A Volcanic ‘Grand Tour’ Part 1

Today I am proud to present part 1 of UKViggens Volcanic ‘Grand Tour’ to you, but as long as it is Friday… you are expecting some riddles!

RIDDLE – Name that volcano! By Suzie.

Once upon a time K met A.
They kissed, married, argued and had a baby!
But did they live happily ever after?

And another evil riddle!!

We are as peas in a pod, head to tail, but to see us we need to be extinct!

1) What feature am I/we?
2) Where will you see me and what is extinct?
3) In what are we commonly found?

Happy hunting! AlanC

Part 2 will be published once you solved the riddles and Suzie and Alan did the Dinging. Expect part 3 on Monday.
The bar is open, have a nice weekend, happy reading and riddling!
Spica
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Etna’s blackened top towers over the arid yet productive lands beyond.

“The Prologue” *
* with thanks to Frankie Howerd in the British late-60s/early-70s sitcom ‘Up Pompeii!’

In days gone by, it was considered an essential element of a young gentleman’s education to undertake a ‘Grand Tour’. While such journeys might have taken in the works of the Flemish masters, or some botanical study in the Swiss Alps, the focus of the ‘Grand Tour’ was to bathe in the sumptuous delights of the antiquities of Italy. Florence, Rome and, of course, Venice were the signature destinations of such a journey of enlightenment and education.

In the 21st Century such places can be visited virtually from one’s armchair, without the need to hire mountain guides to cross the Alps in safety, or tutors trained in the Classics to provide insight as one travels. The same can also be said of volcanoes: with near real-time seismometers, webcams, blogs and page-upon-page of internet information, why bother going to look at them at all?

True up to a point, but for any young gentleman (or lady) who may wish to further their studies in this fascinating field, is there any substitute for feeling the rough crunch of scoria underfoot? Or, maybe, even witnessing a volcanic eruption at first hand? Of course there isn’t!
So, while the Viggen womenfolk indulged their own peculiar desires to cook themselves slowly around a hotel pool, this humble correspondent and his volcanoholic 14-year old son embarked on a ‘Grand Tour’ of their own. All for the boy’s education, you understand.

And, just as the young English gentlemen of the past sought their enlightenment among the art and artefacts of the Renaissance and Roman Empire, so budding volcanoholics must also journey to Italy, and more specifically the Kingdom of the Two Sicilies, for a true educational grounding in the marvels of the magmatic world.

There, within a few short hours of each other, lie the most impressive (Etna), the most active (Stromboli) and the most famous (Vesuvius) volcanoes in the continent, if not the world.

The notion of a ‘Grand Tour’ was obviously still alive and well in 1950s Cumbria: some while ago ‘Fru Viggen’ unearthed the scrapbook compiled by her parents of their honeymoon. Como, Venice, Florence, Pisa and Rome were visited, along with the customary excursion to Pompeii, as evidenced by this ancient relic that dates from 1945.

Vesuvius: meet the world, his wife and their kids!

Vesuvius seems like a good place to start. Wake up nice and early to beat the tourists (we, you understand, are not mere sightseers – we are engaged on scientific studies to seek out and attain higher levels of volcanological understanding!). Nice drive up to the car park to find 20 coaches already there. Oh well, the best laid plans …
So, here we are standing on the rim of the crater of the world’s most famous volcano, surrounded by a mass of people from Texas, Tokyo, Tyneside, Timbuktu … and Esbjerg (a very pleasant couple!). Despite the throng, my first glimpse of the crater as I scrambled to beat the fat bloke to a gap in the crowd by the fence will stay with me forever.

People or no people, it’s a pretty impressive hole in the ground, but I just couldn’t help thinking how even more amazing that crater must have been before the 1906 eruption, when the giant hole was 250 metres DEEP!

Faced with the crowds my mind starts to wander, and I find myself getting fascinated by the array of sensors around that hole in the ground. What do they all do? Which is the spectral gas emission sensor? Is that a differential GPS antenna I can see there? Do they work?

Some of the many sensors that surround the crater of Vesuvius, linked to the observatory located on the mountain’s lower slopes.

In any case, I can’t help thinking there’s not enough of them. Look away from the crater and laid out before you is a smog-diffused vista of packed urban sprawl. From the top the houses, offices and shops appear so small that they meld into a solid mass of … what?

Humanity! Yes, that’s it. There’s one hell of a lot of people down there. Maybe a few thousand fewer than before the government sponsored a campaign for families to move away from the Red Zone (only to create a vacuum of empty buildings into which the Camorra swiftly moved their illegal immigrants, brothels and drug factories), but there are still several millions. Evacuate that lot? Not a chance. Re-read Carl’s posts on the matter. It’s a sobering subject.

Having left the hordes behind at the top, we descended to lower levels and found ourselves eating a slice of pizza at the quiet former base station of the funicular railway.

A railway up Vesuvius? Yes, there was one, and once back home I have become more side-tracked by that than the volcano itself. In 1891 the famed travel company Thomas Cook Ltd claimed to be able to arrange tickets on 555030 km of the world’s 580397 km of railway line, but the only railway that the company actually owned was the 806 metres of funicular line that climbed 391 metres in elevation to the top of Vesuvius. The steepest incline was 63°.

Named ‘Etna’, this is one of the two original cars on the Vesuvius funicular railway, which had two tracks with a continuous-cable mechanism driven by steam engines. The other car was named ‘Vesuvio’. One of them was destroyed in 1887 when mountain guides broke up the line and set fire to the engine house as part of a dispute with the owner. The railway was back in business by 1889.

The opening of the funicular in 1880 inspired the song ‘Funiculì, Funiculà!’ (all of you will know the tune very well, even if you were previously unaware of what it’s all about). Here’s much-missed Luciano singing about a volcanic railway, together with the lyrics in the Neapolitan dialect:

www.youtube.com/watch?v=yTSAZAHiOa8

By 1903 Thomas Cook had opened up an 8-km stretch of line that took passengers from Pugliano in Ercolano (Herculaneum) to the base station of the funicular. The 1906 eruption caused major disruption and a halt to the funicular for a few years, and finally the eruption of 1944 put an end to all that nonsense. The post-war chairlift that replaced the funicular came to an unprofitable end in 1984.

Work fleetingly began on reinstating the rail line in the early 1990s, and then again in the late ‘Noughties’, but today such frivolity seems out of place, especially in a city where the council is forbidden to support organised crime, yet the Camorra own everything – not just the construction companies, but those that sell the materials to the construction companies.

So, now you walk – that’s progress for you!

Seems like a nice place to build a town…

I will freely admit that the ‘Lill-Viggen’ and I are not great ancient history buffs. In fact, one of my most precious possessions is a note that was surreptitiously passed to me by my late, great mentor during a long-winded RAeS historical lecture that states simply: “Old stuff is rubbish”. Despite our general antipathy, it would be rude of us to ignore the most famous volcanic tragedy of all time when in the vicinity, and so on to the Roman ruins of Pompeii (one of the genuine glories of southern Italy is that it can sometimes be difficult to ascertain where the ‘modern world’ ends and the ‘ruins’ begin).

Now, I’m sorry, but the fact that Romans lived in houses (Gosh!), cooked in kitchens (No!), ate food (Really?), slept in beds (Amazing!), bathed, shat, fought and f***ed doesn’t really excite me that much. I was surprised, however, to see that they had developed such good scaffolding. And they had Fanta, too!

Never underestimate the ability of dogs to sleep through anything. It’s difficult to tell if this mutt had died and been perfectly preserved by the layers of ash and pyroclastic flows that entombed Pompeii in 79 AD, or whether it was still just sleeping off the whole ham it had stolen and consumed a few days before the eruption. Interesting to note that, even by the first century, the Romans had obviously mastered the dark art of manhole covers.

In all seriousness, Pompeii is incredible on any level, and even I was reluctantly fascinated to see glimpses of how the inhabitants lived (especially following a recent excellent BBC documentary about the place).

Most of the time, though, I looked up at the omnipresent Vesuvius and just tried to imagine what it must have been like exactly 1,933 years previous (by happenstance we were there on 24 August, the anniversary of the eruption) as the flakes of ash began to fall.

UKVIGGEN

Urban volcanism!

The ironically named Mount Eden, near downtown Auckland.

Most people in the world agree on one thing: it is safer to live far from a volcano then it is living right on top of it. Living next too, or on top of a volcano is like sleeping in a cave with a friendly bear. Sure, it has it’s advantages, you stay nice and warm, you don’t have to worry about other predators, a good part of the year it is nice and quiet, but still….. you know that some day he will grab you and eat you. The inhabitants (some more permanent than others) of Herculanum, Pompeï, Heimaey and the Hawaiian Royal Gardens have found out the hard way.

New Zealand is, apart from being stunningly beautiful, one of the least populated countries in the World. When Western settlers arrived they could have chosen any location to go and build large cities. For some reason however, the inhabitants found it neccesary to build their largest city directly on top of a volcanic field with about 50 scoria cones, maars and tuff rings dotting the landscape. I suppose the knowledge of volcanism was not as developed back then as it is today, but nevertheless it is quite unfortunate.

Photograph by Mollivan Jon. Mount Taranaki.

New Zealand is dominated by subduction volcanism, with famous Mount Taranaki (or Egmont) as one of the most visually stunning stratovolcanoes in the world from both the ground and above, and with the infamous Taupo Volcanic Zone, best known for being one of the worlds “super” volcanoes. At 250 km from Auckland this is already quite a hazard on itself.

The Auckland Volcanic Field is a monogenetic volcanic field, meaning that an eruptive episode only happens once through a vent. Each eruptive episode generates a new vent somewhere within the volcanic field as opposed to “normal” volcanism where a volcanic vent has succesive eruptive episodes causing a volcano to build up and blow up occasionaly. The Auckland Volcanic Field produces basaltic scoria cones, maars and tuff rings (with the exception of the island of Rangitoto which erupted several times). All three are caused by the same type of magma, basaltic magma in this case, but the location the surface penetration, the eruptive flowrate and the total volume of the basalt determine the type of surface expression. The volcanic field has been active for about 150.000 (0.15M) years now. Older volcanic fields are found towards the south; South Auckland (1.5-0.5M), Ngatutura (1.8-1.5M) and Okete (1.8-2.7M).

The source of the basalt is not quite clear however. Basalt is normally not associated with subduction volcanism. Petrology and earthquake data have practically ruled out the possibility of the lava having an origin in melt generated by the subducting Pacific Plate. The Auckland volcanic field also sits some 200 km behind the active volcanic front of the Taupo Volcanic Zone. Furthermore, there is no evidence that the subducted Pacific plate reaches all the way to the Auckland volcanic Field.

Basalt is usually associated with mid-oceanic ridges/spreading centers or hotspot volcanism. Again, petrology has not been able to find much evidence for hotspot volcanism either. Additionaly, the propagation of the volcanic fields is directy opposite to the relative motion of the plate; the oldest volcanic field should have been in the north and the youngest in the south if a hotspot or mantle plume was involved. It is possible that the complex geology with major plates subducting, twisting and turning in the area is causing localised decompressional melting , leading to magma migration upwards right below the city of Auckland. There is some extention ongoing in the area, so this seems like a plausible explanation.

The Pacific plate and the Australian plate in a complicated geological setup

This image shows the subdution margin, the strike-slip faults to the southwest and extention(volcanic back-arc) to the northwest of the subduction margin.

Monogenetic volcanic fields are very interesting and highly unpredictable. The eruptions are not very large or extremely violent, but they can occur pretty much anywhere within the field at any time. With a large city with hundreds of thousands of inhabitants spanning the field, this is exactly what you don’t want. Paricutin in Mexico is the most famous example of this type of volcanism. One day you are happily working your crops, the next day you have to flee from your land because a volcano decided to take over your land. Bad luck, deal with it. Any new eruption within the Auckland Volcanic field will have as much compassion with buildings, streets, highways, parks and emergency shelters as Paricutin had with the crops that were growing there. This is what makes Auckland a relatively dangerous place to live in because it is not clear how much warning time there will be and how accurately the location of an eruption can be predicted with modern equipment.

The reason why new volcanoes pop up at random has to do with the generation of the magma. It is important that the generation occurs very slow. Slow enough to be unable to build a plumbing system that would efficiently conduct the magma to surface. Every new, hot, fresh slug of magma finds it’s own path to the surface, erupts and that’s it. The conduit cools and is no longer usable for the next slug of magma that arrives several decades or hundreds of years later below a slightly different part of the volcanic field. There is not enough magma flowing into one area to create a magma chamber in which the magma can evolve and produce more silicic types of magma.

Ridiculous in Los Angeles, not so ridiculous in Auckland. Bring out Tommy Lee Jones!

We have all seen the Hollywood movie “Volcano” and no doubt that many Los Angeles citizens have had a very good laugh at it (the La Brea tar pits are the surface expression of a leaking oilfield through a fault, it has nothing to do with volcanism whatsoever), but for the citizens of Auckland, those images are not even very far from the truth. The past gives an excellent example of what can happen. The next eruption in the field will most likely follow this scenario:

1 – Magma is forced upward through weak points in the crust.

2 – Either the magma contacts ground-water, or reduced pressure near the surface causes gases to bubble out of solution. The result is a phraetic or steam-blast eruption. The heaviest material is thrown out horizontally to form a tuff ring. Lighter material is blasted vertically to form an eruptive column. After a few days, weeks or months, the volcano falls quiet. Several of Auckland’s volcanos became extinct at this point.

3 – Additional magma may rise in the conduit. If enough magma is supplied, fire fountaining starts through one or more vents. Small lava flows may be produced, which do not escape the tuff ring. Sometimes the eruptions build scoria cones.

4- If fire fountaining continues beyond this point, the scoria cones can coalesce to rise and bury the tuff ring. Lava flows can also fill the surrounding valleys.

5 – Sometimes the outflow of lava is so great that it undermines the cone, which collapses into the flow and is carried away, leaving a horseshoe-shaped breached crater. If lava flows for long enough, nearby valleys are totally filled in and the lava floods the entire area with a large sheet.

Isn’t that just wonderful right in your own neighbourhood?

Map showing the city of Auckland and the eruptive centers.Pick your favourite spot to build your house.

The big question that remains is then: When is the next eruption going to be? Well, you will have to chop off one of the arms of a geologist to get a clear answer on that, but there are usually several hundred to several thousand years between eruptions in this field. The last one was about 600 years ago, so it might be a while before it is “overdue”, but it might be soon as well.

El Nathan