Part of the Afar Triangle, the Nabro Volcano is one of many volcanic caldera complexes in the northeasternmost part of the East African Rift valley region. The twin calderas likely formed during an eruption of about 20 to 100 cubic kilometres consisting of ignimbrite, although the date of their formation is unknown. The subaerial volume of volcanic material within the Nabro Volcanic Range is likely on the order of 550 km3 (130 cu mi).[4]
Although it had undergone no historically reported eruptions,[5] the Nabro Volcano erupted shortly after midnight local time on 13 June 2011, after a series of earthquakes up to magnitude 5.7 in the Eritrea-Ethiopia border region.[5] The ash plume was seen on satellite drifting to the west-northwest along the border, spanning about 50 km wide and several hundred kilometres across in the hours immediately following the reported eruption, and reportedly reaching 15 km (9.3 mi) high.[5]
The MODVOLC noted on the 9 April 2012 that a thermal anomaly was detected at Nabro and that such anomalies had been detected throughout March. The activity is focused on the Southern Caldera wall. The exact nature of the activity is unknown, but activolcans.info noted that there might be a lava lake there.
