Volcano Watch 2007

Alert level is at 4:
Large unconfined dome actively growing towards the north or west; or, large dome with: high levels of pyroclastic flow activity in other directions and/or high rates of dome growth; or intense earthquake swarms or tremor; or with tropical
storm imminent or already affecting the island.

Ongoing pyroclastic activity has been observed on the northwestern sector of the volcano with pyroclastic flows in Tyres Ghaut, Gages Valley and behind Gages Mountain... The most significant event began at about 15:24 (local time), resulting in simultaneous pyroclastic flows in Gages Valley and in Tyres Ghaut and an ash cloud which reached an estimated 8,000 ft. (2,500 m).

Low level gas and ash venting from a vent on the western side of the dome is ongoing. Fortunately the prevailing wind direction remains E-W and the occupied areas of Montserrat have been largely unaffected by ash fall.

As of the 7th of January, growth of the new lava dome inside the crater of Mount St. Helens continues, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash.

During such eruptions, changes in the level of activity can occur over days to months. The eruption could intensify suddenly or with little warning and produce explosions that cause hazardous conditions within several miles of the crater and farther downwind.

As of the 14th of January it has been reported to SWVRC by John Seach in Australia, that eruptions began at Karthala volcano the 12th of January. A red crater glow was observed and residents of Mvouni, a town at 1,000 metres altitude on the volcano's western slope, were woken up by strong fumes.

Source: SWVRC

SAN JUAN, Puerto Rico: A dome of hardened lava over Montserrat's Soufriere Hills volcano has swollen to near-record size and could collapse, sending volcanic material toward a populated area of the Caribbean island, a government scientist said Friday.

The volcano, which had a devastating eruption in 1997, appears stable for now, but a decrease in gas emissions over the last week suggests pressure could be building inside the lava dome, said Vicky Hards, director of the Montserrat Volcano Observatory.

SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m

During 28 February-2 March, lava-dome growth at Soufrière Hills continued and was concentrated on the E and N sides. Ash venting and roaring noises originated from the W side of the dome, above Gages Wall. On 2 March, two small pyroclastic flows traveled down Tyres Ghaut to the NW.

Based on satellite data and pilot reports the Washington VAAC reported continuous ash emissions during 28 February-4 March. Resultant plumes rose to altitudes of 2.1 km (7,000 ft) a.s.l. and drifted mainly W. A thermal anomaly was detected in the crater on satellite imagery. On 6 March, an ash plume rose to altitudes between 1.8-2.7 km (6,000-9,000 ft) a.s.l. and drifted W and NW.

Geologic Summary. The complex dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Now, engineers are using a pulley system to hoist the beachball-sized concrete spheres over the crater before dropping them from a height of about two stories. The balls, each weighing about 70kg, are chained together in clusters of four.

So far, nearly 150 have been tossed into the abyss -- too few to make a real impact.

Witnesses say the mud swallowed up giant boulders as it swept down the mountain, but thankfully no one was injured.

A mudslide from the same volcano killed more than 150 people in 1953, when it washed away a rail bridge plunging a passenger train into the torrent of mud.

The new eruption of Batu Tara on the tiny island with the same name is getting more intense.

An explosive activity has set on. As a safety measurement, mainly to protect them from tsunami (that might be triggered by earthquakes, landslides or pyroclastic flows) around 7,000 inhabitants of the closest neighboring island, Lembata 50 km to the south, were evacuated.

Fishermen, also, have been warned to stay at least 2 miles (3.2 kilometers) from the volcanic island.

Sheveluch volcano had a large explosive eruption early on March 29 as became evident from satellite observations, that showed evidence of an ash plume that reached about 12 km altitude and was moving NE at 20 km per hour. The event appears to have been short-lived; web camera imagery of the volcano at this time shows no further ash production.

Etna is active again. Following a rapid increase of tremor starting at 07h24 this morning (29 March, 2007), SE crater began to emit lava fountains and ash plumes until around 9 am.

The lava continues to flow on Stromboli. Three branches of lava flows originate at the 420 m vent on the Sciara del Fuoco, two of which still reach the sea.

New activity has started at Reventador volcano. In early March, the number of tectonic earthquakes from Reventador had increased. During 8-22 March, steam-and-ash plumes rising to altitudes of 4 km (13,000 ft) a.s.l. were observed sporadically.
On 21 March, noises were reported. The next day, seismic signals changed and indicated possible emissions. On 24 March, local people saw ash plumes and incandescent material near the crater and heard roaring noises. An explosion produced a plume that rose to an altitude of 6.6 km (21,700 ft) a.s.l. and drifted W. Based on reports from IG, the Washington VAAC reported an ash plume to altitudes of 3.7-7 km (12,000-23,000 ft) a.s.l. that drifted NE and WNW during 26-27 March. A thermal anomaly was present on satellite imagery during 24-27 March.

Tungurahua continues to be the most active volcano in South America. During the past week, near-constant explosive activity produced plumes that rose to altitudes of 7-10 km (23,000-32,800 ft) a.s.l. and drifted mainly W, NW, and N. Ashfall was reported from areas downwind and from areas SW within 8 km, on all days except 25 and 27 March.
Noises resembling "cannon shots" and blocks rolling down the flanks were heard on 21, 22, and 25 March; windows rattled as far away as 11 km N in Guadalupe. On 23 March, lahars traveled mainly down NW gorges and affected the roads between Ambato and Baños, and between Baños and Penipe.

Another explosive event occurred at Sheveluch Volcano on March 29 at approximately 17h53 UTC. The Tokyo Volcanic Ash Advisory Center reported a cloud from this event to 40,000 ft above sea level extending northeast from the volcano and moving at 50 knots.

Mild strombolian activity continues at Klyuchevsky volcano. Over the past weeks, explosions were observed throwing lava bombs about 50-100 m above the crater.

During 13-20 April, visual observations suggested that lava-dome growth at Soufrière Hills continued at a reduced rate.
Heavy rains resulted in lahars in several drainages 16-17 April.
During 18-20 April, a gas plume drifted N and NE and a bluish haze containing sulfur dioxide was observed flowing down the N flanks due to light winds coming from the S.