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Anak Krakatau: Indonesian volcano's dramatic collapse | Anak Krakatau: Indonesian volcano's dramatic collapse |
(about 1 hour later) | |
The scale of the dramatic collapse of the Indonesian volcano that led to last Saturday's devastating tsunami in the Sunda Strait is becoming clear. | The scale of the dramatic collapse of the Indonesian volcano that led to last Saturday's devastating tsunami in the Sunda Strait is becoming clear. |
Researchers have examined satellite images of Anak Krakatau to calculate the amount of rock and ash that sheared off into the sea. | Researchers have examined satellite images of Anak Krakatau to calculate the amount of rock and ash that sheared off into the sea. |
They say the volcano has lost more than two-thirds of its height and volume during the past week. | They say the volcano has lost more than two-thirds of its height and volume during the past week. |
Much of this missing mass could have slid into the sea in one movement. | Much of this missing mass could have slid into the sea in one movement. |
It would certainly explain the displacement of water and the generation of waves up to 5m high that then inundated the nearby coastlines of Java and Sumatra. | It would certainly explain the displacement of water and the generation of waves up to 5m high that then inundated the nearby coastlines of Java and Sumatra. |
Indonesia's disaster agency says more than 400 people are confirmed dead with 20 or so still missing. In excess of 40,000 have been displaced. | Indonesia's disaster agency says more than 400 people are confirmed dead with 20 or so still missing. In excess of 40,000 have been displaced. |
The Centre of Volcanology and Geological Hazard Mitigation (PVMBG) has been studying pictures from a number of radar satellites, including the European Union's Sentinel-1 constellation and the German TerraSAR-X platform. | |
Radar has the advantage of being able to see the ground day or night, and to be able to pierce cloud. | Radar has the advantage of being able to see the ground day or night, and to be able to pierce cloud. |
The capability has allowed some initial measurements to be made of Anak Krakatau's lost stature, in particular on its western side. | The capability has allowed some initial measurements to be made of Anak Krakatau's lost stature, in particular on its western side. |
What was once a volcanic cone standing some 340m high is now just 110m tall, says the PVMBG. | What was once a volcanic cone standing some 340m high is now just 110m tall, says the PVMBG. |
In terms of volume, 150-170 million cubic metres of material has gone, leaving only 40-70 million cubic metres still in place. | In terms of volume, 150-170 million cubic metres of material has gone, leaving only 40-70 million cubic metres still in place. |
Quite how much mass was lost on 22 December itself and how much in the following days is unknown. Scientists may have a better idea once they have had a chance to visit the volcano and conduct more extensive surveys. | Quite how much mass was lost on 22 December itself and how much in the following days is unknown. Scientists may have a better idea once they have had a chance to visit the volcano and conduct more extensive surveys. |
But with the eruptions still ongoing and a safety exclusion zone in force - no-one is going near Anak Krakatau. | But with the eruptions still ongoing and a safety exclusion zone in force - no-one is going near Anak Krakatau. |
Cone collapse with tsunami generation was considered a potential hazard before last Saturday. | Cone collapse with tsunami generation was considered a potential hazard before last Saturday. |
Scientists had modelled the possibility six years ago, even identifying the western flank of Anak Krakatau as the section of the volcano most likely to fail. | Scientists had modelled the possibility six years ago, even identifying the western flank of Anak Krakatau as the section of the volcano most likely to fail. |
The study, although simulating a larger event, predicted wave heights and coastal inundation times that were remarkably similar to what actually happened. | The study, although simulating a larger event, predicted wave heights and coastal inundation times that were remarkably similar to what actually happened. |