62.18°W
Current status: normal or dormant (1 out of 5) Soufriere Hills volcano eruptions:
2005-2013, 2004, 1995-2003
1550 ± 50 years, 1480 ± 50 years, 1180 (?), 2460 BC ± 70 years, 4050 BC (?), 8050 BC ± 2000 years
Typical eruption style
Explosive. Construction of lava domes.
Montserrat Island by (c) Google Earth View
Montserrat Island by (c) Google Earth View