| Soufrière Hills | |
|---|---|
 Soufrière Hills (before July 2007) | |
| Highest point | |
| Elevation | 1,050 m (3,440 ft)[1] |
| Prominence | 1,050 m (3,440 ft)[2] |
| Listing | Ribu |
| Coordinates | 16°43′N62°11′W / 16.717°N 62.183°W /16.717; -62.183 |
| Geography | |
  Soufrière Hills Location inMontserrat | |
| Country |  Montserrat |
| Geology | |
| Formed by | Subduction zonevolcanism |
| Mountain type | Stratovolcano |
| Volcanic arc | Lesser Antilles Volcanic Arc |
| Last eruption | 2013[3] |
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TheSoufrière Hills (/ˈsuːfriɛər/)[4] is anactive, complexstratovolcano with manylava domes forming its summit on theCaribbean island ofMontserrat, anoverseas territory of the United Kingdom. After a long period ofdormancy, the Soufrière Hills volcano became active in 1995 and continued to erupt until 2010.[5] Its last eruption was in 2013.[3] 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 have left the island.[6]Chances Peak in the Soufrière Hills was the highest summit on Montserrat until the mid-1990s, but it has since been eclipsed by various rising and falling volcanic domes during the recent volcanic activity.[7]
The volcano isandesitic in nature, and the current pattern of activity includes periods of lava dome growth, punctuated by brief episodes of dome collapse which result inpyroclastic flows, ash venting, and explosive eruption. The volcano is monitored by theMontserrat Volcano Observatory. Volcanic gas emissions from this volcano are measured by amulti-component gas analyzer system, which detects pre-eruptive degassing of rising magmas, improvingprediction of volcanic activity.[8]
TheCentre Hills in the central part of the island and the Silver Hills in the north are older volcanicmassifs related to the subduction zone. There are three main parts of the island: the central zone, subduction and exclusion.[9]
Many volcanoes in the Caribbean are named Soufrière (French for 'sulphur outlet'). These includeLa Soufrière or Soufrière Saint Vincent on the island ofSaint Vincent, andLa Grande Soufrière onGuadeloupe.[10][11]
Seismic activity had occurred in 1897–1898, 1933–1937, and again in 1966–1967, but the eruption that began on 18 July 1995 was the first since the turn of the 20th century.[13] The firstphreatic explosion in this new period of activity occurred on 21 August 1995, and such activity lasted for 18 weeks until it caused anandesitic lava dome formation. This was initially confined by a sector-collapse scar, first identified in the 1930's and calledEnglish's Crater. This period of activity lasted for another 60 weeks, after which there were major dome collapses and two periods of explosive volcanic eruptions and fountain-collapse pyroclastic flows.[14] The explosion blanketed Plymouth, 6 kilometres (3.7 mi) away, in a thick layer of ash and darkened the sky almost completely.
Pyroclastic flows were first observed on 27 March 1996.[15] Although these pyroclastic flows and mudflows were initially confined to unpopulated areas, a major pyroclastic flow on 17 September 1996 caused severe damage to the village of Long Ground, near the volcano.[16] By August 1997, much of the southern part of the island, including most of Plymouth, had been buried by pyroclastic flows.
During this period, the southern portion of the island, including the capital Plymouth, was evacuated three times. The first evacuation lasted from 21 August 1995 – 3 September 1995, after the first phreatic eruption. The second evacuation began on 1 December 1995,[17] due to growth of the lava dome. Residents were allowed back to most areas, including Plymouth, on 1 January 1996,[18] but residents of some areas on the eastern flank of the volcano were not allowed back until 15 January 1996.[19] On 3 April 1996, afterpyroclastic flows and mudflows began occurring regularly, southern Montserrat, including the capital, Plymouth, was permanently evacuated.[20]
Earthquakes continued to occur in threeepicentre zones: beneath the Soufrière Hills volcano, in the ridge running to the northeast, and beneath St George's Hill, about 5 kilometres (3.1 mi) to the northwest.[21] A large eruption on 25 June 1997 resulted in the deaths of nineteen people. Theisland's airport was directly in the path of the main pyroclastic flow and was completely destroyed.[22] Montserrat's tourist industry also collapsed, although it began partially to recover within fifteen years.[23]
The governments of theUnited Kingdom and Montserrat led the aid effort, including a £41 million package provided to the Montserrat population; however, riots followed as the people protested that the British Government was not doing enough for aid relief.[24] The riots followed a £10 million aid offer byInternational Development SecretaryClare Short, prompting the resignation ofBertrand Osborne, thenChief Minister of Montserrat, after allegations that he was too pro-British and had not demanded a better offer.[25]
The BritishdestroyerHMS Liverpool took a major role in evacuating Montserrat's population to other islands, includingAntigua and Barbuda who warned they would not be able to cope with many more refugees.[25] About 7,000 people, or two-thirds of the population, left Montserrat; 4,000 went to the United Kingdom.[26]
The following is a list of Montserrat settlements abandoned by the eruption of the Soufrière Hills volcano:
†Settlement was destroyed
In addition, theW. H. Bramble Airport was destroyed.
On 24 December 2006, streaks of red from thepyroclastic flows became visible. On 8 January 2007, anevacuation order was issued for areas in the Lower Belham Valley, affecting an additional 100 people.[27]
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. In addition, 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 12,000 m (40,000 ft) above sea level.[28]
The volcano has become one of the most closely monitored volcanoes in the world since its eruption began, with theMontserrat Volcano Observatory taking detailed measurements and reporting on its activity to the government and population of Montserrat. The observatory is operated by theBritish Geological Survey, under contract to the government of Montserrat.[29]
The 9 October 2008 issue of the journalScience suggested that two interconnectedmagma chambers lie beneath the surface of the volcano on Montserrat – one six kilometres below the surface and the other 12 kilometres (7.5 mi) below the surface. The journal also showed a link between surface behaviour and the size of the deeper magma chamber.[30][31]
On 5 February 2010, avulcanian explosion simultaneously propelled pyroclastic flows down several sides of the mountain, and on 11 February 2010, a partial collapse of thelava dome sent large ash clouds over sections of several nearby islands, includingGuadeloupe andAntigua. Inhabited areas of Montserrat itself received very little ash accumulation during either event.[32][33]
On 12 February 2010, at 1200 UTC/GMT, Meteosat SEVIRI Channel 7 shows the ash plume from the eruption was caught up within the warm sector of a frontal system heading towards western Europe exacerbating two East Atlantic winter storms. [reference] Violent storms accompanied by torrential rain and high wind passed over Madeira on 20 February and western Europe on 26–28 February. In Madeira there was at least 48 fatalities and damage to infrastructure at a total estimated cost of 4 billion Euros. The storm landfalling in western France (named 'Cyclone Xynthia') resulted in at least 63 fatalities and estimated damage within the range of 1.3-3 billion Euros.[34][35]
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