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Volcano Chaiten

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Michael Dunn

on 26 March 2013

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Transcript of Volcano Chaiten

Effects Chaitén is a small volcano located on the side of the Michinmahuida volcano in southern Chile. It is located on the West coast of South America approximately 150km east of the Peru Chile Trench. This is at a destructive plate margin, the oceanic plate and continental plate converge. The Nazca plate is subducted under the South American plate which is less dense. As the plate descends, there are earthquakes caused in the Benioff zone. Volcanoes occur here because of melting of the plate in the asthenosphere. Location Chaitén is also part of the Andes which is the world’s longest fold mountain chain, the Andes Mountains, which are crumpled up be the tectonic forces pushing these 2 plates together. The oceanic plate dips at a steep angle, while the northern end may be experiencing flat-slab subduction. This low angle of subduction may explain the relative lack of volcanic activity in the northern part of Chile, compared to the extremely active southern volcanic mountains, which was the cause of the Chaitén eruption. Type of eruption The Nazca and South American plates collided. In this subduction zone melting produced magma bodies that rose towards the surface. It was explosive because the lava is Rhyolitic, has high gas pressure and high Silica content. Before 2008, the last time it erupted was 9,400 years ago. Chaitén began to erupt violently in 2008, creating frequent plumes, pyroclastic flows, minor earthquakes and lahars, and building a new lava dome on the north side of the old one. The ash cloud was up to 17 kilometres high and was visible on satellite images for hundreds of kilometres over the Atlantic. In 2008, during the eruption, it produces high Plinian eruption columns of ash, gas and rock which were followed by pyroclastic flows, lahars and ash fall. T was rated a 4 on the VEI. By late May the lava eruptions had created a new dome of 540,000m2 containing 55million m3 of material. Scale of eruption During the first days of the eruption, large volumes of ash were carried downwind to the south east of Chaitén. For example, 30cm of ash was deposited in Futaleufu. Ash fall was also reported in the Argentinian town of Escuel and satellite images showed the ash cloud extending as far as the Atlantic in the following days. Ash from Chaitén has also disrupted air traffic. Many flights were disrupted and delayed. The volume of erupted material was not high in historical terms and the level of sulphur dioxide emitted was low with only about 10 kilotons emitted in the three Plinian eruption columns. Rhyolites have low levels of sulphur and taking these into account only 0.1 cubic km of rhyolite would have been emitted during this phase of the eruption. Many people in the area of Chaitén had to be evacuated as the area became extremely hazardous. Emergency boats had to come and take the residents to a shelter. Lahars (volcanic ash mud flows) had cut communications in areas and made access difficult whilst ash falls up to 15cm deep had blocked rivers and contaminated water supplies. By 14th May 2008 it was confirmed that 90% of Chaitén was flooded due to increased flows of the Rio Blanco or Rio Chaitén but casualties were low with just one death caused by stress. The major impact was on farming, and many farm animals were killed by suffocating on the ash. Between 80-90% of the town of Chaitén reported damaged, 20-30% being completely destroyed and there was extensive damage to the airport and marine facilities. Tasnim & Michael Chaitén Chile Primary:
Even though the area around Chaitén is sparsely populated, more than 5000 people had to be evacuated from nearby towns and the Chilean government ordered the complete evacuation of the town. The Chilean Navy had managed to evacuate 3900 people initially and emergency measures included the following:
-Residents were told not to drink the water
-Chilean officials distributed face masks and fresh water
-The Chilean government ordered a 50km exclusion around the town
-The government issued a monthly disaster stipend of $1200 and $2200 per month per family
-Financial aid to small businesses was granted and 90 day freeze on payment of existing loans on the state bank Banco Estado to aid businesses in trouble Responses Responses Secondary:
Chile's geological created a new program to improve monitoring and hazard mitigation at 43 of Chile's high-threat volcanoes. The program will support studies of the history of eruptions at these volcanoes, assessments of volcanic hazards, and the creation of a real-time monitoring network and early warning system.
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