Eruption (in italian)
A VOLCANOLOGICAL VISIT
dépliant published by Dipartimento della Protezione Civile
and Gruppo Nazionale per la Vulcanologia, Italy
Responsible G. Pasquaré
Text and figures L. Benciolini , G. Pasquaré, F.A. Pasquaré
Drawings M. Pasquaré
Graphic project P. Moneta e D. Noya
web-project: L. Giacomelli , R. Scandone
A short animation shows (697 kb) (click
main phenomena of volcanic activity. (The captions of the figures
are in italian)
UNVEILING A VOLCANO
Stromboli is not only one of the
many beautiful islands of the Mediterranea Sea, but it is the only one
where volcanic activity takes place unceasingly in front of our very eyes,
and where the visitor can see the island's dramatic history unravelled.
The island shows us in detail its eventful history, which, since its remote mergence from the waters of the Tyrrenian Sea, has been characteruzed by violent explosions, quiet but unrelenting lava flows, devasting collapses and rapid, vigorous recostructions, in a succession of events that leave us with an "open book of volcanology".
This brief guide turns the pages of this living book, together with the reader fascinated by nature in motion.
THE AEOLIAN ISLANDS
The Aeolian archipelago, a semicircular
chain whose total length is 75 km, is composed of 7 islands located in
the southern portion of the Tyrrenian Sea, facing the Sicilian coast.
These arcs form due to the collision between ocean crust and continental crust. Such collisions generate a heating process resulting in the partial fusion of the rocks at depth and the subsequent formation of volcanic magmas. Frequently, at the back of the area involved in the compression process caused by the crustal collision, a zone subjected to extension and subsidence is formed, originating a so-called "marginal" sea-basin. The Aeolian arc was created by the collision between the Calabrian-Sicilian continental crust and the Ionian crust, which was of the oceanic type. In this case, the extensional marginal basin associated with the volcanic arc is represented by the Tyrrenian Sea.
The volcanoes making up the Aeolian arc were born along deep fractures on the sea-floor, and some of them reached sea-level only after a long period of submarine growth.
Since their emergence, their growth has been characterized by four periods of eruptive activity:
According to classical mythology,
the Aeolian Island were the home of Aeolus, who kept the winds trapped
in a cave, was able to forecast changes in the weather by watching the
cloud rising from an active volcano, probably Stromboli. As a matter of
fact, nowadays it is wall known that the shape of the cloud coming from
Stromboli is influenced by the fluctuations in atmospheric pressure.
Acvcording to Greek mythology, Mt. Etna was the home of Ephaestus, the god of fire, who worked in his subterranean forge beside the Cyclopes, the one-eyed giants whose only eye resemble the shape of a crater.
Conversely, the god of fire of Roman mythology, Vulcano, had his forge on the Aeolian islands of the same name. At the end of the Middle Ages, the name of the islands of Vulcano was chosen to represent all the "mountains of fire" which we call volcanoes.
Ulysses also landed on the Aeolian Islands and met Aeolus, during his homeward journey narratred by Homer in "The Odyssey".
The Aeolian Islands were first mentioned by Aritotle (384-322 b.C.) who described the formation of a new volcano (probably Vulcanello, nowadays linked to the Island of Vulcano), whose ashes covered the town of Lipari.
Stromboli is mentionned in the writings of Aristotle, Diodoro Siculo, Silio Italico, Lucilio and Pliny the Elder. Strabo (63 b.C.-24 A.D.), a Greek geographer, extolled lipari's "hot waters and puffs of fire", while he described Vulcano as "the island of fire with three breaths emerging from three craters".
Strabo's narrations described Stromboli, called Strogile (circle-shaped)as being characterized by "less violent flames" but "more resounding rumbles".
In the more recent past, a famous Italian poet, Carducci, described the legendary end of Theodoric, the King of the Ostrogoths, who was flung into the crater of an Aeolian volcano by his restless horse.
THE EVOLUTION OF STROMBOLI
The volcano of Stromboli, whose
twin-peaked summit rises to a height of 927 m a.s.l., is characterized
by e distinctive conical shape and symmetrical flanks. However, what we
see is just the subaerial portion of an imposing 3000-m-high volcano, whose
total volume is 25 times as great as the portion rising out the water.
But how was thr Island of Stromboli formed?
In spite of its apparently simple shape, the island conceals the superimposition of more volcanoes, whiwh are still recognizable if one observes the remains of their forms and their various products, which are both lavic and explosive.