By MARK DUNPHY – Fri Oct 07, 2011
On July 31, 2011, a wispy ash plume rose above the volcano and drifted west (up in the below image). The natural-colour satellite image was acquired by the Advanced Land Imager (ALI) aboard Earth Observing-1 (EO-1). Dark gray areas of Anak Krakatau are composed principally of lava flows deposited in the 1970s, ’80s, and ’90s. These flows are topped by a young cinder cone near the center of the island. Green vegetation covers older lavas along the eastern coastline. Image NASA. Instrument: EO-1 – ALI
Anak Krakatau’s alert level has been raised to the second-highest level after the number of volcanic tremors soared from 200 a day to 7,200. A 2-kilometre exclusion zone has also been established around the Indonesian volcano prohibiting tourists and fishermen from getting close to the volcanic island, located in the Sunda Strait between the islands of Java and Sumatra in Indonesia.
Indonesia’s Volcanology and Geology Disaster Mitigation Centre has expressed concern that an eruption could send incandescent rocks down its slopes and a considerable distance into surrounding waters. The Center indicated, however, that a major eruption like that experienced in 1883 is unlikely.
Anak Krakatau, which is Indonesian for ‘Child of Krakatoa’, erupted briefly on Tuesday sending columns of ash and rock hurtling high into the air. The eruption was the biggest since January 2011 when ash was emitted more than 600 m into the air, forcing the evacuation of tens of thousands of residents. The volcano also erupted on 29th October 2010 leading Indonesian authorities to issue a level 2 alert.
The island exploded in 1883, killing approximately 40,000 people, although some estimates put the death toll much higher. The explosion is considered to be the loudest sound ever heard in modern history, with reports of it being heard nearly 3,000 miles (4,800 km) from its point of origin. The shock wave from the explosion was recorded on barographs around the globe.