Volcanic activity worldwide 29 Nov 2014: Bardarbunga volcano, Nyamuragira
samedi nov. 29, 2014 21:00 |
Bardarbunga (Iceland): These two images were posted on the twitter account of the University of Iceland after their recent field expedition. As the lava field continues to expand, new branches of red hot rivers reach its edge and cascade down on the sandy plain below in a spectacular ‘water’fall of glowing lava. Scientists report that by now the Holuhraun lava field covers almost 75 square kilometres which represents an area bigger than the Reykjavik metropolitan area.
The lava lake at the summit of Nyamuragira volcano in DR Congo.Photo: Benoit Smets
The intensity of the eruption declined so that the present amount of emitted lava is only a quarter of what it was at the eruption’s most intense phase. But according to Ármann Höskuldsson, volcanologist at the University of Iceland Earth Science Institute, there are no indications that the volcanic activity will stop anytime soon. He points out that it remains a very intense eruption despite the recent (temporarily?) weakening of its activity. Scientists observed fluctuations in the eruption plume last week due to sporadic emission of powerful lava jets. The lava flow discharge pulsated accordingly.
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Nyamuragira (DRCongo): (29 Nov) For the first time in 75 years, a new lava lake appeared on some of Africa’s most active stratovolcanoes: Mount Nyamuragira in the Democratic Republic of Congo. The neighbouring volcanoes of Nyamugira and Nyiragongo are both part of the Virunga volcanic chain in the East African Rift, situated along DR Congo's border with Rwanda. They are famous as two of the few volcanoes on Earth that have sustained lava lakes for several decades. The previous lava lake at Nyamuragira emptied in 1938 as its lava poured out of the summit and flowed more than 30 kilometres down to Lake Kivu. The new lava lake seems to have formed at the bottom of the 500 m deep crater that was left behind by this 1938 lava flood.
Nyamuragira’s last eruption started in November 2011 and ended in March 2012 by the partial emptying of the magma chamber through the effusion of large lava flows. This eventually resulted in the collapse of the pit crater, an event after which the magma is likely forced to follow a new route higher up to the volcano’s summit. Such reconstruction of the volcano’s plumbing system with transport of magma higher in the volcano’s cone could trigger the formation of a lava lake. Nyamuragira’s past eruptions all seem to follow a typical eruptive cycle of lava being progressively emitted from the volcano’s base to its summit, ending in the formation of a lava lake.
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vendredi, nov. 28, 2014
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Volcanic activity worldwide 25 Nov 2014: Bardarbunga volcano, Zhupanovsky, Fogo, Shiveluch, Dukono, Aso
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