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Die sechste Ausgabe von FLOW ist erschienen.
Allerdings frage ich mich, warum Flow laut eigener Aussage ein Magazin ist "für Frauen, die das Leben anders sehen wollen"...
Viele der Themen sprechen ja auch Männer an. Und ich gehe jede Wette ein, daß ich nicht der einzige Mann bin, der an den schön gestalteten Dekorations- und Kartenbeilagen gefallen findet.
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View of the lava flow of 1792 on the eastern flank of Mount Etna, looking approx ESE from the Etna summit road (SP 92, via Cassone) towards the eastern coast of Sicily (Italy) and the Ionian Sea.
ETNA EXCURSION - STOP 3
We are at about 1280 m a.s.l. here. The small grey smudge in the far distance (upper L) is Calabria (see note on photo), the 'toe' of Italy on the Italian mainland just visible above the mist. Our guide stopped here for us to see the views in all directions, and to see the area where the 1792 lava flow started (behind the viewpoint). The craggy structure of the lava flow indicates a'a structure. The sparseness of the vegetation gives an idea of how long it takes for soil to develop on these lava flows. The shrubs in the foreground are one of the main early colonisers on Etna lavas, these being the Mount Etna broom (Genista aetnensis, endemic to Sardinia and Sicily.
The a'a surface pattern of the lava was created as it flowed and cooled, flow of the lava being slow, uneven and congested by the rapid cooling and solidification of its surface crust.
Like many geological terms, 'a'a' is borrowed from a part of the world where a geological feature is typical or where it was first noticed and described in formal scientific accounts. In the case of 'a'a' this was in the volcanic areas of the Hawai'i Islands, so it is a Polynesian word.
The summit of Mount Etna (Monte Etna) is currently around 3,329 m (10,922 ft) high but this varies with its volcanic activity. It is one of the most active volcanoes in the world and is the highest volcano in Europe. It has many frequently active vents and craters. In plate tectonic terms, it lies close to the geological boundary between Europe and Africa. There were two eruptions in the last month before we arrived, one of them only three days before. Mostly, recent eruptions have been relatively small and only local in their immediate effect, but much more widespread and violent eruptions have happened in the longer term in historical and geological time, and they could happen again. The region is also earthquake-prone (like many other parts of Italy).
GEOLOGICAL NOTES
The two classic lava structures in terrestrial eruptions are a'a (craggy, spiny and blocky appearance) and pahoehoe (rope-like and flowing structures), but there are intermediate structures too. Their formation is related to speed of forward movement of the molten lava which is turn relates to other factors like its viscosity, rate of lava supply and steepness of slope over which the lava is flowing. Viscosity depends on factors like composition of the lava, gas bubble content and temperature. Pahoehoe forms when the key factors favour faster movement and a'a lava when movement is slower.
The lava here is basalt, probably sub-alkaline (tholeiite) (I don't have detailed information for this outcrop or lava flow). The composition and volcanic style of Etna's activity are much more similar to classic oceanic basalt regions like Hawai'i, Iceland, La Réunion and Galà pagos, even though Etna's geological setting does not appear oceanic. A possible explanation is that it is located above a slab window (see below). In this case, magma of basaltic composition would originate in the mantle as with oceanic volcanoes, without being affected much by continental crust material.
Etna is actually a volcanic complex of numerous eruptive centres around the summit crater and on the flanks of the volcano. Etna's oldest known activity is about 500,000 years old (mid-Pleistocene). Most of its volcanic edifice is due to ash and other pyroclastic deposits, and lava flows, so it is classed as a stratovolcano. There are also several calderas, i.e. large bowl-shaped structures with steep sides caused by large-scale downward collapse of the ground above the chamber(s) which supplies the volcano's eruptive material.
The volcano is located above fault complexes related to the collision movement of the African plate and European plate such that Africa in the geological sense lies away to the R of this viewpoint and Europe lies in front of us. A northern promontory of the African plate, usually called the Adriatic or Apulian Platform or Plate is being actively subducted beneath the peninsula of Italy and northern Sicily which are structurally part of Europe (in an oversimplified way). Subduction is taking place in a direction from the R (i.e. from the S) under the European crust beneath the Etna , which sits on the overriding European crust, its volcanicity due at least in part to fault systems associated with this tectonic setting, though it is also ascribed to a local mantle hotspot and a window in the subducting slab.
SOURCES
There is a huge literature on Etna, and the notes above come from many sources, but here are some to start:
- Ball, Jessica.Mount Etna - Italy geology.com/volcanoes/etna/
- Behncke, Boris. [A series of blogs about Etna, e.g. bigthink.com/eruptions/etna-week-part-1-brief-anatomy-of-...]
- Bosellini, A., 2005.Storia geologica d'Italia. Gli ultimi 200 milioni di anni. Zanichelli, Bologna.
- Seach, J. Mt Etna Volcano www.volcanolive.com/etna.html
- Sistema Rischio Vulcanico. Mount Etna. The geological history, recent and current activity, and hazards of Mount Etna volcano, Sicily srv1.rm.ingv.it/srv/srv/study-sites/mount-etna
- Wikipedia. Mount Etna en.wikipedia.org/wiki/Mount_Etna
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LONDON - PARIS - CATANIA - ROME - LONDON ----- DAY 5
Photo from the fifth day of our crazy long distance rail trip from home (London) to Sicily. We spent the first day travelling from home in London to Paris, by Eurostar train, and were meant to the take an overnight train from Paris to Rome that same evening. But our Eurostar train out of London was badly delayed due to 'a fatality [unexplained - perhaps fortunately] on the train'. So we missed our onward connection to Rome and had an unexpected but happy second day in Paris. We left Paris that evening, on the equivalent Rome service arriving in Rome on our third day where we changed for our onward train, arriving in Catania (Sicily) that same evening. Our fourth day was our first full day in Sicily, and we spent this in the centre of Catania itself. We spent our fifth day on an excursion to Mount Etna run by GeoEtnaExplorer. We chose this tour company because the guides are geologists. Our particular tour went high up on the flanks on the summit, but not to the summit proper.
By the end of the whole holiday trip we had seen things and sites from ancient Greek time to modern, so the trip felt like a mini Grand Tour. Or given the rich mythology of Sicily, Etna and the Straits of Messina (Odysseus, the Cyclops, Scylla & Charybdis, etc.) perhaps our trip was like a modern mini Odyssey of our times. Odysseus took ten years to get home. It took us ten trains - but no monsters.
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Photo
Darkroom Daze © Creative Commons.
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ID: DSC_6659 - Version 2
Walking on the lava flow. Much of which is obsidian.
Newberry National Volcanic Monument was designated on November 5, 1990 to protect the area around the Newberry Volcano in the United States. It was created within the boundaries of the Deschutes National Forest and is managed by the U.S. Forest Service. It includes 50,000 acres (20,000 ha) of lakes, lava flows, and spectacular geologic features in central Oregon. These photos are taken from the summit Paulina Peak 7,985 ft, (2,434 m). Just below us are East Lake and Paulina Lake and The Big Obsidian Flow, created 1,300 years ago, covers 700 acres. It is hard to fathom as you drive through the summit area that you are within a 17 square mile caldera at the summit of a 500 square mile volcano, a volcano that remains very active to this day. Newberry is both seismically and geothermally active. Geologists believe the caldera sits over a shallow magma body only 2 to 5 kilometers deep. Visitors see numerous cinder cones (over 400 throughout the area), miles of basalt flows, as well as rhyolite flows of obsidian.