Geografia d'Europa

Location: 37.73N, 15.00E
Elevation: 10,991 feet (3,350 m)

The Geology

In the eastern part of Sicily, an immense gulf which stretched from the Peloritan mountains to the Iblei mountains was filled in by underwater eruptions of lava (which gave life to Etna), and in part by deposits from the Simeto river, which also contributed to the creation of the current Catania plain. The first eruptions took place in this gulf, about half a million years ago, traces of which are conserved in the Aci Castello, Aci Trezza and Ficarazzi zones. The litologic limit or outward reach of Etna's lava flow is 250 Km covering a surface area of about 1260 Km squared. It's the largest vulcano in Europe with an altitude of reaching up to about 3,350 m at the craters edge, whose elevation is variable, since the explosive activity is not always "constructive" but often "destructive" resulting in collapses of the crater walls.

On the west side of the vulcano, a deep depression about 7 by 5 km called the Bove Valley , demonstrates 1,000 m high walls said to be the remains of an antique vulcano destroyed by it's own incredible explosions. The major part of Etna's lava flows are made up of blocks of fragmented scoriae with rough, tormented surfaces (lave aa); in other rarer cases, the lava displays more even surfaces often curled into cord like masses or sometimes slabs (lave phaoehoe).

This last type of lava flow often develops tunnel like systems hardened on the outside with hot lava flowing inside. These lava systems are extremely variable lasting anywhere from a few hours to a few months or even years. The length, distance and size of the lava flow depend essentially on the duration of the eruption, but also on other factors related to morphology of the soil.

Etna's history is long and complex. The oldest lavas, exposed on the lowermost flanks of the volcano, erupted 300,000 years ago. Some of these are pillow lavas, indicating Etna started as a submarine volcano and grew above sea level.

Between 150,000-100,000 several volcanic centers coalesced and calderas formed and filled. Between 65,000-25,000 years ago a major vent grew to the southeast of the present summit. Phreatomagmatic eruptions were common during this period. Most of the summit of this volcano was removed by subsequent caldera collapse. Between 18,000-5,000 years ago four major volcanic centers continued to construct Etna and three calderas formed. Valle del Bove is a depression that formed about 5,000 years ago by gravity sliding on the east flank of the volcano. Most of the cones, craters, and pre-historic lava flows and tephra deposits at the summit of Etna have formed within the last 5,000 years.

Etna has the longest record of historic eruptions. The first recorded eruption was in 1500 B.C. Since then Etna has erupted at least 190 times. Most of these eruptions have a volcanic explosivity index of 1 or 2 and activity consists of gently effusion of lava or Strombolian explosions. Large eruptions are rare.

One of the most dramatic eruptions of Etna was in 1669. Earthquakes began on February 25 and caused great damage in Nicolosi, about 6 miles (10 km) South and East of Catania. The eruption began on March 11 as a 7 mile (12 km) fissure opened from near Nicolosi to Mt. Frumento Supino, 1 mile (2 km) from the summit. Several more vents formed. On April 12 flows arrived at the walls of Catania. Lava rose to the top of the wall and cascaded over. Lava also knocked over a section of was 120 feet (40 m) long. Large parts of the town were destroyed. Lava reached the sea on April 23. The eruption stopped on July 15. The first attempt to divert lava took place at Etna in this eruption. The citizens of Paterno protested to the proposed diversion of lava away from Catania and towards their city. The attempt was largely unsuccessful.

Fatalities are rare at Etna and reported for only 7 eruptions. Typically, people visiting the summit are too close when explosions throw blocks through the air. In 1843, 36 people were killed by a phreatic explosion at the front of a lava flow. Nine people were killed and 23 were injured (150 tourist were in the area) on September 12, 1979, by a 30-second explosion that threw large blocks near the crater rim. Blocks 10 inches (25 cm) in diameter fell 1,300 feet (400 m) away. Two people were killed and 7 others injured by falling volcanic material 1,600 feet (500 m) from the crater in the 1987 phreatic eruption.

Northeast crater is a pyroclastic cone at the summit of Etna. The vent that formed the cone became active in 1911. The cone is made of pyroclasts ranging in size from ash to bombs up to 3 feet (1 m) in length. Strombolian eruptions are common at this vent.

On December 14, 1991 a fissure opened on the southeast flank of Etna. The eruption continued to March 30, 1993. It was the largest eruption at Etna in the last 300 years.

Pictures on Etna, file 1
Pictures of Etna, file 2
Quicktime and MPEG movies of Mount Etna
 

The Fauna

About a century and a half ago, Galvagni, discribing the fauna around Etna, told of the presence of animals which have practically disappeared now, such as, wolves, wild boars and various types of deer. The opening of new roads, deforestation and hunting contributed to the extintion of these large mammals and continue to threaten the life of other species. In spite of this, porcupines, foxes, wild cats, martens, and wild rabbits have survived, as well as, weasels, hedgehogs and various species of mice and bats among the smaller animals.

There are many species of birds. In particular, birds of prey which are a testament to the existense of ample uncontaminated spaces. Among the diurnal birds of prey, we find the sparrow-hawk, buzzards, kestrels, pelligrin falcons and the royal eagle. Among the nocturnal, the barn owl, horn owl and common owl. Herons, ducks and other aquatic birds are can be observed in lake Gurrida, the only expanse of water in the area of Mount Etna.

In the wooded areas, it's possible to catch a glimspe of Jay birds, wild Doves and the Greek Partridge, as well as, many song birds, such as, the Silvia, Gowks and many others. In the upper elevations, around the lava fields, the Wheatear will surprise you with its rapid and irregular flying style. Among the various snake species, which along with lizards populate the underbrush, the only dangerous one is the viper, whose presense has increased in recent years because of a decrease in predators. Last but not least, there is the fantastic and multiform world of insects: butterflies, grasshoppers, crickets, locust, bees, etc. with their fondamental and irreplaceable role in the ecologic balance.
 

The Vegetation

Vegetation in Etna park is characterized by a group of factors, most of important of which is the vulcanic nature of the mountain. The flora is extremely rich and varied offering continous mutations. This all depends on the compactness of the soil and continous changes in the substrate due to diverse lava flows over a period of time, not to mention the variability of the temperature and precepitation in relation to the altitude and slope face. In the lower elevations, where time ago there were forest of holm-oak, we find vineyards, hazel-nut trees and some remaining oak groves, fruit orchards and chestnut trees. At 2000 meters or higher, one finds Beech trees, which in Sicily reaches its southern limit, and Birch trees which are considered endemic.

In addition to wooded areas, the landscape is characterized by thorn bushes, which offer protection to other Etna mountain plants, such as, Violets. Above the limit of thorn bushes, between 2450 and 3000 meters, there are few things able to survive the harsh environmental conditions of Mount Etna. And above this level up to the summit, extends a vulcanic desert where no vegetation survives.

To protect this unique natural enviroment and extrordinary landscape surrounding the vulcano, the Etna Park was divided into four zones. In zone "A", which includes 19,000 hectares, almost all of which is public property, there are no traces of human activity. It's a large area of uncontaminated space, home to various birds of prey, such as, the royal eagle.

Zone "B", which includes 26,000 hectares, is made up of small, private agricultural tracts characterized by examples of antique farm houses, animal shelters, millstones and austere plantation houses, all signs of an mans presense dating back to antique times. In addition to zones A and B, there are 14.000 hectares in zones "C" and "D" set aside for eventual turist facilities, always keeping in mind the protection of the natural landscape.
 

Sources of Information

Bulletin of the Global Volcanism Network, 1995, Smithsonian Institution, Washington, D.C., v. 20, no. 8, p. 2.

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, 404 p.

Lockwood, J.P., and Romano, R., 1985, Lava diversion proved in 1983 test at Etna: Geotimes, p. 10-12.

McClelland, L., Simkin, T., Summers, M., Nielson, E., Stein, T.C., 1989, Global volcanism 1975-1985: Prentice Hall, Englewood Cliffs, New Jersey, and American Geophysical Union, Washington DC, 655 p.

McGetchin, T.R., Settle, M., and Chouet, B.A., 1974, Cinder cone growth modeled after Northeast crater, Mount Etna, Sicily: Journal of Geophysical Research, v. 79, p. 3257-3272.

Simkin, T., and Siebert, L., 1994, Volcanoes of the world: Geoscience Press, Tucson, Arizona, 349 p.
 

Fuente:
http://volcano.und.nodak.edu/vwdocs/volc_images/img_etna2.html
http://www.parks.it/parco.etna/Epun.html