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Archive for March 19th, 2009

Weekly Volcano Watch: 19 March 2009

Posted by feww on March 19, 2009

Volcanic Activity Report: 11 March – 17 March 2009

Source: SI / USGS Weekly Volcanic Activity Report

New activity/unrest:

VoW: Hunga Tonga-Hunga Ha’apai, Tonga

Tonga Islands 20.57°S, 175.38°W; summit elev. 149 m – submarine volcano

An underwater volcanic eruption near the twin islands of Hunga Tonga and Hunga Ha’apai spewed a large column of  off-white smoke into the air. The plume rose to altitudes of about 8 km [possibly as high as 15km.]

tonga-ap
Hunga Ha’apai eruption [March 17-18, 2009] Aerial photo by Trevor Gregory/AP. Source. Image may be subject to copyright.

Observers flying near the area of Hunga Tonga-Hunga Ha’apai (about 62 km NNW of Nuku’alofa, the capital of Tonga) on 16 or 17 March reported seeing an eruption. Photos showed an eruption plume with a wide base that rose from the sea surface and mixed with meteorological clouds. Based on information from the Tonga airport and analysis of satellite imagery, the Wellington VAAC reported that on 18 March, a plume rose to altitudes of 4.6-7.6 km (15,000-25,000 ft) a.s.l. and drifted NE.

Geologic Summary. The small islands of Hunga Tonga and Hunga Ha’apai cap a large seamount located about 30 km SSE of Falcon Island. The two linear andesitic islands are about 2 km long and represent the western and northern remnants of a the rim of a largely submarine caldera lying east and south of the islands. Hunga Tonga and Hunga Ha’apai reach an elevation of only 149 m and 128 m above sea level, respectively, and display inward-facing sea cliffs with lava and tephra layers dipping gently away from the submarine caldera. A rocky shoal 3.2 km SE of Hunga Ha’apai and 3 km south of Hunga Tonga marks the most prominent historically active vent. Several submarine eruptions have occurred at Hunga Tonga-Hunga Ha’apai since the first historical eruption in 1912. GVP reported.


The small islands of Hunga Tonga and Hunga Ha’apai cap a large seamount located about 30 km SSE of Falcon Island. The two linear andesitic islands are about 2 km long and represent the western and northern remnants of a the rim of a largely submarine caldera lying east and south of the islands. Hunga Tonga and Hunga Ha’apai reach an elevation of only 149 m and 128 m above sea level, respectively, and display inward-facing sea cliffs with lava and tephra layers dipping gently away from the submarine caldera. A rocky shoal 3.2 km SE of Hunga Ha’apai and 3 km south of Hunga Tonga marks the most prominent historically active vent. Submarine eruptions were reported here in 1912 and 1937 and from a fissure 1 km SSE of Hunga Ha’apai in 1988. Aerial photo by Tonga Ministry of Lands, Survey, and Natural Resources, 1991 (published in Taylor and Ewart, 1997). Caption: GVP.


Hunga Tonga-Hunga Ha’apai volcano from space. Image captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite  on March 18, 2008. “In this image, the area around the eruption appears bright blue-green, likely resulting from sediment suspended in the water. The brilliant white patch at the center of the sediment-rich area may result from vapor released by the volcano. Northwest of the eruption site, a serpentine pumice raft floats on the water. The highly porous nature of pumice enables this volcanic rock to form floating rafts. (A larger pumice raft resulted from a similar eruption in the Tonga Islands in August 2006.).” Earth Observatory said.


A March 18 photo of Hunga Tonga-Hunga Ha’apai eruption as seen from the Nuku’alofa waterfront. Photo: AP/Matangi Tonga Online. Source. Image may be subject to copyright.

volcanoes-of-tonga
USGS Map of Major Volcanoes of Tonga with the approximate location of
Hunga Tonga-Hunga Ha’apai volcano marked.


Photo dated
Wednesday, March 18, 2009. Source: Xinhua/AFP. Image may be subject to copyright.

Video: Underwater volcano erupts off Tonga

Hunga Tonga-Hunga Ha’apai volcano

Flights were disrupted and airlines alerted after the undersea Hunga Tonga-Hunga Ha’apai volcano erupted.  Air New Zealand flights were forced to divert to  avoid  smoke, which reportedly rose to a height of about 15 km, various media reported.

The volcano located about 12km off the southwest coast off the main island of Tongatapu  is thought to have erupted on Monday. Hunga Tonga-Hunga Ha’apai is one of about 40 submarine volcanoes in the area.

It’s thought that the eruption does not pose an immediate threat to the residents because trade winds are blowing the smokes and  gases away from the island.

“It’s a very significant eruption, on quite a large scale.” Said Tonga’s Geological Service Chief, Keleti Mafi.

Rumble III

On March 13, the underwater volcano Rumble III,  located about 300km northeast of Bay of Plenty, New Zealand, was discovered to have undergone a “startling change” losing about 100m of its summit, with the 800m-wide crater completely missing, apparently in a catastrophic explosion.

Metis Shoal

On February 3, FEWW forecast that Metis Shoal, a submarine volcano located midway between the islands of Kao and Late (about 50 km NNE of Kao), was about to erupt, or was currently undergoing a period of unrest.

FEWW moderators believe that both  Metis Shoal, if indeed it has erupted / is erupting, and Hunga Tonga-Hunga Ha’apai volcanoes may have been triggered simultaneously.

FEWW List of Forgotten Volcanoes

Ongoing Volcanic Activity:

Elevated Volcanic Activity and Information Releases

Wednesday, Mar 18, 2009 at 17:47:50 PDT.

The following U.S. volcanoes are known to be above normal background (elevated unrest or eruptions) or have shown activity that warranted an Information Release (for example, an earthquake swarm).

Times are local to the volcano and in 24-hr format.
Volcano Alert Levels & Aviation Color Codes defined at http://volcanoes.usgs.gov/activity/alertsystem.

Volcano Hazards Program Webcams page links to webcams at 19 of the 169 active volcanoes in the U-S.

Related Links:

Posted in Chaiten, Galeras, Metis Shoal, Redoubt, Rumble III | Tagged: , , , , | 2 Comments »

 
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