2011 Nabro eruption

• 
  Satellite image of Ethiopia/ Eritrea showing the ash plume from Nabro on 13 June 2011.
• 
  False color image from 19 June 2011 showing extent of lava flow on that date.
• 
  True color image from 19 June 2011 showing area affected by tephra deposition, and international boundaries.
• 
  Natural color satellite view of the volcano on 29 June 2011.

• 12 June 2011: Satellite images showed a large volcanic eruption shortly after 22.00 UTC 12 June (close to 01.00 13 June local time), in the Southern Red Sea Region. It was first thought to have originated at Dubbi Volcano, but has been confirmed to be from the Nabro[8][9][10] stratovolcano in Eritrea, near the Ethiopian border.[11][12][13]
• 17 June 2011: The Volcanic Ash Advisory Center (VAAC) reported that the eruption had ceased.
• 18 June 2011 (at noon, local time): NASA's Aqua satellite passed overhead providing MODIS images which showed an ash plume heading in west-north-westerly direction.[14]
• 19 June 2011: The volcano produced the highest level of sulfur dioxide emissions in the earth's atmosphere ever detected from space.[5] Satellite images showed a 15 km long lava flow.[15]
• 20 June 2011: VAAC reported that the SO₂ eruption was continuing.[16]
• 22 to 27 June 2011: The eruption of sulfur dioxide, water vapour, and ash was confirmed to be still active by MODIS pictures taken from the TERRA satellite.[17][18]
• 24 June 2011: NASA Earth Observatory provided this false-color image (below) using the Advanced Land imager on the EO-1 satellite, showing that the lava flow from the 19th had not progressed significantly further, but that the eruption was ongoing.
• 30 June 2011: At least some of the people who have been evacuated are reported to be in Hawra and Wadien.[19]

False color image from 24 June

• 30 June 2011: Eruption satellite images seem to show the volcano has stopped producing the ash cloud.
• 1 July 2011: Eruption satellite images show a fresh ash cloud eruption, diminishing until 4 July, when the ash eruption still appears to be ongoing.[20]
• 6 July 2011: By now the ash cloud seems to have again stopped being produced.
• 7 July 2011: After this date, SO₂ emissions were much reduced.
• 12 July 2011: The eruption was still ongoing.[21]

The eruption has ejected a large ash cloud near the Eritrea–Ethiopia border region, extending over 1,000 km (620 mi) into neighboring Sudan.[24]

The height of the ash cloud peaked at 14,000 m,[25] implying a VEI of 4.[1]

Forecasters predicted correctly[26] that the ash plume might reach Israel,[27] but no flights were cancelled at Ben-Gurion Airport on 14 June.[26] Elsewhere, however, the ash cloud began disrupting air traffic on 14 June with UAE-based Emirates flights being cancelled;[28] flights disruptions extended to other companies the following day.[29] Hillary Clinton, Secretary of State for the United States, shortened her state visit to Ethiopia. Djibouti Airport was closed, and several airlines suspended flights to Ethiopia.[6]

Mek'ele and Asmara were partially covered by volcanic ash.[30]

On 16 June, the inhabitants of Afambo, Nebro, and Sireru were evacuated.[31]

By 19 June, ash had been deposited at least 60 km (37 mi) beyond the Ethiopian border in a WNW–to–SSW direction.[5]

By 20 June, eight villages in the Biddu district of Ethiopia were covered by volcanic ash, affecting at least 5,000 people and polluting springs and streams. One entire community has not been heard from. Save the Children reports many community members, especially children, are sick and in desperate need of medical attention. Vomiting and retching were reported as being common effects.[32]

On 21 June, an Eritrean government statement reported seven people have been killed and three injured.[3][33] It was also reported that the Lake Afrera salt deposits now contain sulfuric acid, making the salt inedible.[22]

On 6 July, reports suggest 48,000 people in the Bidu, Afdera, Erebti, Elidar, Teru and Kori woredas were in need of aid (with ash affecting food and water sources), and that the casualty total had reached 31 dead in the Bidu woreda.[4]

Another 167,153 people, in the Elidar and Kori woredas, were reported as requiring monitoring according to the Afar regional government. However a spokesman for the Ethiopean Government Agriculture Ministry is reported to have said "We have looked at the document and I would like to make it clear that it is not a national document and that we have not endorsed it, the ministry has no record of casualties, it is still too early to say how many people had been affected and needed help."[4]

The erupting volcano is in the Afar Triangle, in the larger Danakil Depression that holds many other active volcanoes. However, neither volcano thought potentially responsible for the eruption had been active in the past century, with Dubbi last erupting in 1861 and Nabro remaining quiet for thousands of years. No eruption of Nabro occurred before in recorded history.[7] Basalt, trachyte and rhyolite are among the rock types which Nabro has produced as lava flows and pyroclastics.[34]

A series of moderate earthquakes occurred near a sparsely populated part of the Eritrea–Ethiopia border, starting at 15:37 UTC on Sunday, 12 June 2011. By 21:37 UTC, at least 19 earthquakes of magnitude 4.5 or greater had occurred.[35] The tremors were associated with this eruption.[36] The initial quake registered a magnitude of 5.1 M_w with a focal depth of 10 km (6.2 mi), and was succeeded by multiple lighter tremors. Hours later, two consecutive magnitude 5.7 M_w earthquakes struck the region at 20:32 and 21:03 UTC, occurring at very similar depths.[37] The latter tremors resulted in localized strong shaking, registering at VII (very strong) on the Mercalli scale near the epicenters.[38]