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Topical Science
Issue 6
June 2017
TOPICAL SCIENCE The Italian Volcanoes
Issue 6, June 2017
Stromboli erupting, June 2017
Contents Volcanic eruptions and why they occur. 1
Vulcano and Vulcanello 2
The southern part of Italy, including Sicily and the Aeolian islands in the Tyrrhenian Sea, contain the most active volcanoes in Europe. The region is geologically unstable, due to subduction of the African tectonic plate under the Eurasian plate.
The picture above , taken by the author, shows an eruption on Stromboli. It was taken during a field trip with the Irish Geological Association, in June 2017, led by Alan Clewlow.
Mount Etna, the largest volcano in Europe.
The Aeolian Islands
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Volcanic Eruptions Volcanic eruptions are among the most spectacular sights that nature has to offer. They occur when molten magma, beneath the earth’s crust, finds a weak spot and bursts through the crust. Weak spots occur wherever tectonic plates meet. One of these places occurs in southern Italy, where the African plate meets the Eurasian plate and sinks under it, in a process called ‘subduction’. Stromboli provides a magnificent display, best seen shortly after sunset, when the ‘fireworks’ are visible with greatest effect. There are several vents within the main crater, each doing its own thing. One vent sends up a column of dark smoke every 20 minutes or so, accompanied by a sound like thunder. Another glows quietly most of the time, occasionally sending up a shower of sparks into the air. Some vents spew out steam, while there is one, which, from time to time, sends a fountain of glowing material high into the sky.
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Topical Science
Issue 6
June 2017
Vulcano, after which all volcanoes are named The island of Vulcano gives its name to all volcanoes. In
geological reckoning, it is relatively young, having first erupted about 100,000 years ago. Large volcanoes on the south of the island produced basalt and andesite lavas. These older calderas eventually collapsed. The Fossa volcano began erupting about 10,000 years ago and formed the cone we see today. The crater is 386 metres above sea level and is quite an easy climb, which can be undertaken without the assistance of a guide, as there is only one track and it is signposted. However, if you are there during the summer months, it is advisable to attempt the climb in the early morning, rather than in the midday heat! The trail allows close up views of lava flows, as shown in the picture on the left.
The Fossa Crater on Volcano. The last major eruption occurred in 1890, but fumarole activity still occurs. Steam can be seen venting from the fumaroles.
Sulphur, Steam, Sulphur Dioxide and Hydrogen Sulphide Even though there has not been a major eruption on Vulcano since 1890, it is still active. Fumaroles in the crater continuously vent steam, as well as gases such as hydrogen sulphide and sulphur dioxide. You can smell these gases from quite a distance and people are warned not to get too close to the fumaroles, as the gases are toxic. There is danger of getting a bad scald from the superheated steam, which is also emitted. Deposits of solid elemental sulphur can be seen in the vicinity of the fumaroles.
Yellow sulphur deposits can be seen on the side of the crater on Vulcano. 2
Topical Science
Issue 6
June 2017
One of the recently formed craters on Mount Etna, on the Italian island of Sicily Mount Etna, situated on the island of Sicily, is an enormous mountain, with a volume of about 350 cubic kilometres! It is the largest volcano in Europe. There have been many eruptions over the years, with the result that there are about 300 craters on this mountain. The first recorded eruption from Mt. Etna occurred around 1500 BC and it has had over 200 eruptions since then, which were historically recorded. It is still active, with eruptions occurring every few months. Several theories have been proposed to account for the activity of Mt. Etna. The most obvious explanation is that, along with the volcanoes on the Aeolian islands, the activity of Etna is due to the subduction of the African plate under the Eurasian plate. However, the geology of Sicily is rather complicated. Some authorities believe that there is a ‘hot spot’ in the mantle underneath Etna. It is also known that the volcano lies at the intersection of several major geological faults. Whatever the explanation, Mt. Etna remains active and it is a fascinating landscape to explore.
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Topical Science
Issue 6
June 2017
Italian Volcanoes
The Aeolian Islands These are a group of volcanic Islands situated in the Tyrrhenian Sea, north of Sicily. The largest of the islands is Lipari, which at one time was an important source of obsidian, or natural glass, formed by the rapid cooling of molten lava. Its volcano is no longer active. In more recent times, pumice was a valuable export.
Thanks to Frank Clissman of the IGA and Alan Clewlow of ‘Volcanic Experiences’, for organizing the field trip to the volcanoes.
Above: The former pumice works on Lipari. Margaret Franklin
Apart from the inhabited islands, a number of impressive rocks and sea stacks occur among the Aeolian islands. Here are two of them. The Aeolian islands are well worth a visit, whether you are interested in geology or not. The scenery is magnificent!
Is a retired chemistry lecturer. Her ‘Topical Science’ column appeared in ‘The Westmeath Independent’ for over three years. ‘Topical Science’ is now published monthly on ISSUU. It attempts to explain scientific concepts in plain language for the general public.
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