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TOPIC: Soufriere Hills Volcano


L

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RE: Soufriere Hills Volcano
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08 January 2007 - Explosive activity
The event onset was recorded on the MVO seismic network at 05:54. Between 06:05-07 there was explosive activity audible as far north as Woodlands in Montserrat (seismically better described as "jetting"; 3 distinct pulses were recorded). The rising ash cloud was visible from all over Montserrat moving out to the WSW south of St Georges Hill and Garibaldi Hill.
Pyroclastic flows travelled down Gages Valley and Tyres Ghaut into the head of the Belham River Valley simultaneously suggesting source high on dome directly behind Gages Mountain. At 06:15 the largest pyroclastic flow to date flow entered the Belham Valley, reaching as far as the edge of Cork Hill, a run out distance of around about 5 km. At 06:25 the ash cloud was reported to have reached 30,000 ft.
Between 06:20-06:25 seismic activity began to wane and by 06:30 seismicity had returned to just above background, dominated by isolated PF signals (extended duration rockfall signals, none or which was especially large, and definitely not suggestive of a collapse) and small long period earthquakes. Pyroclastic activity in Tyres Ghaut continued at higher levels than recent days over the next approx. 1.5 hours establishing an almost regular 7 minute cycle. The run out distances of the individual flows were limited to 1-1.5 km, and each flow was preceded by a minor pulse of ash venting.
At about 08:20 a short period of rumbling/roaring preceding pulse ash venting.
By 09:30 seismicity had returned to background levels.

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Montserrat's Soufriere Hills volcano blasted ash and steam into the air on Thursday, and authorities warned the Caribbean island could see heightened activity in coming days.

The eruption did not affect the northern side of the island, where all of Montserrat's 5,000 residents live, but the Montserrat Volcano Observatory raised the alert status.


The lava dome inside the summit crater of the volcano viewed from the east on 1 August 2006. The eastern side of the crater is open and talus (scree) slopes extend eastwards into the top of the Tar River valley. These steep slopes of loose debris are formed when parts of the summit area of the dome collapse, generating rockfalls or pyroclastic flows. The volume of the dome (and talus slopes) was calculated at about 37 million cubic metres on 1 August. The growth rate of the lava dome through July 2006 was about 5 cubic metres per second, this is less than in previous months.

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On Saturday, May 20, 2006, Montserrat’s residents were warned to stay inside as the Soufriere Hills Volcano covered much of the small Caribbean island in 5 to 7 centimetres of volcanic ash and pebbles. Likewise, air traffic was stopped in the area after the eruption spewed volcanic ash 16 kilometres skyward.

The Terra satellite took this picture of the island of Montserrat on May 22, 2006.

montserrat220506
Credit NASA

In this image, a white plume, likely composed of volcanic ash and steam, flows from the summit. A trail of sediment, appearing in pale blue-green, appears to flow away from the island in the ocean currents. As the volcanic eruption produced debris that rolled down the side of the volcano, it is possible that some of this sediment results from that debris.

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Scientists at the Montserrat Volcano Observatory (MVO) say they recorded signals of increased activity around 6am, Saturday morning. Expecting that this dome collapse episode could go on for hours, the biggest concern was the possibility of explosive periods triggering pyroclastic flows into Tyres Ghaut, which is the upper reaches leading into the Belham River Valley.

Residents of Salem, Olveston, and Old Towne reported stones falling in those communities. Head of the MVO, Dr. Sue Loughlin, confirmed that there was heavy ashing with accompanying small stones on the northwestern side of the island, especially in these villages.

The MVO’s scientist also said that another concern was the threat of tsunamis from the continuing pyroclastic flows of this eruptive event entering the sea. The Commissioner of Police has confirmed that a coastal warning especially for the eastern side of the island was given.

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Montserrat
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The Soufriere Hills Volcano on the island of Montserrat produced a plume of volcanic ash on February 9, 2006, and ongoing emissions of ash and steam continued for the next several days. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard the Aqua satellite captured this image on February 16.



In this image, the volcano’s ash plume blows westward over the Caribbean Sea. According to news reports, the volcanic ash moved over the U.S. Virgin Islands and parts of Puerto Rico, while authorities on Montserrat prohibited access to parts of the island and some of the surrounding waters.

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The Soufriere Hills Volcano on the island of Montserrat produced a faint plume of volcanic ash in late November 2005, continuing a pattern of moderate eruptions that has lasted for months.
The Aqua satellite took this picture on November 19, 2005.


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Montserrat appears in the centre of this image, casting a faint plume of ash toward the southwest over the Pacific. The volcano’s summit is outlined in red, a “hotspot” detected by the satellite.
Montserrat’s island neighbours also appear in this image, some of them fringed by pale blue-green. This light colour probably results from shallower waters near the shore, or from coral reefs. The lighter colours might also be caused by phytoplankton.

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Soufriere Hills Volcano
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The Soufriere Hills Volcano on Montserrat produced a faint but steady plume of ash on September 4-5, 2005.
The Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard the Aqua satellite took this picture on September 5th 2005.


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In this image, a thin plume of volcanic ash drifts westward from the volcano, and red lines outline the volcano’s summit. The volcanic ash appears as a lighter shade of blue over the ocean surface while the clouds are white.
To the northwest of Montserrat, partially obscured by clouds, are the islands of St. Kitts and Nevis.




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