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| Etna through the murk |
The mighty Mt Etna is the subject of the Volcanic Processes Field Course. It takes the stuff we learned in Physical Volcanology and plonks it in the real world setting of a live volcano, and in Europe, you don't get much more live than Etna. It is one of those hills that's always doing
something. Unfortunately for us Etna the mighty chose (apart from one occasion) to gently, serenely smoke for the duration of our trip, but that's nature for you - if you want certainty chose something man made.
The process of getting there started at a very ungodly hour of the morning with a shared taxi to Manchester Airport. I can never sleep on planes, but I knew that there would be little to be done on day one apart from getting there and getting booked into the hotel, so getting a little shut-eye later on was possible. Most people on the VPFC were traveling from Lancaster/Manchester, but a small number were coming into Catania via different routes and that was one of the main issues on arrival there - rounding everyone up. Catania airport is the polar opposite if Reykjavik (mentioned in an earlier post) which is phenomenal in almost every respect. Incoming planes circle around the South East of Etna, dropping altitude as they go, to approach the airport from the seaward side, making for some nerve-jangling cross winds - our pilot thought it was such good fun that he had a second go at landing - yippee!
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| Etna as the plane banked for landing |
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| The view from the airport to the hill taken whilst rounding up stray VPFC students |
On the ground, nerves shredded, everyone rounded up and on the minibuses, I was in a car with Nathan a PhD student along to demo for us. My job was to offer moral support and some of my rudimentary Italian translation skills in an attempt to get us to our destination. We are talking comedy central as Nathan had never driven a car from the other side, and on the opposite side of the road before and every other driver in Catania seemed to know it!! At one point as we searched in vain for a likely gap in the traffic on one of the motorways, a
Carabinieri car slowed along side us and the passenger said something into his radio. It was probably a warning to everyone else that there were a couple of in experienced Brit tourists on the road - Look out!
Nicolosi is tucked away below the small but imposing bulk of the Monti Rossi Cone, and as such Etna cannot be viewed from many places in the town, and then, surprisingly, it comes into view between some houses or along a street with the right angle on it. References to the hill are everywhere, but as is often the case, the locals have a nonchalant attitude to it. Etna has provided a few close calls in the past, but otherwise its just part of the back ground in a town where the shops have to be kept, the bars have to be tended, bread has to be baked, coffee percolated, the streets policed, bins emptied, children taught in school, and the faithful given their daily bread. In other words despite being sat on something big and explosive, life must go on.
Life started each morning with a trip to the local patisserie for genuine wake me up coffee and pastries to die for - at least it did for those who could roll out of bed in time for this treat, and it was a great way to start the day before piling into the minibuses and the hire car to get to the location of the day.
The locations were many and varied over the duration of the course. The rubble strewn trudge up to the rim of the Upper Sylvestre cone was rewarded with fantastic views in all directions and an excellent view of the source of the 2001 lower flow field, which flowed to within a couple of km of Nicolosi. It was possible to make out through the snow (we were above the snow line here, just a few hundred yards from the La Sapienza ski resort that was partially damaged in 2001) the SE rift and the prominent spatter cone around the 2100m vent, leading rapidly to the levee's of the start of the flow field. The lava looped around the northern flank of the Sylvestre cone and can be seen to follow the northern flank of the cone row off into the distance in the direction of Monte Rossi.
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| Dr Mike James talking about the 2001 eruption - the 2100m vent is in the background. |
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| An especially fine field sketch from the rim of the Upper Sylvestre Cone. |
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| View SE from the rim of the Upper Sylvestre Cone. 2001 flow field runs through the right of the image. |
Closer examination of bits of the flow showing through the snow cover revealed its eccentric (rather than central/lateral) origins - the eccentric lavas from an offset independent magma chamber are noted for their amphibole megacrysts (some up to an inch long) and the many xenoliths of the Sicilian sedimentary basement rocks they contain - evidence of the more circuitous rout they have taken and the extras they gathered along the way via interactions with the country rock.
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| Amphibole megacryst below the 2100m vent |
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| Xenolith of sedimentary basement rock in 2001 flow below the 2100m vent |
Further down the flow field, the snow cover was gone and the channel fed nature of the flow was much more evident. In the area SW of Monte Grosso, the flow was easily accessed by a forestry path that crosses the flow and then turns north along the Eastern edge of the flow. Here the scale of the flow was much more evident with armoured levees towering to 10m or more armour topped but flanked by horrendous ankle snapping AA clinker. Close up, the armoured top sections of the levees revealed a texture that we christened the pulled pork texture (I dont know... Maybe we were all feeling hungry). It was clear that this had formed as molten and partially molten material in the channel had dragged past the levee armour at a time when the flow rate was higher.
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| Armoured Levee in the Monte Grosso Area |
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| Close up of the levee with welded aa clinker at the base of the image and above this the armoured section with right to left flow features (Pulled Pork) |
After the forestry path had turned north it crosses the secondary flow. Here we examined a section of a small AA break out that can be seen in cross section. The nature of AA is clear with the clinkery brittle exterior surface at odds with the much smoother, viscous, flowing interior.
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| AA cross section - secondary channel, Monte Grosso Area |
At the front edge of the flow field - its cooling limited extent, the flow takes a many lobed nature as separate break outs vied to be that little bit closer to Nicolosi. The result is a series of humpbacked lobes that have clearly frozen in the act of breaking over the previous flow (from the 1600's I think). looking south east, the peaks of Monte Rossi seem very close, illustrating just how much peril Nicolosi must have been in. The steep forward slopes are frozen in the act of trying to make a few more metres,and as a last gasp of activity (literally), weird petal, blade and spine like structures have extruded like tooth paste, propelled from within until the waning strength of the eruption could make them go no further. These modern art sculptures with their fractal feathery petals are quite unlike the aa clinker that coats the rest of the flow field appearing as the very final show of defiant activity.
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| Late stage spine structures at the main flow front |
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| Main Flow front looking towards Monte Rossi and Nicolosi |
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| A feathery late stage extrusion |
Above the snow line the lava flows are well hidden and a knowledgeable guide is a requirement to successfully connect the various volcanic dots that do conspire to poke their heads above the snows surface. Fortunately, being on a University field course, we had one (Mike) and what he did not tell us he gently poked and prodded us until we worked it out for ourselves. From a parking place a km or so SE of the Sylvestre cone line, a steep forest path climbs to the upper slopes of the southern flank of the famous Valle Del Bove (VDB). The VDB is like a wonder of the geological world. It has the lot - a live volcano, the eastern flank of which is slightly less well bound than it should be due to multiple faults and is therefore gradually slipping into the Mediterranean creating a vast lava flow filled amphitheater. It is an impressive vista to rival other volcanic greats from around the world like the Las Canadas caldera on Tenerife.
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| Valle Del Bove |
Staying above the snow line, our guide (and inquisitor) Mike showed us an assortment of sites that illustrated the multiple ways in which Etna chooses to express herself. She is definitely not happy with just eruption from her central vent, and the instability created by her heavily faulted eastern flank gives rise to zones of weakness through which fresh magma will on occasions push. Frequently the same vent will erupt in a bi-modal manner moving from lively scoria cone building to throwing out cowpat bombs and spatter and even just straight effusion producing loby and ropey structures - the build up of spatter can even force the reactivation of the lava producing fresh flow. The movement of magma within the mountain along fractures and faults is occasionally exposed as well in the form of dykes.
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| Ropey and lobate structures, possibly the result of spatter reactivation |
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| The tip of a dyke exposed above the snow |
