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Nevado del ruiz case study


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Nevado del ruiz case study

  1. 1. Case Study: Nevado Del Ruiz - 1985 Where did it happen?Nevado Del Ruiz is a stratovolcano found in west Colombia where the Nazca plate is being subducted beneath the South American plate. The latest eruption was ash plumes in January 2013. What happened? First seismic activity noticed in 1984. These included fumarole activity, deposits of sulphur on the summit of the volcano and phreatic eruptions. 11th September 1985 major phreatic eruption shoots steam high into the air. Volcanic activity decreases during October1985 but increases during November 1985. At 9:09pm on November 13th 1985 Nevado Del Ruiz erupts sending ash 30km into the air. The total mass of the erupted material was 35 million metric tons. The eruption produced pyroclastic flows which melted glaciers and snow on the summit. This caused lahars which ran down the volcano’s sides at 40 miles per hour and reached a maximum width of 50m. Why did it happen? As the Nazca plate is subducted beneath the South American plate it melts. This magma is lighter because it is mixes with gases, water and soil from the surface. The magma rises forming a volcano. The pressure builds up until eventually the volcano erupts. The lahars were formed when the heat from the eruption melted glaciers on top of the volcano. The water from the glaciers mixes with volcanic debris and surges down the volcano. Primary effects Secondary effects E n v i r o n m e n t a l The pyroclastic flows melted glaciers forming lahars which were 30m deep, 50m wide and travelled at 12m per second. 150000 animals killed by lahars. Land made more fertile by the mud from the lahars. E c o n o m i c 3400 hectares of agricultural land was lost in the eruption. Cost the Colombian economy $7.7billion dollars, 20% of GDP for 1985. S o c i a All roads and communications were destroyed in the areas affected by the eruption. 50 schools, 2 hospitals, 58 industrial plants and 343 23000 people were killed by the lahars and 5000 were injured. 8000 people were made homeless The Armero tragedy – a lahar
  2. 2. l commercial establishments were damaged or destroyed. Damaged water supplies swept through a town killing ¾ of the inhabitants. Immediate responses Long term responses Colombian Red Cross and Civil Defence personnel were the first to organize rescue and medical care. Colombian military provided helicopters to airlift victims for medical care, distributed supplies and established field medical care and shelter facilities Health workers administered 80000 doses of tetanus and typhoid vaccines. Colombia established a plan for warning and evacuation of areas at risk from another eruption. Public education campaign started in early 1986 to educate people about the dangers of the volcano. Red Cross circulated flyers about the volcanic hazard with information about evacuation procedures and warning systems. Hazard maps distributed in towns. Evacuation route markers were painted on buildings. How was the hazard managed? The hazard was not managed because despite many warning signs a year before the eruption there was no evacuation of areas at risk in spite ofscientists saying there was a risk of lahars. A hazard map was published but it was poorly distributed and had many errors such as, there was no key to indicate what colours meant on the map. Many people who survived the lahars said they had not seen the map. Why was the death toll so high?The death toll was so high because there was no evacuationand people living in places such as Armero were unaware of continuing activity. Plus 3 days after the disaster the government still had no plan of action plan which prevented government aid from reaching people in need.