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Shammu
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Re: Volcanoes
«
Reply #210 on:
August 30, 2008, 11:56:37 PM »
Asama
As of the 22nd of August, the Global Volcanism Network (GVN) has reported that the Tokyo VAAC reported an eruption plume that on 14th August rose to an altitude of 3 km a.s.l. and drifted S.
Asama, Honshu's most active volcano, is located at the junction of the Izu-Marianas and NE Japan arcs and has an historical record dating back at least to the 11th century. The modern cone of Maekake-yama is situated E of the horseshoe-shaped remnant of an older andesitic volcano, Kurofu-yama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic and rhyolitic lava cone was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 years BP, and by growth of the Ko-Asama-yama lava dome on the E flank. Maekake-yama is probably only a few thousand years old, but has had several major Plinian eruptions, the last two of which occurred in 1108 and 1783 AD.
The Current Colour Code for Asama is currently at the
ORANGE
~~~~~~~~~
Mayon
As of the 14th of August, the Philippine Institute of Volcanology and Seismlogy (PHIVOLCS) reported that on 10 August, a mild explosion from Mayon produced an ash plume to an altitude of 2.7 km (8,900 ft) a.s.l. and drifted ENE. PHIVOLCS reported that during the previous few weeks seismic activity had increased slightly and incandescence at the crater had intensified. The Alert Level remained at 1. The 7-km Extended Danger Zone (EDZ) on the SE flank and the 6-km Permanent Danger Zone (PDZ) in all other areas remained in effect.
PHIVOLCS is keeping a tight watch over Mayon volcano after it monitored a mild explosion in the mountain at 0912hrs Sunday, a PHIVOLCS bulletin at noontime said. Mt. Mayon emitted smoke that reached a height of around 200 metres above the summit, said the PHIVOLCS bulletin. The smoke from the volcano summit later drifted east northeast. "The volcano is undergoing an episode of increased activity probably related to magma movement and though no major eruption is indicated, steam and ash explosions may occur in the following days," added the bulletin. The PHIVOLCS reiterated that Alert Level 1 remained over Mt. Mayon as of Sunday. It has also reminded the public that the seven-kilometre extended danger zone at the southeastern flank and the six-kilometre permanent danger zone at other areas remain off-limits due to threats from sudden small explosions and rockfalls from the upper slopes.
In view of the above, PHIVOLCS reiterates that Mayon volcano’s status remains at Alert Level 1. The public, however, is reminded that the 7-km Extended Danger Zone (EDZ) at the southeastern flank of the volcano and the 6-km radius Permanent Danger Zone (PDZ) at other areas remain off-limits due to the continuing threat from sudden small explosions and rockfalls from the upper slopes. Active river channels and those areas perennially identified as lahar-prone around the volcano should be avoided when there is heavy and prolonged rainfall. PHIVOLCS is keeping a tight watch over Mayon and shall immediately report any significant development to all concerned.
The Mayon Volcano is an active stratovolcano in the Philippines on the island of Luzon, in the province of Albay in the Bicol Region. The near perfectly cone shaped volcano is situated 15 kilometres northwest of Legazpi City. Mayon Volcano is one of the candidates of the New 7 Wonders of Nature. Mayon is classified by volcanologists as a stratovolcano, or composite volcano. Its symmetric cone was formed through alternate pyroclastic and lava flows. Mayon is the most active volcano in the country, having erupted over 47 times in the past 400 years. It is located between the Eurasian and the Philippine Plate, at a convergent plate boundary: where a continental plate meets an oceanic plate, the lighter continental plate overrides the oceanic plate, forcing it down; magma is formed where the rock melts. Like other volcanoes located around the rim of the Pacific Ocean, Mayon is a part of the "Pacific Ring of Fire". It is renowned as the "Perfect Cone" volcano because of its almost perfectly conical shape.
The Current Colour Code for Mayon is currently at the
YELLOW
~~~~~~~~~
Kasatochi
As of the 30th of August, the Alaska Volcano Obsetrvatory (AVO) reported that seismic activity at Kasatochi volcano continues to slowly decline following the eruptions on August 7th. Possible intermittent tremor occurred for several hours on August 27th and was detected by the AVO seismic network on Great Sitkin Island 25 miles west of Kasatochi. Satellite views were cloudy this week.
Located at the northern end of a shallow submarine ridge trending perpendicular to the Aleutian arc, Kasatochi is small 2.7 x 3.3 km wide island volcano with a dramatic 750-m-wide summit crater lake. The summit of Kasatochi reaches only 314 m above sea level, and the lake surface lies less than about 60 m above the sea. A lava dome is located on the NW flank at about 150 m elevation. The asymmetrical island is steeper on the northern side than the southern, and the volcano's crater lies north of the centre of the island. Reports of activity from the heavily eroded Koniuji volcano to the east probably refer to eruptions from Kasatochi. A lava flow may have been emplaced during the first historical eruption in 1760.
The Current Colour Code for Kasatochi is currently at the
ORANGE
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Shammu
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Re: Volcanoes
«
Reply #211 on:
August 30, 2008, 11:58:39 PM »
Mt. Cleveland
As of the 30th of August, the Alaska Volcano Obsetrvatory (AVO) reported that satellite views were most cloudy this week. A weak thermal anomaly was detected on August 24th. The lack of recent activity prompted AVO to lower the Aviation Colour Code/Alert Level to YELLOW on August 25.
Beautifully symmetrical Mt. Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mt. Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name for Mt. Cleveland, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks of the volcano. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Mt. Cleveland (Miller et al., 1998). In 1944 Mt. Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterised by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
The Current Colour Code for Mt. Cleveland is currently at the
YELLOW
~~~~~~~~~
Chikurachkil
As of the 29th of August, the Kamchatkan Volcanic Eruption Response Team (KVERT) has reported that according to satellite data, significant ash plumes have not been observed since August 3rd. But ash explosions up to 6 km (or 19,700 ft.) ASL are still possible. The activity of the volcano could affect low-flying aircraft. Chikurachki volcano is not monitored with seismic instruments. KVERT has satellite monitoring and receives occasional visual observations of this volcano. According to satellite data, clouds obscured the volcano most time of the week, ash plumes or clouds were not observed on the rest of the time.
Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red colour. Frequent basaltic plinian eruptions have occurred from Chikurachki during the Holocene. Lava flows from 1816-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centres is located immediately to the south of Chikurachki. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.
The Current Colour Code for Chikurachki is currently at the
YELLOW
~~~~~~~~~~~~~
San Cristobal.
As of the 17th of July, the Instituto Nicaragüense de Estudios Territoriales (INETER) informs that a news article reported that San Cristóbal produced a series of small explosions on the 11th of July, sending a plume of gas and ash NW. The article also noted that INETER had detected a series of tremors in recent weeks.
The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km to the west of San Cristóbal; it and the eroded Moyotepe volcano, 4 km to the NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the San Cristóbal complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.
The Current Colour Code for San Cristobal is currently at the
ORANGE
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Re: Volcanoes
«
Reply #212 on:
August 31, 2008, 12:00:45 AM »
Chaiten
As of the 28th of August, the Global Volcanism Network (GVN) reported that SERNAGEOMIN reported that on web camera views, pilot observations, and analysis of satellite imagery, the Buenos Aires VAAC reported that during 20-23 and 26 August ash plumes from Chaitén rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted SE, E, and NE. A thermal anomaly over the lava dome was detected on satellite imagery during 22-23 August.
Chaitén is a small, glacier-free late-Pleistocene caldera with a Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. The north side of the rhyolitic, 962-m-high obsidian lava dome occupying the 3.5-km-wide caldera is unvegetated. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km away from the volcano to the north and south. The caldera is breached on the SW side by a river that drains to the bay of Chaitén, and the high point on its southern rim reaches 1122 m. Two small lakes occupy the caldera floor on the west and north sides of the lava dome. Moreno (1985 pers. comm.) noted that the nearby volcano of Yelcho listed by the International Association of Volcanology and Chemistry of the Earth's Interior (1973) does not exist.
The Current Colour Code for Chaiten is currently at the
ORANGE
~~~~~~~~~
Llaima
As of the 28th of August, the Global Volcanism Network (GVN) reported that steam plumes from the pyroclastic cones in Llaima's main crater were visible during periods of clear weather on 16 August. Steam plumes rose from the W flank where lava flows were active in February and July. On 17 August, sporadic gas-and-ash emissions were observed. Cloud cover prevented observations during 18-20 August. On 21 August, three explosions produced ash plumes that rose to an altitude of 3.6 km (11,800 ft) a.s.l. and drifted E. Gas and steam was emitted in between explosions; resultant plumes rose to an altitude of 3.4 km (11,200 ft) a.s.l. and drifted 9 km E. During an overflight, scientists observed steam-and-gas plumes being emitted from a small crater in the N sector of the main crater. A larger crater, about 100 m in diameter, in the central sector emitted ash. The ash plumes rose to an altitude of 3.4 km (11,200 ft) a.s.l. and drifted E. A thin layer of ash blanketed the E flank. Ash-and-gas plumes from the main crater drifted W on 22 August. On 23 August, observers reported that incandescent material was ejected less than 1 km above the crater. The next day, an ash plume drifted about 1.5 km SSE. Ash blanketed some areas of the flanks. The Volcanic Alert Level remained at Yellow.
Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other, Pichillaima, to the SE. The massive 3125-m-high, dominantly basaltic-to-andesitic stratovolcano has a volume of 400 cu km. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following the eruption of the 24 cu km Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7200 years ago, construction of the present edifice began, characterised by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century.
The Current Colour Code for Llaima is currently at the
YELLOW
~~~~~~~~~~
Sakura-Jima
As of the 28th of August, the Global Volcanism Network (GVN) reported that based on information from JMA, the Tokyo VAAC reported an explosion from Sakura-Jima on 23 August. The altitude and direction of a possible resultant plume were not reported.
Sakura-Jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km wide Aira caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakura-Jima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4850 years ago, after which eruptions took place at Minami-dake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
The Current Colour Code for Sakura-Jima is currently at the
ORANGE
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Re: Volcanoes
«
Reply #213 on:
August 31, 2008, 12:02:56 AM »
Suwanose-Jima
As of the 28th of August, the Japan Meteorlogical Agency (JMA) has reported that based on reports from JMA, the Tokyo VAAC reported explosions from Suwanose-jima during 24-26 August. Resultant plumes rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. during 25-26 August.
The 8-km-long, spindle-shaped island of Suwanose-Jima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. Only about 50 persons live on the sparsely populated island. The summit of the volcano is truncated by a large breached crater extending to the sea on the E flank that was formed by edifice collapse. Suwanose-Jima, one of Japan's most frequently active volcanoes, was in a state of intermittent Strombolian activity from On-take (also called Otake), the NE summit crater, that began in 1949 and lasted nearly a half century. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, after which the island was uninhabited for about 70 years. The SW crater produced lava flows that reached the western coast in 1813, and lava flows reached the eastern coast of the island in 1884.(JMA)
The Current Colour Code for Suwanose-Jima is currently at the
YELLOW
~~~~~~~~~~~
Semeru
As of the 28th of August, the CVGHM reported that the Darwin VAAC reported that based on pilot reports and observations of satellite imagery, the Darwin VAAC reported that during 21-22 August ash plumes from Semeru rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted W.
Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises abruptly to 3676 m above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. Semeru has been in almost continuous eruption since 1967.
The Current Colour Code for Semeru is currently at the
ALERT LEVEL 2
~~~~~~~~~~~
Krakatau
As of the 21st of August, the CVGHM reported that according to a news article, explosions and earthquakes from Anak Krakatau averaged 120 per day approximately during 11-17 August. Monitoring personnel observed active lava flows, ejecting rocks, and emissions of "smoke."
The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 AD, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.
The Current Colour Code for Krakatau is currently at the
ALERT LEVEL 2
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Re: Volcanoes
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Reply #214 on:
August 31, 2008, 12:05:10 AM »
Dukono
As of the 28th of Auguat, the Volcano Society of Indonesia (VSI) has reported to INTLVRC that based on analysis of satellite imagery, the Darwin VAAC reported that on 24 August an ash plume from Dukono rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted NW. On 26 August, ash plumes rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted W and WNW.
Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.
The Current Colour Code for Dukono is currently at the
ALERT LEVEL 1
~~~~~~~~~
Galeras
As of the 28th of August, the Observatory Vulcanológico and Sismológico de Pasto - INGEOMINAS, informs that continuous the predominant seismicity associated with the dynamics of flowed inside the volcanic system, in relatively superficial levels and originated by magmatic processes as as much hidrotermales. The registry of a cluster of earthquakes (great amount of events in a relatively short time) associated with the fracturing of the solid part of the volcanic system stands out, which happened between 2306hrs of the 19th of August and at 1000hrs on the 20th of August; this seismicity was located to 2 km to the West-Southwest of the volcanic cone, with depths between 1 and 4 km with respect to the top and with local magnitudes of up to 1.6 on the Richter scale. They continue of significant way the sulphur dioxide emissions to the atmosphere (origin gas typical magmatic), that come in the last characterising the process months, with values measured during the last week of up to 6000 tonnes daily. By action of winds, the preferential dispersion appeared towards the north-western flank of the volcano. Concerning surface activity, days 22, 24 and 25 of August, the column of gas discharge was observed, with dispersion by action of winds towards the north the first two days and towards the south on the 25th of August. The columns reached heights near 1 km with respect to the top of Galeras and sometimes they were observed of gray colouration, possibly associated with some solid particle content and large ash. Since it has been mentioned, the general evaluation of the phenomenon allows to demonstrate the existence of a magmatic body in relatively superficial levels, that its process of degasification maintains, probably with a system of conduits, that make possible the exit of gases and with possible ash emissions.
Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic Galeras volcanic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has affected the volcano. This has contributed to large-scale edifice collapse that has occurred on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.
The Current Colour Code for Galeras is currently at
LEVEL III
~~~~~~~~~~~
Nevado del Huila
As of the 28th of August, the National Institute Of Sismología, Volcanology, Meteorology And Hidrologia, INGEOMINAS reported that in the present week a total of 570 seismic events was registered. Of them, 382 are related to fracturing of rock, 162 with the dynamics of flowed within the volcanic conduits, 20 events Hybrid type and 6 pulses of tremor of low magnitude. Of the seismicity registered by the volcano during the week, one respectively stands out the occurrence of two associated events to fracturing of rock the days 24th of August 25th at 1636 hours and at 1137 hours; first of them it had a magnitude of 3.4 on the Richter scale and it was located to 6.3 km to the SW of the Central Tip to a depth of 8 km, the second it had a magnitude of 2.8, and it was located at 2.3 km to the E of the Central Tip to a depth of 1.86 km. Today a movable measurement of the SO2 flow was realised, in the section spoolable that communicates the South of Corinth (Huasano path) with the South of Santander de Quilichao (Mandivá path), the SO2 flow was calculated at 3,272 tonnes/day, in a column with preferential dispersion towards the WNW. The volcano continues with slight increases in the seismic activity that is registered daily, being predominant the seismicity of low magnitude, with the exception of the happened events of the 24th and 25th of August.
Nevado del Huila, the highest active volcano in Colombia, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The 5365-m-high andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. The high point of the complex is Pico Central. Two glacier-free lava domes lie at the southern end of the Nevade del Huila volcanic complex. The first historical eruption from this little known volcano was an explosive eruption in the mid-16th century. Two persistent steam columns rise from Pico Central, and hot springs are also present.
The Current Colour Code for Nevado del Huila is currently at
ORANGE
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Re: Volcanoes
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Reply #215 on:
August 31, 2008, 12:07:09 AM »
Pacaya
As of the 30th of August, the National Institute Of Sismología, Volcanology, Meteorology And Hidrologia, (INSIVUMEH) has reported that for Atmospheric Conditions: Cleared. Pluvial Precipitation: 14.4 mm. Wind speed: 5.0 km/hr. Direction: Southwest. Activity: From the capital city it is possible to observe the gas plume that rises to 400 metres on the crater, nevertheless this is due to the little wind speed and not to a greater activation. The lava flow of the flank, stays in the South flank in the middle of the west the volcanic building with 2 flows fed by the same source, reaching, 200 meters.
The eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. Pacaya is a complex basaltic volcano constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the Cerro Grande lava dome and a younger volcano to the SW. Collapse of Pacaya volcano about 1100 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (MacKenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity at Pacaya has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of MacKenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the cone.
The Current Colour Code for Pacaya is currently at
ORANGE
~~~~~~~~~~~
Fuego
As of the 30th of August, the National Institute Of Sismología, Volcanology, Meteorology And Hidrologia, (INSIVUMEH) has reported that for Atmospheric Conditions: Cleared. Pluvial Precipitation: 6.0 mm. Wind speed: 0.0 km/hr. Direction: Southeast. Activity: White fumaroles to 100 metres of height that moves to the southwest. In the night, until this hour 10 explosions have been observed, 8 of them accompanied by weak rumblings and degassing sounds similar to airplane turbines. The flow of lava stays in direction of the Ravine Santa Teresa, with approximated length of 250 to 300 metres.
The Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta volcano dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta volcano may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango volcano, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.
The Current Colour Code for Fuego is currently at
ORANGE
~~~~~~~~~~
Santa Maria
As of the 30th of August, the National Institute Of Sismología, Volcanology, Meteorology And Hidrologia, (INSIVUMEH) has reported that for Atmospheric Conditions: Cleared. Pluvial Precipitation: 0.0 mm. Wind speed: 0.0 km/hr. Direction: Southwest. Activity: In the morning 2 explosions have been observed a weak one, a moderate one expelling gray ash to 300 and 600 metres from height dispersing towards the southwest. From the 2200 hours constant avalanches of blocks have been observed from the cupola of the crater of the Cono Caliente.
The symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit of Volcán Santa María to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.
The Current Colour Code for Santa Maria is currently at
ORANGE
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Re: Volcanoes
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Reply #216 on:
August 31, 2008, 12:09:07 AM »
Soufriere Hills
As of the 30th of August, the Monstserrat Volcano Observatory (MVO) reported that much of the activity at the Soufriere Hills Volcano this week has been triggered by heavy rainfall on Montserrat, with a pyroclastic flow on the 25th of August and several lahars. Other observations are consistent with continuing slow extrusion of lava on the western flank of the dome. There was a rainfall-induced pyroclastic flow at approximately 0110 hours local time on Monday, 25 August, after almost one hour of heavy rainfall. The flow was on the western flank of the volcano and lasted for less than 15 minutes. The flow split into two parts. The larger part travelled towards Lee’s Yard, but did not go as far as the flow on the 28th of July 2008. The other part of the flow was mainly contained in a gully and travelled as far as Amersham. At the time of the flow, the wind was blowing towards the north so there was a strong smell of volcanic gases in most areas of Montserrat. The smell of gases continued to be noticeable throughout the night. Ashfall was reported from all parts of Montserrat north of the volcano. Woodlands received the heaviest ashfall, with up to half a centimetre of dark wet ash. There was a heavy dusting of ash in Salem, Olde Town and Olveston. Lahars in the Belham River and various ghauts around the volcano were recorded on 25, 26 and 27th of August. On two occasions, there was a heavy thunderstorm centred on the volcano but no rainfall in inhabited areas. Despite some public concern about volcanic activity, there was none.
On clear nights, several distinct points of red glow can be seen on the dome. Most of these are in the scar that was created by the explosion on 28 July and then excavated by the pyroclastic flow on 25 August. There are at least two areas of glow to the north of this scar which indicate the presence of hot rock near the surface of the dome. Seismic activity continues. MVO recorded 18 rockfalls, 12 long period, 13 hybrid and 5 volcano-tectonic events this week. Most of the rockfalls were on the western side of the dome. Most of the hybrid and volcano-tectonic events have been recorded since 27 August and are located below the dome, at depths down to 2.5 km. Reliable measurements of the sulphur dioxide (SO2) flux were only possible for three days at the start of the week because the change in wind direction moved the plume outside the monitoring network. The average flux for the week was 466 tonnes per day (t/d) with a minimum of 239 and a maximum of 758. These values are lower than those seen since the explosion on 28 July. Lava extrusion is expected to continue. The extrusion rate has been relatively low since it started on 28 July, but an increase cannot be ruled out. The pyroclastic flow on 25 August has enlarged and steepened the rockfall gully over the Gages Wall. Because of this, further pyroclastic flows may occur without any warning, especially when there is heavy rainfall. The Hazard Level is 3.
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 east, was formed during an eruption about 4000 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.
The Current Colour Code for Soufriere Hills is currently at
ALERT LEVEL 3
~~~~~~~~~
Ubinas
As of the 21st of August, the El Observatorio Volcanológico de los Andes del Sur (OVDAS-SERNAGEOMIN) reported that based on SIGMET reports and pilot observations, the Buenos Aires VAAC reported that on 18 August ash plumes from Ubinas rose to altitudes of 5.5-6.4 km (18,000-21,000 ft) a.s.l. and drifted W.
A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I volcano was followed by construction of Ubinas II volcano beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.
The Current Colour Code for Ubinas is currently at
YELLOW
~~~~~~~~~
Karymsky
As of the 29th of August, the Kamchatkan Volcanic Eruption Response Team (KVERT) has reported that activity of the volcano continues and ash explosions up to 6.0 km (or 19,700 ft.) ASL are possible. The explosive activity of the volcano could affect low-flying aircraft in the vicinity of the volcano. Seismic activity of the volcano was above background levels on August 24-27 and at background levels on August 21-23rd. According to seismic data, possible ash-gas explosions up to 3.2 km (10,500 ft) ASL occurred at the volcano, weak intermittent volcanic tremor was registered on August 21-22. According to satellite data, a thermal anomaly was registered over the volcano on August 24, 26-28th, ash cloud extended to the southeast from volcano on August 27th.
Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, which is located immediately south of Karymsky volcano. The caldera enclosing Karymsky volcano formed about 7600-7700 radiocarbon years ago; construction of the Karymsky stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.
The Current Colour Code for Karymsky is currently at
ORANGE
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Re: Volcanoes
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Reply #217 on:
August 31, 2008, 12:10:59 AM »
Bezymianny
As of the 29th of August, the Kamchatkan Volcanic Eruption Response Team (KVERT) has reported that growth of the lava dome continues. Sudden ash emission related to this activity could affect low-flying aircraft in the vicinity of the volcano. Seismic activity of the volcano did not exceed background levels. According to visual data, moderate gas-steam activity was observed on August 25-28, clouds obscured the volcano on the other days. According to satellite data, a thermal anomaly was registered over the lava dome and over the deposits of pyroclastic flow.
Prior to its noted 1955-56 eruption, Bezymianny volcano had been considered extinct. The modern Bezymianny volcano, much smaller in size than its massive neighbours Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral volcano that was built between about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of Mt. St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.
The Current Colour Code for Bezymianny is currently at
YELLOW
~~~~~~~~~~~~~
Sheveluch
As of the 29th of August, the Kamchatkan Volcanic Eruption Response Team (KVERT) has reported to INTLVRC that activity of the volcano continues and ash explosions up to 10 km (32,800 ft.) ASL could occur at any time. The activity of the volcano could affect international and low-flying aircraft. Seismicity was slightly above background levels all week: volcanic earthquakes and a weak volcanic tremor were registered at the volcano all week. According to visual data, gas-steam activity with some amount of ash from avalanches was observed on August 22, 25-28, clouds obscured the volcano on the other days of the week. According to satellite data, a thermal anomaly was registered over the lava dome all week, gas-steam and weak ash plumes extended 80 km (50 mi) to the southeast from volcano on August 26-27.
The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskoi volcano group. The 1300 cu km Shiveluch is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.
The Current Colour Code for Sheveluch is currently at
ORANGE
~~~~~~~~~~
Colima
As of the 29th of August, the Government of the State, through the State Unit of Civil Defence-Colima reports that they have not been able to register activity during last the twenty-four hours, nor is report on damages or affectation in the adjacent populations. Most of the time, in the zone where it is the volcano persists the cloudiness, water precipitations and electrical activity, conditions associated to the passage of the tropical wave no. 26, that affects the states of the centre, the south and the west of the country; it is for that reason that reminds the population to avoid the permanence in bordering ravines, before the possibility of lahars (mud flows). Also, it follows the restriction effective for the over-flights that do not have scientific aims or of civil defence, and is prohibited the permanence of people other people's to these activities in ravines of the volcano.
The Colima volcanic complex is the most prominent volcanic centre of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.
The Current Colour Code for volcano Colima is
YELLOW
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Re: Volcanoes
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Reply #218 on:
August 31, 2008, 12:12:58 AM »
Popocatepetl
As of the 30th of August, the El Centro Nacional de Prevención de Desastres de la Secretaría de Gobernación (CENAPRED) has reported that in the last 24 hours the monitoring system detected 4 low intensity exhalations accompanied by steam and gas emmision. The other monitored parameters remain without important changes. At the moment of this report there is not visibility to the volcano due to the clouds. From high to low probability the expected activity scenarios in the next hours, days or weeks are: moderate exhalations, some with ash emissions; occasionally mild incandescence during nights and sporadic low level explosions with low probabilities of incandescent fragment at short distance to the crater. There is a permanent monitoring of the volcano to detect any change. The traffic light of volcanic alert remains in YELLOW Phase 2.
Volcano Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 250-450 m deep crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas south of the volcano. The modern volcano was constructed to the south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 AD, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since pre-columbian time.
The Current Colour Code for volcano Popocatepetl is
YELLOW
~~~~~~~~~~~~~~~~~
Tungurahua
As of the 30th of August, the Instituto Geofísico (IG) has reported that the level of activity of the volcano continues with a descendent tendency. In the morning of today superficial signals of activity in the volcano were not observed.
The IG reports that seismicity: In the last 24 hours, a total of 26 earthquakes of long period (LPs) has been entered that denote a moderate level of flowed movements of inside the volcano. Volcanic explosions have not taken place. Observations, Emissions and Ash: The volcano has remained most of the time dimmed but in the morning of today one was sprightly and any superficial manifestation in the zone of the crater was not observed. Noises: Originating noises of the volcano have not been reported. Rains and Lahars: In the morning of today slight rains in the zone were registered, but it did not have reports of lahars.
The official colour of the volcanic alarm light remains on
ORANGE
~~~~~~~~~~~~
Okmok
As of the 30th of August, the Alaska Volcano Observatory (AVO) informs that seismicity at Okmok volcano has declined and significant ash plumes have not been observed since August 19th. The Aviation Colour Code/Alert Level was reduced to YELLOW/Advisory on August 27th. A clear satellite view on August 28th showed a weak steam plume and a weak thermal anomaly. Although the level of seismicity has declined and it appears that ash is no longer being erupted, it is possible for vigorous ash emissions to resume at any time.
The broad, basaltic Okmok shield volcano, which forms the NE end of Umnak Island, has a dramatically different profile than most other Aleutian volcanoes. The summit of the low, 35-km-wide volcano is cut by two overlapping 10-km-wide calderas formed during eruptions about 12,000 and 2050 years ago that produced dacitic pyroclastic flows that reached the coast. More than 60 tephra layers from Okmok have been found overlying the 12,000-year-old caldera-forming tephra layer. Numerous satellitic cones and lava domes dot the flanks of the volcano down to the coast, including 1253-m Mount Tulik on the SE flank, which is almost 200 m higher than the caldera rim. Some of the post-caldera cones show evidence of wave-cut lake terraces; the more recent cones, some of which have been active historically, were formed after the caldera lake, once 150 m deep, disappeared. Hot springs and fumaroles are found within the caldera. Historical eruptions have occurred since 1805 from cinder cones within the caldera.
The Current Colour Code for Okmok is currently at the
YELLOW
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Re: Volcanoes
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Reply #219 on:
August 31, 2008, 12:16:04 AM »
Mt. Etna
As of the 24th of July it has been reported by INGV-CT that an inspection of Etna's summit craters on 15 July revealed degassing from the Northeast Crater and to a lesser degree from the BN-1 crater of the Bocca Nuova. Explosive activity was restricted to Vent 2 of the active NW-SE-trending fissure E of the summit craters and characterised by weak Strombolian activity and diffuse ash emissions. During 15 and 17 July lava flows were active in the Valle del Bove. On 17 July, no explosive activity was seen along the fissure.
Mt. Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BC. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur at Mt. Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater (the latter formed in 1978). Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.
The Mt. Etna is currently at the
ORANGE
~~~~~~~~~~~~~
Rabaul
As of the 28th of August, the Rabaul Volcano Observatory (RVO) has reported that ash plumes from Rabaul caldera's Tavurvur cone continued to be emitted during 18-22 August, although less so than during 16-18 August. Some prolonged ash-free intervals were immediately followed by explosions that produced ash plumes. The plumes drifted NW and caused ashfall in areas downwind. Occasionally incandescence at the summit was observed and roaring noises were heard. Explosions also ejected incandescent lava fragments. Based on analysis of satellite imagery, the Darwin VAAC reported that on 23 August ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted NW.
The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbour utilised by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims of Rabaul. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.
The Rabaul volcano is currently at the
ALERT LEVEL 2
~~~~~~~~~~~
KIlauea
As of the 30th of August, it has been reported to INTLVRC direct from the Hawaiian Volcano Observatory (HVO), that the Kilauea summit continued to produce small amounts of ash and elevated amounts of sulfur dioxide gas from the Halema`uma`u vent. At the east rift eruption site, Pu`u `O`o cone continued to produce high amounts of sulfur dioxide gas; lava flows through tubes to the ocean.
Last 24 hours at Kilauea summit: The Halema`uma`u vent was very noisy yesterday with multiple rock impact sounds becoming frequent and loud in time with the episodic seismic tremor bursts. Some of these sounds were heard by NPS eruption crew personnel at Jaggar Museum overlook. In the evening, incandescence could be seen to also pulse in time with those bursts; the brightness decreased considerably after 1 am, just after the episodic tremor bursts stopped. This morning, the white plume is rising from the vent and being blown southwest over the Ka`u Desert. Ash production continued; the collection this morning included increased amounts of volcanic glass material in the form of small tears and blobs, delicate and coarse hair, and irregular shreds, some like twisted braids and some in irregular shapes. Wall rock and alteration fragments were still part of the mix. Sulfur dioxide emission rates remained elevated and variable; the most recent average measurement was 700 tonnes/day on August 28 compared to a pre-2008 background rate between 150-200 tonnes/day. The summit tiltmeter network recorded minor oscillations. The network of GPS receivers that span the summit recorded weak contraction across the caldera. Episodic seismic tremor stopped at 0045 hours this morning, after having been nearly continuous for more than 48 hours; this morning, tremor levels resumed at values nearly identical to those before the episodic tremor began. The number of RB2S2BL earthquakes beneath Halema`uma`u Crater decreased but are still well above background values of 40/d. Forty two earthquakes were located beneath Kilauea, 31 of them beneath the summit caldera focused on the Halema`uma`u vent, 6 on south flank faults, 5 on Koa`e faults, andfour beneath the southwest rift zone.
Last 24 hours in the middle east rift zone vents and flow field: Magma continued to degas through Pu`u `O`o Crater resulting in an emission of 1,500 tonnes/day of sulfur dioxide on August 28th, down from a high of 7,100 tonnes/day on July 18th and near background values of about 2,000 tonnes/day. No incandescence was observed overnight within the crater. The tiltmeter on the north side of Pu`u `O`o cone recorded minor oscillations. GPS receivers recorded no change in distance across the crater. Seismic tremor levels are at low values near Pu`u `O`o and the TEB vent. Lava from the TEB vent and the rootless shield field flows through tubes to the ocean. Yesterday, HVO geologists found no active surface flows anywhere on the flow field; Waikupanaha ocean entry was generating a strong steam plume with no explosions evident. There had been a bench collapse sometime between Monday and Thursday, most likely at around 2200 hours on Wednesday night, August 27th, based on seismic evidence. No incandescence was observed overnight from rift zone to the top of the pali above the abandoned Royal Gardens subdivision. GOES-WEST imagery shows a prominent coastal steam plume blowing offshore at 0615 hours.
The Kilauea volcano is currently at the
ORANGE
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Re: Volcanoes
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Reply #220 on:
August 31, 2008, 12:16:48 AM »
Mt. Erebus
As of the 1st of August, the Mt. Erebus Volcano Observatory (MEVO) reports that lava flows of more viscous phonotephrite, tephriphonolite and trachyte are erupted after the basanites. The upper slopes of Mt. Erebus are dominated by steeply dipping (~30°) tephriphonolite lava flows with large scale flow levees. A conspicuous break in slope at approximately 3200 metres is a summit plateau representing a caldera. The summit caldera itself is filled with small volume tephriphonolite and phonolite lava flows. In the centre of the of the summit caldera is a small, steep-sided cone composed primarily of decomposed lava bombs and a lag deposit of anorthoclase crystals. It is within this summit cone that the active lava lake continuously degasses and periodically erupts.
CAVEAT: Despite the database of information on the geology of Mt. Erebus, there is still much to be learned about the volcano. The relative lack of knowledge becomes apparent when Mt. Erebus is stacked up against other active volcanoes of the world. There are many reasons for this comparative lack of knowledge, including the scarcity of rock exposures due to snow and ice cover, the remoteness of the volcano, the extreme environment, the brief field season (<6 weeks per year) and its non-threatening nature (i.e. no large populations are in jeopardy because of Mt. Erebus, unlike Vesuvius in Italy or Popocatepetl in Mexico).
Despite the above factors limiting the Mt. Erebus knowledge base, clearly much has been learned about the volcano over the past 25+ years. Nearly all exposed lava flow sets on Mt. Erebus have been physically sampled. Nearly all of these have been examined petrographically and petrologically. The summit lava flows on Mt. Erebus have been extensively mapped and dated by the 40Ar/39Ar method. The flank flows have been mapped in less detail, but many have also been dated. Tephra from Mt. Erebus has been found in glaciers on the volcano, mapped, geochemically examined and dated. The morphological characteristics of the edifice have been combined with the geochronological data to provide an evolutionary history of Mt. Erebus. And the physical and eruptive characteristics of the summit lava lake has been observed nearly every year for the past 25 years.
Mt. Erebus, Ross Island, Antarctica is the world's southern-most active volcano. Discovered in 1841 by James Ross, it is one of only a very few volcanoes in the world with a long-lived (decades or more) lava lake. Scientific research, sponsored by the U.S. National Science Foundation (NSF) since began the early 1970ís had included basic study of the petrology and geophysics of the volcano, the eruptive history, activity and degassing behavior of the lava lake, and the overall impact of the volcano on the Antarctica and global environment.
The Current Colour Code for Mt. Erebus is
ORANGE
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Indonesia Raises Alert Level for Erupting Volcano
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Reply #221 on:
October 08, 2008, 12:50:00 AM »
Indonesia Raises Alert Level for Erupting Volcano
Tuesday , October 07, 2008
The alert level for a volcano in central Indonesia has been raised after it began spewing hot clouds and lava, a vulcanology official said on Tuesday, Reuters reported.
The volcano erupted Monday, shooting clouds of smoke and flames into the night sky.
Indonesia's volcanology center said Mount Soputan, roughly 1,350 miles northeast of capital Jakarta on Sulawesi island, billowed smoke plumes as high as 3,200 feet.
The nearest villages are five miles from the crater's mouth, well out of the danger zone, the agency said on its Web site. Although no evacuations were ordered, people were warned to stay at a safe distance because it might spew lava.
Indonesia, a tropical archipelago straddling a major fault line known as the "Pacific Ring of Fire," has more active volcanoes than any other nation. The 3,280-foot Mount Soputan has been one of the most active.
Indonesia Raises Alert Level for Erupting Volcano
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Montserrat volcano erupts; fires in former capital
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Reply #222 on:
December 04, 2008, 10:24:01 PM »
Montserrat volcano erupts; fires in former capital
Wed Dec 3, 3:58 pm ET
SAN JUAN, Puerto Rico – The volcano on the tiny Caribbean island of Montserrat has burst into action, spewing columns of ash and hurling glowing red rocks that set vegetation and a few buildings ablaze in the island's deserted capital, scientists said Wednesday.
The explosion late Tuesday at the cloud-shrouded Soufriere Hills volcano — the first in nearly six months — occurred without any seismic activity, according to scientists who monitor any the volcano.
None of the island's 4,500 people were injured or evacuated.
Chief scientist Roderick Stewart said by telephone that bushes and a few buildings burned for several hours in Plymouth, the capital city that was abandoned when volcano erupted in 1997 and killed 19 people.
"I'm quite surprised there's still stuff that can burn there," Stewart said.
"This is the sort of event we've been expecting since the last explosion in July," Stewart said "It seemed to be triggered by a collapse."
The explosion on the western side of the volcano was smaller than when the lava dome partially collapsed in late July and spewed ash some 40,000 feet (12 kilometers) into the air. That explosion was preceded by about three days of earthquakes.
The Soufriere Hills volcano sprang to life in 1995. More than half the British Caribbean territory's 12,000 inhabitants moved away. An eruption in 1997 buried much of the south and killed 19 people.
Montserrat volcano erupts; fires in former capital
~~~~~~~~~~~~~
I guess I need to up-date this topic, since it's been a while.
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Re: Volcanoes
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Reply #223 on:
December 04, 2008, 10:26:56 PM »
CERRO MACHIN
As of the 26th of November, the Gobal Volcanism Network (GVN) reported that Observatory Vulcanológico and Sismológico de Manizales reported that between the 19th and 23rd of November, the activity of the volcano Cerro Machín continued to present/display low levels of seismic activity, registering 68 earthquakes of low magnitude, of which 66 are associated to processes of fracture to the interior of volcanic complex (type VT) and 2 to flowed gas transit and (type LP); these events were located mainly in the dome and to the south of the same with depths between 2 and 7 km it stands out the occurrence of two earthquakes on the 23rd at 1504 and 1505 hrs, with magnitudes of 2.0 and 1.1 on the Richter scale, respectively, which was reported like senses by the people who live in the neighbourhood of the volcano.
The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the south and contains three forested dacitic lava domes. Voluminous pyroclastic flows traveled up to 40 km from the volcano during eruptions in the mid-to-late Holocene perhaps associated with formation of the caldera. Late-Holocene eruptions produced dacitic block-and-ash flows that traveled through the breach in the caldera rim to the west and south. The latest known eruption of Volcán Cerro Machín took place about 800 years ago.
The colour code at Cerro Machin is currently at
YELLOW
~~~~~~~~~~~~~~
REDOUBT
As of the 2nd of December, the Alaska Volcano Observatory (AVO), reported that seismic activity remains at low levels. No unusual activity observed in mostly clear satellite views.
On 5 November, AVO raised the Aviation Colour Code for Redoubt to Yellow and the Volcano Alert Level to Advisory because of significant changes in gas emission and heat output during the previous several months. The changes were a departure from the long-observed background activity. ASTER satellite images from 13 October detected warming near the summit craters; evidence of warming had been directly observed in July 2008. Fumarolic activity and water flowing beneath Drift Glacier on the N flank had produced a 45-m-wide melt or collapse hole at an elevation of about 1,700 m (5,600 ft) on the Drift Glacier. On 2 November, a slushy debris-flow deposit originated from about the location of the 1966-68 vent. During 6-11 November, no activity was observed on satellite imagery and seismicity remained low.
Redoubt is a 3108-m-high glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mt. Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. The volcano was constructed beginning about 890,000 years ago over Mesozoic granitic rocks of the Alaska-Aleutian Range batholith. Collapse of the summit of Redoubt 10,500-13,000 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of large clay-rich lahars, one of which dammed Lake Crescent on the south side and reached Cook Inlet about 3500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.
The colour code at Redoubt is currently at
YELLOW
~~~~~~~~~~~~
AKAN
As of the 4th of December, the Japanese Meteorological Agency (JMA) has reported that an eruption from Akan (also known as Meakan-dake, which means Meakan Peak) of the Akan volcanic complex on the 28th of November. Ash plumes rose to an altitude of 2 km (6,600 ft) a.s.l. and drifted N, E, and SE. Ash was deposited on the E flank up to 4 km away from the crater. The Alert Level remained at "near-crater warning" (levels 2 and 3 on a 5-level scale).
Akan is a 13 x 24 km, elongated caldera that formed more than 31,500 years ago immediately SW of Kutcharo caldera. Growth of four post-caldera stratovolcanoes, three at the SW end of the caldera and the other at the NE side, has restricted the size of the caldera lake. The 1-km-wide Nakamachineshiri crater was formed during a major pumice-and-scoria eruption about 13,500 years ago. Of the Holocene volcanoes of the Akan volcanic complex, only the Me-Akan group, east of Lake Akan, has been historically active, producing mild phreatic eruptions since the beginning of the 19th century. Me-Akan is composed of 9 overlapping cones. The main cone of Me-Akan proper has a triple crater at its summit. Historical eruptions at Me-Akan have consisted of minor phreatic explosions, but four major magmatic eruptions including pyroclastic flows have occurred during the Holocene.
The Current Colour Code for Akan is currently at the
ORANGE
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Re: Volcanoes
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Reply #224 on:
December 04, 2008, 10:28:55 PM »
SAN CRISTOBAL
As of the 27th of November, INETER informs that according to a news article, seismic activity from San Cristóbal increased on the 14th and 17th of November. The article also noted that INETER reported explosions and subsequent ash-and-gas emissions from the crater on the 21st of November. Ashfall was reported in areas to the S.
The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km to the west of San Cristóbal; it and the eroded Moyotepe volcano, 4 km to the NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the San Cristóbal complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.
The Current Colour Code for San Cristobal is currently at the
ORANGE
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BARREN IS.
As of the 20th of November, the Global Volcanism Network (GVN) reported that based on a pilot observation, the Darwin VAAC reported a lava flow from Barren Island on the 17th of November. A possible low-level ash plume was seen drifting W on satellite imagery. On the 18th of November, a pilot reported that an ash plume rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted WSW.
Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit of volcano that rises from a depth of about 2,250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the W, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. The morphology of a fresh pyroclastic cone that was constructed in the centre of the caldera has varied during the course of historical eruptions. Lava flows fill much of the caldera floor and have reached the sea along the western coast during historical eruptions.
The Current Colour Code for Barren Is. is currently at the
ORANGE
~~~~~~~~~~
DALAFFILLA
As of the 27th of November, the Global Volcanism Network (GVN) reported that during the 19th-24th of November, the MODIS satellite continued to detect thermal anomalies over the area near Dalaffilla and Alu volcanoes from the eruption that began on the 3rd of November.
Dalaffilla, also referred to as Gabuli, is a small, but steep-sided conical stratovolcano that rises 300 m above surrounding lava fields SE of Alu volcano. This morphology, unusual for the Erta Ale Range volcanoes, results from the extrusion of viscous, silicic lava flows with primary slopes up to about 35 degrees. These silicic flows extend primarily to the east; on the west they are blocked by walls of a horst structure along the crest of the Erta Ale range. Other basaltic lava flows from regional fissures surround the 613-m-high volcano. Fumarolic activity occurs in the 100-m-wide summit crater and has weathered surrounding lava flows.
The Current Colour Code for Dalaffilla is currently at the
ORANGE
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