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Report on Soufriere Hills (United Kingdom) — 22 November-28 November 2000

Soufriere Hills

Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
22 November-28 November 2000
Managing Editor: Gari Mayberry

Please cite this report as:

Global Volcanism Program, 2000. Report on Soufriere Hills (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 22 November-28 November 2000. Smithsonian Institution and US Geological Survey.

Weekly Report (22 November-28 November 2000)

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)

The MVO reported that during 17-24 November volcanism continued at an elevated level, with the continued growth of the lava dome and a significant increase in the number of detected rockfall signals. The latter parameter more than doubled relative to the previous week. On the other hand, the number and energy of long-period earthquakes decreased. The lava spine that was growing on top of the lava dome was estimated at over 1,085 m a.s.l. on 17 November, but partially collapsed sometime during 18-19 November. Rockfalls and small pyroclastic flows traveled down the notch between the NE and N lobes of the 1995-98 dome. Ash clouds associated with this activity reached no higher than 3 km a.s.l. Towards the end of the week rockfall activity down the E flank decreased. The Washington VAAC reported low-level ash clouds visible during the week; these traveled to the NW and WNW.

Geological Summary. 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. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded 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.

Sources: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)