Mt Etna case study 1991 - 1993

Background InformationMt Etna is located on the island of Sicily in ItalyItaly is an MEDC and had a GDP per capita of over $20,000 in 1991More than 25% of the population of Sicily live on the flanks of Mt EtnaThe lava from previous eruptions provide fertile soil for growning citrus fruit and vines, Mt Etna itself is a tourist attraction and has ski slopes Mt Etna is the largest volcano in Europe – it is a stratovolcano which has formed on top of an ancient shield volcano which creates a wide variety of eruption types. It erupts much more frequently than composite cone volcanoes like Mt Pinatubo

Nature of the event

Mt Etna is located on a destructive plate margin between the African and Eurasian platesThe northern edge of the African plate is being subductedThe eruption in 1991 started on 14th December and lasted for 473 days which was the most volumous eruption from Etna in over 300 years (250 million m³)The lava flowed down the SE flank of the volcano into the Valle del BoveThe acidic lava had a low effusion rate (rate and volume of lava emitted in m³/sec) which posed very little threat to human life

ImpactsSocialThere were NO deaths as a result of the eruptionThe lava destroyed the springs which provided the water supply to the town of Zafferana with a population of 8,000 peopleSeveral people who lost homes and farm land in the Val del Bove blamed the government 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 they had 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 for damage to property ran into millions of Lira EnvironmentalVineyards and Chestnut orchards were destroyed

Management & ResponsesImmediate / short termDuring 1992 the Italian authorities built an earth barrier over 400 metres long and 20 metres high in order to stop the lava reaching the town of Zafferana – this contained the lava for about a month before overflowing. 3 smaller embankments were then builtThe US marines then became involved in ‘Operation volcano buster’ in which they used explosives to blast a hole in the lava tube and then used helicopters to drop concrete blocks into the main lava flow in order to slow down the lavaFinally, a diversion channel was dug and explosives were used to divert the lava onto an adjacent flank of the volcanoThe overall outcome of these interventions resulted in the lava flow stopping 850 metres from Zafferana but some geologist argued that the eruption was ending anyway

Management & ResponsesLong termThe Institute of volcanology in Sicily (INGV) has continued to improve methods of monitoring since the 1992 eruption – by measuring radon gas to detect lava movements with in the volcano, using GPS to examine changes in slope angle of the volcano and using highly sensitive seismometers to measure minute tremors which might indicate lava being forced into the volcano The responses involved many different organisations including the police, fire brigade, the civil defence department, the local council, geologists, volcanologists, the Italian army, Italian Red Cross and the US army