Bulletin of the Global Volcanism Network, April 2006

From: Ed Venzke

Global Volcanism Program

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
2
000.html>.

Information Contacts: Patricia Nadeau and Glyn Williams-Jones,
Department of Earth Sciences, Simon Fraser University, Burnaby, Canada
(Email: panadeau@sfu.ca, glynwj@sfu.ca); Kirstie Simpson, Geological
Survey of Canada, Vancouver, Canada (Email: ksimpson@nrcan.gc.ca);
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@ibw.com.ni).

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@igepn.edu.ec); 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@tboeckel.de).

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@ucn.cl, emedina@ucn.cl,
kgm001@ucn.cl; 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@unsa.edu.ar; URL:
http://www.unsa.edu.ar/natura/); Ricardo Valenti and Sergio Haspert,
Servicio Metereologico Nacional, Argentina (Email:
rvalenti@meteo.edu.ar; sergio_sah@email.com); Hugo G. Delgado, Instituto
de Geofisica, Universidad Nacional Autonoma de Mexico (UNAM), Coyoacan
04510, Mexico, D.F. (Email: hugo@tonatiuh.igeofcu.unam.mx); 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@higp.hawaii.edu); 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@pcmail.nerc-bas.ac.uk).

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@vsi.esdm.go.id; 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@hvomail.wr.usgs.gov).

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@kcs.iks.ru), 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@dino.gi.alaska.edu), and the Alaska Division of Geological and
Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK
99709, USA (Email: cnye@giseis.alaska.edu); Tokyo Volcanic Ash Advisory
Center (VAAC) (URL:
http://www.jma.go.jp/JMA_HP/jma/jma-eng/jma-center/vaac/; Email:
vaac@eqvol.kishou.go.jp).

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).

Forwarded with permission from ASU Volcano List Moderator.

-




No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.8.4/364 - Release Date: 6/14/2006


__._,_.___
Messages in this topic (1) Reply (via web post) | Start a new topic
Messages | Files | Photos | Links | Database | Polls | Members | Calendar

You are receiving Individual Emails Change Delivery Settings
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe New Message Search
Find the message you want faster. Visit your group to try out the improved message search.



Share feedback on the new changes to Groups

Visit Your Group
SPONSORED LINKS
Weather
Science
Computer science
Science education
Weather equipment
Weather stations
.



No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.9.10/383 - Release Date: 7/7/2006