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Mount Etna Volcano



=Introduction=


Mount Etna is an amazing historical landmark that still continues to amaze in present time. Mount Etna has brought a lot of pride to towns spread throughout Sicily. The numerous eruptions have left nice scenery and have made the mountain a big tourist trap. Those whom have populated the surrounding areas of the mountain have developed a sense of pride to be part of this great landmark. However, this pride sometimes comes with a price. The loss of homes, buildings, vegetation, and in some extreme cases, lives.

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Figure 1.1: Map of Etna Volcano and surrounding cities

=Background=

Mount Etna is an active volcano that is unlike most volcanoes. Mount Etna holds the longest record for the most historical eruptions among all volcanoes in the world at 209. Scientists have approximated that Etna was formed around 80 million years ago. Mount Etna has the highest elevation in Europe at 3350 meters high. However, due to the many reoccurring eruptions, the altitude changes with every eruption. Etna is located in Sicily, Italy, just above Sicily’s second largest city of Catania (see figure 1.1). The Mount Etna volcano is a near continuously active volcano and is considered the second most active volcano, second only to Kilauea on Hawaii. Etna has two types of eruptions; the first and majority being effusive (lava flows), which is not very dangerous or harmful, the other eruption type is mildly explosive (strombolian) eruptions, also particularly not too dangerous. This stratovolcano has four eruptive craters;
Ø Voragine or the Central Crater which is 250 meters wide
Ø Bocca Nova (the New Mouth) formed in 1968
Ø The Crater of North-East formed in 1911
Ø
The Crater of South-East formed in 1971 (see figure 1.2)
It is not known whether Mount Etna is near a subduction zone or located over a hotspot. There is a continuous debate saying that because there are two different types of magma coming out of Mount Etna it means that it is moving from a hotspot to a volcanic island-arc due to a subduction zone, “which formed the Aeolian Islands to the north of Sicily, [and] is moving southward underneath Mount Etna”. Others say that this is false because there are plenty of examples of two different magmas erupting from one volcano and that Mediterranean is an incredibly complicated part of the world that doesn’t conform to simple plate tectonics”. (Trivedi, National Geographic)

Mt Etna has the longest period of documented eruptions in the world. Etna is noted for the wide variety of eruption styles. The volcano is at its most spectacular when when both summit and flank eruptions occur simultaneously. The structure of Mt Etna consists of a series of nested stratovolcanoes, characterised by summit calderas, the most important one being the Ellittico Caldera, which formed about 14,000-15,000 years ago. Historically Mt Etna has produced effusive activity; however several pyroclastic deposits related to Plinian eruptions have been identified. Under open vent conditions, ash emission only occurs during flank eruptions of Mt Etna volcano. Structural and seismic data indicate that the regional deformation in the Etna area is generally dominated by N-S compression as the result of subduction of the African tectonic plate under the Eurasian plate.

Etna’s reputation as a relatively friendly volcano comes mainly from the fact that its lavas are very fluid. This type of lava is easily ejected to the surface, unlike the viscous magmas produced by subduction-zone volcanoes. But Etna's magmas also contain a great amount of gas, which can make eruptions much more explosive. During a particularly violent phase, Etna gives off up to 20,000 tons of sulfur dioxide a day, making the volcano one of nature's worst air polluters. The high sulfur content of Etna's magma is hard to understand. This characteristic is more typical of subduction-zone volcanoes than of basaltic volcanoes (Scientific American).
The large mountain of Etna was also popular to ancient Greeks. The ancient Greeks called Etna “The Realm of Vulcan”, who was the Greek god of fire.

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Figure 1.2: Explosion from the vent of a small intracrater cone at the Southeast Crater on 25 July 1997. The point from which the photo was taken now lies buried under about 100 m of lava and pyroclastics erupted from the Southeast Crater in 1998-2001

The Violent Eruption of 1669


The most violent and disastrous eruption of Mount Etna occurred in 1669. The eruption destroyed the city of Nicolosi as well 16 other villages.
The
cinder cone built up at the erupting vent, the lava flow became known as Monti Rossi (red hills), and is still a prominent landmark today.
Just the first day of eruption left the city of Nicolosi buried by lava flows, as well as the dextruction of two nearby villages (see figure 1.3). There was an extremely high volume content in the eruption, while the next 3 days only caused more devastation. As the lava flowed south, day 3 totalled up to 7 villages being destroyed. Nearly a month passed, the lava flow managed to engulf two more towns and reached the outer limits of the large city of Catania. The lava flow that wiped out several towns was now stalled at the city walls of Catania. While the walls protected the city, the lava flowed to the harbor and filled it up. The worst happened when the walls of Catania proved to be too little for the constant lava flow. Walls built across major roads also stalled the lava flow, but did not prevent the western side of Catania being destroyed.


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Figure 1.3: Illustration of the eruption of 1669 the destroyed numerous amounts of buildings.

Figure 1.3: Illustration of the eruption of 1669 the destroyed numerous amounts of buildings.


Q: Because of Mount Etna’s frequent eruptions, the neighboring population is fairly well prepared, describe some of the actions that have been put into place or that can quickly be implemented in this area in case of an eruption.



Mount Etna and mankind have coexisted for hundreds of years now. The population surrounding the very active mountain of Etna has grown very fond of their amazing tourist attraction. The neighboring populations have taken much pride in their mountain and refer to themselves as “Etnei”, which means Etneans. Much pride is also due to the beautiful site of mount Etna on a clear day (see figure 1.4). The everyday life of Sicilians is dominated by the overwhelming presence of Mount Etna. This is clearly shown even through simple products that have Etna plastered all over them (see figure 1.5). Though the people of Sicily feel positive about the active volcano, the thought of its damage can make any positive become a negative. Etneans know that there homes and neighboring buildings are at risk when it comes to the ever so often Etna eruptions. Despite the fact that Mount Etna is regularly active, those who reside on or near it are seldom in danger. The probability of having one’s home destroyed by the lava flow is slim. Most damage that occurs comes from fallen ash. When an eruption occurs, activities generally continue as normal, but precautions are always taken to ensure safety. Only seven of Etna’s numerous eruptions have reported deaths; only two that have been considered disasters.
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Figure 1.4: A surrounding town with a view of Mount Etna


In case of an eruption of Etna, the people of Sicily are optimistic that belongings can be secured and they can flee before the slow-moving lava reaches their homes. In historical eruptions of Etna, it is not the lava flow that have killed civilians, but the ash blown from the volcano.
An alert system with a hardware warning system was created to mitigate any volcanic hazard, which will indicate areas affected by ash and lapilli fallout. The system is based on a relation between the pattern of volcanic tremor amplitude and explosive activity. When these activities exceed a fixed threshold, data will be directly faxed to the Civil Defense and Municipalities from the Meteorological Office. In the case of an imminent flank eruption there will be premonitory seismicity or other phenomena that may help recognize the location of the eruption. Once the event is foreseeable, local authorities will take measures to evacuate the population of any threatened area, if necessary.
At times when an eruption produces extensive lava flows, efforts are made to divert the flows away from buildings and other inhabited areas by means of blasting the walls of its "main feeding channel" with dynamite and other explosives. One operation like this took place in 1983 when an eruption produced a lava flow. In this case explosives were used to divert some of the flow into an artificial bed. This method is in a way a last resort, as its effectiveness varies between each different eruption.
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Figure 1.5: Sicilian products like honey with Mount Etna on the label.

=Conclusion=
Every year that passes, is another year that Mount Etna has glorified Sicily. It seems as every eruption of Etna brings more and more tourists. For now the surrounding towns are safe, but sleeping with an eye and an ear open is a must when you have the world’s most active volcano in your backyard.


=References=

http://ursispaltenstein.ch/blog/images/uploads_img/how_volcano_works.jpg

http://www.vulcanoetna.com/en_faq.php

Living with volcanoes: The sustainable livelihoods approach for volcano-related opportunities by Iian Killman Vol. 172, Issues 3-4


http://images.google.com/images?um=1&hl=en&rls=com.microsoft:*:IE-SearchBox&rlz=1I7SUNA&q=map+of+mount+etna&&sa=N&start=18&ndsp=18

http://decadevolcano.net/photos/etna_photos.htm

Contribution: http://news.nationalgeographic.com/news/2001/08/0829_tvmountetna_2.html

Scientific American; Apr2003, Vol. 288 Issue 4, p58, 8p