Mount Etna
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| Mount Etna | |
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 Mount Etna viewed from the air |
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| Elevation | 3,329 meters (10,924 feet) (varies)[1] Width of cone - 40km approx |
| Location | Sicily, Italy |
| Prominence | 3,329.6 m |
| Coordinates | [1] |
| Type | Stratovolcano (composite type) |
| Age of rock | 500,000 years |
| Last eruption | 2008 |
| Easiest route | rock climb |
Mount Etna (also known as Muncibeddu in Sicilian and Mongibello in Italian, a combination of Latin mons and Arabic gibel, both meaning mountain[2], in Latin, Aetna) is an active volcano on the east coast of Sicily, close to Messina and Catania. Its Arabic name was Jebel Utlamat (the Mountain of Fire). It is the largest active volcano in Europe, currently standing 3,329 m (10,924 ft) high, though it should be noted that this varies with summit eruptions; the mountain is 21 m (69 ft) lower now than it was in 1981. It is the highest mountain in Italy south of the Alps. Etna covers an area of 1,190 km² (460 sq mi) with a basal circumference of 140 km. This makes it by far the largest of the three active volcanoes in Italy, being about two and a half times the height of the next largest, Mount Vesuvius.
Mount Etna is one of the most active volcanoes in the world and is in an almost constant state of eruption. The fertile volcanic soils support extensive agriculture, with vineyards and orchards spread across the lower slopes of the mountain and the broad Plain of Catania to the south. Due to its history of recent activity and nearby population, Mount Etna has been designated a Decade Volcano by the United Nations.
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[edit] Geological history
Volcanic activity at Etna began about half a million years ago, with eruptions occurring beneath the sea off the then coastline of Sicily. 300,000 years ago, volcanism began occurring to the southwest of the present-day summit, before activity moved towards the present centre 170,000 years ago. Eruptions at this time built up the first major volcanic edifice, forming a strato-volcano in alternating explosive and effusive eruptions. The growth of the mountain was occasionally interrupted by major eruptions leading to the collapse of the summit to form calderas.
From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating large pyroclastic flows which left extensive ignimbrite deposits. Ash from these eruptions has been found as far away as Rome, 800 km to the north.
Thousands of years ago, the eastern flank of the mountain experienced a catastrophic collapse, generating an enormous landslide in an event similar to that seen in the 1980 eruption of Mount St. Helens. The landslide left a large depression in the side of the volcano, known as 'Valle del Bove' (Valley of the Ox). Research published in 2006 suggests that this occurred around 6000 BC, and caused a huge tsunami which left its mark in several places in the eastern Mediterranean. It may have been the reason that the settlement of Atlit Yam (Israel), now below sea level, was suddenly abandoned around that time. (Pareschi et al., Geophys. Res. Lett., 33, doi:10.1029/2006GL027790)
The steep walls of the Valley have suffered subsequent collapse on numerous occasions. The strata exposed in the valley walls provide an important and easily accessible record of Etna's eruptive history.
The most recent collapse event at the summit of Etna is thought to have occurred about 2,000 years ago, forming what is known as the Piano Caldera. This caldera has been almost entirely filled by subsequent lava eruptions, but is still visible as a distinct break in the slope of the mountain near the base of the present-day summit cone.
[edit] Historical eruptions
The first known record of an eruption at Etna is that of Diodorus Siculus.
The Roman poet Virgil gave what was probably a first-hand description of an eruption in the Aeneid:
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(edition of Theodore C. Williams, ca. 1908 [lines 569 - 579]) |
In 396 BC, an eruption of Etna is said to have thwarted the Carthaginians in their attempt to advance on Syracuse during the First Sicilian War.
[edit] 1669 eruption
Over the last 2000 years, activity at Etna has been generally effusive, with occasional explosive eruptions from the summit. Its most destructive eruption during this time occurred in March 1669, when an estimated 830,000,000 m³ of pyroclastic material was ejected. The eruption was preceded by two months of increasingly powerful earthquakes centered on the southern slopes of the mountain, which eventually encouraged most villagers there to abandon their homes. On 11 March, a 9 km-long fissure opened up on the southern flank of the mountain, stretching from an elevation of 2,800 m down to 1,200 m. Activity steadily migrated downslope, and the largest vent eventually opened near the town of Nicolosi. The cinder cone built up at the erupting vent became known as Monti Rossi (red hills), and is still a prominent landmark today.
Nicolosi was quickly destroyed by lava flows, and two nearby small villages were also destroyed during the eruption's first day. The eruption was extremely voluminous, and a further four villages were destroyed in the following three days as the lava flowed south. In late March two larger towns were destroyed, and the lava reached the outskirts of Catania in early April.
At first, lava piled up against the city walls, which were strong enough to withstand the pressure of the flow. However, while the city was temporarily protected, lava flowed into its harbour and filled it in. On 30 April, lava flowed over the top of the city walls, which then gave way. Catanians built walls across major roads to halt the flow of the lava, which were fairly effective but did not prevent the destruction of the western side of the city.
During the eruption, Catania residents also attempted to divert the flows much further upstream. According to a possibly apocryphal tale, their efforts were met with armed resistance from the citizens of a town which would have been threatened by the diverted flow [1]. Whether this event really occurred or not, a law was subsequently passed to forbid the artificial diversion of lava flows. This law was only repealed in 1983.
[edit] Recent eruptions
Another very large lava flow from an eruption in 1928 led to the first (and only) destruction of a town since the 1669 eruption. In this case, the town of Mascali was obliterated in just two days, with the lava destroying every building. The event was used by Mussolini's Fascist regime for propaganda purposes, with the evacuation, aid and rebuilding operations being presented as models of fascist planning. Mascali was rebuilt on a new site, and its church contains the Italian fascist symbol of the torch, placed above the statue of Christ.
Other major 20th-century eruptions occurred in 1949, 1971, 1981, 1983 and 1991-1993, as well as the 21st-century eruption in 2001. In 1971, lava buried the Etna Observatory (built in the late 19th century), destroyed the first generation of the Etna cable-car, and seriously threatened several small villages on Etna's east flank. In March 1981, the town of Randazzo on the northwestern flank of Etna narrowly escaped from destruction by unusually fast-moving lava flows. The 1992 eruption saw the town of Zafferana threatened by a lava flow, but successful diversion efforts saved the town with the loss of only one building a few hundred metres from the town's margin.
In 2002-2003, the biggest series of eruptions for many years threw up a huge column of ash that could easily be seen from space and fell as far away as Libya, 600 km south across the Mediterranean Sea. Seismic activity in this eruption caused the eastern flanks of the volcano to slip by up to two metres, and many houses on the flanks of the volcano experienced structural damage. The eruption also completely destroyed the tourist station Piano Provenzana, on the northeastern flank of the volcano, and part of the tourist station around the Rifugio Sapienza on the south flank. Footage from the eruptions was recorded by Lucasfilm and integrated into the landscape of the planet Mustafar in the 2005 film Star Wars Episode III: Revenge of the Sith. The Rifugio Sapienza is near the site of a cable car station which had previously been destroyed in the 1983 eruption; it has now been rebuilt.
Following a rather silent, slow and non-destructive lava outflow on the upper southeastern flank between September 2004 and March 2005, intense eruptions occurred at the Southeast Crater in July-December 2006. The most recent eruptions occurred in March-May 2007, again at the Southeast Crater, with four episodes of lava fountaining[citation needed], the latest being on 7 May 2007. Ash emissions and Strombolian explosions started from a vent on the eastern side of the Southeast Crater in mid-August 2007.
On 4 September 2007 Etna violently erupted at around 8:00 p.m. local time, spewing lava up to 400 m into the air along with strong winds that sent ash and smoke into the underlying towns. This Southeast Crater eruption was visible far into the plains of Sicily, ending the following morning between the hours of 5 to 7 am local time. Catania-Fontanarossa Airport shut down operations during the night for safety precautions. A similar paroxysm occurred during the night of 23-24 November 2007, lasting for 6 hours and causing ash and lapilli falls to the north of the volcano. Again, the source of the activity was the Southeast Crater. Following several months of rather minor activity from the Southeast Crater and flurries of seismic activity especially on all sides of the mountain, a new powerful eruptive paroxysm occurred on the late afternoon of 10 May 2008. Due to bad weather, it was not possible to see much of the activity at the vent, but several branches of lava traveled down the eastern flank of the volcano, into the Valle del Bove depression. This latest paroxysm lasted about 4 hours, ending on the evening of 10 May 2008.
A new eruption started on the morning of 13 May 2008 immediately to the east of Etna's summit craters, accompanied by a swarm of more than 200 earthquakes and significant ground deformation in the summit area. On the afternoon of the same day, a new eruptive fissure opened at about 2800 m above sea-level, with a number of vents displaying Strombolian activity and emission of lava flows toward the Valle del Bove. During the following 24 hours the lava traveled approximately 6 km to the east, but thereafter its advance slowed and stopped, the most distant lava fronts stagnating about 3 km from the nearest village, Milo. Ash emissions became more frequent between 16 and 18 May and produced small but spectacular clouds, whereas the rate of lava emission showed a gradual diminution. As of 19 May, the eruption is continuing, although at much reduced vigor.[3]
Dikes have been built on several occasions to stem and redirect the flows of molten lava.[4]
[edit] Unusual Characteristics
In the 1970's Etna erupted smoke rings, one of the first captured events of this type, which are extremely rare. The ring of toxic gas had killed birds and sea life around the Mediterranean
[edit] See also
[edit] Footnotes
- ^ a b The elevation varies with volcanic activity. It is frequently given as 3,350 m, but many sources that support this concede that it is approximate. The coordinates given here, which are consistent with SRTM data, are from a 2005 GPS survey. The elevation data are based on a [LIDAR ([Light Detection and Ranging)] survey carried out in June 2007 (Neri et al., "The changing face of Mount Etna's summit area documented with Lidar technology", Geophysical Research Letters, vol. 35, L09305, doi:10.1029/2008GL033740
- ^ (Italian) Note di toponomastica
- ^ Etna: Attività in corso Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania
- ^ Recent dike-induced large-scale block movement at Mount Etna and potential slope failure Nature, 25 January 1990
[edit] References
- Smithsonian Institution Global Volcanism Program: Mount Etna
- Chester, D. K.; Duncan, A. M., Guest, J. E., and Kilburn, C. R. J. (1985). Mount Etna: The Anatomy of a Volcano. Stanford University Press, 412 pp. ISBN 0-8047-1308-1.
[edit] External links
- Exhaustive coverage of Mt. Etna geology and history
- Mount Etna Live Webcam
- Stromboli Online, with info on Etna as well as excellent photo galleries and video clips of Etna's past eruptions including those of the 1990s and the 2000s
- Mt. Etna eruption of 2001, photos and information
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