Soufrière Hills

The Soufrière Hills

Ash and steam plume, 11 October 2009

Before and after a partial dome collapse

The Soufrière Hills are the major mountains of the British overseas territory of Montserrat in the West Indies. The name is from the French language, and means "Sulphur Hills", which gives an idea of the nature of these unquiet heights.

The Soufrière Hills are an active, complex stratovolcano with many lava domes forming its summit. The highest point (and the territory top) is Chances Peak, which reaches over 3,000 feet, depending on the state of its lava dome.

After a long period of dormancy, the volcano 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 lava dome growth, punctuated by brief episodes of dome collapse which result in pyroclastic flows, ash venting, and explosive eruption.

Eruption Activity

1995–1999

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 19th century in Montserrat.

In 1995 when pyroclastic flows and mudflows began occurring regularly, Plymouth was evacuated, and a few weeks later a pyroclastic flow covered the city in of debris many feet deep. The first phreatic explosion in this new period of activity occurred on 21 August 1995, and such activity lasted for 18 weeks until it caused an andesitic lava dome. This was initially confined by a sector-collapse scar. This period lasted for another 60 weeks, after which there were major dome collapses and two periods of explosive Vulcanian eruptions and fountain-collapse pyroclastic flows. It blanketed Plymouth, 4 miles away in a thick layer of ash and darkened the sky almost completely. Earthquakes continue to occur in three epicentral zones: beneath the Soufrière Hills volcano itself, in the ridge running to the north-east and beneath St George's Hill, about 3 miles to the north-west.

A large eruption on 25 June 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.

The British destroyer HMS Liverpool took a large role in evacuating Montserrat's population to other islands; this included Antigua and Barbuda]], who warned they would not be able to cope with many more refugees. About 7,000 people, or two-thirds of the population, left Montserrat; 4,000 to the United Kingdom.

Since 1999

On 24 December 2006, streaks of red from the pyroclastic flows became visible. On 8 January 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 40,000 feet above sea level.

On 5 February 2010, a vulcanian explosion simultaneously propelled pyroclastic flows down several sides of the mountain, and on 11 February 2010, a partial collapse of the lava dome sent large ash clouds over sections of several ncite gearby islands including Guadeloupe and Antigua. Inhabited areas of Montserrat itself received very little ash accumulation through either event.

Further eruptions began in 2012.

Observation

The volcano has become one of the most closely monitored volcanoes in the world since its eruption began. The Montserrat Volcano Observatory takes 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.

The 9 October 2008 issue of the journal Science suggests that two interconnected magma chambers lie beneath the surface of the volcano on Montserrat, one 4 miles beneath the surface and the other at 8 miles below the surface. They also show a link between surface behaviour and the size of the deeper magma chamber.

In popular culture

Soufrière Hills is the namesake of the Jimmy Buffett song "Volcano".

Pictures

• 
  Ash Plume from Soufrière Hills, 10 March 2004.
• 
  22 September 1997 10:46 AM Eruption of the Soufrière Hills volcano on the Caribbean island of Montserrat.
• 
  The airport destroyed by the eruption of The Soufrière Hills Volcano.

Outside links

("Wikimedia Commons" has material about Soufrière Hills)

• Montserrat Volcano Observatory (MVO)
• British Geological Survey
• USGS Info on Soufrière Hills Volcano
• Satellite imagery of 11 February 2010 eruption
• Montserrat Volcano Observatory (MVO) - Current monitoring of the Soufrière Hills Volcano in Montserrat.
• 2009 activity at Soufrière Hills Volcano, from NASA Earth Observatory
• Photos taken from a passenger jet of an eruption