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Eruption: Soufriere, Montserrat Januray 2010


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Bilder/images: Soufriere Eruption mit Lava flows und Pyroklastischen Strömen im Januar 2010, während einer Filmexpedition mit Vulkane.net (Infoseiten über Vulkangefahren ). Mehr Bilder und einen Bericht vom Soufriere sind "vulkane.net" zu finden!

Abstract:

The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the east, was formed during an eruption about 4000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.
(GVN)


Eruption NEWS:

ALERT LEVEL 4.
15 to 22 January 2010
Activity at the Soufrière Hills Volcano been variable this week.
Dome growth has continued and increased activity is occurring in cycles between 6 and 8 hours apart. These cycles involve ash venting and rockfalls and pyroclastic flows. The intensity of these cycles has decreased slightly through the week. The distribution of activity is to the north through to west, although the largest pyroclastic flows are occurring to the northeast and west.
There have been one hundred and ninety six rock fall signals, thirty-eight long period events, and eighteen hybrid earthquakes recorded this week. A small swarm of seven larger hybrid earthquakes occurred on 20 January.
On 18 January a sustained event occurred on the western side of the volcano lasting 45 minutes. This small dome collapse event produced large pyroclastic flows that travelled down the Gages valley into Spring Ghaut and on into Aymer's Ghaut, reaching the sea at Kinsale to the south of Plymouth 4 km from the dome. Observations from the helicopter have shown that several houses have been buried and set on fire in Kinsale. Ash clouds associated with these pyroclastic flows reached approximately 10,000 ft.
Light ashfall has occurred in northwestern Montserrat occasionally this week.

As of the 12th of December, the Monstserrat Volcano Observatory (MVO) reported that activity at the Soufrière Hills Volcano has been at a high level this week. There have been 957 rockfall signals, 207 long period events, 3 volcano-tectonic and 106 hybrid earthquakes recorded. Activity has continued in cycles although these cycles have become more irregular in time in the last few days. Pyroclastic flow and rockfall activity has been concentrated on the northern side of the volcano. Abundant pyroclastic flows have occurred in Tuitt's Ghaut, directly onto Farrell's plain and into Tyers Ghaut. The runout distance and frequency of pyroclastic flows in Tyers Ghaut have increased through the week with runout distance frequently reaching 2 km from the lava dome. On the 8th and 9th of December pyroclastic flows were dominant down Tyers Ghaut to the northwest.
At around 0640 hrs on the 10th of December there was a notably large seismic signal recorded associated with a relatively large pyroclastic flow down Tyers Ghaut. This flow had a runout distance of 3.5 km, stopping just beyond the west end of Lee's village. Helicopter observations have shown that the head of Tuitt's Ghaut down the to junction with Whites Bottom Ghaut is full of pyroclastic flows deposits such that there is now a continuous surface across from Farrell's plain. The head of Tyers Ghaut is also now nearly full. This means that future pyroclastic flows are likely to be less confined by topography and will spread more readily across the northern flanks of the volcano. There have been a few small to moderate pyroclastic flows in the Tar River, these are thought to have been formed by degradation of the old pre-2009 dome. One pyroclastic flow was observed in Gingoes Ghaut on the 9th of December. Owing to technical problems with equipment there were no gas measurements made this week. The Hazard Level is 4 (as of the 10th of December). There is no access to Zone C and only daytime access (0630 hrs to 1730 hrs) to Zone B.


Some important links:
  1. the GVN
  2. USGS, U.S. Geological Survey (Volcano Hazards Program)
  3. Montesrrat Volcano Observatory (MVO)
  4. MVO (News)

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