VolcanoWatch Weekly [7 October 2009]

VOW:  Ambrym

Destructive acid rain caused by eruption

According to press reports, an eruption from Benbow Crater occurred on 10 February [1979.]  Gases from the eruption caused acid rainfall on the SW portion of Ambrym Island, destroying most vegetation within 24 hours, contaminating water supplies, and burning some inhabitants. Jean-Luc Saos, Director of Mineral Resources for the New Hebrides government, reported a high concentration of HCl and sulfur compounds in the volcanic gases. Although heavy ashfalls have occurred in the area in the past, this is the first report of acid rains. More …

View of the Marum cone at Ambrym looking SW, 7 June 2007. Incandescence from the active lava lakes can be seen reflected in the clouds (left). Courtesy of Steven Clegg.

Lava lake inside Mbwelesu crater within Marum cone at Ambrym, 7 June 2007. Courtesy of Steven Clegg.

A hazy layer of vog—volcanic fog—overlies Malekula and a few other islands of the Vanuatu archipelago in this natural-color satellite image. The source of the vog is Ambrym, a volcano in the southeast (lower right) corner of this scene. The haze extends over the Coral Sea several hundred kilometers to the northwest. Ambrym emits sulfur dioxide—the gas responsible for the formation of vog— intermittently. (Kilauea Volcano has recently affected the residents of Hawaii with similar vog emissions.)  The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite acquired this natural-color image on October 6, 2009. [Large earthquake measuring up to 8.2 Mw struck Vanuatu region  on October 7, 2009 at 22:03 UTC. FEWW] NASA image by Jeff Schmaltz, MODIS Rapid Response, NASA Goddard Space Flight Center. The Rapid Response Team provides twice-daily images of this region. Caption by Robert Simmon.

Ash plume from Ambrym Volcano, Vanuatu October 4, 2004, 23:00 UTC.  Source: NASA/MODIS Rapid Response System.

View into the Mbwelesu crater on the Marum cone at Ambrym, captured 7 September 2008. Lava can be seen through two gaps in the crusted-over lava lake (enlarged insets). Courtesy of Arnold Binas.

Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations. Caption: GVP

Ambtym
Country: Vanuatu
Subregion Name: Vanuatu
Volcano Number: 0507-04=
Volcano Type: Pyroclastic shield
Volcano Status: Historical
Last Known Eruption: 2009
Summit Elevation: 1334 m 4,377 feet
Latitude: 16.25°S 16°15’0″S
Longitude: 168.12°E 168°7’0″E

SI /USGS Weekly Volcanic Activity Report
(30 September – 6 October 2009)

New activity/Unrest:

• Chaitén, Southern Chile
• Cleveland, Chuginadak Island
• Galeras, Colombia
• Gaua, Banks Islands (SW Pacific)
• Karymsky, Eastern Kamchatka (Russia)
• Kliuchevskoi, Central Kamchatka (Russia)
• Sakura-jima, Kyushu
• Shiveluch, Central Kamchatka (Russia)
• Soufrière Hills, Montserrat

News From GVP:

On 29 September, people living in Chaitén town, 10 km SW of Chaitén’s Domo Nuevo 1 (Phase I) and Domo Nuevo 2 (Phase II) lava-dome complex, noticed that the eruption column was larger. Scientists conducted an overflight and saw a third lava dome (Phase III) in the SW area of the complex, which had filled up a depression left by a collapse on 19 February.

According to news articles from 2 October, increased seismicity at Gaua was detected during the previous two weeks. Villagers living nearby reported ashfall and sulfur odors.

An explosive eruption from Galeras on 30 September prompted INGEOMINAS to raise the Alert Level. An ash plume rose to an approximate altitude of 12.3 km (40,400 ft) a.s.l. and drifted E, then N. —GVP

Ongoing Activity:

• Batu Tara, Komba Island (Indonesia)
• Dukono, Halmahera
• Kilauea, Hawaii
• Langila, New Britain
• Popocatépetl, México
• Rabaul, New Britain
• Reventador, Ecuador
• Sangay, Ecuador
• Suwanose-jima, Ryukyu Islands (Japan)

Related Links:

• Messages From Earth’s Powerhouse
• Weekly Volcano Watch: 19 March 2009

• A New Era of Intense Volcanic Unrest May Have Begun
• Tonga’s Metis Shoal may be erupting
• Rumble III Volcano “blew its top!”
• Volcanoes
• Earthquakes

FEWW Volcanic Activity Forecast

• Sumatra’s Mt Kerinci Erupts

• Sumatra’s Mt Kerinci Erupts
• Volcano Watch Weekly: 23 April 2009

• Weekly Volcano Watch: 16 April 2009
• Weekly Volcano Watch: 2 April 2009

• FEWW Volcano Links
• Volcanoes
• FEWW Earthquake Links

Other Related Links:

• U.S. Volcano Status Map
• Elevated Activity Page
• U.S. Volcano Webcams

Recent Posts on Chaitén:

• Chaitén: A New Phase of Activity?
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