| Soufriére Hills Volcano - Montserrat |
The Soufrière Hills volcano (Sulphur Hills) is an active complex stratovolcano with many lava domes forming its summit on the Caribbean island of Montserrat. After a long period of dormancy, it became active in 1995, and has continued to erupt ever since. Its eruptions have rendered more than half of Montserrat uninhabitable, destroying the capital city, Plymouth, and causing widespread evacuations: about two thirds of the population left the island.
The volcano is andesitic in nature and the current pattern of activity includes periods of dome growth, punctuated by brief episodes of dome collapse which result in pyroclastic flows, ash venting, and explosive eruption. |
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| Activity |
Seismic activity had occurred in 1897–1898, 1933–1937, and again in 1966–1967, but the eruption that began on July 18, 1995, was the first since the 17th century. When pyroclastic flows and mudflows began occurring regularly, Plymouth was evacuated, and a few weeks later a pyroclastic flow covered the city in several metres of debris. A large eruption on June 25, 1997, resulted in the deaths of nineteen people. The island's airport was directly in the path of the main pyroclastic flow and was completely destroyed. Montserrat's tourist industry was also destroyed. However, it is now regenerating. The governments of the United Kingdom and Montserrat led the aid effort, including a £41 million package provided to the people of Montserrat; however, riots followed as the people protested that the British Government was not doing enough to aid relief.
On December 24, 2006, streaks of red from the pyroclastic flows became visible. On January 8, 2007, an evacuation order was issued for areas in the Lower Belham Valley, affecting an additional 100 people.
At 11:27 pm local time on Monday, 28 July 2008, an eruption began without any precursory activity. Pyroclastic flow lobes reached Plymouth.
These involved juvenile material originating in the collapse of the eruption column. Further, a small part of the eastern side of the lava dome collapsed, generating a pyroclastic flow in Tar River Valley. Several large explosions were registered, with the largest at approximately 11:38 pm. The height of the ash column was estimated at 12 kilometres (40,000 feet) above sea level. |
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| The volcano has become one of the most closely monitored volcanoes in the world since its eruption began, with the Montserrat Volcano Observatory taking detailed measurements and reporting on its activity to the government and population of Montserrat. The observatory is operated by the British Geological Survey under contract to the government of Montserrat. |
| 2008 |
| Dome growth paused between March 2007 and May 2008. During 25th April to 2nd May the level of volcano-tectonic earthquakes at Soufrière Hills increased, and was the highest since February 2006. On 29 May produced an ash plume to an altitude of 3 km altitude which drifted SW and generated a pyroclastic flow. New lava extrusion from Soufrière Hills started from the west side of the lava dome between the 28th July and 8th August. Lava dome has continued to grow from August to November 2008. On 3rd December 2008, an eruption at Soufriere Hills volcano ejected rocks into the island's abandoned capital Plymouth, setting buildings on fire. Buildings burned for several hours. |
| April-September 2009 |
| Soufriere Hills volcano on Montserrat has been relatively quiet for six months. There has been no extrusion of new lava, and no explosions in that period. Surface activity was restricted to rockfalls and occasional small pyroclastic flows from the dome, together with mudflows. While gas emission has remained unchanged, the number of earthquakes recorded has fallen to the lowest level seen during the eruption cycle. This suggests the long-term activity has changed at the volcano. It could possibly mean the "beginning of the end" of the eruption cycle. Formal end of eruption criteria have not yet been met. However, the risks to people living near the volcano have not changed, and sudden resumption of explosive and extrusive activity can rapidly pose a threat to adjacent areas. |
| October 2009 Eruptions |
Renewed eruptions occurred at Soufriere Hills volcano on Montserrat on 5th October 2009. A swarm of earthquakes began at 9pm on 4th October. Two hours of vigorous ash emission began at 10 pm on 5th October. The eruptions were followed by intermittent ash emissions. This was the first eruptions at the volcano since April 2009.
During the week 9-16 October activity has been high at Soufriere Hills volcano, Montserrat. A new lava dome has been growing at the volcano since 9th October 2009. Seismic activity during the week consisted of 1224 rockfall signals, 382 long period events, and one volcano tectonic earthquake. Pyroclastic flows occurred in all the major valleys that drain the volcano except the Tar River valley. Pyroclastic flows began on 9-10 October and extended south of the volcano. From 11 October pyroclastic flows extended down the Tyers Ghaut. Pyroclastic flows have reached about 3 km down the White River to the south; 1.5 km down the Gages valley to the west; and 3 km down Tuitts and Whites Bottom Ghaut in the east. Dome growth is located at the volcano summit which is responsible for the radial flow of pyroclastic flows. Lahars occurred in Belham valley on 14th October. |
| 2010 Eruptions |
| Large pyroclastic flows occurred at Soufriere Hills volcano at 2:49 pm on 8th January 2010. The pyroclastic flows were caused by a collapsing tephra column, similar to the events in the summer of 1997. The flows traveled northeast down Whites Bottom Ghaut and reached the sea. The flow which moved down Tuitts Ghaut stopped a few hundred metres from the sea. Pyroclastic flows also traveled northwest down Tyers Ghaut and into the Belham valley. The event lasted 11 minutes and was not preceded by seismic activity. Ashfall occurred on the northwestern side of the volcano. Residents said it was one of the largest eruptions they have witnessed at the volcano, since its reawakening in 1995. At 1:28 am on 10th January there was another explosion at the volcano. The seismic signal lasted 7 minutes. The eruption produced pyroclastic flows which traveled rapidly northeast down White Bottom and Tuitts Ghaut. Flows also moved northwest down Tyers Ghaut and down the Gages valley towards Plymouth. A third smaller explosion occurred at 8:27 pm on 10th January. Scientists don't believe there was a major collapse of the dome, but a significant amount of material was lost. Hazard level 4 remains in place around the volcano, which means there is no access allowed in zone C, and only daytime access to zone B. |
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| Maps of Montserrat |
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