Bulletin of the Global Volcanism Network, April 2006

[Kristi Diller <Kristi.Diller@xxxxxxx>]

*****************************************************
Bulletin of the Global Volcanism Network, April 2006
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From: Ed Venzke <venzkee@xxxxxx>


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

Bulletin of the Global Volcanism Network
Volume 31, Number 4, April 2006

Augustine (Alaska) Dome building eruptions continuing through late March 
2006 and later
Santa Maria (Guatemala) During October 2005 to January 2006, occasional 
ash plumes
Masaya (Nicaragua) Intermittent ash eruptions November 2003-March 2005; 
continuing incandescence
Sangay (Ecuador) Some conspicuous plumes during 2004-2005; climbers 
photos from January 2006
Lascar (Chile) Five-day eruption sequence in April 2006; plume seen 220 
km away
Michael (S Sandwich Isl.) Lack of new thermal signals suggesting any 
eruption since October 2005
Soputan (Indonesia) Late 2005 phreatic and Strombolian eruptions; ash 
plume to ~ 5.8 km altitude
Bulusan (Philippines) Eruptions and earthquakes in March and April 2006 
after years of little activity
Kilauea (Hawaii) Maps of past years surface lava flows and photos of 
lava entering the sea
Karymsky (Kamchatka) During April 2006, emerging ash plumes remained 
visible for up to 145 km
Bezymianny (Kamchatka) Pyroclastic flows on 9 May extend 7-8 km; plumes 
over 500 km long


Editors: Rick Wunderman, Catherine Galley, Edward Venzke, and Gari Mayberry
Volunteer Staff: Veronica Bemis, Jerry Hudis, Zahra Harji, Jackuelyn 
Gluck, Robert Andrews, and Stephen Bentley



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

Although the previous report (BGVN 31:01) noted Augustines events 
through 22 February 2006, this one overlaps and further discusses some 
aspects of behavior during late January through 1 February 2006. This 
report then continues with summaries of Alaska Volcano Observatory (AVO) 
reports during 24 February to 26 March 2006.

After eight months of increasing seismicity, gas-and-steam emissions, 
and phreatic eruptions in December 2005, Augustine began magmatic 
eruptions on 11 January 2006 (BGVN 30:12). Eruptions continued 
throughout January, producing ash clouds up to ~ 9 km altitude. The 
eruption was described by Jon Dehn (University of Alaska Fairbanks, 
personal communication) as occurring in the following three phases: I) 
11-28 January; II) 29 January-4 February; and III) 5 February and into 
at least late March.

During 11 January to 21 March 2006 (70 days), the Anchorage Volcanic Ash 
Advisory Center (VAAC) issued text reports (Volcanic Activity 
Advisories) on Augustine 567 times (averaging 8.1 reports per day). 
These alerted the aviation community to the ongoing airborne-ash hazards.

Augustine lies ~ 277 km SW of Anchorages airport, a key hub for flights 
across the North Pacific. According to the US Department of 
Transportation, during 2003 Anchorages airport supported the largest 
tonnage of any in the US, and functioned as the 8th busiest in the US by 
value of shipments. Augustines eruptions can potentially impact 
aviation and operations at the airport, and more generally, they 
complicate North Pacific air travel.

Plumes, 28 January-1 February. AIRS SO2 retrievals for Augustine plumes 
on 28 and 29 January were provided by Fred Prata (figure 1). He 
commented that the SO2 "blobs" seem to spread out rather than elongate 
into a plume shape, possibly because of calm winds or intermittent 
ejections.

Figure 1. Atmospheric SO2 from the AIRS instrument for Augustine plumes 
on 28 and 29 January 2006. Details of the processing and resulting 
analysis are included on the four panels, which correspond to these 
dates and times (UTC): a) 12:11:25 on 28 January, b) 21:47:25 on 28 
January, c) 23:29:25 on 28 January, and d) 12:53:25 on 29 January. All 
images provided courtesy of Fred Prata (Norwegian Institute for Air 
Research).

Shortly after the 28-29 January plumes mentioned above, on 30 January, 
an overflight by AVO confirmed a ~ 5-km-tall volcanic cloud and small 
explosions and associated pyroclastic flows. The airborne observations 
indicated that a considerable amount of ash was being produced during 
this time period from small explosions and associated pyroclastic flows. 
Figures 2 and 3 show images from 30 January. AVO also presented 31 
January thermal infrared images similarly indicative of vigorous 
eruptions and fresh pyroclastic flows (figure 4).

Figure 2. Aerial view of Augustine during an eruption on 30 January 
2006. The volcano was shrouded in ash cloud. The plume blew NE. Courtesy 
of Pavel Izbekov, AVO/UAF-GI.

Figure 3. A MODIS satellite image for 30 January at 12:30:00 showing an 
Augustine ash and steam plume. This image was collected at approximately 
the same time as an AVO overflight, and shows the volcanic cloud moving 
NE at ~ 4.8 km altitude. Processing and interpretation courtesy of Dave 
Schneider, USGS-AVO. Image courtesy of MODIS Rapid Response Project at 
NASA/GSFC.

Figure 4. Two 31 January 2006 (at 22:50:44 AST; 1 February 2006 UTC) 
night-time ASTER thermal infrared (TIR) images showing hot pyroclastic 
flow deposits on Augustines N flank. The image on the left also shows a 
broad ash and SO2 plume extending ENE. Image processing and 
interpretation courtesy of Rick Wessels (AVO-USGS); ASTER data courtesy 
of NASA/GSFC/METI/ERSDAC/JAROS, and US/Japan ASTER Science Team.

Rene Servranckx looked at several images from 1 February 2006 and sent 
associated messages and links to the Volcanicclouds listserv. He found a 
hotspot at Augustine and identified various cloud features from plumes. 
Using a NOAA-12 IR image taken at 1542 UTC, Servranckx could not detect 
an ash signature in the split window.

On 4 February, Ken Dean (UAF) posted a message on the Volcanicclouds 
listserv discussing Augustine for 28 January-1 February. He noted that, 
regarding SO2 detection in northern Alaska, they had been monitoring the 
atmospheric transport direction using Puff, a modeling routine for 
predicting the atmospheric dispersal of ash clouds. Generally speaking, 
trajectories were to the N and over Fairbanks. Accordingly, lidar 
systems at both the UAFs Geophysical Institute and ~ 50 km N of 
Fairbanks at the Poker Flat Rocket Range were turned on to see if they 
could detect volcanic aerosols from the eruption. Lidar uses laser 
energy to probe the atmosphere, where it can detect suspended material 
such as volcanic aerosols in identifiable regions. Preliminary results 
indicated volcanic aerosols at 4.6-6.6 km altitude in the atmosphere 
above both Fairbanks and Poker Flats. There could also have been 
volcanic aerosols at lower altitudes in the weather clouds.

Dean also noted that ground-based event-monitoring collectors set out by 
Cathy Cahill (UAF) sampled volcanic aerosols and possible traces of ash 
at Fairbanks. He noted that these observations and trajectories were 
consistent with Pratas SO2 observations and Servranckxs back trajectories.

24 February-26 March 2006. On 24 February, AVO noted repeated and 
ongoing unrest during the past week. This included relatively low but 
above-background seismicity that indicated small, intermittent rockfalls 
and avalanches from the lava dome. Satellites detected a persisting 
thermal anomaly in the summit area. These data, along with a 20 February 
visit to the island, indicated continued slow growth at the summit lava 
dome. A veil of fresh, light ash dressed Augustines flanks. The ongoing 
AVO reports into March noted similar processes and observations, and 
soon included mention of ash plumes, a lava flow, and a pyroclastic flow.

An overflight of the volcano on 1 March revealed a short, stubby lava 
flow that extended NE from the dome, terminating at ~ 1 km elevation. 
AVO noted a small dilute ash plume as well as a 20-minute interval of 
elevated seismicity at 1010 on 5 March, interpreted as a small explosion 
with associated ash emission, although low clouds obscured web-camera 
views. On 6 March AVO reported seismic signals and the low-light camera 
in Homer suggested rockfalls and avalanches. Although Augustines plumes 
in this time frame were generally characterized as local, dilute, and 
under ~ 1 km above the summit, pyroclastic flows were also seen on 6 March.

Early on the morning of 8 March, AVOs seismometers began recording 
periods of discrete, repetitive, small events. These signals were taken 
to indicate ongoing dome growth, observations consistent with those from 
web cameras, which revealed minor ash emissions and mass wasting. 
Reports on 8 and 9 March discussed seismicity sufficiently elevated as 
to sometimes saturate several instruments. In addition, cameras 
portrayed two areas of high thermal flux. AVO initially interpreted 
these observations as including elevated rates of lava extruding into 
the dome, possibly with vigorous lava movement, and block-and-ash flows.

Later reports disclosed further details from around 9 March. AVOs 8-10 
March reports noted that the summit was steaming more vigorously than 
the previous 3-4 weeks. A brownish-orange plume rose from the top of the 
summit lava dome. Fumaroles on the S and W side of the dome were the 
source of the most vigorous steaming. Areas of bare ground on the upper 
W and S flanks had substantially enlarged since 1 March. The greatest 
amounts of steam came from bare areas on the upper NW flank. Web-camera 
images and observations from overflights on 8 and 9 March indicated 
regular small-scale collapses of the summit lava dome. Usually these 
collapse events produce block-and-ash flows and small diffuse ash 
clouds. Block-and-ash flows to the E to NE sectors extended to within 
about 1 km of the coastline. Dilute ash clouds were observed rising from 
the block-and-ash flows to about the level of the summit and drifting 
away with the wind.

10 March seismicity included prolonged volcanic tremor and an increase 
in the frequency of small volcano-tectonic earthquakes. Block-and-ash 
flows, rock avalanches, and rockfalls originating from the summit lava 
dome continue to be recorded by the seismic network, particularly at the 
E flank station.

The 10 March report stated that Satellite and low-light camera images 
obtained intermittently throughout the week show that thermal anomalies 
in the summit area and on the upper NE flank persist. On several 
evenings this past week, a low-light camera at the AVO site in Homer 
captured hot avalanches in progress and prolonged periods of 
incandescence. AVO also received several reports from observers in Homer 
and Nanwalek of summit glow in the evening hours. Airborne measurements 
of gas emissions made on March 9 indicate both SO2 and CO2 gas in the 
plume. This is the first time since the fall of 2005 that CO2 has been a 
component of the gas plume and likely indicates the presence of new 
magma entering the volcanic system.

The AVO report for 17 March chronicled low-level eruptive activity. It 
said that the past weeks seismicity changed from periods of prolonged 
tremor and closely spaced discreet events to episodic short-duration 
events. Observers interpreted the change as indicating that steady 
effusion of lava and dome growth had given way to slower effusion of 
lava and intermittent block-and-ash flows, rock avalanches, and 
rock-falls from the summit lava dome. On several evenings during the 
week, clear atmospheric conditions enabled low-light cameras at the AVO 
site in Homer to capture hot avalanches and prolonged periods of 
incandescence in both the summit area and on the upper NE flank. 
Satellite images also showed thermal anomalies.

The 17 March report said that overflights indicated two lava flows were 
seen on the N and NE flanks. They advanced slowly. Occasional collapses 
of the lava flow fronts shed hot blocks and produce minor ash emissions. 
Estimates using photographs indicated that the new lava dome stood ~ 70 
m higher than the one formed in 1986.

Little new information was discussed in AVO reports issued on 20-26 
March. The 26 March report included the remark that satellite views were 
then obscured by cloud cover; however, vigorous steaming from the summit 
was visible with the on-island web camera.

Correction. A previous Augustine report (BGVN 30:12; issued in early 
2006) had a typographic error in the title: Eruptions begin 11 January 
2005 and eight outbursts occur by late January). The year has since 
been changed on our website to 11 January 2006.

Geologic Summary. 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 volcanos summit. The latest episode of edifice collapse occurred 
during Augustines 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: Jon Dehn, Cathy Cahill, Ken Dean, and Pavel E. 
Izbekov, Geophysical Institute, University of Alaska Fairbanks, 903 
Koyukuk Drive, P.O. Box 757320 Fairbanks, AK 99775-7320 USA; 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); Fred Prata, Norwegian Institute for 
Air Research, P.O. Box 100, 2027 Kjeller, Norway; Rene Servranckx, 
Montreal Volcanic Ash Advisory Centre, Canadian Meteorological Centre, 
Meteorological Service of Canada, 2121 North Service Road, Trans-Canada 
Highway, Dorval, Quebec, H9P 1J3 Canada; 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, P.O. Box 757320, Fairbanks, AK 99775-7320, USA, and Alaska 
Division of Geological & Geophysical Surveys, 794 University Ave., Suite 
200, Fairbanks, AK 99709, USA.


Santa Maria
Guatemala
14.756 N, 91.552 W; summit elev. 3,772 m
All times are local (= UTC - 6 hours)

This summary of activity at Santa Marias Santiaguito lava-dome complex, 
taken largely from Instituto Nacional de Sismologia, Vulcanologia, 
Meteorologia e Hidrologia (INSIVUMEH) reported for October 2005 to 
January 2006. During this interval Santa Maria continued to emit 
occasional ash plumes.

During 26-31 October 2005, several explosions took place and plumes rose 
to a maximum of ~ 5 km altitude on 28 October. In early November, 
several explosions occurred producing ash plumes to an altitude of ~ 5 
km. A few weak avalanches of volcanic material were observed SW of the 
lava dome.

Explosions produced several ash plumes to ~ 5 km altitude during 11-14 
November 2005. Several small pyroclastic flows traveled down the SW, NE, 
and S flanks of Caliente dome. Frequent avalanches of volcanic material 
occurred off of the fronts of active lava flows mostly to the W of 
Caliente dome, and less frequently to the S and NE. An ash-and-gas 
emission on 14 November produced a cloud that was visible on satellite 
imagery.

During 17-21 November, Santa Maria produced weak-to-moderate explosions, 
sending ash plumes to an altitude of ~ 4.6 km. Several small pyroclastic 
flows traveled down the SW and NE flanks of Caliente dome, stopping at 
the base of the dome. Avalanches spalled off of the fronts of active 
lava flows and traveled SW.

On 24 November at 0955, an eruption produced an ash cloud to an altitude 
of ~ 4 km accompanied by a pyroclastic flow to the S. Fine ash fell 6-7 
km S of the volcano, impacting properties in the area.

Moderate-to-strong explosions in December produced ash plumes that rose 
~ 1.5-2.5 km. Pyroclastic flows occasionally accompanied explosions and 
traveled towards the SW. Several avalanches of volcanic material also 
occurred during the report period.

Throughout January 2006, explosions continued to occur sending resultant 
ash emissions to the SW. Lava avalanches originated from the SW edge of 
the Caliente dome and from the fronts of active lava flows on the SW 
flank. An explosion on the morning of 11 January 2006 generated a small 
pyroclastic flow that traveled down Caliente dome to the NE. INSIVUMEH 
reported on 16 January that a slight decrease in explosive activity was 
observed during the previous month. On 16 January there were reports of 
a small amount of ashfall 25 km SW in the urban area of San Felipe 
Retalhuleu.

During 1-3 February, weak-to-moderate explosions took place at 
Santiaguitos lava-dome complex, producing plumes that rose to a maximum 
height of 1 km above the volcano. On 1 February at 0657 and 0708, 
moderate explosions were accompanied by pyroclastic flows. Lava 
extrusion at Caliente dome produced block-and-ash flows that descended 
the domes S, E, and W sides. Several explosions on 9 February also 
produced small pyroclastic flows that traveled down the SW and SE sides 
of Caliente dome. On 15-17 February, pyroclastic flows traveled SW and 
NE, associated with avalanches of incandescent volcanic material spalled 
off of active lava-flow fronts.

On 4, 6, and 7 March, satellite imagery showed small ash plumes emitted 
from the lava-dome complex. The plumes reached ~ 3 km above the volcano. 
On 6 March around 0733, a moderate explosion produced an ash plume and 
pyroclastic flows. A strong explosion later that day, at 1025, sent an 
ash plume ~ 3 km above the volcano that deposited ash throughout the 
volcanic complex. The explosion was accompanied by pyroclastic flows 
down the NE and SW flanks. Fine ash drifted S falling on properties in 
that area. On 12 March, there were avalanches of volcanic blocks and 
ash. On 13 March, a pyroclastic flow traveled down the S flank of 
Caliente dome.

Geologic Summary. Symmetrical, forest-covered Santa Maria volcano is one 
of the most prominent of a chain of large stratovolcanoes that rises 
dramatically above the Pacific coastal plain of Guatemala. The 
3,772-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 Volcan Santa Maria 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.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, 
Meteorologia e Hidrologia (INSIVUMEH), Unit of Volcanology, Geologic 
Department of Investigation and Services, 7a Av. 14-57, Zona 13, 
Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/).


Masaya
Nicaragua
11.984 N, 86.161 W; summit elev. 635 m
All times are local (= UTC - 6 hours)

Previously reported behavior at Masaya through 22 September 2003 
consisted primarily of incandescence from Santiago crater (BGVN 28:10). 
Monthly reports prepared by the Instituto Nicaraguense de Estudios 
Territoriales (INETER) since that time noted continuing seismicity and 
incandescence through March 2005. A small explosions was reported on 29 
November 2003. Masaya Volcano National Park workers also reported two 
ash-and-gas explosions at 0121 on 12 December 2003. A collapse event 
within the crater was noted on 22 June 2004. A report from the 
Washington Volcanic Ash Advisory Center (VAAC) noted that on 4 July 2004 
at 0015 local time, a narrow plume of steam and/or ash from Masaya was 
visible on satellite imagery extending to the SW. An hour later the 
plume had extended ~ 12 km from the summit. The report below notes 
changes induced in Santiago crater after a landslide in early March 
2005. A magnitude 1.9 earthquake at a depth of 2.2 km below Masaya on 30 
March 2005 was followed by rumbling noises and gas-and-ash emissions.

Field work during February-March 2005. Patricia Nadeau and Glyn 
Williams-Jones sent us a report of an intensive, multi-component field 
campaign conducted at Masaya from 16 February 2005 to 12 March 2005. Two 
FLYSPEC ultraviolet spectrometers were used in tandem with two Microtops 
sun photometers to constrain passive SO2 and aerosol fluxes and also to 
evaluate potential downwind loss of SO2 by conversion to aerosols. 
Additionally, self-potential geophysical measurements were performed at 
Masayas summit in a preliminary attempt to delineate the hydrothermal 
system of the volcano.

On the morning of 3 March, Park workers reported that a landslide had 
occurred within Santiago crater the previous night. A visibly diminished 
plume from the craters active vent suggested that the landslide may 
have caused a blockage that reduced the escape of SO2 (figures 5 and 6).

Figure 5. A photo taken from the tourist parking lot on 1 March 2005 
showing the inner crater at Masaya emitting a large plume prior to the 
2-3 March 2005 landslide. The diameter of the crater in this view is 
estimated to be 150-200 m. Courtesy of Patricia Nadeau and Glyn 
Williams-Jones.

Figure 6. A view into the Santiago Crater at Masaya and its diminished 
plume rising from the inner crater, as taken from the tourist parking 
lot on 3 March 2005. The diameter of the outer crater is approximately 
500 m; the inner crater is about 200 m across. Courtesy of Patricia 
Nadeau and Glyn Williams-Jones.

The visual observations were supported by subsequent SO2-flux 
measurements, which confirmed a significant drop in SO2 emissions from 
an average of ~ 300 tons/day prior to the landslide to an average of ~ 
80 tons/day following the landslide (figure 7). This decrease in 
emissions led to concerns over the possibility of a small vent-clearing 
explosion such as the one that occurred on 23 April 2001 (BGVN 26:04). 
That explosion was preceded by a similar drop in SO2 emissions for 
several weeks due to a blockage of the vent that was active at the time. 
The 2001 explosion resulted in the opening of a new vent, which has 
since been the site of Masayas degassing. After the 2001 explosion, the 
previously active vent no longer degassed and was assumed to be 
completely inactive.

Figure 7. Graph showing Masayas daily SO2 fluxes during 25 February 
2005-17 April 2005 (normalized to a wind speed of 1 m/s) before and 
after the landslide during the night of 2-3 March 2005. Courtesy of 
Patricia Nadeau and Glyn Williams-Jones.

In the days following the 2 March 2005 landslide, gas output was 
monitored closely, both visually and with the FLYSPEC, for any further 
decreases, which could have been indicative of further blockage and 
possible pressurization. Visual observations of the crater on the nights 
of 4 March and 11 March revealed that while the currently degassing vent 
was not incandescent, the older vent (believed to be inactive after the 
April 2001 explosion) was indeed incandescent, though not degassing 
(figure 8).

Figure 8. A photo taken from the second parking lot overlooking Masayas 
Santiago Crater captured the scene at two vents within the inner crater 
on 10 March 2005. The younger, actively degassing vent and plume are in 
the foreground; the older, non-degassing vent is in the background. The 
latter vent was incandescent at night. The diameter of the active vent 
in this view is estimated to be 30-40 m. Courtesy of Patricia Nadeau and 
Glyn Williams-Jones.

As of 10 March, the visible gas emissions were the lowest seen, despite 
the apparent open conduit, as indicated by incandescence in the old 
vent. Rumbling and sloshing sounds from within the crater had increased 
from sporadic to nearly constant. However, the days following were 
marked by a decrease in acoustical noise, as well as the apparent 
beginning of a climb back to higher SO2 emission rates (~ 120 tons/day 
on 16 March). These observations were consistent with devlopments in the 
upper conduit.

Geologic Summary. Masaya is one of Nicaraguas most unusual and most 
active volcanoes. Masaya lies within the massive Pleistocene Las Sierras 
pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera 
with steep-sided walls up to 300 m high. The caldera is filled on its NW 
end by more than a dozen vents erupted along a circular, 4-km-diameter 
fracture system. The twin volcanoes of Nindiri and Masaya, the source of 
historical eruptions, were constructed at the southern end of the 
fracture system and contain multiple summit craters, including the 
currently active Santiago crater. A major basaltic plinian tephra was 
erupted from Masaya about 6,500 years ago. Historical lava flows cover 
much of the caldera floor and have confined a lake to the far eastern 
end of the caldera. A lava flow from the 1670 eruption overtopped the N 
caldera rim. Masaya has been frequently active since the time of the 
Spanish conquistadors, when an active lava lake prompted attempts to 
extract the volcanos molten gold. Periods of long-term vigorous gas 
emission at roughly quarter-century intervals have caused health hazards 
and crop damage.

References: Williams-Jones, G., Horton, K. A., Elias, T., Garbeil, H., 
Mouginis-Mark, P. J., Sutton, A. J., and Harris, A. J. L., Accurately 
measuring volcanic plume velocity with multiple UV spectrometers: 
Bulletin of Volcanology, in press.

Williams-Jones, G., Delmelle, P., Baxter, P., Beaulieu, A., Burton, M., 
Garcia-Alvarez, J., Gaonach, H., Horrocks, L., Oppenheimer, C., Rymer, 
H., Rothery, D., St-Amand, K., Stix, J., Strauch, W., and van Wyk de 
Vries, B., (2001?), Projecto Laboratorio Geofisico-Geoquimico Volcan 
Masaya, Geochemical, geophysical, and petrological studies at Masaya 
volcano (1997-2000), on INETER website at 
<http://www.ineter.gob.ni/geofisica/vol/masaya/doc/gases-glyn2000/gases-glyn2000.html>.

Information Contacts: Patricia Nadeau and Glyn Williams-Jones, 
Department of Earth Sciences, Simon Fraser University, Burnaby, Canada 
(Email: panadeau@xxxxxx, glynwj@xxxxxx); Kirstie Simpson, Geological 
Survey of Canada, Vancouver, Canada (Email: ksimpson@xxxxxxxxxxx); 
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/VAAC/); Wilfried Strauch and Martha Navarro, 
Instituto Nicaraguense de Estudios Territoriales (INETER), Apartado 
Postal 2110, Managua, Nicaragua (Email: ineter@xxxxxxxxxx).


Sangay
Ecuador
2.002 S, 78.341 W; summit elev. 5,230 m
All times are local (= UTC - 5 hours)

Our previous report was in 1996 (BGVN 21:03); this report covers the 
time interval January 2004 to January 2006. According to a 2004 annual 
summary on the Instituto Geofisico (IG) website, Sangay was one of the 
most active volcanoes in Ecuador, and has been in eruption for ~ 80 
years. Its isolated location (figure 9) has meant it has been thought of 
as a relatively small hazard risk. For this reason, monitoring has been 
less than for other Ecuadorian volcanoes. Thermal, visual, and satellite 
monitoring during 2002-2004 confirmed the central crater as the source 
of frequent explosions and continuing steam-and-gas emissions.

Figure 9. Satellite imagery showing the region around the city of 
Riobamba (center) in Ecuador), including Sangay (lower right), 
Chimborazo (upper left), Tungurahua (upper right), and Licto (center) 
volcanoes. An eruption plume can be discerned coming from Tungurahua, 
but the date of the image is unknown. The city of Riobamba is about 50 
km NW of Sangay. Courtesy of Google Earth.

During 2004 observers did not see lava flows or pyroclastic flows. An 
abnormally large eruption cloud was detected on 14 January 2004; it 
contained dominantly steam and gases, with minor ash content. Although 
only clearly detected and reported then, such events are thought to 
occur with considerable frequency.

Ramon and others (2006) summarized Sangays activity as continuously 
erupting since 1934. Thermal images taken during the last three years 
showed that only one of the three summit craters was active and 
documented a lack of new, visible lava flows.

On 14 January 2004 a plume from Sangay was observed around 0500. The 
plume extended about 45 km E and most likely contained ash. During this 
time a hotspot was also visible on the satellite imagery. On 27 January 
2004 a narrow ash plume emitted by Sangay rose to 6 km altitude and 
drifted SW.

On 1 May 2004, based on a pilots report, the Washington VAAC noted that 
ash from an eruption at Sangay produced a plume to a height of ~ 6 km 
altitude at 1750. Ash was not visible on satellite imagery.

On 28 December 2004 around 0715 a plume from Sangay, most likely 
composed of steam with little ash, was detected. The plume was E of the 
volcanos summit at a height of ~ 6.4 km altitude. A hotspot was 
prominent on satellite imagery, but ash was more difficult to distinguish.

On 16 October 2005 around 0645 Sangay emitted an ash plume. The plume 
moved SSW very slowly, corresponding to a possible height of ~ 6.7 km 
altitude. By 0900 the plume was too thin to be visible on satellite 
imagery and thunderstorms developed in the area, further obscuring the 
ash cloud. Based on information from the IG, on 26 October 2005 the 
Washington VAAC noted that ash was seen over Sangay at 0758. No ash was 
visible on satellite imagery.

Climbers photo journal. Climbers Thorsten Boeckel and Martin Rietze 
created a website briefly describing a trek to Sangays summit during 
4-12 January 2006. Several of their posted photos from that trip appear 
here (figures 10-13; unfortunately, the photos, which are strikingly 
beautiful, were generally presented without much geographic context). 
The team included at least one local guide and was aided by horses. 
Settlements on the approach and return included the mountain village St. 
Eduardo, which they described as ~ 50 km S of Riobamba.

Figure 10. A vista of Sangay at nightfall in early January 2006. 
Direction of view is approximately WNW. Photo credit to Boeckel and Rietze.

Figure 11. Photograph documenting the climbers tent camp high on the 
snowbound slopes of Sangay during their descent. Exact location on 
Sangay unknown; this was labeled day 4/5," and should correspond to 7 
or 8 January 2006. Photo credit to Boeckel and Rietze.

Figure 12. A topographic high forming part of the Sangay structure, 
gently steaming, apparently seen from the summit. This corresponds to 7 
or 8 January 2006. Photo credit to Boeckel and Rietze.

Figure 13. A crater on Sangay as seen by the climbers from the summit or 
upper flanks, described by them as the snow covered east crater. This 
photo corresponds to 7 or 8 January 2006. Photo credit to Boeckel and 
Rietze.

Except for some degassing, the group saw no other activity. Although 
local residents indicated that the last eruption had occurred about 2 
months prior to their visit, intermittent eruptions pose hazards to 
climbers; in 1976 two climbers were killed by explosions from Sangay 
(SEAN 01:10).

Geologic Summary. The isolated Sangay volcano, located E of the Andean 
crest, is the southernmost of Ecuadors volcanoes, and its most active. 
The dominantly andesitic volcano has been in frequent eruption for the 
past several centuries. The steep-sided, 5,230-m-high glacier-covered 
volcano grew within horseshoe-shaped calderas of two previous edifices, 
which were destroyed by collapse to the E, producing large debris 
avalanches that reached the Amazonian lowlands. The modern edifice dates 
back to at least 14,000 years ago. Sangay towers above the tropical 
jungle on the E side; on the other sides flat plains of ash from the 
volcano have been sculpted by heavy rains into steep-walled canyons up 
to 600 m deep. The earliest report of a historical eruption was in 1628. 
More or less continuous eruptions were reported from 1728 until 1916, 
and again from 1934 to the present. The more or less constant eruptive 
activity has caused frequent changes to the morphology of the summit 
crater complex.

Reference: Ramon, P., Rivero, D., Bvker, F., and Yepes, H., 2006, 
Thermal monitoring using a portable IR camera: results on Ecuadorian 
volcanoes in Cities on Volcanoes IV"; 23-27 January 2006.

Information Contacts: P. Ramon, Instituto Geofisico-Departamento de 
Geofisica (IG), Escuela Politecnica Nacional, Casilla 17-01-2759, Quito, 
Ecuador (Email: pramon@xxxxxxxxxxxx); 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/VAAC/); Thorsten Boeckel and Martin Rietze, c/o 
Kermarstr.10, Germerswang, D-82216, Germany (URL: 
http://www.tboeckel.de/, Email: tboeckel@xxxxxxxxxxx).


Lascar
Northern Chile
23.37 S, 67.73 W; summit elev. 5,592 m

Lascars eruption on 4 May 2005 (BGVN 30:05) was followed by a new 
eruptive cycle, which began on 18 April 2006 and lasted 5 days. 
Observers familiar with Lascar judged this eruptive episode unusual 
compared to those observed previously in terms of eruptive character, 
frequency, and duration time. The Volcanic Ash Advisory Center (VAAC) in 
Buenos Aires and Servicio Metererologico Nacional of Argentina detected 
the eruption from satellite images, and aircraft warnings were posted. 
All of the times cited are in UTC (local time = UTC - 4 hours).

Eruptions start, 18 April. Four explosions registered (at 1520, 1722, 
1900, and 2100 hours UTC). The first explosion, the largest of four, was 
visible from El Abra cooper mine (220 km NW) and reached ~ 10 km above 
the summit crater (figure 14). The shape of the eruptive column 
suggested that it reached the tropopause (~ 15 km altitude in this 
region). The white to gray plume, containing little ash but a large 
amount of water, dispersed to the NNE.

Figure 14. Lascars first explosion of 18 April 2006 as photographed 
from El Abra copper mine, 220 km NW from volcano. Courtesy of personnel 
at the El Abra copper mine.

The second explosion reached 3 km above the summit crater, while the 
third and fourth explosions reached 800 m. These latter eruptive plumes 
were gray colored, had higher contents of ash than the first explosion, 
and were dispersed NNE. Only slight ash fall was registered on the N 
side of the volcano. No seismic activity or eruption noises were 
registered. Analysis of GOES satellite images (figure 15) indicated that 
for the first and second eruptive plumes the mean horizontal velocities 
were 70 and 85 km/hour, respectively, while the maximum plume areas were 
~ 8,240 and 1,074 km^2, respectively. Minimum volumes erupted were ~ 4.1 
x 10^6 and ~ 0.54 x 10^6 m^3 assuming a hypothetical ash fall deposit of 
0.5 mm over the stated areas. The third and fourth explosions were not 
detected by satellite.

Figure 15. GOES satellite image capturing Lascars first and second 
eruptive plumes. Rivers and international borders are also shown. Image 
is for 1829 UTC on the 18 April 2006. The first plume (oblong black area 
labeled cloud in Spanishnube) stretched over N Argentina and S 
Bolivia. A second plume appears as a much smaller dark area between 
Lascar and the first plume. It lay over the NE Chilean border. Courtesy 
of Comision Nacional de Asuntos Espaciales (CONAE), Argentina.

19-22 April eruptions and comparative calm that followed. On 19 April 
2006 at 1504 hours (UTC) an explosion generated a gray-colored eruptive 
column that reached 3 km above the summit crater and was dispersed NNE. 
Slight ash fall was noted on the N side of the volcano. Neither seismic 
activity nor eruption noises were reported. Two explosions were recorded 
20 April at 1505 and 1739 hours (UTC). The first eruptive plume reached 
2.5 km above the summit crater and contained a small amount of ash. The 
plume from the second explosion, the larger of the pair, reached 7 km 
above the crater. The eruption lasted 1 hour and 50 min. Both plumes 
were dispersed N and slight ash fall was registered on the N side of the 
volcano. No seismic activity or eruption noises were registered.

Analysis of satellite data from the sequence of GOES images (figure 16) 
indicated that the first and second eruptive plumes had mean horizontal 
velocities of 40 km/h, while the maximum areas were ~ 430 and ~ 800 
km^2, respectively. Minimal volumes erupted were ~ 0.4 x 10^6 and ~ 0.2 
x 10^6 m^3, again assuming a hypothetical 0.5 mm ash-fall deposit.

Figure 16. GOES satellite image of Lascar showing the second eruptive 
plume (black circle) at 1807 hours (UTC) of 20 April eruption dispersed 
to NE. Courtesy of Servicio Meteorologico Nacional and Comision Nacional 
de Asuntos Espaciales (CONAE), Argentina.

Two explosions were recorded on 21 April 2006 at 1248 and 1547 UTC, each 
lasting ~ 15 minutes. Their eruptive columns reached 3 km above the 
summit crater and rapidly dispersed ESE. Seismic activity and eruption 
noises were not noted.

On 22 April at 1518 UTC an explosion generated an eruptive column that 
reached 3 km above the summit crater; it was blown SE. Local inhabitants 
heard subterranean noises. On 23 April at 1600 UTC an explosion 
generated a gray-colored eruptive column that reached 2.5 km above the 
summit crater and dispersed NNW (figure 17). Seismic activity and 
eruption noises were not registered. During the following 2 days, the 
color of the plume was white and its top remained ~ 1.5 km above the 
crater.

Figure 17. Photograph of Lascar taken 23 April 2006 from the SW border 
of the Atacama salar (salt pan), ~ 40 km SW of the volcano. Courtesy of 
Gabriel Gonzalez.

Other studies. After the 4 May 2005 eruption (BGVN 30:05), a team of 
scientists from Universidad Catolica del Norte (UCN) carried out a gas 
sampling campaign on new fumaroles around the S edge of the central 
active crater. They used the direct sampling of fumaroles technique 
described by Giggenbach (1975) and Giggenbach and Goguel (1989). Gas 
data showed increasing amounts of H2O, H2S, and CH4 with respect to 
samples taken in 2002 from inside the active crater (Tassi et al., 
2004). However, acid gases also displayed very high values. During 
December 2005 a team of scientists from UCN and Universidad Autonoma de 
Mexico (UNAM) carried out field investigations to generate hazard maps.

Scientists from Universita degli Studi di Firenze (Italy) and 
Universidad Catolica del Norte (Chile) are conducting a systematic gas 
sample campaign at Lascar and other active volcanoes in the Central 
Volcanic Zone (e.g. Putana, Lastarria, and Isluga). Finally, scientists 
from the Universidad Catolica del Norte, the Universidad Nacional de 
Salta and SEGEMAR (Argentina) are processing data from Landsat Thematic 
Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) and Advanced 
Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images, 
with the objective of understanding the behavior of Lascar volcano 
during the 1998-2004 period.

References: Giggenbach, W., 1975, A simple method for the collection and 
analysis of volcanic gas sample: Bulletin of Volcanology, 39, 132145.

Giggenbach, W., and Goguel, R., 1989, Collection and analysis of 
geothermal and volcanic water and gas discharges: DSIR Chemistry, Rept. 
No. 2401.

Matthews, S., Gardeweg, M., and Sparks, R., 1997, The 1984 to 1996 
cyclic activity of Lascar volcano, northern Chile: cycles of dome 
growth, dome subsidence, degassing and explosive eruptions: Bulletin of 
Volcanology, v. 59, p. 72-82.

Tassi, F., Viramonte, J., Vaselli, O., Poodts, M., Aguilera, F., 
Martinez, C., Rodriguez, L., and Watson, I., 2004, First geochemical 
data from fumarolic gases at Lascar volcano, Chile: 32nd International 
Geological Congress, Florence, August 20-28, 2004.

Viramonte, J., Aguilera, F., Delgado, H., Rodriguez, L., Guzman, K., 
Jimenez, J., and Becchio, R., 2006, A new eruptive cycle of Lascar 
Volcano (Chile): The risk for the aeronavigation in northern Argentina. 
Garavolcan 2006, Tenerife, Spain.

Geologic Summary. Lascar is the most active volcano of the northern 
Chilean Andes. The andesitic-to-dacitic stratovolcano contains six 
overlapping summit craters. Prominent lava flows descend its NW flanks. 
An older, higher stratovolcano 5 km to the east, Volcan Aguas Calientes, 
displays a well-developed summit crater and a probable Holocene lava 
flow near its summit (de Silva and Francis, 1991). Lascar consists of 
two major edifices; activity began at the eastern volcano and then 
shifted to the western cone. The largest eruption of Lascar took place 
about 26,500 years ago, and following the eruption of the Tumbres scoria 
flow about 9000 years ago, activity shifted back to the eastern edifice, 
where three overlapping craters were formed. Frequent small-to-moderate 
explosive eruptions have been recorded from Lascar in historical time 
since the mid-19th century, along with periodic larger eruptions that 
produced ashfall hundreds of kilometers away from the volcano. The 
largest historical eruption of Lascar took place in 1993, producing 
pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Information Contacts: Felipe Aguilera, Eduardo Medina, and Karen Guzman, 
Programa de Doctorado en Ciencias mencion Geologia and Departamento de 
Ciencias Geologicas, Universidad Catolica del Norte, Avenida Angamos 
0610, Antofagasta, Chile (Email: faguilera@xxxxxx, emedina@xxxxxx, 
kgm001@xxxxxx; URL: http://www.geodoctorado.cl; 
http://www.ucn.cl/FacultadesInstitutos/Fac_geologia.asp); Jose G. 
Viramonte, Raul Becchio, and Marcelo J. Arnosio, Instituto GEONORTE and 
CONICET, Universidad Nacional de Salta, Buenos Aires 177, Salta 4400, 
Argentina (Email: viramont@xxxxxxxxxxx; URL: 
http://www.unsa.edu.ar/natura/); Ricardo Valenti and Sergio Haspert, 
Servicio Metereologico Nacional, Argentina (Email: 
rvalenti@xxxxxxxxxxxx; sergio_sah@xxxxxxxxx); Hugo G. Delgado, Instituto 
de Geofisica, Universidad Nacional Autonoma de Mexico (UNAM), Coyoacan 
04510, Mexico, D.F. (Email: hugo@xxxxxxxxxxxxxxxxxxxxxxxx); Buenos Aires 
Volcanic Ash Advisory Center (VAAC), Servicio Meteorologico 
Nacional-Fuerza Aerea Argentina, Buenos Aires, Argentina (URL: 
http://www.meteofa.mil.ar/vaac/vaac.htm, 
http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html).


Michael
Antarctica
57.78 S, 26.45 W; summit elev. 990 m

The last reported activity of Mount Michael was noted in the SI/USGS 
Weekly Report of 12-18 October 2005. At that time the first MODVOLC 
alerts for the volcano since May 2003 indicated an increased level of 
activity in the islands summit crater and a presumed semi-permanent 
lava lake that appeared confined to the summit crater. Those alerts 
occurred on 3, 5, and 6 October 2005. Since that time there has been no 
additional information concerning Mount Michael and presumably little to 
no activity.

Geologic Summary. The young constructional Mount Michael stratovolcano 
dominates glacier-covered Saunders Island. Symmetrical 990-m-high Mount 
Michael has a 700-m-wide summit crater and a remnant of a somma rim to 
the SE. Tephra layers visible in ice cliffs surrounding the island are 
evidence of recent eruptions. Ash clouds were reported from the summit 
crater in 1819, and an effusive eruption was inferred to have occurred 
from a N-flank fissure around the end of the 19th century and beginning 
of the 20th century. A low ice-free lava platform, Blackstone Plain, is 
located on the N coast, surrounding a group of former sea stacks. A 
cluster of parasitic cones on the SE flank, the Ashen Hills, appears to 
have been modified since 1820 (LeMasurier and Thomson 1990). Vapor 
emission is frequently reported from the summit crater. AVHRR and MODIS 
satellite imagery, the most recent from October 2005 has revealed 
evidence for lava lake activity in the summit crater of Mount Michael.

Information Contacts: Matt Patrick, Luke Flynn, Harold Garbeil, Andy 
Harris, Eric Pilger, Glyn Williams-Jones, and Rob Wright, HIGP Thermal 
Alerts Team, Hawaii Institute of Geophysics and Planetology (HIGP) / 
School of Ocean and Earth Science and Technology (SOEST), University of 
Hawaii, 2525 Correa Road, Honolulu, HI 96822, USA 
(http://hotspot.higp.hawaii.edu/, Email: patrick@xxxxxxxxxxxxxxx); John 
Smellie, British Antarctic Survey, Natural Environment Research Council, 
High Cross, Madingly Road, Cambridge CB3 0ET, United Kingdom (URL: 
http://www.antarctica.ac.uk/, Email: jlsm@xxxxxxxxxxxxxxxxxxxxx).


Soputan
Sulawesi, Indonesia
1.108 N, 124.725 E; summit elev. 1,784 m
All times are local (= UTC + 8 hours)

Our last report covered events through July 2005 (BGVN 30:08); this 
report includes activity that took place in late December 2005 and also 
presents a discussion of the wide discrepancy of cloud-height estimates 
between ground, aircraft, and satellite remote-sensing observations.

Activity during 21-27 December 2005. A phreatic eruption began at 
Soputan on 26 December 2005 around 1230 following heavy rain. Observers 
concluded that rainwater contacted lava at the volcanos summit. On 27 
December at 0400, a Strombolian eruption began that lasted about 50 
minutes. Incandescent material was ejected ~ 35 m, and avalanches 
spalling off the margins of the summit traveled as far as 750 m E. 
Booming noises were heard 5 km from the summit. The Darwin VAAC reported 
that an ash plume reached a height of ~ 5.8 km altitude and drifted SE.

As of 28 December, eruptive activity continued, producing ash plumes to 
a height of ~ 1 km above the volcano. Strombolian eruptions ejected 
incandescent material up to 200 m above the summit. Pyroclastic 
avalanches traveled ~ 500 m E and SW. This was Soputans fourth event in 
2005, with previous activity on 14 and 20 April, and on 12 September. 
The Alert Level remained at 2, since the volcano is about 11 km from the 
nearest settlement. Visitors were prohibited from climbing Soputans 
summit and from camping around Kawah Masem.

October 2005 eruption plume height discussion. The Darwin Volcanic Ash 
Advisory Centre and the Cooperative Institute for Meteorological 
Satellite Studies (CIMSS) at the University of Wisconsin  Madison 
collaborated to compare various estimates for the height of the 27 
December cloud (BGVN 30:08). The eruption height had been initially 
reported at less than 6 km altitude on the 27th by an airline pilot, and 
1 km above the summit (~ 2.8 km altitude) by ground observers on the 
28th. Darwin VAAC, on reviewing hourly MTSAT imagery on the 27th, 
estimated the plume top at 15 km altitude operationally and then 12.5 km 
altitude in post-analysis studies.

Michael Richards of CIMSS used an established remote-sensing technique 
known as CO2 slicing (Menzel et al., 1983, Richards et al., 2006), to 
obtain heights of the cloudscape around Soputan after the eruption. The 
technique takes advantage of the fact that the emissive infrared CO2 
bands available on the MODIS satellite become more transmissive with 
decreasing wavelength, as the bands move away from the peak wavelength 
of CO2 absorption at 15 um. There were two good MODIS images obtained 
over the eruption on the 27th, with the first, at 0210 UTC or 1010 local 
time. These images were taken at close to the time of the peak cloud 
height observed on MTSAT imagery, and the CO2 slicing technique appears 
to validate the post-analyzed VAAC height of ~ 12.5 km altitude.

The different results for the height of the eruption cloud illustrate 
the difficulty that observers would have had viewing the cloud from any 
angle. Weather clouds in the tropics typically extend up to 16 km or 
more altitude. Cirrus cloud from a storm complex can obscure the view of 
a satellite for hours. On the other hand, middle-level clouds, such as 
altostratus, will typically lie between aircraft cruising altitudes and 
the ground, meaning that pilots at cruising altitude may not associate 
any eruption cloud with a volcano on the ground, unless the cloud is 
obviously volcanic. Ground observers are completely unable to view the 
full height of the cloud if it is penetrating through the middle-level 
clouds.

The appearance of the cloud on true-color, near-infrared and infrared 
imagery is consistent with an ice-rich (glaciated) volcanic cloud, 
in-line with the CVGHM account of water interactions at the ground, and 
also with a high water loading in the atmosphere. The extensive areas of 
cloud in the area hindered satellite detection of the eruption until 
after the pilot report of the eruption had been received.

Geologic Summary. The small Soputan stratovolcano on the southern rim of 
the Quaternary Tondano caldera on the northern arm of Sulawesi Island is 
one of Sulawesis most active volcanoes. The youthful, largely 
unvegetated volcano rises to 1784 m and is located SW of Sempu volcano. 
It was constructed at the southern end of a SSW-NNE trending line of 
vents. During historical time the locus of eruptions has included both 
the summit crater and Aeseput, a prominent NE-flank vent that formed in 
1906 and was the source of intermittent major lava flows until 1924.

References: Menzel, W. P., Smith, W. L., and Stewart, T. R., 1983, 
Improved cloud motion wind vector and altitude assignment using VAS: 
Journal of Applied Meteorology, v. 22, p. 377-384.

Richards, M. S., Ackerman, S. A., Pavolonis, M. J., Feltz, W. F., and 
Tupper, A.C., 2006, Volcanic ash cloud heights using the MODIS 
CO2-slicing algorithm: AMS 12th, conference on aerospace and range 
meteorology, Atlanta, Georgia, USA 
(http://ams.confex.com/ams/pdfpapers/104055.pdf).

Information Contacts: Centre of Volcanology and Geological Hazard 
Mitigation, Jalan Diponegoro 57, Bandung 40122, Indonesia (Email: 
dali@xxxxxxxxxxxxxx; URL: http://www.vsi.esdm.go.id/); Andrew Tupper and 
Rebecca Patrick, Darwin Volcanic Ash Advisory Centre (VAAC), Australian 
Bureau of Meteorology (URL: 
http://www.bom.gov.au/info/vaac/soputan.shtml); Michael Richards and 
Wayne Feltz, Cooperative Institute for Meteorological Satellite Studies 
(CIMSS), University of Wisconsin, 1225 West Dayton Street, Madison, WI 
53706, USA.


Bulusan
Luzon, Philippines
12.770 N, 124.05 E; summit elev. 1,565 m
All times are local (= UTC + 8 hours)

Bulusan, after remaining relatively quiet since 1995, erupted multiple 
times during March and April 2006. There were no casualties or damage 
from these eruptions. On 21 March at 1044 the summit crater erupted, 
sending a column of ash 1.5 km into the sky accompanied by lightning and 
rumbling noises. Ash drifted N, W, and SW of the volcano and an hour 
after the event light ash fell on neighborhoods such as Barangays Cogon, 
Tinampo, Gulang-Gulang, and Bolos in the town of Irosin, as well as 
Barangays Puting Sapa and Bura-Buran in the town of Juban.

Ash ejected at 1058 on 22 March coincided with an explosion-type 
earthquake. Three other earthquakes were recorded at 2330, 2332, and 
2337. The hazard status had been raised to Alert Level 1; the area 
within a 4 km radius of the summit is a Permanent Danger Zone.

On 29 April the volcano erupted in a similar fashion, emitting ash 
nearly 1.6 km into the air. There was no sign of lava and no reports of 
rumbling noises. It was reported that ash rained on nearby communities.

Geologic Summary. Luzons southernmost volcano, Bulusan, was constructed 
within the 11-km-diameter dacitic Irosin caldera, which was formed more 
than 36,000 years ago. A broad, flat moat is located below the prominent 
SW caldera rim; the NE rim is buried by the andesitic Bulusan complex. 
Bulusan is flanked by several other large intracaldera lava domes and 
cones, including the prominent Mount Jormajan lava dome on the SW flank 
and Sharp Peak to the NE. The summit of Bulusan volcano is unvegetated 
and contains a 300-m wide, 50-m-deep crater. Three small craters are 
located on the SE flank. Many moderate explosive eruptions have been 
recorded at Bulusan since the mid-19th century.

Information Contacts: R. Punongbayan and E. Corpuz, Philippine Institute 
of Volcanology and Seismology (PHIVOLCS), Department of Science and 
Technology, PHIVOLCS Building, C.P. Garcia Avenue, Univ. of the 
Philippines Campus, Diliman, Quezon City, Philippines (URL: 
http://www.phivolcs.dost.gov.ph/); Inq7.net, a venture between The 
Philippine Daily Inquirer Inc., and GMANetwork Inc. (http://news.inq7.net/).


Kilauea
Hawaiian Islands, USA
19.425 N, 155.292 W; summit elev. 1,222 m
All times are local (= UTC - 10 hours)

This report covers the interval 31 January 2005 to 7 February 2006 and 
is drawn exclusively from U.S. Geological Survey Hawaiian Volcanic 
Observatory (USGS HVO) sources. During this interval, active lava flows 
during tended to remain along the W to central portions of the existing 
field (figures 18 and 19). On 31 January 2005, lava from Kilauea began 
pouring into the ocean at two entry points. The Ka`ili`ili entry to the 
E of the flow field was the largest and was fed by the large W arm of 
the Prince Kuhio Kalaniana (PKK) lava flow. The West Highcastle ocean 
entry was supplied by the W branch of the W arm of the PKK lava flow.

Figure 18. A series of maps portraying Kilaueas surface lava flows at 
various times during 31 January 2005 to 7 February 2006. New vents 
opened at the southern base of Pu`u `O`o on 19 January 2004. Map panels 
are as follows: a) A map with features as of February 2005, b) as of 
April 2005, c) as of May 2005, d) as of 31 July 2005, and e) as of 30 
September 2005. Courtesy of Christina Heliker, USGS HVO.

Figure 19. Map portraying Kilaueas near-shore and coastal lava flows 
areas in the vicinity of East Laeapuki and East Kamoamoa as of 23 
September 2005. Courtesy of Christina Heliker, USGS HVO.

 From 7 February 2005 to 20 February 2005, lava flows were visible on 
the Pulama pali fault scarp and on the coastal flat. Instruments 
recorded a few small earthquakes and no tremor at Kilaueas summit. At 
Pu`u `O`o, volcanic tremor remained moderate. Small amounts of 
deformation were recorded.

On 21 February 2005 a new ocean entry formed, named E Lae`apuki. The 
entry was located between the other two ocean entries (Ka`ili`ili and 
West Highcastle) that had been active since 31 January 2005. This was 
the first time there had been three ocean entries active since early 
2003 (figures 18-20).

Figure 20. Photos of Kilauea activity taken along the coast on 21 
February 2005. (A) A photo showing the walls of a large crack into which 
lava pours at E Lae`apuki. Sea cliff is to the right, at shelfs edge 
beyond the glow. (B and C, respectively) The top and bottom of lava 
falls at E Lae`apuki ocean entry looking W. (D) A closer view focused on 
showing the base of the lava falls. The sea cliffs height is ~ 12 m. 
Courtesy of HVO.

During 23-26 February 2005, lava from Pu`u `O`o entered the sea at three 
ocean entriesWest Highcastle, East Laeapuki, and Ka`ili`ilispots 
along 4.7 km of the islands SE coast (figure 21). Lava may have stopped 
flowing into the sea at the W entry (West Highcastle) on 26 February 
2005. The number of surface lava flows diminished in comparison to the 
previous weeks, and small earthquakes continued to occur at Kilaueas 
summit without accompanying tremor. Tremor remained at moderate levels 
at Pu`u `O`o, and as of 28 February 2005, deflation had occurred at Pu`u 
`O`o for more than a week and at the summit since 24 February 2005.

Figure 21. A Kilauea photograph taken on 23 February 2005 depicting 
active lava delta construction at E Lae`apuki ocean entry. Note the fan 
building outward from the sea cliff and the person (upper right) for 
scale. Courtesy of USGS HVO.

During the month of March 2005, lava from Kilauea continued to enter the 
ocean at the Ka`ili`ili and E Lae`apuki, but there were no signs of 
activity at the West Highcastle entry. Surface lava flowed down the 
Pulami pali fault scarp and the coastal flat. Small earthquakes occurred 
at Kilaueas summit, and no tremor was recorded. Tremor remained at 
moderate levels at Pu`u `O`o.

On 29 March 2005, lava from Kilauea entered the ocean at five areas. The 
largest, named Kamoamoa, consisted of six or more places where lava 
entered the water along the front of a growing lava delta (figure 22). 
At one of the two Highcastle entries, a cascade of lava streamed down 
the old sea cliff. A bright glow came from Ka`ili`ili entry, and a weak 
glow from E Highcastle entry. Seismicity remained above background 
levels at Kilaueas summit, consisting mainly of tremor and some 
long-period earthquakes. Surface waves from an M 8.7 earthquake on 28 
March 2005 off Sumatra, Indonesia disturbed tilt measurements at Kilauea 
but otherwise the tilt change was small.

Figure 22. A photo taken 25 March 2005 showing Kilaueas new Kamoamoa 
ocean entry, located just NE of East Laeapuki. Descending lava poured 
over an old sea cliff to land upon, and flow across, an old delta; it 
then dropped into the sea, forming a new delta. Courtesy of USGS HVO.

Lava from Kilauea continued to flow into the ocean at several points 
during 1-13 April 2005. Seismicity remained above background levels at 
Kilaueas summit, consisting mainly of tremor and some long-period 
earthquakes. Volcanic tremor was at moderate levels at Pu`u `O`o. During 
14-19 April, surface lava flows from Kilauea were visible on the Pulama 
pali fault scarp but lava was not seen entering the ocean.

Seismicity remained above background levels at Kilaueas summit during 
14-19 April 2005, consisting mainly of tremor and some long-period 
earthquakes. Volcanic tremor was at moderate levels at Pu`u `O`o. 
Episodes of inflation and deflation occurred during the week.

During 21-25 April, there were fewer surface lava flows visible at 
Kilauea than during the previous week. On 24 April a small amount of 
lava again began to enter the sea. Seismicity remained above background 
levels at Kilaueas summit, consisting mainly of tremor and some 
long-period earthquakes.

During 27 April-3 May 2005, lava entered the ocean at the Kamoamoa 
entry. Numerous surface lava flows were visible on the coastal flat. 
Seismicity remained above background levels at Kilaueas summit, 
consisting of both tremor and long-period earthquakes.

A third ocean entry, in the E Lae`apuki area, became active on 5 May 
2005. That entry and the Far E Lae`apuki entry were both being fed by 
lava falls down the old sea cliff and were relatively small. Based on 
the brighter glow, the Kamoamoa entry was thought to be more 
substantial. By the morning of 9 May lava was streaming over the old sea 
cliff in four locations: two falls went into the sea and two other falls 
landed on an old delta. The branch of the PKK flow feeding E Lae`apuki 
sprung numerous new lava flows on 9 May. The next day, the middle branch 
of the PKK flow developed an open-channel stream on the Pulama pali; it 
was 10-20 m wide, 500-600 m long, and moving rapidly.

Ocean entries remained active during 11-17 May 2005 in the E Lae`apuki 
and Kamoamoa areas. By 16 May the E Lae`apuki and E Kamoamoa entries 
both had benches ~ 350 m long and up to 75 m wide. A large plume from 
West Highcastle on 10 May probably recorded a collapse of part of that 
lava delta, which has been inactive for the past several weeks following 
growth in March and April. The middle branch of the PKK flow remained 
active and extended down Pulama Pali. The E branch reached out farther 
but was narrower and contained fewer breakouts. The W branch was reduced 
to a cluster of breakouts about halfway down the pali. Glow was seen 
from all of the Pu`u `O`o crater vents, as well as the MLK vent at the 
SW foot of the cone.

During 18-31 May 2005, lava from Kilauea continued to enter the sea at 
three areas. Surface lava flows were visible on the coastal plain and on 
the Pulama pali fault scarp. During 1-4 June 2005 lava entered the sea 
at three points along the S flank of Kilauea, and then at only two 
points through 7 June. Small surface lava flows were visible on the 
Pulama pali fault scarp and the coastal flat.

Lava again entered the sea at three points on 13 June. During the 14-21 
June lava continued to enter the sea and there was a small number of 
lava flows on the Pulama pali fault scarp. On 22 June lava in the W 
branch of the current flow descended onto the coastal flat for the first 
time in several months. On 24 June it was noted that Kilaueas summit 
continued its inflation, while Pu`u `O`o was deflating during the same 
period.

On 27 June part of the active E Lae`apuki lava delta collapsed. Lava 
stored within the delta gushed out onto the surface and into the water. 
Fountains of lava reported to be about 25 m high spurted from the 
central part of the delta soon afterward. Lava also entered the sea 
during 4-5 July and a few surface flows were on Pulama pali.

During 6-19 July 2005, lava continued to enter the sea at E Kamoamoa and 
E Lae`apuki. The latter entry was much larger, with several entry 
points. E Kamoamoa barely glowed. Surface lava was visible along the PKK 
lava flow throughout the month of July. Background volcanic tremor 
remained above normal levels at Kilaueas summit and at moderate levels 
at Pu`u `O`o. Slight inflation and deflation occurred at the volcano. An 
M 4.5 earthquake occurred on 25 July at 2209 along the SE edge of 
Kilaueas SW rift zone at a depth of ~ 30 km.

Up to seven ocean-entry points were visible off the W-facing front of 
the E Lae`apuki lava delta during 3-9 August; still others were hidden 
from view off the E-facing front. On Pulama pali, the W branch of the 
PKK flow reached its greatest extent of the week on 5 August, when it 
broadened to include hundreds of meters of scattered breakouts and 
reached from 460 m down to 260 m elevation. During 15-16 August 2005, 
surface lava at Kilauea was again visible on the W and E branches of the 
PKK lava flow. Lava continued to enter the sea at the E Lae`apuki entry 
through 5 September. Background volcanic tremor was near normal levels 
at Kilaueas summit and at moderate levels at Pu`u `O`o cone. There were 
small periods of inflation and deflation at Kilaueas summit and Pu`u 
`O`o. By 22 August, surface lava on the W branch of the PKK lava flow 
was no longer visible. On 27 August, part of a lava-bench collapsed.

Throughout September, lava entered the sea at the E Lae`apuki area with 
surface lava flows visible on the Pulama Pali fault scarp. Lava filled a 
scar left by the lava-bench collapse on 27 August. Background volcanic 
tremor continued to remain around normal levels at the summit. Volcanic 
tremor was at moderate levels at Pu`u `O`o. On 11 September, substantial 
deflation at the volcano was followed by sharp inflation. On 19 
September, several small shallow earthquakes occurred along the Kao`iki 
fault system with small amounts of inflation and deflation.

In October 2005, lava from Kilauea continued to enter the sea at the E 
Lae`apuki area, and surface lava flows were visible along the PKK lava 
flow. Lava flows continued to enter the sea at E Lae`apuki area, mostly 
NE of the point of the lava delta. On 18 October, weak surface lava 
flows were visible at Kilauea and one cascade of lava flowed off of the 
western front of the E Lae`apuki delta.

Activity during November 2005 was similar to the previous month. Lava 
continued to enter the sea at the E Lae`apuki area and surface lava 
flows were visible on the Pulama pali fault scarp. Background volcanic 
tremor was near normal levels at Kilaueas summit.

A lava-bench collapse in the E Lae`apuki area on 29 November 2005 was 
the largest bench collapse of the current eruption, which began in 
January 1983. The collapse lasted several hours, sending the 137,588 m^2 
of bench and an additional 40,467 m^2 of adjacent cliff, into the sea. 
The collapse left a 20-m-high cliff, from which a 2 m thick stream of 
lava was emitted from an open lava tube. Cracks had been observed on the 
inland portion of the bench several months earlier; visitors were not 
allowed near the bench, but a viewing area was provided ~ 3 km away. 
Growth of the new delta at E Lae`apuki was continuing as of 6 December 
2005. At that time breakouts were also active on Pulama Pali.

During December, lava from Kilauea continued to enter the sea at the E 
Lae`apuki area and surface lava flows were visible on the Pulama pali 
fault scarp.

 From 28 December 2005 to 9 January 2006, lava from Kilauea continued to 
enter the sea at the E Lae`apuki area building a new lava delta with 
surface lava flows visible on the Pulama pali fault scarp. Background 
volcanic tremor was near normal levels at Kilaueas summit. Volcanic 
tremor reached moderate levels at Pu`u `O`o. Small amounts of 
deformation occurred. On 10 January, the summit deflation switched 
abruptly to inflation after a loss of 5.2 urad. Relatively high tremor 
occurred at this time. The tremor quickly dropped, becoming weak to 
moderate when deflation ended, with seismicity punctuated by a few small 
earthquakes. By 13 January, background volcanic tremor was near normal 
levels at Kilaueas summit and reached moderate levels at Pu`u `O`o. On 
14 January, the lava delta was about 500 m long (parallel to shore) and 
still 140 m wide. By the end of the month the lava delta was 615 m long 
and 140 m wide. Background volcanic tremor was near normal levels at 
Kilaueas summit, with numerous shallow earthquakes occurring at the 
summit and upper E rift zone during several days.

During 2-7 February 2006, lava from Kilauea continued to enter the sea 
at the E Lae`apuki area and surface lava flows were visible on the 
Pulama pali fault scarp. Background volcanic tremor was near normal 
levels at Kilaueas summit, with numerous shallow earthquakes continuing 
to occur at the summit and upper E rift zone. Volcanic tremor reached 
moderate levels at Pu`u `O`o. Small amounts of inflation and deflation 
were reported. From mid-to-late February, surface lava flows were not 
visible on Kilaueas Pulama pali fault scarp due to lava traveling 
underground through the PKK lava tube until reaching E Lae`apuki lava 
delta and flowing into the sea. Observations on 7 February 2006 revealed 
that the lava delta had broadened 120 m W since 30 January 2006.

Geologic Summary. Kilauea volcano, which overlaps the east flank of the 
massive Mauna Loa shield volcano, has been Hawaiis most active volcano 
during historical time. Eruptions of Kilauea are prominent in Polynesian 
legends; written documentation extending back to only 1820 records 
frequent summit and flank lava flow eruptions that were interspersed 
with periods of long-term lava lake activity that lasted until 1924 at 
Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was 
formed in several stages about 1500 years ago and during the 18th 
century; eruptions have also originated from the lengthy East and SW 
rift zones, which extend to the sea on both sides of the volcano. About 
90% of the surface of the basaltic shield volcano is formed of lava 
flows less than about 1100 years old; 70% of the volcanos surface is 
younger than 600 years. A long-term eruption from the East rift zone 
that began in 1983 has produced lava flows covering more than 100 sq km, 
destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. 
Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: 
http://hvo.wr.usgs.gov/; Email: hvo-info@xxxxxxxxxxxxxxxxxxx).


Karymsky
Kamchatka Peninsula, Russia
54.05 N, 159.43 E; summit elev. 1,536 m

Karymsky was last reported on in BGVN 30:11. After frequent explosions 
from December 2004 to June 2005 (BGVN 30:06) a brief decrease in seismic 
and volcanic activity took place but this ended in late June when ash 
and gas plumes rose to 3 km above the crater. Seismicity remained above 
background levels throughout August-December 2005. During this period, 
ash and gas plumes and thermal anomalies were observed at the volcano.

Seismic activity indicated that ash explosions from the summit crater of 
Karymsky continued during 14-20 January 2006. Ash plumes extending 6-9 
km S from the volcano were observed on 12 January and a thermal anomaly 
over the dome was observed during 13-15 January. According to seismic 
data, two possible ash plumes rose to 3.0-3.4 km altitude on 14-15 January.

According to reports from pilots of local airlines, ash emissions from 
Karymsky rose to 4-5 km altitude during 30-31 January. The ash plumes 
extended 13-29 km to the SW and SE, respectively. A thermal anomaly was 
visible at the lava dome during 27 January to 3 February, except when 
the volcano was obscured by clouds on 28 January. KVERT warned that 
activity from the volcano could affect nearby low-flying aircraft.

Strombolian activity continued through April 2006. During 10 February to 
10 March, a large thermal anomaly was visible at the crater and numerous 
ash plumes were visible on satellite imagery extending as far as 140 km. 
On 9 March, a pilot reported an ash plume at a height of ~ 3 km altitude.

During 17-24 March, several ash plumes were visible on satellite imagery 
at a height of ~ 4 km altitude and extending SE and E. A thermal anomaly 
was seen at the volcano during periods of visibility. About 40-450 small 
earthquakes occurred daily.

During 7-14 April satellite imagery showed ash plumes extending ~ 40-145 
km E and SE of the volcano, and a large thermal anomaly at the crater. 
Karymsky remained at Concern Color Code Orange from January to April 2006.

Geologic Summary. Karymsky, the most active volcano of Kamchatkas 
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.

Information Contacts: Olga Girina, Kamchatka Volcanic Eruptions Response 
Team (KVERT), a cooperative program of the Institute of Volcanic Geology 
and Geochemistry, Far East Division, Russian Academy of Sciences, Piip 
Ave. 9, Petropavlovsk-Kamchatskii 683006, Russia (Email: 
girina@xxxxxxxxxx), the Kamchatka Experimental and Methodical 
Seismological Department (KEMSD), GS RAS (Russia), and the Alaska 
Volcano Observatory (USA); 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/; 
Email: tlmurray@ usgs.gov), the Geophysical Institute, University of 
Alaska, P.O. Box 757320, Fairbanks, AK 99775-7320, USA (Email: 
eisch@xxxxxxxxxxxxxxxxxx), and the Alaska Division of Geological and 
Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 
99709, USA (Email: cnye@xxxxxxxxxxxxxxxxx); Tokyo Volcanic Ash Advisory 
Center (VAAC) (URL: 
http://www.jma.go.jp/JMA_HP/jma/jma-eng/jma-center/vaac/; Email: 
vaac@xxxxxxxxxxxxxxxxxx).


Bezymianny
Kamchatka Peninsula, Russia
55.98 N, 160.59 E; summit elev. 2,882 m
All times are local (= UTC + 13 hours)

This report describes a substantial eruption on 9 May 2006, and events 
before and shortly afterwards. Bezymianny was last reported on in BGVN 
30:11, covering a series of events during mid-January through late 
December 2005.

An explosive eruption occurred on 30 November 2005. Seismicity decreased 
subsequently and from January to the end of April 2006, Bezymianny 
remained comparatively calm; fumarolic activity and a small thermal 
anomaly were observed during periods of good visibility. A 1 April 
aerial photo of the summit area appears as figure 23.

Figure 23. Bezymianny aerial photo taken on 1 April 2006, showing the 
large dome within the breached summit crater. Labels indicate both a 
fissure on the domes flank and a large extrusive block (or spine) on 
the domes top. Considerable areas discharged light steam. Photo by Yu. 
Demyanchuk and provided courtesy of KVERT.

During 28 April to 5 May, Bezymiannys lava dome continued to grow. 
Seismicity was above background levels during 30 April to 3 May. 
Incandescent avalanches were visible on 4 May. At the lava dome, 
fumarolic activity occurred and thermal anomalies were visible on 
satellite imagery. Bezymianny was at Yellow on the four stage Concern 
Color Code (low to highGreen, Yellow, Orange, Red).

On 7 May the Concern Color Code was raised to Orange due to an increase 
in seismicity and the number of incandescent avalanches (14 occurred on 
6 May in comparison to 4-6 during the previous 2 days). Intense 
fumarolic activity occurred, with occasional small amounts of ash. KVERT 
reported that an explosive eruption was possible in the next 1 or 2 weeks.

9 May eruption. On 9 May around 1935, the Concern Color Code was raised 
to Red, the highest level, due to increased seismicity and incandescent 
avalanches. A gas plume rose higher than 7 km altitude and a strong 
thermal anomaly was visible on satellite imagery.

An explosive eruption occurred on 9 May during 2121 to 2145. The 
explosion produced an ash column that rose to a height of ~ 15 km 
altitude. A co-ignimbrite ash plume was about 40 km in diameter and 
mainly extended NE of the volcano. Ash plumes extended more than 500 km 
ENE from the volcano. Pyroclastic flows deposits extended 7-8 km from 
the volcano.

On 10 May around 0100, seismicity returned to background levels and the 
Concern Color Code was reduced to Orange. Small fumarolic plumes were 
observed during the early morning of the 10th and lava probably began to 
flow at the lava dome.

By 11 May seismic activity was still at background levels. Gas and steam 
plumes were visible above the volcano. A thermal anomaly was noted at 
the volcano on 10-11 May. Lava effusion was probably occurring at the 
lava dome. This was interpreted to mean that the likelihood of a large, 
ash-producing eruption had diminished.

Geologic Summary. Prior to its noted 1955-56 eruption, Bezymianny 
volcano had been considered extinct. The modern Bezymianny volcano, much 
smaller in size than its massive neighbors 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 1,000-year 
quiescence, began with the dramatic 1955-56 eruption. This eruption, 
similar to that of Mount 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.

Information Contacts: KVERT and AVO (see Karymsky).

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