Bulletin of the Global Volcanism Network, January 2006

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Bulletin of the Global Volcanism Network, January 2006
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From: Ed Venzke <venzke@xxxxxxxxxxxxxx>


Global Volcanism Program, Smithsonian Institution <http://www.volcano.si.edu/>

Bulletin of the Global Volcanism Network
Volume 31, Number 1, January 2006

Karthala (Comoros Islands) Looking at the 2005 eruptionâ??s precursors, deposits, and human 
impact
Nyamuragira (DR Congo) To the N, swarms of long-period, along-rift earthquakes
Nyiragongo (DR Congo) Continuous ash plumes and active lava lake
Barren Island (India) November 2005-January 2006 ash emissions, lava flows, and pyroclastics
Lamongan (Indonesia) Above-background seismicity during 5-6 January 2005
Lopevi (Vanuatu) Correction to previously published MODIS hotspot data
Aoba (Vanuatu) Crater-lake photos and satellite temperatures data show ongoing activity
Galeras (Colombia) Eruption begins on 24 November 2005 sending ash plumes into air
Santa Ana (El Salvador) Post-eruption lahars but seismicity and SO2 fluxes both often low
Augustine (Alaska, USA) January 2006 eruptions; pyroclastic flows, ash plumes, and aviation 
hazards
Cleveland (Alaska, USA) 6 February 2006 eruption on remote, non-instrumented  island
Tanaga (Alaska, USA) Weak, moderate depth seismicity

Editors: Rick Wunderman, Catherine Galley, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Jerome Hudis, Jackie Gluck, William Henoch, Veronica Bemis, and 
Stephen Bentley



Karthala
Comoros Islands, western Indian Ocean
11.75°S, 43.38°E; summit elev. 2,361 m
All times are local (= UTC + 3 hours)

After the 11 July 1991 phreatic eruption, 14 years of quiescence at Karthala was disrupted in 2005 
by two strong explosive events. These events, 
occurring on 16 April 2005 (BGVN 30:04) and 24 November 2005 (BGVN 30:11), resulted in 
deposits of fine ash scattered over a large part of the 
island. This report presents some further observations and analyses of the November event by 
scientists from the Comoros and Reunion.

Seismic precursors. The seismicity on figure 1 delineates four periods during 2005: (1) From the 
beginning of the year until the 16 April 
explosive event, an interval characterized by significant seismicity. (2) From the 16 April event 
until just prior to the 25-26 August seismic 
crisis, an interval with relatively low seismicity (only 102 events recorded in 116 days). (3) An 
interval from 26 August to 23 November that 
began during the 25-26 August seismic crisis when 190 events occurred. Moderate seismicity 
following the seismic crisis ramped up after 27 
October until the 24 November eruption. This period was characterized by a total of 1,063 seismic 
events, an average of 12 earthquakes per day. 
(4) From the 24 November eruption until the end of the year, an interval of relatively low seismicity 
similar to the second period. The 24 
November earthquake swarm began at 1902, dropped significantly at 1950, and restarted at 2021 
with sustained tremor.

Figure 1. Cumulative distribution of earthquakes registered at Karthala during the year 2005. 
Courtesy of KVO.

The investigators noted that the seismic crisis of 25-26 August 2005 marked the beginning of the 
new eruptive cycle. It preceded the November 
2005 eruption, but was much more subdued than the build up before the eruptions in April 2005 
and July 1991 (BGVN 16:06 and 16:08). Earthquakes 
were located by KVO using Sismalp (the French Alps Seismic Network). Uniquely, for the November 
2005 seismic crisis, the hypocenters were 
500-1,000 m shallower than those of April 2005. This could be attributed to shallower magma 
storage for the last eruption.

Activity during 24 November-5 December 2005. The beginning of the 24 November eruption was 
visible from Moroni (the capital city of the Comoro 
Islands) with lightning, rumblings, and a large dark plume at the summit. Ash first fell on the E 
coast of the island around 2300 on 24 November 
and the tremor intensity significantly dropped. On the W part of the island, ash started to fall on 
25 November at 0500 with very strong 
intensity. Evacuation became very difficult, schools remained closed, and some people used masks 
to breathe. Ashfall was so intense that the 
authorities required the inhabitants to remain in their homes. The United Nations Office for the 
Coordination of Humanitarian Affairs (OCHA) 
reported that, according to the local authorities, ~ 2,000 people fled from their villages in the 
region of Bambao in the central part of the 
island, and sought refuge in less exposed areas, such as Mitsamiouli, Mboude, and Oichili.

At 0700 on 25 November the sky was darkened by ash (figures 2 and 3). Part of the population 
fled towards the N of the island. It was only 
around 0900 that the sky partially cleared; however, ash continued to fall with decreasing intensity 
during the day. Ash deposits covered 
three-quarters of the island. The international airport located in the N part of the island remained 
free of ash deposits. The Toulouse Volcanic 
Ash Advisory Center issued an advisory to limit risks for air traffic; however, the eruption did not 
halt airport operations. Satellite imagery 
on 25 November revealed an ash cloud reaching ~ 11.6 km altitude.

Figure 2.  An ash plume from Karthala at 1000 on 25 November 2005 led to ash-draped surfaces 
and heavily filtered sunlight in the capital, 
Moroni (population variously estimated at 20,000-63,000 residents, located 13 km NW of the 
summit). Ashfall was very heavy until 1200, then 
decreased throughout the rest of the day. Courtesy of Hamid Soule, KVO.

Figure 3.Downtown Moroni as it appeared at 1000 on 25 November 2005 after the eruption of 
Karthala. Courtesy of Dominique Meyer-Bisch, Embassy 
of France in Comoros Islands.

During 25 November, about 30 seismic events were recorded by KVO, causing concern about the 
possibility of a crack or fissure opening on 
Karthalaâ??s flank, as occurred in April 1977 (SEAN 02:03). During the night, red glow at the 
summit was clearly visible from the coast.

On 26 November, a field excursion found a lava lake in the Chahale crater (figure 4). Prior to the 
eruption that craterâ??s floor had been covered 
by a water lake some tens of meters deep. In contrast to the crusted-over lava lake of April 2005 
(BGVN 30:04), in November it was almost 
entirely liquid, with a very large fountain in its center. By 30 November the lava lake had solidified 
over ~ 80 % of its surface (figure 5). On 
5 December it was almost entirely solid, with only two small spatter cones active (figure 6).

Figure 4. On 26 November 2005 investigators ascended Karthala and observed a molten-surfaced 
lava lake inside Chahale crater. The lake was about 
60-80 m in diameter. Many parts of the lake had a molten surface covered by a chilled skin, 
although some large blocks of cooler material also 
lay scattered in the lake. This picture was taken looking down from the craterâ??s N edge. 
Courtesy of Christophe Roche, French school teacher in 
Moroni.

Figure 5. On 30 November 2005 a field excursion allowed investigators to observe the ongoing 
solidification of the lava lake inside Karthala's 
Chahale crater. The only incandescence plainly visible appears in the lake's central area. This 
picture was taken looking from the crater's NW 
edge. Courtesy of Francois Sauvestre, KVO.

Figure 6. A Karthala excursion on 5 December 2005 allowed scientists to observe an almost 
entirely solidified lava lake. Two small (5-m high) 
spatter cones had developed over the area previously hosting the most intense incandescence, and 
some small zones adjacent to them still 
remained incandescent.  The cones stopped being active on 8 December. This picture was taken 
looking from the NW edge of the crater. Courtesy of 
Francois Martel-Asselin.

Eruptive products. The landscape at the summit illustrated the style and intensity of the eruption. 
Measurements of ash deposit thickness were 
difficult to make. Along the coast ash deposits were between a few millimeters and a few tens of 
millimeters thick. On the W side of the 
caldera, ~ 1.5 km from the crater, 70 cm of ash deposits were measured at the same location 
where 40 cm of ash had fallen in April 2005, an 
increase of 30 cm in thickness. Closer to the crater, the thicknesses were not measured because 
they were greater than 1.5 m.

Field work revealed that on the edge of the caldera, ballistic blocks had fallen from the 
phreatomagmatic phase at the beginning of the 
eruption. Closer to the central crater the density of volcanic debris increased strongly. In an area 
covered by several tens of centimeters of 
ash, blocks impacted the ground leaving an amazing number of craters on the surface (figure 7). 
Distinctive tephra deposits, presumably related 
to lava fountains were identifiable everywhere around the central crater (figure 8). These juvenile 
deposits spread 500 m N from the central 
crater, whereas they extended only 100 m or less to the S. Products of this magmatic phase were 
clearly erupted or carried by wind to the N, and 
they must have ascended higher than 300 m, the depth of the Chahale pit crater. On 8 December 
2005 at about 1000 (15 days after the eruption), 
both seismic and explosive activity stopped.

Figure 7. Bomb impact craters on the N and E sides of Karthala's summit  convey a surprising 
intensity of ballistic bombardment. This picture 
was taken from the summit (E side of Chahale crater) looking to the N. Courtesy of Philippe Crozet.

Figure 8. An area around Karthalaâ??s summit was covered by tephra deposits. The approximately 
2-m high vegetation that remained after the 
eruption of April 2005 was reduced to about 1-m high in this later, though undated, photo. A 1-
m-thick layer of tephra was measured 700 m from 
the eruptive center. This picture was taken on the W part of the caldera looking NW. Courtesy of 
Francois Martel-Asselin.

Human impact. This eruption was more explosive and longer than the two preceding eruptions in 
spite of weaker seismicity, and a significant 
quantity of ash fell in water cisterns. According to OCHA, there were about 118,000 people living 
in 75 villages that were affected by the 
cistern contamination. Wind continued to raise large quantities of ash that again fell on the 
dwellings and into cisterns. In contrast to the 
April 2005 eruption, no coastal residents reported smelling sulfurous odors. After the end of the 
eruption, few long period earthquakes were 
recorded.

Background. The southernmost and largest of the two shield volcanoes forming Grand Comore 
Island (also known as Ngazidja Island), Karthala 
contains a 3 x 4 km summit caldera generated by repeated collapse. Elongated rift zones extend 
to the NNW and SE from the summit of the 
Hawaiian-style basaltic shield, which has an asymmetrical profile that is steeper to the south. The 
lower SE rift zone forms the Massif du 
Badjini, a peninsula at the SE tip of the island. Historical eruptions have modified the morphology 
of the compound, irregular summit caldera. 
More than twenty eruptions have been recorded since the 19th century from both summit and 
flank vents. Many lava flows have reached the sea on 
both sides of the island, including during many 19th-century eruptions from the summit caldera 
and vents on the northern and southern flanks. An 
1860 lava flow from the summit caldera traveled ~13 km to the NW, reaching the western coast 
north of the capital city of Moroni.

Information Contacts: Nicolas Villeneuve, Centre de Recherches dâ??Etudes Geographiques de 
lâ??Universite de La Reunion (CREGUR), Universite de La 
Reunion, BP 7151, 15 Avenue, Rene Cassin, 97715 Saint-Denis, Reunion, France (Email: 
Nicolas.Villeneuve@xxxxxxxxxxxxxxx); Anthony Finizola and 
Patrick Bachelery, Laboratoire des Sciences de la Terre de lâ??Universite de la Reunion (LSTUR), 
Universite de La Reunion, BP 7151, 15 Avenue, 
Rene Cassin, 97715 Saint-Denis, Reunion, France; Francois Sauvestre and Hamid Soule, Centre 
National de Documentation et de Recherche 
Scientifique (CNDRS), Place France, BP 169, Moroni, Republique Federale Islamique des Comores 
(Email: obs_karthala@xxxxxxxxxxx, cndrs@xxxxxxx; 
URL: http://volcano.ipgp.jussieu.fr:8080/karthala/stationkar.html); Karthala Volcano Observatory 
(KVO), Centre National de Documentation et de 
la Recherche Scientifique des Comores, BP 169, Moroni, Republique Federale Islamique des 
Comores.


Nyamuragira
Democratic Republic of Congo
1.408°S, 29.20°E; summit elev. 3,058 m
All times are local (= UTC + 2 hours)

Nyamuragira last erupted during May 2004; weak but steady ash emissions continued until 1 June 
2004, when satellite imagery indicated that the 
eruption had ceased (BGVN 29:05). The volcano, whose name is sometimes written as Nyamlagira 
and Nyamulagira, was the scene of several seismic 
swarms in middle and late 2005.

On 6 July 2005, the Goma Volcano Observatory (GVO) reported that a significant seismic crisis had 
occurred at Nyamuragira in late June 2005. The 
crisis consisted of swarms of mainly long-period earthquakes, which increased in number daily 
and peaked on 26 and 27 June. Most of the events 
occurred within a 10 km radius around Nyamuragiraâ??s summit caldera and were aligned 
roughly N-S. The depths of the earthquakes ranged from 0 to 
30 km, with two main areas of concentration; one between 15 and 25 km deep, and the other 
between 0 and 4 km. Based on precursory activity 
before previous historical eruptions at Nyamuragira, GVO reported that a new eruption might 
occur in the next 2-4 months. They stressed that an 
eruption would not threaten the city of Goma or other inhabited areas.

Beginning on 23 October 2005, GVO again recorded heightened seismic activity along the East 
African Rift and around the Virunga volcanoes when a 
swarm of long-period earthquakes occurred N of Nyamuragira. More than 140 events were 
recorded at a station 19 km E of the volcano. On 27 
October at 1500, another swarm of long-period earthquakes began beneath the same area. More 
than 300 events were recorded until at least 28 
October. At 2010 on that day, a M 4.5 tectonic earthquake occurred N of Lake Tanganika, followed 
by several aftershocks. The Alert Level for the 
nearby city of Goma remained at Yellow.

Background. Africaâ??s most active volcano, Nyamuragira is a massive high-potassium basaltic 
shield volcano that rises about 25 km N of Lake Kivu 
across the broad East African Rift Valley NW of Nyiragongo volcano. Nyamuragira, also known as 
Nyamulagira, has a volume of 500 km^3, and 
extensive lava flows from the volcano blanket 1,500 km^2 of the East African Rift. The broad low-
angle shield volcano contrasts dramatically 
with its steep-sided neighbor Nyiragongo. The 3,058-m-high summit of Nyamuragira is truncated 
by a small 2 x 2.3 km caldera that has walls up to 
about 100 m high. Historical eruptions have occurred within the summit caldera, frequently 
modifying the morphology of the caldera floor, as 
well as from the numerous fissures and cinder cones on the volcanoâ??s flanks. A lava lake in the 
summit crater, active since at least 1921, 
drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks 
more than 30 km from the summit, reaching 
as far as Lake Kivu.

Information Contacts: Baluku Bajope and Kasereka Mahinda, Observatoire Volcanologique de 
Goma, Departement de Geophysique, Centre de Recherche 
en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo (Email: ocha.volcan@xxxxxxx); Toulouse 
Volcanic Ash Advisory Center (VAAC), Meteo-France, 
42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (Email: vaac@xxxxxxxx; URL: http://
www.meteo.fr/aeroweb/info/vaac/); TOMS Volcanic 
Emissions Group, NASA Goddard Space Flight Center, Code 613.3, Greenbelt, MD 20771, USA 
(URL: http://skye.gsfc.nasa.gov/).


Nyiragongo
Democratic Republic of Congo
1.52°S, 29.25°E; summit elev. 3,470 m
All times are local (= UTC + 2 hours)

During May and June 2004, eruptions of Nyiragongo produced ash plumes that rose to a maximum 
of 6 km altitude (BGVN 29:06). According to the 
Toulouse VAAC, eruptions continued through July, producing plumes to a maximum of 5.5 km 
altitude. On 7 and 28 September 2004, short-lived 
plumes that may have contained ash were visible on satellite imagery. The Alert Level for the 
nearby city of Goma remained at Yellow.

An eruption on 3 November 2004 produced a thin W-drifting plume to 3.6-4.9 km altitude that 
was visible on satellite imagery. On 22 November a 
narrow SW-drifting plume was discerned on satellite imagery at 5 km altitude. A narrow plume was 
seen again on satellite imagery on 23 November 
at 1130, although no ash was identifiable.

The Goma Volcano Observatory (GVO) reported that during 10-17 November 2004 continuous 
volcanic tremor was recorded at all seismic stations 
around Nyiragongo. Visual observation on 12 and 13 November revealed that the lava lake surface 
had widened considerably, with strong lava 
fountains. Numerous Peleâ??s hair and scoriae were seen on the coneâ??s S, W, and N sides. A 
gas plume and incandescence were visible above the 
volcano. All fractures that opened during the 2002 eruption on the S flank had widened slightly 
and showed minor temperature increases.

During 18-29 November 2004, continuous banded tremor at high amplitudes occurred beneath 
the volcano, but the amplitudes seemed to be lower than 
during 9-18 November. Visual observations on 25-26 November revealed a slight decrease in the 
level of the lava lake, although strong lava 
fountains and a high flux of lava and gases continued. Peleâ??s hair, scoriae, a gas plume, and 
incandescence were still present. Measurements of 
the fractures on the slopes showed that they remained stable.

The Toulouse VAAC reported faint SO2 plumes from Nyiragongo visible on satellite imagery on 8 
and 10 December. During 29 November to 12 
December, volcanic activity remained at relatively high levels. Nearly continuous high-amplitude 
tremor was recorded at all seismic stations on 
the volcano. Observations of the crater area on 9 and 10 December revealed that the level of the 
lava lake remained stable compared to previous 
visits and that strong lava fountaining was present. Peleâ??s hair and scoriae fell in the area 
around the volcano, gas plumes rose above the 
volcano, and strong incandescence was visible at night.

In May 2005 a visiting group from Societe de Volcanologie Geneve (SVG) estimated that the lava 
lake was approximately 200 x 150 m across. They 
observed lava fountaining in the lake to tens of meters high (figure 9).

Figure 9. This photo presents Nyiragongo's  lava lake in a view from a point on the second 
platform, which lies ~250 m below the summit. The 
inner pit with the new lava lake formed after the 2002 lateral eruption.  The exact date when the 
photo was taken in January 2006 is unknown. 
Photo copyright Marc Caillet and provided courtesy of Pierre Vetsch, SVG.

On 7 September 2005, high-resolution satellite imagery showed a thin plume emitted from 
Nyiragongo. The plume was not confirmed by other data. 
Another thin plume visible on satellite imagery on 10 October; it was not confirmed by SO2 data.

As of 28 October 2005 Nyiragongo remained very active, but stable, with a large active lava lake in 
the crater. A gas plume was emitted and 
incandescence was visible at night from several tens of kilometers away. On 7 and 13 November 
thin plumes from Nyiragongo that may have 
contained some ash were observed on satellite imagery.

In January 2006 a group from Stromboli Online undertook an expedition to Nyiragongo and 
photographed the lava lake (figure 10).

Figure 10.This photo of Nyiragongo's lava lake was taken from the Belvedere (Bastion) on the 
crater's W rim. The lake is ~ 300 m wide and its 
surface sat ~585 m below the rim. The second platform cuts across the bottom foreground. The 
exact date when the photo was taken in January 2006 
is unknown.  Photo courtesy of  Marco Fulle.

Background. One of Africaâ??s most notable volcanoes, Nyiragongo contained a lava lake in its 
deep summit crater that was active for half a 
century before draining catastrophically through its outer flanks in 1977. In contrast to the low 
profile of its neighboring shield volcano, 
Nyamuragira, 3470-m-high Nyiragongo displays the steep slopes of a stratovolcano. Benches in 
the steep-walled, 1.2-km-wide summit crater mark 
levels of former lava lakes, which have been observed since the late-19th century. Two older 
stratovolcanoes, Baruta and Shaheru, are partially 
overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily 
along radial fissures south of Shaheru, east of 
the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by 
voluminous lava flows that extend long distances down 
the flanks of the volcano, which is characterized by the eruption of foiditic rocks. The extremely 
fluid 1977 lava flows caused many fatalities, 
as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: Goma Volcano Observatory (see Nyamuragira); Jurg Alean, Roberto Carniel, 
and Marco Fulle, Stromboli Online, Rheinstrasse 
6, CH-8193 Eglisau, Switzerland (URL: http://stromboli.net/; Email: jalean@xxxxxxxxxxxxx); Pierre 
Vetsch and Marc Caillet, Societe de 
Volcanologie Geneve (SVG), PO Box 6423, CH-1211 Geneva 6, Switzerland (URL: http://
www.volcan.ch/); Toulouse Volcanic Ash Advisory Center (see 
Nyamuragira).


Barren Island
Andaman Islands, India
12.278°N, 93.858°E; summit elev. 354 m

Activity continued at Barren Island since the volcanoâ??s latest eruption that began 28 May 2005 
(BGVN 30:05, 30:07, and 30:09). The MODVOLC 
Alerts Team web site has shown that the MODIS (moderate resolution imaging spectroradiometer) 
satellite recorded nearly daily thermal anomalies 
from 26 May 2005 (two days earlier than observed by other means). The thermal anomalies 
continued through 21 January 2006. In contrast, no 
thermal anomalies were recorded by satellites in the year prior to 26 May 2005.

D. Chandrasekharam of the Indian Institute of Technology and members of the Indian Coast Guard 
observed that since 4 November the volcano 
emitted large volumes of gas and ash emissions, and lava flows had reached the sea. 
Chandrasekharam stated that the early 2006 activity was more 
intense than when the eruption began in May 2005. The recent activity was preceded by about ten 
moderate earthquakes in the region, including M 
4.8 and 4.5 events on 3 November.

During 12-15 November 2005, ash plumes emitted from Barren Island were visible on satellite 
imagery drifting predominantly SSW, but they were no 
longer visible on 16 November. Ash plumes were visible on satellite imagery on 19 and 20 
December at a maximum height of ~ 3.7 km, and during 
21-23 December at a maximum height of 4.6 km. Satellite imagery showed a thin ash plume from 
Barren Island extending WNW during 5-7 January 2006.

Two earthquakes occurred in January 2006. On the 6th, an M 5.4 event struck 137 km E of Barren 
Island, and on the 21st, an M 5.6 event struck 
104 km NNW of the island.

To monitor the ongoing volcanism, a team from the Geological Survey of India, including M.M. 
Mukherjee, P.C. Bandopadhyay, Tapan Pal, and Sri 
Prasun Ghosh, approached aboard the Indian Coast Guard Ship C.S. GANGA DEVI during 12-13 
January 2006. The party sailed to within 0.8 km of 
Barren Island and studied the nature of the eruption from shipboard. The eruption resembled 
fireworks projecting different colors over the 
crater and on the slope of the cone. Dense clusters of incandescent pyroclasts of various sizes 
ejected forcefully from the crater mouth â??with 
ballistic trajectories.â?? Apart from eruption from the main crater, a â??glow of fireâ?? from the 
N flank of the cone and thin layers of red hot 
materials on W slope were observed. The Darwin VAAC reported that ash plumes from Barren 
Island during 26-27 January rose to ~ 3 km.

Background. 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 a volcano that rises from a depth of ~ 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 west, 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 center 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.

Information Contacts: D. Chandrasekharam, Indian Institute of Technology, Department of Earth 
Sciences, Bombay 400076, India (Email: 
dchandra@xxxxxxxxxx; URL: hhtp://www.geos.iitb.ac.in/dchandra); Dhanapati Haldar, Presidency 
College, Kolkata, 4/3K/2 Ho-Chi-Min Sarani, 
Shakuntala Park, Biren Roy Road (West), Kolkata-700 061, India (Email: haldar2115@xxxxxxxxxxx); 
Geological Survey of India, 27 Jawaharlal Nehru 
road, Kolkata 700 016, India (URL: http://www.gsi.gov.in/barren.htm); Indian Coast Guard, 
National Stadium Complex, New Delhi 110 001, India 
(URL: http://indiancoastguard.nic.in/indiancoastguard/); Darwin Volcanic Ash Advisory Center 
(URL: http://www.bom.gov.au/info/vaac/); MODVOLC 
Alerts Team, Hawaii Institute of Geophysics and Planetology (HIGP), University of Hawaii at Manoa, 
1680 East-West Road, Post 602, Honolulu, HI 
96822, USA (URL: http://modis.higp.hawaii.edu/).


Lamongan
Java, Indonesia
8.00°S, 113.342°E; summit elev. 1,651 m

Elevated seismicity occurred at Lamongan on 5-6 January 2005. From 1200 to 0700 on 5 January, 
22 events occurred with Modified Mercali Intensity 
(MMI) of 1. At each of three times (0331, 0447, and 0524) observers noted an event of MMI 3. 
During this period, instruments detected continuous 
tremor with an amplitude of 3 to 15 mm. On 5 January there were 282 local tectonic earthquakes 
and 53 volcanic A-type earthquakes. The volcano 
alert level was raised to 2.

On 6 January 2005, 107 volcanic A-type earthquakes were recorded. Local tectonic earthquakes 
over the two day period occurred 159 times, of 
which 10 of them were events had Modified Mercali Intensity (MMI) of 1-3.

Background: Lamongan, a small (1,631-m high) stratovolcano located between the massive 
Tengger and Iyang-Argapura volcanic complexes, is 
surrounded by numerous maars and cinder cones. The currently active cone has been constructed 
650 m to the SW of Gunung Tarub, the volcanoâ??s 
high point. As many as 27 maars with diameters from 150 to 700 m, some containing crater lakes, 
surround the volcano, along with about 60 cinder 
cones and spatter cones. Lake-filled maars, including Ranu Pakis, Ranu Klakah, and Ranu Bedali, 
are located on the eastern and western flanks; 
dry maars are predominately located on the northern flanks. None of the Lamongan maars has 
erupted during historical time, although several of 
the youthful maars cut drainage channels from Gunung Tarub. Lamongan was very active from the 
time of its first historical eruption in 1799 
through the end of the 19th century, producing frequent explosive eruptions and lava flows from 
vents on the western side of the volcano ranging 
from the summit to about 450 m elevation.

Information Contact: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, 
Northern Territory Regional Office, PO Box 40050, 
Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).


Lopevi
Vanuatu, SW Pacific
16.507°S, 168.346°E; summit elev. 1,413 m

An error occurred in the March 2005 issue of BGVN (30:03) in a table included in the article on 
Lopevi. The table had listed MODVOLC thermal 
anomalies, but it mistakenly included those for both Lopevi and Ambrym. The corrected table for 
Lopevi thermal anomalies only is provided here 
(table 1).

Table 1. MODVOLC thermal anomalies as observed from the MODIS satellite for Lopevi volcano for 
the period July 2003 to March 2005. The fourth 
column shows radiance in watts per square meter, per steradian, per micron (W m-2 sr-1 um-1) in 
MODIS band 21 (central wavelength of 3.959 um). 
Courtesy of the Hawaiâ??i Institute of Geophysics and Planetology.

     Date          Time (UTC)      Sensor       Spectral radiance

     28 Sep 2004     1410        Aqua MODIS           0.937
     28 Sep 2004     1410        Aqua MODIS           1.052
     30 Jan 2005     1130        Terra-MODIS          0.710
     05 Feb 2005     1355        Aqua MODIS           0.983
     05 Feb 2005     1355        Aqua MODIS           1.426

     No thermal anomalies were measured from June 2003 to March 2005.

Background. The small 7-km-wide conical island of Lopevi is one of Vanuatuâ??s most active 
volcanoes. A small summit crater containing a cinder 
cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger 
crater. The basaltic-to-andesitic volcano has been 
active during historical time at both summit and flank vents, primarily along a NW-SE-trending 
fissure that cuts across the island, producing 
moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 
1,413-m-high volcano date back to the mid-19th 
century. The island was evacuated following eruptions in 1939 and 1960. The latter eruption, from 
a NW-flank fissure vent, produced a 
pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western 
coast.

Information Contacts: MODVOLC Alerts Team, Hawaiâ??i Institute of Geophysics and Planetology 
(HIGP), University of Hawaii and Manoa, 168 East-West 
Road, Post 602, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Aoba
Vanuatu, SW Pacific
15.40°S, 167.83°E; summit elev. 1,496 m
All times are local (= UTC + 11 hours)

As previously reported, a new eruption at Aoba began 27 November 2005 in one of the crater 
lakes (Lake Voui). The eruption formed a cinder cone 
in the lake (figures 11 and 12) that contained a crater with a small hot lake (BGVN 30:11 and 
30:12).

Figure 11. A view of Aobaâ??s Lake Voui on 18 January 2006, showing the new island and its 
steaming internal lake. Courtesy Alain Bernard.

Figure 12. Steam rising from the lake on the island in the middle of Aobaâ??s Lake Voui, 18 
January 2006. Courtesy Alain Bernard.

On 31 January a high, dark ash plume caused ashfall in the S part of the island. Small eruptions 
continued in February.

Alain Bernard recently processed a 26 January 2006 nighttime ASTER (Advanced Spaceborne 
Thermal Emission and Reflection Radiometer) image. 
Figure 13 shows the ASTER product called AST_04 (TIRâ??thermal infrared radiometer, 8.12-11.65 
um wavelengthsâ??band 10) unprocessed image of Aoba 
with Lakes Voui and Lakua. The TIR bands, with a spatial resolution of 90 m, give the ability to 
detect small thermal anomalies (a few degrees 
C), perform thermal mapping, and monitor temporal variations in the lake surface temperature. As 
shown in figure 14, Lake Vouiâ??s temperature in 
early January 2006 dropped by ~ 10°C to a mean of 25.4°C (down from 35.7°C one month 
earlier). Temperature differences between Voui and Lakua 
dropped to 4.3°C, reaching almost to the background levels observed in July 2005 (see plot 
â??Temperature data from Lake Voui at Aoba, October 
1998-December 2005 . . .â??; BGVN 30:11). There is still a strong thermal anomaly of 46.1°C 
inside the new island (figure 13).

Figure 13. A thermal image of Aobaâ??s lakes Voui and Manaro Lakua (to the W and E, 
respectively) for 26 January 2006 at 1124 UTC (2224 local). 
The image results from the ASTER On-Demand L2 Brightness Temperature at the Sensor. This 
AST_04 product is the brightness temperature data as 
recorded by the satellite, not the temperature of the target at the ground level. To retrieve the 
actual surface temperature, one needs to 
correct for atmospheric effects (absorption of water vapor, etc.) that significantly alter the spectral 
radiance during the travel from the 
ground to the satellite. A new method for this correction, developed by Alain Bernard and called 
AST_SW (SW stands for "split window"), is 
explained on his ("multispectral") website. Courtesy of Alain Bernard.

Figure 14. A plot of computed temperatures from 1 October 2005 to 1 February 2006 for 
Aobaâ??s Lake Voui. The two different symbols distinguish 
processed MODIS and ASTER thermal data. A similar plot for an earlier period appeared in BGVN 
30:11. Courtesy of Alain Bernard.

As of 11 February 2006 at 1011 hours (10 February 2006 at 2311 UTC), Alain Bernard reported 
that Lakes Voui and Lakua temperatures were, 
respectively, 27.2°C and 23.2°C (delta T = 4°C). The maximum temperature for the mud pool 
was ~ 57°C.

Background. Aoba is a massive 2,500 km^3 basaltic shield volcano that is the most voluminous 
volcano of the New Hebrides archipelago. A 
pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an 
elongated form. A broad pyroclastic cone containing 
three crater lakes is located at the summit of the Hawaiian-style shield volcano within the 
youngest of at least two nested calderas, the 
largest of which is 6 km in diameter. Post-caldera explosive eruptions formed the summit craters 
of Lake Voui (also spelled Vui) and Lake Manaro 
Ngoru about 360 years ago. A tuff cone was constructed within Lake Voui about 60 years later. The 
latest known flank eruption, about 300 years 
ago, destroyed the population of the Nduindui area near the western coast.

Information Contacts: Alain Bernard, IAVCEI Commission on Volcanic Lakes, Universite Libre de 
Bruxelles (ULB), CP160/02, avenue F.D. Roosevelt 
50, Brussels, Belgium (Email: abernard@xxxxxxxxx; URL: http://www.ulb.ac.be/sciences/cvl/aoba/
Ambae1.html; 
http://www.ulb.ac.be/sciences/cvl/multispectral/multispectral2.htm); Esline Garaebiti, 
Department of Geology, Mines, and Water Resources 
(DGMWR), Port-Vila, Vanuatu (Email:esline@xxxxxxxxxxxxxx).


Galeras
Colombia
1.22°N, 77.37°W; summit elev. 4,276 m
All times are local (= UTC - 5 hours)

Galeras was last reported on in BGVN 30:09, covering the period from July 2004 to mid-October 
2005. During July through October 2004, eruptions 
generated ash and gas plumes that caused ashfall in surrounding areas. On 21 November 2004 
Galeras erupted explosively. During January - 
September 2005, low-level relatively shallow seismicity and small gas-and-ash emissions 
continued. Occasional steam plumes were visible from 
Pasto in October 2005. Seismicity fluctuated and some instrumentally measured deformation 
continued.

During the first week of November 2005, low-level seismicity included several tornillo earthquakes 
(long-period seismic events related to 
pressurized fluid flow at shallow depth). Small amounts of deformation were recorded at the 
volcano. During 9-14 November, a large number of 
tornillo earthquakes were reported by Instituto Colombiano de Geologia y Mineria (INGEOMINAS). 
The earthquakes were similar to those that 
occurred before eruptions in 1992-93. Activity during October suggested that the volume of 
magma beneath the volcano was greater than that 
inferred to have been present during the 1992-93 eruptions. Due to increased activity, the Alert 
Level was raised to 2 (probable eruption in 
days or weeks) on 14 November.

According to news reports, on 14 November local authorities recommended an evacuation of as 
many as 9,000 people living in towns near the 
volcano, including Pasto (to the E), La Florida (to the N), and Narino (to the N). Heightened 
seismicity continued during 16-22 November. 
According to news articles, only ~ 1,000 residents had actually left as of 18 November.

On 24 November at 0246 seismic signals indicated the beginning of an eruption. Ash fell in the 
towns of Fontibon, San Cayetano, Postobon, and in 
north Pasto. Around this time, INGEOMINAS raised the Alert Level to 1 (eruption imminent or 
occurring). The Washington VAAC observed a small 
puff of ash NE of the volcano at ~ 4.6 km altitude. Activity decreased by the next day, so the Alert 
Level was reduced to 2. Thousands of people 
had been evacuated during the week prior to the eruption.

Due to a decrease in activity, on 28 November INGEOMINAS reduced the Alert Level to 3. Low levels 
of seismicity and deformation were continuing. 
Although poor weather conditions obscured the volcano most of the time, steam and gas 
emissions were photographed on 2 December coming from 
several locations on the active cone, including the main crater. The plume rose 1 km above the 
summit on 3 December.

Through 12 December, seismicity indicated fluids moving within the volcano, small changes in 
deformation occurred, and gas rose to a height of ~ 
500 m. Based on information from the US Geological Survey, the Washington VAAC reported that a 
pilot observed an ash plume from Galeras on 23 
December at an altitude of ~ 7.3 km and drifting W.

During 23 December to 2 January 2006 there were emissions of gas and small amounts of ash. On 
23 December four ash plumes rose to ~ 3 km 
altitude and drifted to Consaca. A cluster of 33 volcano-tectonic earthquakes, reaching a 
maximum M 1.2, occurred beneath the volcanoâ??s crater 
during 29-30 December. The SO2 flux varied between 300 and 1,500 metric tons per day (t/d).

Gas emissions with small amounts of ash, and heightened seismicity, continued through 9 January. 
The SO2 flux at the volcano varied between 490 
and 1,500 t/d. A lava dome was visible in the main crater during an overflight on 13 January. 
Around this time, there was an increase in the 
amount of seismicity and deformation. The Washington VAAC reported that a pilot observed an 
ash plume on 23 December at an altitude of ~ 7.3 km 
and drifting W.

During 23 January to 6 February, the lava dome in the main crater continued to grow; seismicity 
associated with the movement of fluids 
continued, with an average of 200 small earthquakes per day, and slight deformation was 
recorded. SO2 flux of about 300 t/d was measured. Strong 
degassing occurred in several sectors of the active cone and around the lava dome. Steam rose to 
900 m above the volcano. During a field visit 
on 8 February, scientists found pyroclastic-flow deposits high on the SE flank.

The rate of seismicity the week of 13-20 February averaged 190 small earthquakes per day, while 
the SO2 flux was about 200 metric tons per day. 
Steam rose to ~ 1.1 km above the volcano on 19 February and incandescence was visible at parts 
of the lava dome. The volume of the dome in the 
main crater was approximately 1.5 times larger than when it was first observed on 13 January. 
Seismicity increased to an average of 280 small 
earthquakes per day during 20-27 February. SO2 flux also rose, to about 600 t/d. On 26 February 
a cluster of earthquakes included an M 4.8 
volcano-tectonic earthquake followed by 35 smaller earthquakes. Slight deformation was recorded 
at the volcano. Steam and gas rose to ~ 700 m 
above the volcano. Galeras remained at Alert Level 3 through February 2006.

Background. Galeras, a stratovolcano with a large breached caldera located immediately west of 
the city of Pasto, is one of Colombiaâ??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.

Information Contacts: Diego Gomez Martinez, Observatorio Vulcanologico y Sismologico de Pasto 
(OVSP), INGEOMINAS, Carrera 31, 1807 Parque 
Infantil, PO Box 1795, Pasto, Colombia (Email: dgomez@ ingeomin.gov.co; URL: http://
www.ingeomin.gov.co/pasto/; Email: ovp@xxxxxxxxxxxxxxx); 
Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/
SP23, NOAA Science Center Room 401, 5200 Auth 
Rd., Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/); El Pais (URL:http://elpais-
cali.terra.com.co/paisonline/).


Santa Ana
El Salvador
13.853°N, 89.630°W; summit elev. 2,381 m
All times are local (= UTC - 6 hours)

Previous comments regarding terminal phases of the 1 October 2005 eruption (BGVN 30:09) 
included: . "Following the eruption of 1 October, small 
explosions, degassing, and low-to-moderate seismicity occurred at Santa Ana during 5-11 
October . . .. During an aerial inspection of the 
volcano on 11 October, no changes were observed at the crater."

Carlos Pullinger (Servicio Nacional de Estudios Territoriales, SNET) later noted that "The 1 October 
eruption only lasted about 1 hour. After 
that we had some small activity, probably associated [with] degassing on Sunday evening [2 
October] and at about the same time the continuous 
rains produced the first of a series of lahars that affected the communities close to the shore of 
Coatepeque lake. During the rest of the week 
it was very difficult to know what was going on because of continuous rains and cloudy 
conditions."

Pullinger further noted that some eye witnesses said that they had observed a column on 2 
October. SNET registered strong and continuous tremor 
during approximately 1900-2400 (local time) on 2 October. Much of this activity coincided with 
rain-induced lahars. Over 300 mm of rain fell on 
the volcano that day. Using both witness reports and seismicity, SNET inferred that on 2 October 
the volcano possibly generated strong degassing 
or even geyser-type activity. However, there was no confirmation of ashfall deposits from these or 
other post-1 October events.
The same type of seismicity continued intermittently until 5 October, but with much less intensity 
than on 2 October.  SNET could not tell if 
there was any volcanic activity related to these events, or if it was mainly lahars.  After the 5th 
continuous tremor was not recorded.

Post-eruption behavior.  SNET reported that, in general, following Santa Anaâ??s 1 October 2005 
eruption, seismicity was relatively stable and 
there were generally low-level gas emissions (figure 15).

Figure 15. A graph showing Santa Anaâ??s SO2 flux (vertical bars) and average daily seismic 
amplitude (RSAM, solid line) during 15 August-31 
December 2005. The eruption of 1 October 2005 is indicated with an arrow. Courtesy of SNET.

Storms on 12 October 2005 caused lahars that traveled E towards Lake Coatepeque (see ASTER 
image of the region in BGVN 30:09). On 22 October, a 
lahar was reactivated in the Potrero Arriba area, NE of the volcano. During 22-25 October, the 
volcano was subjected to increased tremor and a 
slight increase in seismicity associated with gas emissions. On 28 October volcanic activity 
appeared to increase slightly and sulfur-dioxide 
emission rates during 28 and 29 October averaged 257 metric tons per day. The Alert Level within 
a 5-km radius around the volcanoâ??s central 
crater was at Red, the highest level.

During the month of November 2005 seismicity, volcanic activity, and gas emissions all remained 
for the most part at relatively low levels. 
There were slight increases on 13, 17, and 26 November; but the 17 November increase was 
attributed to noise from strong winds. On 26 November 
only slight changes were noted in the color of the lagoon in the craterâ??s interior, but gas 
emissions rose to ~ 300 m above the volcano. Small 
earthquakes occurred during November 2005, inferred to be associated with the fracturing of 
rocks and gas pulses. Sulfur-dioxide emissions were 
low during the first part of November, with 100 to 200 metric tons recorded daily, and during the 
latter part of November, with between 100 and 
~ 1,500 metric tons recorded daily.

During December 2005, seismicity was above background levels. Observations of Santa Anaâ??s 
crater on 28 December revealed that there were 
continuous emissions of steam and gas from the lagoon and fumaroles located within the crater 
(figure 16). Gas rose 200-500 m above the crater 
and drifted SW (figure 17). Small earthquakes occurred, but gas emissions rose to over ~ 2,500 
tons per day (figure 15). The Alert Level 
remained at Red, the highest level, within a 5-km radius around the volcanoâ??s summit crater.

Figure 16. A photo taken from the crater rim at Santa Ana showing steam and gas emissions from 
both the lagoon and fumaroles located within the 
crater. Courtesy of SNET.

Figure 17. A photo of Santa Ana showing the 28 December 2005 gas emission that rose 200-500 
m above the crater rim. Courtesy of SNET.

 From 30 December 2005 to early January 2006, seismic and steam emissions were moderate at 
Santa Ana. Seismicity was slightly above normal 
levels with small earthquakes occurring, which were interpreted as being associated with gas 
pulses. Low-level emissions of steam and gas from 
the lagoon and fumaroles within the crater remained the same as in December 2005. Gas rose 
200-500 m above the crater and drifted SW. The 
sulfur-dioxide flux ranged between 180 and 1,476 metric tons per day. The Alert Level remained 
at Red, the highest level, within a 5-km radius 
around the volcanoâ??s summit crater.

Background. Santa Ana, El Salvadorâ??s highest volcano, is a massive, 2,381-m-high andesitic-
to-basaltic stratovolcano that rises immediately W of 
Coatepeque caldera. Collapse of the volcano during the late Pleistocene produced a voluminous 
debris avalanche that swept into the Pacific 
Ocean, forming the Acajutla Peninsula. Reconstruction of the volcano subsequently filled most of 
the collapse scarp. The broad summit of the 
volcano is cut by several crescentic craters, and a series of parasitic vents and cones have formed 
along a 20-km-long fissure system that 
extends from near the town of Chalchuapa NNW of the volcano to the San Marcelino and Cerro la 
Olla cinder cones on the SE flank. Historical 
activity, largely consisting of small-to-moderate explosive eruptions from both summit and flank 
vents, has been documented since the 16th 
century. The San Marcelino cinder cone on the SE flank produced a lava flow in 1722 that traveled 
13 km to the E.

Information Contacts: Servicio Nacional de Estudios Territoriales (SNET), Alameda Roosevelt y 55 
Avenida Norte, Edificio Torre El Salvador, 
Quinta Planta, San Salvador, El Salvador (URL: http://www.snet.gob.sv/)


Augustine
southwestern Alaska, United States
59.363°N, 153.43°W; summit elev. 1,252 m
All times are local (= UTC - 9 hours)

Following a period of increased seismicity at Augustine that began in May 2005, discrete seismic 
events on 9 and 11 December may have perturbed 
the hydrothermal system, initiating small steam explosions. On 12 December, a plume extended 
75 km SE of the volcano, and its S and E flanks 
were dusted with ash (likely non-juvenile). Additional steam explosions took place later in the 
month, and the smell of sulfur was reported by 
residents in villages on the E side of Cook Inlet.  The first major eruptions at Augustine occurred 
on 11 January 2006, when two discrete 
explosions produced an ash cloud that reached 9 km altitude (BGVN 30:12) and the Concern Color 
Code was raised to Red. Further eruptions 
occurred on 13, 14, and 17 January. After the eruption at 0758 on 17 January, seismicity 
diminished significantly and AVO lowered the color code 
from Red to Orange late on 18 January.

By the morning of 19 January seismicity remained fixed at lower levels; it decreased further on 20 
January but was still above background. 
Periods of quiescence and low seismicity in the intervals between eruptive events are not unusual 
at Augustine, having occurred during the 1976 
and 1986 eruptive episodes. During 23-26 January, satellite observations indicated the persistence 
of faint thermal anomalies and steaming 
continued at the summit.

Occasional intervals of increased seismicity were observed for the next few days. On 27 January 
2006 an explosive eruption began at about 2000 
and lasted for 9 minutes. AVO raised the color code from Orange to Red. According to the National 
Weather Service (NWS), an ash cloud reached a 
maximum altitude of around 9 km and drifted SE. Augustine erupted again at 2337 on 27 January 
2006. This event lasted 1 minute and no ash was 
detected above 3 km. A third eruption occurred at 0204 on 28 January 2006 and lasted 2 minutes. 
Ash drifted SE at an altitude of about 8 km 
according to NWS. A fourth eruption occurred at 0742 on 28 January and lasted 3 minutes; the ash 
cloud drifted SE at a maximum altitude of 7.5 km.

Another explosive event began at 1430 on 28 January. Seismic activity continued and continuous 
ash emission was observed in AVO web camera 
images. NWS reported ash to 9 km altitude travelling SSW. Following this explosion, Augustine was 
in a state of continuous eruption accompanied 
by persistent ash emission until around 3 February.

Overflight observations on 29 January suggested that pyroclastic flows were being produced. NWS 
radar indicated that ash clouds from events at 
1117 on 29 January, and 0325 and 0621 on 30 January, rose to 7.5 km altitude. Other than during 
these three events an ash-rich plume rose to 
about 4 km altitude. On 30 January, Alaska Airlines canceled all flights into and out of Anchorage 
because of the potential danger of ash. 
Flights resumed on 31 January.

On 1 February AVO lowered the Concern Color Code from Red to Orange. Although seismic data 
indicated sustained eruptive activity, ash clouds to 
altitudes greater than 4.5 km altitude had not been observed on NWS radar since 0621 on 30 
January. Low-level explosions, pyroclastic flows, and 
production of ash continued (figure 18).

Figure 18. A satellite image showing the Augustine eruption on 2 February 2006. On that day the 
Alaska Volcano Observatory reported a continuous 
ash plume accompanied by low-level explosions and pyroclastic flows of hot ash and rock 
fragments. This image was taken by the Moderate 
Resolution Imaging Spectroradiometer (MODIS) onboard the Terra satellite. Augustine is partially 
outlined in this image, indicating a ground 
surface much hotter than its surroundings; the volcanoâ??s ash plume is pale gray-beige, barely 
darker than the nearby weather clouds. However, 
the weather clouds can be discerned from the ash by their distinct dot-like pattern. NASA image 
courtesy Jeff Schmaltz, MODIS Rapid Response 
Team at NASA GSFC.

By 3 February seismic data indicated that low-level explosions, block-and-ash-flows, and 
sustained production of ash were continuing 
intermittently and had changed little in character or intensity since 1 February. Seismicity dropped 
significantly on the evening of 3 February. 
Observers on an overflight on 3 February saw a steam-rich, ash-poor plume emerge from the 
cloud tops and reach no higher than 2 km altitude. NWS 
reported no ash in satellite or radar data.

Observations by AVO scientists during visits on 8 February, as well as satellite and seismic data 
and other remote observations, indicated that 
a lava dome was present at the summit. Streams of gas, ash, and incandescent blocks were 
observed descending the upper NE flank on the evening 
of 7 February and early on the 8th, indicating that small-volume collapses of the lava dome were 
occurring and that the dome was actively 
growing. Seismicity remained at low levels, though still above background. Low-level ash plumes 
and occasional pyroclastic flows on the flanks 
continued. A persistent thermal signal was observed in satellite data. Incandescence was visible 
from Homer.

On 11 February, seismic data indicated that the new lava dome at Augustineâ??s summit 
continued to grow. Seismic stations on the flanks of the 
volcano recorded rockfalls and pyroclastic flows associated with small-volume collapses of the lava 
dome. A plume composed of gas, steam, and 
small amounts of ash continued to be emitted from the summit, and low-level, dilute ash clouds 
were likely present in the vicinity of the volcano.

Just before midnight on 12-13 February a low-light camera operated by the University of Alaska 
Fairbanks captured a small hot avalanche down the 
north flank of the volcano. The event was also recorded on AVOâ??s pressure sensor on 
Augustine Island. A light dusting of new ash on the E flank 
of the volcano may have been related to this avalanche event. Satellite data on 13 February showed 
a persistent thermal anomaly at the volcanoâ??s 
summit. Together, these data suggested that the lava dome continued to grow and underwent 
occasional, minor collapse events.

On 16 February, clear satellite views showed a strong thermal anomaly in the summit crater area. 
Seismometers continued to record rockfalls and 
small pyroclastic-flow signals indicative of occasional, minor collapses of the lava dome. Over 10-
16 February, the number of these events 
declined steadily, suggesting that the rate of lava effusion was slowing. An observation flight on 
16 February obtained good views of the 
summit: a new, steaming, blocky lava dome occupied the summit crater. The dome filled much of 
the crater and extended as a rubbly tongue 500-800 
m down the upper N flank. Dark aprons of collapse debris, including large steaming blocks, extend 
downslope to the N. The rim of the summit 
crater was largely snow-free and mantled by thick, coarse, pyroclastic deposits, likely from the 
explosive events in January. The dome resulted 
from the largely non-explosive extrusion of degassed lava following the cessation of explosive 
activity on January 30.

By the end of this report period (22 February) unrest was continuing. Seismicity remained above 
background levels. Rockfalls and avalanches from 
the lava dome continued but appeared to be declining in frequency. Satellite images continued to 
show a persistent thermal anomaly. A plume 
composed of variable amounts of gas, steam, and small amounts of ash likely continued 
intermittently from Augustineâ??s summit. Dome building 
eruptive activity may continue intermittently over the next several months.

Aviation hazard. Tina Neal (USGS-AVO) provided some thought-provoking insights into 
Augustineâ??s aviation-ash issues. The following quote with 
minor modification is information she sent in a 14 February email message to the Volcanicclouds 
listserve, some follow up messages, and a review.

â??Volcanologists often rely upon pilot observations to provide the all-important visual 
confirmation and description of distant volcanic events. 
What we need to remember, however, is that it is quite difficult to get more than snippets of 
information in a PIREP [aviation pilot report]: 
Pilots and controllers are often extremely busy and controllers cannot ask more than very basic 
follow up questions. Air traffic communication 
protocols put a premium on succinct transmissions. I was lucky enough recently to hear this play 
out in real time during an Augustine eruption 
when I happened to be visiting the Anchorage Air Traffic Control facility and was allowed to plug in 
to monitor the sector around Augustine. 
While we should continue to encourage full and detailed PIREPs following the VAR [Volcanic Activity 
Report] format, we should not be terribly 
surprised when the return is not very complete. Similarly, follow up communications directly with 
the pilot, possible in some cases, are 
difficult and not the highest priority of Observatory staff.

â??Thus far for the Augustine eruption, we do have documentation of impacts from the ash 
clouds and the distal fine ash and SO2 cloud from 
explosive events, largely taken from PIREPS passed to AVO by the FAA and the National Weather 
Service. In addition to these instances below, 
flight routes were moved in anticipation of possible ash cloud motion following several explosions, 
and flight cancellations did occur.

â??[1.] On 14 January a jet aircraft about [80 km E] of Yakutat at FL310 [9.4 km altitude, at 59 
deg. 30.65 min. N, 139 deg. 8.89 min. W; ~800 km 
from Augustine] skimmed through the top of the â??brownâ?? cloud for about 10 minutes and 
reported smelling a â??dirty, musty odor.â?? The pilot climbed 
to FL330 and deviated to the NE around the cloud. [The plane was out of service for two days.] 
Borescope inspection upon landing showed no 
damage and no ash accumulation.[Later anaysis suggested the ash cloud encountered may have 
been a combination of 5 separate drifting ash clouds 
from 5 separate discrete events during 13-14 January.]
  	â??[2.] On the same day, another jet near the same location saw a brown haze layer about 
2000 feet [610 m] thick and made a climbing turn to 
avoid it.

â??[3. On] 31 January [there were reports of a] light sulfur smell from several aircraft over 
Anchorage.

â??[4.] AVO received the followings email account about a possible encounter between a Cessna 
Cherokee and a distant ash cloud from Augustine on 
30 January (we have yet to follow up for any further information and verification).

â??I am traveling in the Bristol Bay Area and was in Togiak last night. Last night I started 
coughing and sneezing and on the flight to Dillingham 
this morning the pilot and I noticed volcanic ash in the air from ground level and according to the 
pilot up to 7,000 feet [2.1 km altitude]. 
The ash is very fine but is sticking to the wind screen of the aircraft. Along with the ash my eyes 
were stinging and I noticed a little burning 
in my nose. As we approached the Dillingham area and got out of the mountains the air quickly 
cleared. At this time it seems to only be in the 
mountains and according to the pilots in different places all the way to King Salmon. I do not know 
if you have received these reports yet.â??

In addition, Volcaniclouds discussions included this message from Ken Dean (Geophysical 
Institute-AVO). It provided some further discussion and 
references on past eruption-cloud behavior from Mt. Cleveland (1,250 km SW of Augustine).

â??. . . there was an incident on 22 February 2001 attributed to a volcanic cloud from the 
eruption of Cleveland Volcano on 19 Feb. 2001. A PIREP 
from a B747 near San Francisco [California] reported a strong (sulfur) smell and particles in the 
cabin. At first we thought this was an 
erroneous report since it was so far from the eruption and satellite date did not show anything in 
the region of the aircraft. However, when we 
ran the Puff dispersion model using re-analysis data, the simulated volcanic cloud encountered the 
aircraft at the time of the PIREP. This was a 
match in space, time and altitude. Note: Puff runs using predicted data were somewhat ambiguous 
regarding this encounter but the re-analysis 
data were much more definitive.â??

References: Dean, K.G., Dehn, J., Papp, K.R., Smith, S., Izbekov, P., Peterson, R., Kearney, C., and 
Steffke, A., 2004, Integrated satellite 
observations of the 2001 eruption of Mt. Cleveland:  Alaska, J. Vol. Geophys. Res., v. 135, p. 63, 
doi10.1016/j.jvolgeores.2003.12.013.

Simpson, J.J., Hufford, G.L., Pieri, D., Servranckx, R., Berg, J.S., and Bauer, C., 2002, The February 
2001 Eruption of Mount Cleveland, Alaska: 
Case Study of an Aviation Hazard:  Weather and Forecasting, v. 17, p. 691-704.

Background. Augustine volcano, rising above Kamishak Bay in the southern Cook Inlet about 290 
km SW of Anchorage, is the most active volcano of 
the eastern Aleutian arc. It consists of a complex of overlapping summit lava domes surrounded by 
an apron of volcaniclastic debris that 
descends to the sea on all sides. Few lava flows are exposed; the flanks consist mainly of debris-
avalanche and pyroclastic-flow deposits formed 
by repeated collapse and regrowth of the volcanoâ??s summit. The latest episode of edifice 
collapse occurred during Augustineâ??s largest historical 
eruption in 1883; subsequent dome growth has restored the volcano to a height comparable to 
that prior to 1883. The oldest dated volcanic rocks 
on Augustine are more than 40,000 years old. At least 11 large debris avalanches have reached the 
sea during the past 1,800-2,000 years, and 
five major pumiceous tephras have been erupted during this interval. Historical eruptions have 
typically consisted of explosive activity with 
emplacement of pumiceous pyroclastic-flow deposits followed by lava dome extrusion with 
associated block-and-ash flows.

Information Contacts: Anchorage VAAC, Alaska Aviation Weather Unit, National Weather Service, 
6930 Sand Lake Road, Anchorage, AK 99502, USA 
(URL: http://aawu.arh.noaa.gov/vaac.php); Alaska Volcano Observatory (AVO), a cooperative 
program of the U.S. Geological Survey, 4200 University 
Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), Geophysical Institute, 
University of Alaska, PO Box 757320, Fairbanks, 
AK 99775-7320, USA, and Alaska Division of Geological & Geophysical Surveys, 794 University 
Ave., Suite 200, Fairbanks, AK 99709, USA; Jesse 
Allen, NASA Earth Observatory; Tina Neal, U.S. Geological Survey-Alaska Volcano Observatory; Ken 
Dean and Pavel E. Izbekov, Geophysical 
Institute, University of Alaska.


Cleveland
Aleutian Islands, United States
52.825°N, 169.944°W; summit elev. 1,730 m
All times are local (= UTC - 9 hours)

According to the Alaska Volcano Observatory (AVO), Mount Cleveland, a volcano on an uninhabited 
island in the central Aleutian chain, erupted at 
0757 on 6 February 2006, sending a cloud of ash to 6.7 km (22,000 ft) altitude. Officials at AVO 
issued a Code Red warning for the volcano 
because the ash cloud was near a level where it could interfere with jet traffic, said Chris 
Waythomas, a U.S. Geological Survey geologist. 
There were no reports of falling ash. The nearest community is Nikolski, a tiny Aleut village of 31 
people 73 km E of the volcano.

Clevelandâ??s last major eruptive period was in March 2001 when three explosions occurred and 
the volcano produced significant ash plumes (BGVN 
26:04). Discussion of that episode was renewed briefly at the end of the Augustine report in this 
issue (BGVN 31:01). That discussion (and cited 
references) noted that the ash cloud from a Cleveland eruption on 19 February 2001 had a 
modeled path that carried the cloud S, passing over 
Northern California. Two days after the eruption, aviators flying near San Francisco, California, 
smelled sulfurous gases, presumably from the 
Cleveland eruption. There were also minor ash emissions from July to October 2005 (BGVN 30:09).

AVO downgraded the level of concern color code for Cleveland from Red to Orange on 7 February 
2006 at 1655 hours. No new ash emissions or 
thermal anomalies have been detected in clear to partly cloudy satellite views from the morning of 
8 February. AVO noted that Cleveland does not 
have a real-time seismic network and therefore it is unable to monitor seismic changes.

Background. Beautifully symmetrical Mount 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 Mount 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 Mount 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 Cleveland (Miller 
et al., 1998). In 1944 Cleveland produced the 
only known fatality from an Aleutian eruption. Recent eruptions from Mount Cleveland have been 
characterized by short-lived explosive ash 
emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Information Contacts: Alaska Volcano Observatory (see Augustine), Washington Volcanic Ash 
Advisory Center (VAAC), Satellite Analysis Branch 
(SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd., Camp Springs, MD 
20746, USA (URL: http://www.ssd.noaa.gov/).


Tanaga
Aleutian Islands, United States
51.885°N, 178.146°W; summit elev. 1,806 m

The Alaska Volcano Observatory (AVO) detected an increase in seismic activity beneath Tanaga 
beginning on 1 October 2005, with 15-68 earthquakes 
occurring daily. Previously, less than one earthquake had occurred per month since the seismic 
network was installed in 2003. The earthquakes 
were centered roughly 2 km NE of the summit at depths of 10-20 km below sea level. The largest 
event was M 1.7, with most earthquakes at M 
0.5-1.5. Tanaga was at Concern Color Code Green on 5 October.

During 5-7 October, there was a marked increase in the rate of seismicity. The located 
earthquakes ranged in magnitude from 0.5 to 1.9 and 
ranged in depth from 6 to 12 km beneath the summit. In response, AVO raised the Concern Color 
Code to Yellow on 7 October. AVO reported that 
while the seismic activity represented a significant increase in rate, the size, depth, and character 
of the events were not indicative of 
imminent eruptive activity.

Elevated seismic activity below the young vents continued through 28 October 2005, although the 
rate of small earthquakes decreased slightly 
from the previous week. The activity that began on 1 October was at the highest level recorded 
since the seismic network was installed in 2003, 
so the Concern Color Code remained at Yellow. An unusual seismic signal on 17 October that 
persisted for several minutes may have been a 
landslide or small phreatic explosion, but satellite images detected no airborne ash. Beginning on 
24 October, AVO observed weak, nearly 
continuous volcanic tremor in the vicinity of Takawangha volcano of the Tanaga volcano cluster. 
This was the first recorded tremor of this type. 
The daily number of small earthquakes continued to diminish from its peak in early October, but 
stayed above background levels.

AVO reported on 25 November 2005 that for several weeks seismicity beneath young volcanic 
vents on Tanaga Island decreased significantly from 
levels recorded in early October. Satellite images showed no anomalous temperatures or evidence 
of ash emissions. AVO reported that, based on 
the decrease in earthquake counts and frequency of tremor episodes, the likelihood of an eruption 
had diminished. Therefore, AVO downgraded the 
Concern Color Code to Green. According to AVO, the most recent eruptive activity at Tanaga was a 
lava flow observed in 1914.

Background. Tanaga volcano, the second largest volcanic center of the central Aleutians, is the 
central and highest of three youthful 
stratovolcanoes oriented along a roughly E-W line at the NW tip of Tanaga Island. Arcuate ridges to 
the east and south may represent the rim of 
an older caldera that cuts an older shield-like volcano. Most Holocene eruptions originated from 
Tanaga volcano itself, which consists of two 
large cones, the western of which is the highest, constructed within a caldera whose 400-m-high 
rim is prominent to the SE. At the westernmost 
end of the Tanaga complex is conical Sakaja, a 1,304-m-high double cone that may be the 
youngest of the three volcanoes (Marsh, in Wood and 
Kienle, 1990). A thick blanket of fine ash that may have accumulated over the past several 
thousand years covers much of Tanaga Island.

Information Contacts: Alaska Volcano Observatory (see Augustine).


http://www.volcano.si.edu/

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