SI/USGS Weekly Volcanic Activity Report 21-27 October 2009

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The Smithsonian Institution/United States Geological Survey Weekly Volcanic Activity Report for 21-27 October 2009 is available on the Global Volcanism Program website. The following is a summary and not a substitute for the full report.

• The current report: Weekly Volcanic Activity Report.
• Previous reports: Weekly Reports Archive.
• The SI/USGS map of volcanoes discussed this week.

New activity/unrest: Chaitén (Chile), Ebeko (Russia), Kliuchevskoi (Russia), Mayon (Philippines), Nevado del Huila (Colombia), Reventador (Ecuador), Soufrière Hills (Montserrat).

Ongoing activity: Batu Tara (Indonesia), Colima (Mexico), Dukono (Indonesia), Fuego (Guatemala), Karymsky (Russia), Kilauea (Hawaii, USA), Pacaya (Guatemala), Rabaul (Papua New Guinea), Sakura-jima (Japan), Santa María (Guatemala), Shiveluch (Russia).

Note: a.s.l. = ‘above sea level’.

NEW ACTIVITY/ UNREST

Chaitén (Chile). The lava-dome complex continued to grow during 1-15 October. On clear days steam from the E part of the complex and ash-and-steam plumes from the central part were observed. Small emissions originated from numerous areas. An explosion on 14 October produced a dense ash cloud that drifted W, and Buenos Aires VAAC reported continuous emissions on 21 October. Plumes rose to altitudes of 1.8-2.4 km a.s.l. and drifted SSE. The alert level remaind at Red.

Ebeko (Russia). A possible eruption plume was reported by Tokyo VAAC to have risen to 8.8 km a.s.l. and drifted E. Emissions continued the next day.

Kliuchevskoi (Russia). During 16-23 October seismic activity was above background levels and satellite imagery revealed a daily thermal anomaly. Strombolian activity ejected tephra 500 m above the crater and fumarolic plumes were noted during 16 and 18-22 October. The Level of Concern Color Code remained at Orange.

Mayon (Philippines). On 28 October a minor ash explosion produced a brownish ash plume that rose 600 m above the crater and drifted NE. The Alert Level remained at 2.

Nevado del Huila (Colombia). A possible eruption was reported by Washington VAAC on 20 October. An ash plume was seen on satellite imagery drifting 45 km S and increased seismicity was reported. Another ash cloud was seen on satellite imagery drifting S later that day. On 21 October continuous gas emissions rose and pulses of ash emissions produced plumes that drifted E. Observations during an overflight on 23 October revealed that gas-and-ash emissions originated from two locations. The area of greater discharge was between Pico Central and the lava dome, while fewer emissions came from the fissure that opened in April 2007, NE of Pico Central. Lava-dome growth was concentrated on the N end of the lava dome, an area also exhibiting a thermal anomaly detected with a thermal imaging camera. Ashfall and sulfur odors were reported in several inhabited areas on 23 and 24 October. Washington VAAC reported that on 24 October an eruption produced an ash plume that rose to 9.1 km a.s.l. and drifted WSW. During 25-26 October, thermal anomalies were seen on satellite imagery. A plume drifted WSW on 25 October and a gas-and-ash plume drifted 90 km NW and SW on 26 October. The Alert Level remained at Orange (II).

Reventador (Ecuador). Steam-and-gas plumes with little to no ash content rose 2-4 km above the crater and drifted NW, W, and S on 21 October, and an explosion that day ejected incandescent material from the crater, and blocks rolled down the flanks. A few explosions on 22 October generated ash-and-steam plumes with little to no ash content that rose 4 km and drifted NW, E, and SE. Overflight observations revealed a small lava flow on the N flank and a larger flow with four branches on the S flank. Some of the base of the lava dome had been removed, and small spines were present, especially on the S side of the dome. Thermal images revealed that material in the crater was 400 degrees Celsius and the lava-flow fronts were 250 degrees Celsius. Roaring noises were heard on 25 October.

Soufrière Hills (Montserrat). During 16-25 October activity at the lava dome was at a high level. The new lava dome on the W side of the summit reported on 9 October continued to grow, and was considerably higher than the older lava dome to the E. Seismicity was high and cycles of low-level tremor occurred at regular intervals. Several pyroclastic flows descended S along the White River to the sea, and small pyroclastic flows traveled NE down Tuitts Ghaut and W down Gages valley. Rockfalls occurred on the S and SE flanks of the lava dome. Multiple ashfalls were reported in inhabited areas, and lahars traveled NW down the Belham valley. During 23-25 October, seismicity decreased and ash plumes generated by pyroclastic flows drifted W. The Hazard Level remained at 3.

ONGOING ACTIVITY

Batu Tara (Indonesia). Darwin VAAC reported ash plumes drifting 65 km W and NW at 2.1 km a.s.l. on 27 October.

Colima (Mexico). On 22 October a grey plume rose to 4 km a.s.l. and drifted SW. On 23 October white plumes drifted NE and N, one at 4.2 km a.s.l.

Dukono (Indonesia). Darwin VAAC reported ash plumes to 2.1-2.4 km a.s.l. and drifting 45-95 km NE and E during 22-23 and 26-27 October.

Fuego (Guatemala). Washington VAAC reported an apparent ash plume on 20 October drifting SSW. Multiple ash emissions on 21 October produced an ash cloud that drifted 55 km S, and emissions were also reported on the next day. On 26 October, a diffuse gas-and-ash plume drifted W, and explosions produced plumes that rose to 4.4-4.8 km a.s.l. and drifted 10 km S and SW. Ash fell downwind, rumbling and degassing sounds were reported, and avalanches of blocks descended the flanks. On 27 October, a few ash clouds seen on satellite imagery drifted 90 km NW.

Karymsky (Russia). Seismic activity was above background levels during 16-23 October and possibly indicated that ash plumes rose to 3.9 km a.s.l. Tokyo VAAC reported that eruptions during 24-25 October produced plumes that rose to 3.4-3.7 km a.s.l. Ash was not identified on satellite imagery. The Level of Concern Color Code remained at Orange.

Kilauea (Hawaii, USA). During 21-27 October lava flowed SE from underneath Kilauea’s Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha ocean entry on most days. Thermal anomalies detected in satellite images and visual observations revealed active surface lava flows. For a few days an active lava flow advanced on the coastal plain, burning vegetation and pavement along the former Kalapana access road. Intermittent incandescence was seen from the Pu’u ‘O’o crater floor and an East wall vent.

Pacaya (Guatemala). On 23 and 26 October white and blue plumes from MacKenney cone rose 50-150 m and drifted W and SW. Multiple lava flows on the S flank traveled 75-350 m SSW.

Rabaul (Papua New Guinea). During 16-22 October diffuse white plumes and grey ash plumes rose from Tavurvur cone. Ash plumes rose 700 m above the crater. Ashfall was reported to the NW.

Sakura-jima (Japan). Tokyo VAAC reported that explosions during 21-22, 24-25, and 27-28 October produced plumes that rose to altitudes of 1.5-2.4 km a.s.l. Some plumes drifted W, SW, S, and SE.

Santa María (Guatemala). Washington VAAC reported multiple ash plumes from the Santiaguito lava dome complex that drifted less than 20 km SW on 22 October. Explosions on 23 and 26 October produced ash plumes that rose above Caliente dome to 3-3.3 km a.s.l. which drifted W and SE and caused ashfall downwind. Avalanches descended the SW flank of the dome. Degassing sounds resembling aircraft engines were heard.

Shiveluch (Russia). During 16-23 October seismic activity was above background levels and possibly indicated that ash plumes rose to 4.5 km a.s.l. Analyses of satellite imagery revealed a large thermal anomaly over the lava dome. Multiple hot avalanches were observed descending the lava dome. Deposits on the SE flank from a small pyroclastic flow were noted. Fumarolic plumes rose to 2.8-5 km a.s.l. during 16, 18-20 and 22 October. The Level of Concern Color Code remained at Orange.

ACKNOWLEDGEMENTS AND DISCLAIMER

The foregoing is a summary of the Smithsonian Institution/United States Geological Survey Weekly Volcanic Activity Report covering 21-27 October 2009. It is provided for information only, and is based on but not a substitute for the full report, which comes with its own criteria and disclaimers. The map base is derived from the Smithsonian Institution/USGS/US Naval Research Laboratory This Dynamic Planet website.

For all our coverage of the SI/USGS Weekly Volcanic Activity Reports: Weekly Volcanic Activity Reports « The Volcanism Blog.