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From: Berhane Habtemariam (Berhane.Habtemariam@gmx.de)
Date: Tue Jun 28 2011 - 09:57:54 EDT
Eritrean Volcano Ejects More SO2 And Ash
By Mark Dunphy - Tue Jun 28, 1:59 pm
The Nabro volcano in Eritrea, north east Africa, continued to erupt Tuesday
despite a statement from the Toulouse-based
<http://www.meteo.fr/vaac/archives/NABRO/e.20110627050900.NABRO.201125.20110
6270600.html> Volcanic Ash Advisory Centre (VAAC) that the eruption had
stopped.
The stratovolcano has continued to emit large volumes of ash, SO2 (sulphur
dioxide) and water vapour since it erupted for the first time in recorded
history on 12 June 2011.
Since then much of northern Ethiopia has been shrouded by a large ash plume
that has reportedly contributed to at least seven deaths and resulted in
food shortages in some regions. The Mines at the Ministry of Energy and
Mines confirmed that inhabitants of the area have been moved to safer
locations while at the same time they are being given basic provisions.
The ash plume also temporarily affected air traffic two weeks ago it drifted
as far away as Israel, Jordan, Turkmenistan and the Central African Republic
(CAR).
A still image from the MODIS satellite showed a thick ash plume drifting
over Eritrea's border into Ethiopia Tuesday afternoon. The volcanic ash was
drifting SW. Winds in the region were light NE when the below images were
captured at midday Tuesday.
Meanwhile, the below pair of satellite images are among the first detailed
pictures of the erupting vent and lava flows. They were acquired by the
Advanced Land Imager (ALI) aboard the Earth Observing-1 (EO-1) satellite on
June 24, 2011.
The bright red portions of the false-colour image (top) indicate hot
surfaces. Hot volcanic ash glows above the vent, located in the centre of
Nabro's caldera. To the west of the vent, portions of an active lava flow
(particularly the front of the flow) are also hot. The speckled pattern on
upstream portions of the flow are likely due to the cool, hardened crust
splitting and exposing fluid lava as the flow advances. The bulbous
blue-white cloud near the vent is likely composed largely of escaping water
vapour that condensed as the plume rose and cooled. The whispy, cyan clouds
above the lava flow are evidence of degassing from the lava.
The natural-colour image (lower) shows a close-up view of the volcanic plume
and eruption site. A dark ash plume rises directly above the vent, and a
short, inactive (cool) lava flow partially fills the crater to the north. A
gas plume, rich in water and sulfur dioxide (which contributes a blue tint
to the edges of the plume) obscures the upper reaches of the active lava
flow. Black ash covers the landscape south and west of Nabro.
Part of the Afar Triangle, Nabro is one of many volcanic caldera complexes
in the north easternmost part of the East African Rift valley region. The
stratovolcano is located in the Danakil Depression, close to Eritrea's
border with Ethiopia and north of Djibouti, and has not erupted in at least
150 years. According to data, a similar volcanic eruption in Eritrea
occurred in 1861, in Dubbi, Southern Denkel.
Nabro is the most prominent of 3 large volcanoes (Nabro, Dubbi, Mallahle) in
the region, each containing a large summit caldera. Nabro comprises lava
domes, lava flows, and two calderas, 8 and 5 km in diametre.
The volcano is located along the Great Rift Valley, also known as the East
African Rift. the divergent plate boundary extends from the Afar Triple
Junction southward across eastern Africa, and is in the process of splitting
the African Plate into two new separate plates, the Nubian Plate and the
Somali Plate. Seismic activity is frequent in Ethiopia In 1961 alone three
thousand tremors were recorded from the centre of the Wollo province
resulting in a 20km fissure being opened on the slopes of the Borkena
graben.
<http://www.irishweatheronline.com/wp-content/uploads/2011/06/Nabro-volcano-
and-ash-plume-at-midday-Tuesday.-Image-Modis.jpg> Nabro volcano and ash
plume at midday Tuesday. Image Modis
Nabro volcano and ash plume at midday Tuesday. Image Modis
<http://www.irishweatheronline.com/wp-content/uploads/2011/06/a2.jpg> NASA
Earth Observatory image by Robert Simmon, using EO-1 ALI data. Caption by
Robert Simmon.
NASA Earth Observatory image by Robert Simmon, using EO-1 ALI data. Caption
by Robert Simmon.
<http://www.irishweatheronline.com/wp-content/uploads/2011/06/b2.jpg> NASA
Earth Observatory image by Robert Simmon, using EO-1 ALI data. Caption by
Robert Simmon. Instrument: EO-1 - ALI
NASA Earth Observatory image by Robert Simmon, using EO-1 ALI data. Caption
by Robert Simmon. Instrument: EO-1 - ALI
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