Mt Etna case study 1991 - 1993


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GCSE or A-level case study on the 1991 - 1993 eruption of Mt Etna

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Mt Etna case study 1991 - 1993

  1. 1. Mt Etna is located on the island of Sicily inItalyItaly is an MEDC and had a GDP per capitaof over $20,000 in 1991More than 25% of the population of Sicilylive on the flanks of Mt EtnaThe lava from previous eruptions providefertile soil for growning citrus fruit andvines, Mt Etna itself is a tourist attractionand has ski slopesMt Etna is the largest volcano in Europe – itis a stratovolcano which has formed on topof an ancient shield volcano which createsa wide variety of eruption types.It erupts much more frequently thancomposite cone volcanoes like Mt Pinatubo
  2. 2. Mt Etna is located on a destructive platemargin between the African and EurasianplatesThe northern edge of the African plate isbeing subductedThe eruption in 1991 started on 14thDecember and lasted for 473 days whichwas the most volumous eruption from Etnain over 300 years (250 million m³)The lava flowed down the SE flank of thevolcano into the Valle del BoveThe acidic lava had a low effusion rate (rateand volume of lava emitted in m³/sec)which posed very little threat to human life
  3. 3. SocialThere were NO deaths as a result of the eruptionThe lava destroyed the springs which provided the water supply to the town ofZafferana with a population of 8,000 peopleSeveral people who lost homes and farm land in the Val del Bove blamed thegovernment for not acting soon enoughIn interviews made during the late 1990s with people from the Zafferana area,when asked about their fear of a future eruption, many of them expressed that theyhad no fear because "when there will be a lava flow it will be diverted anyway".EconomicThe total cost of the management and responses as well as insurance claims fordamage to property ran into millions of LiraEnvironmentalVineyards and Chestnut orchards were destroyed
  4. 4. Immediate / short termDuring 1992 the Italian authorities built an earth barrier over 400 metres long and 20 metreshigh in order to stop the lava reaching the town of Zafferana – this contained the lava for abouta month before overflowing. 3 smaller embankments were then builtThe US marines then became involved in ‘Operation volcano buster’ in which they usedexplosives to blast a hole in the lava tube and then used helicopters to drop concrete blocks intothe main lava flow in order to slow down the lavaFinally, a diversion channel was dug and explosives were used to divert the lava onto anadjacent flank of the volcanoThe overall outcome of these interventions resulted in the lava flow stopping 850 metres fromZafferana but some geologist argued that the eruption was ending anyway
  5. 5. Long termThe Institute of volcanology in Sicily (INGV) has continued to improve methods of monitoringsince the 1992 eruption – by measuring radon gas to detect lava movements with in thevolcano, using GPS to examine changes in slope angle of the volcano and using highly sensitiveseismometers to measure minute tremors which might indicate lava being forced into thevolcanoThe responses involved many different organisations including the police, fire brigade, the civildefence department, the local council, geologists, volcanologists, the Italian army, Italian RedCross and the US army