Chronology of the Present Eruption
Chronology of the Present Eruption
PERIOD ACTIVITY
Seismic 1992 – July 1995 Period of pre-eruptive seismic activity
18 distinct earthquake swarms occur in the south of the island, with the largest swarm occurring in June 1994.
Phreatic July 18 – November 15, 1995
Phreatic explosions associated with heating shallow or ground water. Initial activity: cold pyroclastic surges and steam jets in the northwest crater. Further vents opened on 28 July, 20, 22 and 28 August.
12 to 13 August 1995
Strong earthquake swarm beneath St George’s Hill, with over 30 felt earthquakes. 21 August 95, first large phreatic eruption, which blanketed Plymouth in a thick ash cloud and caused darkness for about 15 minutes. First evacuation of southern Montserrat initiated shortly afterwards. Earthquake swarms continue.
September, 1995
An oxidised spine appears in English’s Crater. This was accompanied by the first swarm of hybrid earthquakes, from 22 to 29 September. 17 October 95: mudflow from the southeast side of the crater. 30 October 95: another large phreatic eruption.
Dome growth and collapse, November 15, 1995 – March 1996
Magma appears at the surface. Lava dome growth starts in English’s Crater and develops slowly (0.2 – 0.5 m3s-1). 1 to 2 December 95, evacuation of southern Montserrat, until 1 January 96. Dome growth rate increases in February (~2 m3s-1). January to March 96, continued dome growth in English’s Crater, with hybrid earthquake swarms, small rockfalls from the dome, minor pyroclastic flows and continued slow deformation.
April – September 1996
The Tar River valley is subjected to increasingly large pyroclastic flows, which reach the coast for the first time on May 12. Growth rate increases (3-5 m3s-1) and dome growth is concentrated in the northeast sector of the crater. 25 to 29 July 96, high rate of magma production of about 10 m3s-1, leads to major collapses and pyroclastic flows in Tar River valley on July 28.
September 17, 1996
Explosive activity followed 9 hours of a continuous series of dome collapses and pyroclastic flow generation. 1.5 m diameter ballistic blocks reach Long Ground (2.1 km from the dome), where houses were destroyed. The eruption plume reaches 14 km, and about 600,000 tonnes of ash was deposited in southern Montserrat. Rocks and pumice fell in the south of the island. About one-quarter of the dome was removed during the dome collapses and subsequent explosion.
October 1, 1996 – February 1997
A new dome begins slow growth in the collapse scar on October 1. Intense earthquake swarms occur in November and early December. Growth rate increases from mid-December. Following partial collapse of the December 11 dome on 19 December, dome growth switched back to the October 1 dome.
The “Santa Lobe” grew rapidly on top of the dome, and between 25 December and 5 January, was extruding at the highest sustained rate seen during this eruption. The dome expanded to the east, over Castle Peak, which started to erode away as rockfalls fell over and round the Peak. 1 to 2 February 97, further degradation of the Galway’s Wall, allowing dome material to collapse over the wall for the first time.
March – April 1997
A new lobe appears above Galway’s Wall, on the SW side of the dome. 30 March 97, first sizable pyroclastic flows to the south, over Galway’s Wall and reach 3.6 km down into the White River valley. Galway’s Soufriere and Great Alps waterfall covered by pyroclastic deposits.
May – June 24, 1997
Dome growth switches to the north and increases substantially (7-8 m3s-1). The dome has a volume of over 60 x 106 m3 and completely fills English’s Crater. In June, the first pyroclastic flows and rock falls move down Mosquito and Tuitts Ghauts on the northern flanks of the volcano.
June 25, 1997
A major collapse (at 12:55 LT) lasting about 20 minutes releases 6.4 x 106 m3 of material in three pulses. Pyroclastic flows reach to within 50m of Bramble Airport, and ash-cloud surges sweep over Farrell’s Plain. A surge-derived flow moves down the Belham River valley. Surge reached into Belham valley as far as Cork Hill. 19 fatalities.
June 26 – August 3, 1997
Continued elevated extrusion with dome growth at the head of the valley leading to Plymouth (Fort Ghaut). A major dome collapse on August 3, sent pyroclastic flows through central Plymouth, with burning of buildings on the side of Fort Ghaut.
August 4 – 12, 1997
A series of 10 Vulcanian explosions lasting 1-2 minutes occur approximately every 12 hours. Large flow lobe overtopped Fort Ghaut into Dagenham as far as the Technical College. Pumice flows extending to 5 km run down drainage channels on the flanks. Ballistic blocks of 1-2 m diameter reach distances of 1.7 km. Pumice lapilli and ash are dispersed over the island. The extrusion rate during this period is about 10 m3s-1. A 300 m diameter explosion crater is formed.
Dome Growth August 12 – September 21, 1997
Rapid (7-8 m3s-1) dome growth resumes. Pyroclastic flows destroy buildings in the Spanish Point area and the terminal building at Bramble airport. On 9 September MVO is moved from site in Old Towne to new facility at Mongo Hill in the north. A major dome collapse (14 x 106 m3) occurs on September 21, to north-east of the volcano engulfing the area between Trant’s Yard and White’s Yard, destroying W. H. Bramble airport terminal building and entering the sea at various points along the coast.
Vulcanian explosions September 22 – October 21, 1997
Second period of 76 repetitive Vulcanian explosions occurred at approximately 10 hour intervals, but with little or no precursory activity. Ash clouds were sent up to 40,000 feet with pumice fragments falling over all the island.
Dome growth October 22 – December 24, 1997
Dome growth resumes, with two major dome collapses occurring on November 4 and 6. Pyroclastic flows run down the White River Valley to form a coastal fan. Activity is accompanied by earthquake swarms.
JMajor collapse December 25 – 26, 1997
Dome volume: 113 x 106 m3. Height: 1030 m. A major hybrid earthquake swarm merges into a continuous tremor by the end of Christmas day. The SW flank of the volcano and the section of the dome in the Galway’s wall area suffers a massive collapse at 03:01 LT on December 26, and a debris avalanche (40-45 x 106 m3) cascades down the White River valley. The dome is undermined, and a high-energy pyroclastic surge sweeps out to sea, devastating 10 km2 of southern Montserrat. This major collapse is referred to elsewhere as the “Boxing Day” event.
Dome growth December 26, 1997 – January 4, 1998
High level of earthquake activity and small pyroclastic flows to south-west. Dome growth resumed in scar left by dome collapse.
January 4 – 16, 1998
Dome growth resumes in the collapse scar. Low seismicity.
January 17 – March 1, 1998
Increase in Seismicity. Rockfalls and ash venting with plumes to 1.8 km. Small pyroclastic flows down White River valley result in ash fall in Antigua. A period of vigorous ash-venting occurs in early February.
March 2 – 7, 1998
Very low seismicity, significant decrease in rockfall activity. Large spine appeared.
March 8 – 10, 1998
Dome growth ceases.
Dome degradation and residual activity March 11 – 2 July, 1998
Degradation of the dome and residual activity. Small pyroclastic flows and rockfalls accompanied by small-scale Vulcanian explosions and periods of ash-venting. Seismic activity continues.
July 03, 1998
Approximately 20% of the dome complex collapses down Tar River valley. A small explosion follows, and the associated ash cloud surge hits Long Ground.
July 4 – 24, 1998
After a few days of increased activity, the number of rockfalls and VT earthquakes decline to (and remain at) low levels.
July 25, 1998
Swarm of 68 VT earthquakes. No outward changes to the volcano.
July 26 – September 20, 1998
Low-level activity. Small pyroclastic flows and rockfalls continue to degrade the dome.
August 19, 1998
Rockfalls followed by vigorous ash venting produce a tremor lasting 2 days. Low levels of activity with occasional periods of tremor correlated with increased venting.
September 20 – 21, 1998
Small pyroclastic flows and rockfalls continued to degrade the dome.
October 13 – November 12, 1998
Frequent pyroclastic flows down Tar River and White River. A large scar develops in the dome, slicing it in two from east-south-east to west-north-west from the July 3 scar to above Gages.
November 13 – 28, 1998
Small pyroclastic flows, rockfalls and ash venting. Several episodes of low amplitude seismic tremor coupled with ash venting.
November 28 – 29, 1998
Heavy rain resulting in extensive mudflows down all flanks of the volcano. Up to one metre of new material was deposited on Belham Bridge and further deposition in Plymouth and on the airport runway.
December 6 – 13, 1998
Continued degradation of the dome with occasional ash and steam venting episodes.
December 14, 1998
Dome collapse down Tar River valley, pyroclastic flows reached the sea and generated an ash cloud to 20,000 ft.
December 15 -19, 1998
Rockfalls, small pyroclastic flows and vigorous ash venting. Maximum ash cloud height is 4.6 km. An explosive event triggers a pyroclastic flow down Tar River on December 19
December 21, 1998
Large seismic signal correlated with vigorous ash and steam venting. Dense black jets carried rocks to 80 m above the vent. Followed by a relatively quiet period with few rockfalls and small pyroclastic flows.
December 28, 1998
Mudflows follow heavy rain. The Belham River valley and Plymouth areas are particularly affected. Fresh deposits up to 0.5 m thick at Belham Bridge.
December 29, 1998 – February 28, 1999
Continued degradation of the dome by rockfall activity, ash and steam venting. Slight increase in seismicity. Small dome collapse pyroclastic flows between January 13 and 20. Occasional larger pyroclastic flows with ash clouds to 15,000 feet, from the 21 January.
March 1 – May 21
1999 Increased activity. Small explosions, ash venting and dome collapse pyroclastic flows. Ash clouds to 6.1 km. There were 23 events in March and 21 events in April with the peak in activity occurring in early April with up to 3 events per day.
May 22 – 23, 1999
VT earthquake swarm (121 events) followed by a small dome collapse down the Tar River valley. Ash cloud reaches 5.8 km.
May 23 – June 4, 1998
Continued degradation of dome by rockfall activity, occasional ash and steam venting episodes.
June 05, 1999
Northeast sector dome collapse. A large hole is formed in the dome above Tuitt’s Ghaut. The dome continues to be degraded by rockfall activity. Occasional episodes of ash & steam venting.
Major collapse July 20, 1999
Large dome collapse down Tar River. Ash cloud reaches 10.7 km with ashfall as far north as Saba. The end of July sees slightly elevated levels of activity, with small explosions and pyroclastic flows.
Dome degradation and residual activity August 1999 Low levels of activity. Reduced gas emissions and ground deformation. Small dome collapses.
September 3 – 9, 1999
Substantial explosion on September 3, followed by collapse events and enhanced rockfall activity.
September 10, 1999
Hurricane Floyd passes to the north. The heavy rain triggers a number of mudflows.
September 11 – October 20, 1999
Low-level activity. Reduced gas emissions and ground deformation. Small dome collapses with associated pyroclastic flows and low levels of volcano deformation.
October 20, 1999
Passage of Hurricane Jos to the north of the island produces 14 cm of rain in 6.5 hours. Mudflows down all flanks of the volcano.
October 21 – November 2, 1999
Slightly elevated activity with small explosions and pyroclastic flows, possibly as a result of water infiltration into the volcano following the heavy rain from Hurricane Jose.
November 3 – 9, 1999
Swarm of 213 hybrid earthquakes (the first since March 1998) followed by two explosions on November 8 and 9, sending ash to 20,000 – 25,000 feet followed by periods of tremor. Fall-out from the explosions contained small pumice fragments. Long period earthquakes dominate the seismic signals.
November 17 – 19, 1999
Passage of Hurricane Lenny. Heavy rain causes mudflows down all flanks. Several small ash venting episodes and small explosions, probably related to the heavy rain.
Dome growth November 27, 1999 – January 2000
New lava dome observed in the base of the old crater within the 1995-98 lava dome. Observations on 29 November 99 show that the new dome is about 100 m wide at its base and about 60 m tall. By mid January the volume of the dome is estimated at 15 million cubic meters.
February 2 – 11, 2000
First substantial pyroclastic flows from the new dome down the Tar River valley onto the delta. Rockfall and seismic activity increase significantly.
Collapse March 20, 2000
Dome collapse, apparently triggered by heavy rainfall. Almost all the new material collapses down Tar River. Accompanied by small vulcanian explosions and extensive mudflows.
Dome growth March 21, 2000 – November 2000
Resumption of dome growth, accompanied by hybrid and long period earthquakes, banded tremor and rockfall activity. Small dome collapse on May 6. Small pyroclastic flows down Tuitt’s Ghaut and White’s Ghaut.
November 13 – December 2000
Dome reaches 1077 m, the highest altitude to date. On December 7, the total dome volume is estimated at 122 million cubic meters, with an average extrusion rate of approximately 3 m3s-1.
March 21, 2000 – November 2000
Continued dome growth, accompanied by hybrid and long period earthquakes. Small dome collapse on May 6. Small pyroclastic flows down Tuitt’s Ghaut and White’s Ghaut.
November 13, 2000 – December 2000
Dome reaches 1077 m, the highest altitude to date. On December 7, the total dome volume is estimated at 122 million cubic meters, of which 64 million cubic metres resides in the new dome since March 2000, with an average extrusion rate of approximately 3 m3s-1.
January 2001 – February 25, 2001
Dome growth continues into the new year with a new lobe being extruded on the NE flank on February 23 and 24. This is accompanied by sustained rockfall and small pyroclastic flows down Tuitt’s Ghaut. A small collapse (<1 million cubic meters) occurs on February 25.
February 26 – March 2, 2001
Four days of banded tremor followed by increased extrusion to the south, infilling the (25 February) collapse scar with dark rubbly lava.
March 3 – May 17, 2001
Dome growth appears to cease. Seismic activity at very low levels.
May 18 – July 2001
Renewed growth of the southern lobe. A massive headwall developed over the next two months above the White River Valley, which acted as the source of almost continuous rockfall activity. Activity increases with rockfalls, small pyroclastic flows to the Tar River Valley, and a small collapse to the north on June 30. By late July, the dome has a volume of approximately 162 million cubic meter, the largest accumulated volume in the current eruption.
Major collapse July 29, 2001
Major collapse of the eastern flank following a day of torrential rainfall and mudflows down the Belham River. The event started at 17:00 LT and lasted 8-9 hours. Near continuous pyroclastic flows run down the Tar River to the sea. Long Ground affected by pyroclastic surges. Strong SE winds blow ash as far as Puerto Rico and the Virgin Islands. 45 million cubic meters of material is removed from the dome, and the summit region lowered by 150 m.
Dome growth August 3 – October 2001
Dome growth resumes in the collapse scar. A 2-month period of almost continuous banded tremor begins on August 14, followed by rockfalls and small pyroclastic flows. Small collapse event, of several million cubic metres of unconsolidated talus on the southeast flank of the pre-July 29 dome, on October 14.
November 9 – December 2001
Summit reached an altitude of 876m on November 9. Direction of extrusion switches to the west. By mid-November the summit region is dominated by a number of vertical spines and had reached a height of 970 m. An increasing number of rockfalls and small pyroclastic flows occur towards the end of the year. Small collapse on December 28. A plume densely laden with ash was blown to the west. This deposited up to one centimetre of ash in the Plymouth area.
January – February 2002
High levels of activity. The summit of the dome had a broad, blocky appearance, with spectacular incandescence observable at night.
February 25 – 26, 2002
A 90 m spine is extruded overnight, with the apex reaching an altitude of 1080 m. This was one of a series of spines which grew in late February. This is the highest point measured on the dome during the entire eruption. The estimated volume of the active dome at this stage was 38 million m3.
March 2002
Rockfall and seismic activity increases, and a succession of large spines are extruded at the summit. Pyroclastic flows reach the sea at the Tar River fan.
April – May 2002
Dome growth switches to the SE in the second week of April. Seismic activity increases. Massive lobe formation and tallus accumulation with rockfalls and pyroclastic flows to the east. Decline in activity towards the end of May.
June – July 2002
Growth rate continues to decline (approx. 0.1 m3s-1 by the end of July). Heavy rain overnight on July 3, triggered substantial mudflows in the centre of Plymouth. Rockfall activity on the dome subsequently showed a slight increase and a small, low ash cloud drifted over Plymouth.
July 21 – August 29, 2002
New lobe develops on the north face (approx. 0.86 m3s-1). Increased rockfalls to the north and small pyroclastic flows down Tuitt’s and White’s Ghauts. NE buttress and part of the central buttress are buried. on
August 21, 2002
During a period of intense rainfall a small collapse occurred in the Tar River Valley. This was primarily a slump of the talus that had accumulated on the southeast sector of the dome during April and May.
September 2002
Around September 24, direction of growth switches briefly to the west resulting in pyroclastic flows down the western flanks. A near vertical spine has extruded in the central area. After a few days growth switches back to the north. On September 29, a minor (2-3 million m3) dome collapse generates pyroclastic flows that reach the sea at Spanish Point.
October 2002
On October 2, ~4 million m3 of dome material collapses to the east, possibly triggered by heavy rainfall (15 mm over 40 minutes recorded at St. George’s Hill). A moderate mudflow in the Belham Valley is followed by 6 hours of sustained pyroclastic flows. On October 8, areas on northern side of the Belham Valley are evacuated. Intense rainfall on October 22, produces large mudflows down the Belham valley, with standing waves to 2.5 m high. Activity declines towards the end of October.
December 2002
A 4-5 million m3 dome collapse down White’s Ghaut occurs on December 8, followed by a marked increase in SO2 emission rates. Ash clouds drifted to 10,000 feet to the west-northwest of the volcano and four millimetres of ash were deposited in Plymouth and Richmond Hill. The collapse was followed by several days of weak banded tremor
Activity increases throughout December, with pyroclastic flows and rockfalls affecting the N and NE flanks. A large spine is extruded during the night of December 26 – 27. Incandescence observable at night.
January – March 2003
Dome growth continues to the NE with pyroclastic flows and rockfalls occurring in White’s Ghaut, Tar River Valley, Tuitt’s Ghaut and the top of Tyre’s Ghaut and Farrell’s Plain. On January 20, MVO completes its move to the new building at Fleming’s. By March the summit of the dome is at 1098 m, the highest recorded in the history of the eruption.
April – May 2003
In April, dome growth is focused to the SE, with pyroclastic flows confined to the Tar River. On April 22 a spine extruded from the dome reaches a record height of 1163 m. In May growth switches to the NE before becoming directed to the centre.
June – July 2003
A new easterly shear lobe develops, directed eastwards into the Tar River Valley, followed by two weeks of vigorous pyroclastic flows. Around mid June growth slows (possibly ceasing altogether). A prominent hybrid earthquake swarm begins on the 9 July, merging into continuous tremor on July 12.
Major collapse July 12 – 13, 2003
Third large dome collapse of 1999-2003 dome. The collapse volume is approximately 120 million m3 – the largest volume event of the current eruption. Large vertical explosions generate ash clouds up to 15 km height. Major pyroclastic flows travel down Tar River to the sea, producing phreatic explosions. Heavy ash fall affects the whole island with the deepest deposits to the NW of the volcano (150 mm in Lime Kiln Bay).
July 13 – 15, 2003
Three discrete vertical vulcanian explosions deposit pumice and lithic clasts across the island. Ash clouds reach up to 12 km height.
Cessation of Dome Growth July 2003 – August 2003
A brief period of dome growth occurs from July 21 – 28, followed by intense ash venting on August 1. Ash clouds do not reach higher than 6 km. Dome growth ceases in early August, and activity declines.
September 2003 – March 2004
A hybrid earthquake swarm (over 200 events) occurs on September 27, followed by a 20 hour period of ash venting and tremor on September 30. The volcano is quiet and seismic activity low. On December 18 there is a marked increase in SO2 emissions reaching 3 600 tonnes/day in contrast to the 500 tonnes/day average over the last month.
March 02, 2004
A period of low-level tremor began at around 19:00 local time, lasting until 14:44 the following day. This included around 10 small hybrid earthquakes, although few of these were individually large enough to trigger the seismic event detection systems.
March 03, 2004
Explosion and dome collapse event. Pyroclastic flows down Tar River reach the sea at the Tar River Fan. Ash clouds associated with the explosion reach altitudes of about 7 km. Low-level tremor for about 18 hours. A further small explosion on March 5 is followed by a period of ash venting.
March 6, 2004 – Present
Moderate to low tremor continues from late March to May. Intense rain on May 21, triggers large mudflows in the Belham Valley with standing waves up to 2 metres high. No evidence of further dome growth.
May 2004 – February 2005
Seismicity at low levels, with a swarm of volcano-tectonic events in late June to July. October 1-15 sees a period of very high sulphur dioxide degassing, up to 13000 tonnes/day on October 8. Low levels of activity are punctuated by rainfall-induced mudflows and hybrid earthquakes and some seismicity beneath Garibaldi and St George’s Hill.
February 2005 – April 2005
Episode of intense degassing from February 9 to March 10, including potent hydrogen sulphide smell, which is detectable on other islands. On March 6-7, a swarm of shallow volcano-tectonic earthquakes is detected. No new magma reaches the surface and activity declined.
Phreatic April 15, 2005 – April 19
2005 Vigorous phreatic activity begins. Nineteen VT events are accompanied by periods of volcanic tremor beneath St George’s Hill. High gas emissions and light ash reach Plymouth. Two new steam vents are observed, one outside the crater, but no new magma is detected.
April 20, 2005 – June 27, 2005
Further new vents open up in the crater, releasing steam and ash, accompanied by VT earthquakes and fracturing of the rocks below the crater floor.
Explosions 28-June-2005 A moderate explosion generates a 7km plume, causing PDCs that reach the sea at Tar River, and move beyond Farrell’s Wall.
July-2005
A series of moderate explosions (approximately 0.3 million cubic meters DRE) is associated with high amplitude seismicity and plumes up to 10km in height. Magma ascent rates are variable but high.
Dome growth August 2005 – December 2005 A new dome is detected on August 8, along with deformation suggesting a small crypto dome. Dome growth is asymmetric, and the extrusion rate is estimated at 0.5 to 1.0 cubic metres per second.
December 20, 2005 – February 9, 2006
Dome growth rate increases (to 3.2-3.9 cubic metres per second) and endogenous growth is detected. Rockfalls are frequent and spine extrusion is observed.
February 9, 2006 – February 27, 2006
Tremor is detected, followed by vigorous steam and ash venting. Growth of the dome accelerates to 10 cubic metres per second and a new lobe is extruded towards Gages Valley. By February 27, dome volume is 50 million cubic metres.
March 2006 – May 2006
Dome growth slows but continues, reaching 1006m asl.
Dome collapse May 20, 2006. The dome collapses producing a 20km-high plume and removing all growth since.
August 2005
(100 million cubic metres) as well as the remnant on Gages Wall and the talus on the NE margin of Tar Valley. PDCs and mudflows reach the sea in the Tar Valley, generating a small tsunami. The sulphur dioxide release is tracked across the Pacific and vigorous ash and steam venting is recorded. Dome growth continues within hours.
Cessation of Dome Growth May – November 2006
Dome growth continues at accelerated rates, with several small collapses accompanied by seismic swarms. In late August and September, two vents emerge, with vigorous steam and ash emissions. Sulphur dioxide is close to or below eruption average.
December-2006
During November and December, growth of the dome shifts to the west side, and culminates in a vigorous extrusive episode on December 24, generating a 4km plume. This is followed by PDCs into Tyre’s Ghaut, and Gage’s Valley.
January 08, 2007
Increased dome growth on January 7 culminates in a collapse of the dome the following day, and 3-4 million cubic metres of PDCs into the Belham Valley. The plume reaches a height of 9km.
February 2007 – March 2007
Dome growth varies in direction throughout February and into March, reaching a height of 1063m asl and a volume of 204 million cubic metres. Seismicity and gas emissions are relatively low.
April 2007 – April 2008
On April 4, dome growth ceases, with the dome height at 1050m asl. A few VT earthquakes are accompanied by high sulphur dioxide levels initially, then both seismicity and gas emissions decrease. Periodic lahars and rockfalls occur, especially rainfall-induced, and early 2008 sees a dramatic increase in sulphur dioxide emission. However, to April 2008, the dome volume remains at ~200 million cubic metres.
Seismic May 05, 2008
There was a small pyroclastic flow on the eastern flank of the Soufriere Hills Volcano (at 2:00am LT) on May 5. Light ashfall was reported in the Old Town area and fresh ash was evident in the Corkhill and St George’s Hill areas for several days afterwards..The flow may have been triggered by very heavy rainfall at the time, which also generated lahars. A brief swarm of volcano-tectonic earthquakes occurred at the same time as the flow. These were located at a very shallow depth beneath the dome.
Explosions and ash venting May 13, 2008
There was a small eruptive event at the Soufriere Hills Volcano (3:05 pm LT) on May 13. The event occurred without any warning signals and was accompanied by a single long-period earthquake. It was also heard at MVO. There were no pyroclastic flows on the flanks of the volcano. The ash cloud rose to about 10,000 feet above sea level, and drifted to the northwest over Iles Bay, Belham, Old Town and Olveston. Ashfall was light in all these areas. After the first pulse, ash generation continued for about fifteen minutes, with two or three distinct pulses of darker ash.
Continuous gentle ash emission from the Gage’s vent was apparent on May 15. A new fumarolic area also became evident on the south-east side of Chances Peak and appears to be emitting moderate amounts of water vapour with very little force.
May 23, 2008
Intermittent mild ash venting occurred in several pulses from the Gage’s vent, originally accompanied by a long period seismic event. The ash plume rose to slightly less than 3,000 feet (~ 900 m) above the volcano. Light ash fall most likely affected the Plymouth and St George’s Hill areas.
May 29, 2008 May 29
(2:38 pm LT) an explosion occurred without any precursory sign, producing (i) an ash plume reaching 10,000 feet (3,000 m) above sea level and (ii) a pyroclastic flow behind Gage’s mountain on the Plymouth side. The sound produced by the explosion was reportedly heard in Olveston, Salem, Flemmings and further north at the secondary school. Helicopter observation indicated that the pyroclastic flow and explosion originated from the Gage’s vent.
Residual activity May 30, 2008 – July 19, 2008
The pause in dome growth continues and seismic activity remains low. Erosion of the dome talus continues on the Tar River (E) side on a regular basis, producing minor rockfalls. Mild ash venting from the Gage’s vent continues intermittently. Sporadic heavy rainfalls triggered some minor mudflows down the Belham river.
Seismic July 20, 2008
A small swarm of volcano-tectonic earthquakes started on July 20 (9:10 pm LT). These were located at shallow depths beneath the volcano.
Explosions and ash venting July 21, 2008
Mild eruptive activity with three eruptive events overnight and one in the morning. There was continuous seismic activity throughout each of the first three events, typical of ash venting or pyroclastic flows. The first three events lasted for approximately 50, 40 and 75 minutes respectively. The last of these generated the largest seismic signals. The fourth event was much smaller. All four events generated ash columns rising more than 2 kilometers (6,000 feet) above sea level. The ash clouds drifted to the west over Plymouth and St George’s Hill. There was very light ashfall in parts of Old Towne overnight.
July 21, 2008
Seismic activity increased significantly with renewed onset of hybrid and long period earthquake activity. There was also a short series of eruptive events on July 27. This first event generated a non-energetic ash column which rose to about 2.5 kilometers (8,000 feet) above sea level. The ash cloud was blown to the west and north-west, and there was ashfall in Plymouth and St George’s Hill. There were two other eruptive events in the next 45 minutes. These were much smaller, with ash clouds below 1.5 kilometers (5,000 feet) above sea level.
July 28, 2008 – July 29, 2008
Eruptive event on July 28, which generated a large ash column, pyroclastic flows and falls of fresh airborne pumice in Iles Bay, Salem Olveston, Runaway Ghaut and Palm Loop. The source of the explosion was from Gage’s vent. Satellite images indicate that the vent has been enlarged by the explosion, is probably now a crater, and has dimensions of approximately 150 by 60 metres, elongated in an east-west direction.
A partial dome collapse is also believed to have occurred towards the Tar River Valley. The ash column was reported to reach a maximum height of about 12 kilometers (40,000 feet) above sea level. Satellite imagery shows that the ash was blown mainly to the north-west. There were reports of ashfall from St Croix, Puerto Rico and Guadeloupe. There were two minor eruptive events July 29, which generated small ash clouds.
Dome growth August 08, 2008
Lava extrusion resumed on the western side of the dome at a very low rate (< 0.1 cubic metre per second). Seismic activity is low apart from rockfalls. The explosion crater generated on July 28 was apparent and is almost completely filled with new lava. The lava had spilled over the lower, western, side of this crater generating the rockfalls below the Gages Wall.
August 25, 2008
Rainfall-induced pyroclastic flow August 25 (1:10am LT). The flow was on the western flank of the volcano and lasted for less than 15 minutes. The larger part travelled towards LeeΓÇÖs Yard, while the other part of the flow travelled in the direction of Plymouth but stopped before Amersham Estate. The wind direction was to the North at the time, and ashfall was reported from most of Montserrat, however, heavy dusting of dark wet ash occurred in Salem, Olde Town and Olveston. Dome glow seen in the scar created by the explosion on July 28.
September 04, 2008
The dome remains essentially the same with the rockfalls into the gully which developed in the Gage’s valley on the western side of the dome. A new feature.
October 08, 2008
Although the rate of lava extrusion has declined significantly, thermal imagery confirmed that the major E-W oriented fracture in the dome that is aligned with Gages valley and extends vertically over a few tens of meters, is associated with very elevated temperatures (hot lava).
Residual activity and cessation of dome growth October 15, 2008
Mudflows have occurred on October 15 and 16, due to the passage of hurricane Omar North of Montserrat. Headward erosion in the talus slope of the dome on the Tar River side has significantly increased in the past week most likely in the for-mentioned period of intense rainfall. This has created a large gap in the talus and exposed the core of the dome forming a large vertical cliff. Erosion continues to undermine the base of the dome on Tar River side.
Phreatic October 20, 2008
Three (3) small pyroclastic flows in the Tar River Valley, 2 between 9:00am (LT) and 10:00 am (LT) and one in the afternoon. They generated small ash clouds that drifted over unpopulated areas to the West and Southwest towards Plymouth. These pyroclastic flows were probably caused by the current slightly increased seismic activity and continued interaction of the hot dome with water from the intense rainfall following passage of hurricane Omar on October 14-17.
Dome degradation and residual activity October 26, 2008
Limited visual observations confirm that a few small pyroclastic flows have reached about 1.5 km from the dome on the Tar River side. Headward retrogressive erosion down several V-shaped chutes continues at the base of the dome on the Tar River side and on the SE side of the dome further deepening the moat in the talus around the dome. Ongoing erosion on the western flanks of the dome talus pile on the Galway’s side has formed a well-incised network of gullies leading into the White River. There is no evidence of ongoing lava extrusion.
October 27, 2008
December 1, 2008 Weak ash venting and gas puffs may have occurred briefly on a few occasions. Analysis of ground deformation data as of mid-October 2008 indicates that lengthening of the baseline that extends from the North of the island to the South through the volcano has continued at a slow rate. This provides evidence that the magma chamber of Soufriere Hills volcano continues to inflate, likely as a result of magma influx from depth. The newest vent on the north-west flank of the dome is unchanged.
Explosion and partial dome collapse December 02, 2008
An explosion took place on the western side of the lava dome (9:35pm LT). The event started with a small dome collapse which was followed, within 15 seconds, by a pyroclastic flow. It sent large blocks to distances up to a kilometer from the dome.
There were no reports of air-fall pumice or ballistics in inhabited areas, and ash was blown to the west over the sea. The pyroclastic flow generated extensive pyroclastic surges that rose up to the south face of St. George’s Hill, Aymer’s Ghaut in the south and Richmond in the north. The deposits from the pyroclastic flow appear to contain very little pumice, indicating the source material came from the dome and was not fresh lava. This is consistent with a dome collapse.
Incandescent blocks were scattered over the north-western side of Gage’s mountain, implying a vertical element to the explosion. The pyroclastic flow was on the western flank of the volcano. It travelled down Gage’s Valley and into Plymouth and appears to have reached the sea. Buildings were set alight in Plymouth and could be seen burning from Salem for several hours afterwards. The explosion and pyroclastic flow both generated ash columns, which reached a height of 40,000 feet above sea level. The ash was blown to the west over Plymouth and there was no ash fall in inhabited areas.
Residual activity December 5, 2008 – December 9, 2008
Small pyroclastic flows, some hybrid earthquakes associated with ash-venting from the North-West vent, and volcano-tectonic events continue to occur. All the monitoring data indicates that the magma chamber beneath the Soufriere Hills volcano continues to inflate.
Dome growth December 10, 2008
Re-start of dome growth, caused by lava extrusion on the south-west flank of the dome, has been linked with the occurrence of pyroclastic flows on December 10 December. Extrusion appears to be taking place high up on the dome and the lava is filling up the area between the dome and Chance’s Peak.
December 11, 2008 – December 19, 2008
There were frequent pulses of ash coming from several places spread over the north-west face of the dome. Night glow was visible on the north-west face from December 16 onwards, including strong variable glow from behind Gage’s Mountain. The visible activity was accompanied by frequent rockfalls, and generated several small pyroclastic flows, all of which travelled down the Gage’s Valley. Pyroclastic flows continue with the largest flow, on December 17, generating an ash cloud which reached approximately 10,000 feet above sea level.
None of the flows travelled beyond the fan of deposits above Plymouth. Continued erosion of the steep eastern face of the dome occurs towards the Tar River valley.
December 20, 2008
December 24, 2008 Activity increases with lava extrusion on the north, west and south-west side of the dome, as well as further rockfalls and pyroclastic flows on Chance’s Peak’s side, Plymouth and in Tyer’s Ghaut.
December 24, 2008
a large pyroclastic flow reached Plymouth and possibly the sea, with an associated ash plume reaching approximately 10,000 feet. No ash fall was reported over populated areas during this event. Lava extrusion continued over the week, and incandescence was visible on the dome at night. Large incandescent blocks were also visible in the upper and middle parts of Tyer’s Ghaut.
December 26, 2008 – January 2, 2009
Activity continues to increase with lava extrusion on the top, north, west and south-west side of the dome, as well as further ash venting at the top of the dome. Pyroclastic flows occurred down Chances PeakΓÇÖs side, Plymouth and in Tyer’s Ghaut. Tyers Ghaut has been rapidly filling up with the flow deposits. As a result, the flows reached farther down slope and entered the upper part of the Belham river. Ash fall was reported at Isles Bay, Garibaldi Hill, Old Towne, Salem and Olveston. Lava extrusion continues and widespread incandescence was visible on the dome at nights.
Explosions January 03, 2009
After a period of heightened seismic activity, two main explosions occurred on January 3 (04:47am and 07:07am LT). Both explosions had a significant jet component reaching at least 500 m above the dome and the plume reached heights over 35,000 feet (~11 km) above sea level. Ash fall affected most of the island due to southwards winds from 4,000 feet (1.2 km) elevation upwards. All observed samples from the explosions are pumiceous and indicate that most of the material involved in the eruptions was from new magma. Both explosions produced column collapses and resulting pyroclastic flows to the West of the volcano that reached Plymouth.
Cessation of Dome Growth January 4, 2009 – February 23, 2009
The level of activity dropped dramatically and there have been no signs of the old dome stability being compromised by the explosions. The background activity returned to low levels, suggesting either very low lava extrusion rate or non-energetic lava extrusion. This is supported by the lack of rockfalls and dome incandescence at night.
Dome degradation and Residual activity February 24, 2009 – February 25, 2009
On February 24 (9:55pm LT) a pyroclastic flow occurred towards the Tar River Valley. Deposits from this flow show that it travelled as far as the old coastline. On February 25 (3:35pm LT) a pyroclastic flow reached half-way down Tyer’s Ghaut.
February 26, 2009 – 29 February 2009
Activity at the Soufriere Hills Volcano remain at a low level. There was one pyroclastic flow in the Tar River Valley on March 6 (10:30 am LT). This flow reached the sea. Seismic activity remains low, with rockfalls and volcano-tectonic events occurring at times. The average daily flux remains above the long-term daily average for the entire eruption.
29 February -15 May 2009
Activity at the Soufriere Hills Volcano remained at a low level. There were two pyroclastic flows in the Tar River Valley. There was a large PF on March 6 (10:30 am LT) which reached the sea and a small PF on 24 April. Seismic activity remained low, with rockfalls and volcano-tectonic events occurring at times. Lahar activity was high, with significant lahars on 8 & 9 April, 4, 5 & 8 May, and 12-15 May.
15 May 2009
An especially high-amplitude isolated VT occurred.
16 May- 17 July 2009
Seismic activity remained low, but small pyroclastic flows occurred in this period on 24 May (17:05 ECT), 9 June (4:12 ECT), and 20 June (10:40 ECT) into the Tar River Valley. On 21 May a small explosion signal was detected (9:14 ECT), followed by a second larger signal (15:03 ECT) and ash venting. A strong PF signal occurred on 21 May, with ash drifting over Gages Mountain. A rockfall signal recorded 11:54 ECT 23 May had a low-frequency, possibly explosive, component.
18 July 2009
15 VT events occurred in a 20-minute period. This swarm was unusual in that the earthquake amplitude increased in size as the swarm progressed.
19 July- 3 October 2009
Seismic activity remained very low during this period.
4 October- 8 October 2009
A swarm of 24 VTs occurred at 00:45 UTC on 5 October (local time 8:45 pm on 4 October) after a marked drop in gas output 3 days before. Ash venting from the southern portion of the dome summit and associated tremor followed the VT swarm and lasted for 2 hours, with a plume reaching 6 km. Deposits observed later indicated there were multiple PFs associated with this ash venting and over the next 3 days, 12 more PFs occurred. Seismic activity continued over the next few days and consisted of sporadic VT events, occasional LP events and short bands of low-amplitude tremor.
Dome growth: Phase 5 Episode 1 9 October- 30 October 2009
New dome growth marking the beginning of Episode 1 of Phase 5 was observed on 9 October with extrusion occurring in a chute above the White River. Throughout the rest of October, growth appeared to have been focused on the summit of the dome, with active faces above both White’s and Tuitt’s Ghauts and above the White River (the predominant active area). A short-lived blocky spine was seen on 29 October but not the next day, so it is assumed that it collapsed overnight.
31 October- 6 November 2009
A new pattern of seismic activity started on 31 October, with many small semi-regular hybrid events. By 1 November, these were occurring in regular cycles 8 hours apart, with the events coalescing into continuous tremor at the height of each cycle. On 4 November PFs went into Gingoes Ghaut for the first time. In early November the direction of dome growth switched from SW to W, which continued into early December.
6 November- 19 November 2009
Seismic activity shifted back to continued LP events, rockfalls, LP/rockfalls and occasional short bands of tremor, declining until mid-November. On 10 November, PFs travelled down Gages Valley following dome growth occurring over Gages Peak. Some of this PF was channeled into Spring Ghaut.
19 November 2009
Seismicity increased with a series of nine large VT/hybrid earthquakes.
Dome growth and explosions: Phase 5 Episode 2 20 November 2009- 8 January 2010
A shift in seismic activity marked the beginning of Episode 2 of Phase 5 lasting until 8 January 2010.
Episode 2 was characterised by activity focussed on the northern and western side of the lava dome, PFs dominantly northeastward into Tuitt’s Ghaut (although simultaneous PFs in different directions remained commonplace), and cyclic seismic activity. On 21 November LP activity resumed and peaked on 26 November.
Tremors occurred on 23 November for 24 hours, then waned and began occurring in 4 hour period cycles which consisted of small hybrids/lps merging to tremor. After a week the tremors waned but cyclicity continued. Low-amplitude cycle peaks occurred together with ash venting and an increase in frequency of PFs, typically in more than one direction. These peaks typically lasted between 30 minutes and 2 hours, with ash plumes reaching heights of 5 km.
On 28 November, regular hybrid earthquake activity replaced the LP activity and as before, the hybrids merged into continuous tremor at regular intervals. These hybrid events were much larger than the small hybrid events seen at the end of October. Continuous tremor associated with ash venting became dominant by around 7 December and continued until 8 January.
Also in early December there was a shift in the direction of dome growth and rockfall /PF activity to northeast and the west simultaneously and PFs started moving down Tyer’s Ghaut. As a result, the Hazard Level was increased from 3 to 4 on 10 December. Abundant short-runout PFs caused Tyer’s Ghaut to become filled so later flows were less confined, travelling farther North onto Farrell’s Plain or West into the next Ghaut (locally known as Hussy’s Ghaut). On 29 December a short-lived blocky spine grew in the same location as the 29 October spine.
8 January 2010
Activity significantly increased with a Vulcanian explosion (14:49 ECT) lasting 11 minutes with a plume reaching a height of 25,000 ft. This explosion was the largest in a series of 5 Vulcanian explosions. Fountain collapse PFs flowed into White’s Bottom Ghaut, Tar River Valley, Farrell’s Plain, Tyer’s Ghaut/Belham valley, Gages, Gingoes Ghaut , and White River Valley. The PF into the Belham Valley had the longest runout of all PFs into the Belham Valley.
10 January 2010
A Vulcanian explosion with a plume reaching 22,000 ft occurred at 01:28 ECT. Fountain collapse PFs flowed into White’s Bottom Ghaut, Farrell’s Plain, Tyer’s Ghaut/Belham valley, and Gages. Another Vulcanian explosion occurred at 20:27 ECT with a plume reaching 18,000 ft. Fountain collapse PFs flowed into Tyer’s Ghaut/Belham valley and Gages.
Dome growth and explosions: Episode 3 Phase 5 11 January 2010
Dome profiles indicated that new lava had been added to the summit region, marking the beginning of Episode 3 of Phase 5.
Seismic cyclicity restarted and continued until the February 11 dome collapse. The seismicity of Episode 3 had weaker cycle peaks weaker than those of Episode 2. The focus of dome growth was in a similar area on the northern and western flanks, although perhaps more focused on the west than in Episode 2.
18 January 2010
5 February 2010
An extended period of sustained PFs occurred down the Gages valley with flows entering Spring Ghaut and reaching the sea at Kinsale for the first time in the eruption.
5 February 2010
A 30 m high pyramidal dome observed which was destroyed by a Vulcanian explosion (13:49 ECT) with a plume reaching 22,000 ft. Fountain collapse PFs flowed into White’s Bottom Ghaut, Tar River valley, Farrell’s Plain, Tyer’s Ghaut/Belham Valley, Gages, Gingoes Ghaut , and White River Valley.
8 February 2010
Vulcanian explosion (19:57 ECT) with a plume reaching 15,000 ft. The PFs from this Vulcanian explosion were confined to Gages. This was the smallest of the series of 5 Vulcanian explosions.
Large partial dome collapse and cessation of lava extrusion 11 February 20104
Major partial collapse of lava dome and extensive PFs impacted the northern flanks of the volcano starting at 11:52 ECT and lasting almost two hours, ending Episode 3 of Phase 5. Large PFs entered the sea between White’s Bottom Ghaut and Trants Bay, completely inundating the region, and pyroclastic surges were seen travelling greater than 1 km offshore. After about 50 minutes of near-continuous activity on the north and northeast flanks, there was an increase in the level of seismicity for about an hour. Several peaks in PF activity and at least two explosions were recorded on the seismic data. An energetic blast-type pyroclastic surge also occurred, as deduced from the extensive damage to buildings in the Harris, Streatham and Farrell’s Plain region. Two pulses of PFs occurred down the Belham Valley reaching Cork Hill. Seismicity associated with the activity waned at 13:40 ECT. Ash was carried to neighboring islands including Antigua, Guadeloupe, Dominica, Martinique and St Lucia, disrupting air travel in the Eastern Caribbean.
Pause: Dome degradation and residual activity 11 February 2010-present
The volcano has been in a paused state since the 11 February dome collapse. There has been continued decline in the amount of rockfalls and PFs. All except one have been confined to 1) the west above Gages valley 2) the north from the head of the 11 February collapse scar and 3) the east-south eastern side at the head of the Tar River valley. VT events have occurred at similar rates to other pauses.
Low-frequency seismicity, encompassing long-period events, hybrid events and long-period rockfalls, has been extremely low. The occurrence of hybrid earthquakes declined in March 2010 and has remained at a low level since. Beginning in April 2010, seismic activity remained low and constant except for the VT activity on 26 April, 23 June, 25 June, and 2 July, 3 December 2010 and 23 February and 28 March 2011, sometimes associated with phreatic ash venting.
23 February 2010
Hazard Level was reduced from 4 to 3.
23 June 2010
VT string consisting of 6 VTs lasting for about 15 minutes beginning 18:37 UTC.
25 June 2010
VT string consisting of 6 earthquakes lasting for about 15 minutes beginning at 15:26 UTC followed by ash venting from at least 2 locations 1) a strong fumarole in the base of the 11 February 2010 collapse scar and 2) the summit of the dome at the southern edge of the crater.
2 July 2010
Five VT earthquakes for over 30 minutes beginning at 15:43 UTC and associated ash venting. The ash venting was accompanied by about 1.5 hours of low-level seismic tremor.
3 December 2010
VT string of 11 earthquakes for over 30 minutes beginning at 12:08 UTC and an associated visible increase in gas output. Ash venting occurred approximately 1 hour after the occurrence of the seismicity and lasted for several hours.
23 February 2011
VT string consisting of 19 VT earthquakes in 47 minutes.
28 March 2011
VT string consisting of 36 VT earthquakes in just over an hour.
4 November 2011
Hazard Level was reduced from 3 to 2.
22 March 2012
VT String consisting of 49 events began at about 20:04 UTC (16:04 local time) and lasted for 47 minutes.
23 March 2012
VT string consisting of 52 events began at 07:10 UTC (03:10 local time) and lasted until 09:27 UTC. This VT string consisted of the largest magnitude VT on record. This was followed by clear increase in degassing from a new fumarole on the flank behind Gages Mountain and mild ash venting from a new vent in the February 2011 collapse scar. The ash venting began around 08:00 local time and lasted into the afternoon, with ash rising to about 6000 feet above sea level (3000 feet above the volcano).
