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Sunday, February 28, 2010


Mount Vesuvius is best known for its eruption in AD 79 that led to the destruction of the Roman cities of Pompeii and Herculaneum and the death of 10,000 to 25,000 people. It has erupted many times since and is today regarded as one of the most dangerous volcanoes in the world because of the population of 3,000,000 people living nearby and its tendency towards explosive (Plinian) eruptions. It is the most densely populated volcanic region in the world...

severe eruptions occurring in 1660, 1682, 1694, 1698, 1707, 1737, 1760, 1767, 1779, 1794, 1822, 1834, 1839, 1850, 1855, 1861, 1868, 1872, 1906, 1926, 1929, and 1944. but not during the subsequent 66 years, probably due to formation of a plug stoppering it....

Following the 1631 eruption until 1944 every few years saw a comparatively small eruption which emitted 0.001-0.01 kmĀ³ of magma. It seems that for Vesuvius the amount of magma expelled in an eruption increases very roughly linearly with the interval since the previous one, and at a rate of around 0.001 cubic kilometres (0.00024 cu mi) for each year. This gives an extremely approximate figure of 0.06 cubic kilometres (0.014 cu mi) for an eruption after 60 years of inactivity.

from Wikipedia. Pressure is building & the longer it takes the more explosive, literally, the result.

The escape plan requires 2 weeks notification, is only aimed at moving out the 600,000 nearest & takes as worst case assumption an eruption equivalent to the 1631 one. Here's hoping but this sounds more like an emergency plan based around what is available now rather than what will be needed in a real worst case.

Of course if I wanted to be really alarmist I would say this
Though the caldera has no visible volcanic cone, it dwarfs nearby Vesuvius. "Most of the metropolitan area of Naples is located within the caldera," says Giuseppe De Natale of the National Institute of Geophysics and Volcanology's (INGV) Vesuvius Observatory in Naples...

"A major eruption, like the one 39,000 years ago, would leave large parts of Europe buried under a thick layer of ash," says Agust Gudmundsson of the Royal Holloway University of London, one of the researchers involved in the drilling project. Since then, smaller eruptions have occurred every few centuries.

According to a study of the region by Roberto Isaia of the INGV and colleagues, Campi Flegrei [name of the whole Caldera] is "one of the highest risk volcanic areas on Earth" and may now be primed for a blast. Isaia and colleagues found deposits from an intense period of eruptions around 4000 years ago. Before the eruptions the Earth's crust rose by several metres all across the caldera. Worryingly, crustal uplift is exactly what has happened recently. Since the late 1960s, the port of Pozzuoli near the caldera's centre has risen by around 3 metres. Hazard planners should prepare for eruptions in decades or less, Isaia concludes

In geological timeframes 79BC or indeed 4,000 years ago are not long periods. On those alone the odds should be 1/29 of Vesuvius or 1/57 of the whole Naples Caldera exploding within a lifetime. Because it has been so long since any eruption & we see such a substantial rise in ground level it seems likely the real odds are very much shorter.

The article quoted is about the Campi Flegrei Deep Drilling Project which is planning to drill seven holes in the region (see map).

Though the researchers on this particular project point out that any risk is small, it will begin amid debate about whether such endeavours are safe, given the unknowns of a volcano's interior. A few say drilling might even trigger a major eruption.

It is rather playing with fire but I don't see that there is much choice. It is going to go sometime in some direction. Anything the authorities can find out about where & when is likely to be vital. Personally I would put an automated drilling platform out beyond the Bay of Naples & hope to divert it out there. To do that will require somebody willing to take strong action on something for which the odds, in any given year, are long. It will require the power of something like martial law before there is a sign of a problem, to settle the inevitable lawyerly disputes. Better that than needing to impose the full thing as it erupts.

I am not just trying to raise a scare story here - I firmly believe the science & indeed engineering exists to channel this eruption - we have the technology to do almost anything we set ourselves to. The question is whether the political will exists to do something now to prevent the death of hundreds of thousands, possibly millions, while it is still, relatively, far off. The rise in the land makes it clear the pressure is growing & it is going to have to go somewhere some time.

PS During the Middle Ages Naples was, for a long time, the largest city in Europe despite not being a great national, cukltural or religiuos power. I assume that is because land fertilised by vulcanism is particulalry fertile. Giving with one hand & taking away with the other.

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