Thursday, February 09, 2012

Few days back Tam had a history post on Pompeii

which reminded me of something I've read: after a whole bunch of eruptions/disasters in various places, one of the things you read is some variation of "The locals didn't know the mountain was a volcano." Little or no record keeping other than verbal, and that apparently not touching on nastiness like "The last time the hill over there caught fire".

Which caused me to look for some more volcano stuff at the library, which led to a dvd about Mount Nyiragongo. Which the locals damn well DO know is an active volcano, but which doesn't prevent a bunch of them from starting to rebuild homes on top of the lava from the eruption the ran like hell from not long before. Even after they were warned that there is the possibility of very fast-moving lava rising up from crevices that run underneath the freaking town.

Which brings me to the reason for this whole mess: carbon dioxide. The stuff seeps up from lava degassing in many volcanoes; sometimes it seeps into a lake and, when things get disturbed, surges up out of solution, flows downhill and kills things. Nyiragongo is doing the same charging to Lake Kivu(right next to a big city, of course), but the stuff is also seeping up over large areas of the countryside and gathering in low spots. And killing people.

Ma Nature; she's got lots and lots of ways of turning you into fertilizer.


Keith said...

Call it a calculated risk.

In dry regions, volcanoes often get good rainfall which allows cultivation, and there are frequently good springs around the base, and sometimes for several tens of miles from the base of the mountain, like those in the Amboseli game park, north of Kilimanjaro.

On sicily, Etna is green when the rest of the island is brown in the summer, fortunately Etna's current activity is basaltic, so it produces nice fire fountains and lava flows - it is infact erupting at the moment -

you have to be acting stupid to get hurt by a basaltic volcano.

Much of the fertility of Etna is from a much earlier period in its activity when it produced more silicious magma, in more explosive eruptions, producing layers of "ash" (tuff) which quickly formed fertile soils rather than rocky lava flows.

Volcano gasses are nasty, but elevated CO2 works wonders for plant productivity.

There is also the issue of geologists trying to make work for themselves. It is an interesting course, hence far more do it than will ever manage to find work in the field - unless a government is willing to let them suckle OPM (sounds like "opium, but is far more addictive and corrupting - Other People's Money) from the state titty.

Some of the hot springs are interesting too.

I've holidayed at some in the Bay of Naples, which were very good, even if I first had to sign a form saying that I accepted the risks of radon!

Others can be downright alkaline - like magadacadi, and some of the salinas in northern Chile.

Others acidic.

and still more insidious, with high levels of things like arsenic and fluoride.

I tried to get a company interested in fluorspar exploration in an area where the local kids have black teeth which drop out when they get to their twenties, due to fluoride in the water - the weren't interested.

There was also an area of Ireland near a Tertiary age volcano, where people's hair was falling out due to arsenic in well water.

Check out "Komatiites", none have been erupted for the last 2.5G years, if they were, they'd be terrifying, with eruption temperatures of around 1800 C - hot enough to melt valleys in the underlying rocks, viscosity low enough to have turbulent flow, and flow lengths estimated to be up to 1500 km.

They were first correctly identified as lavas by a pair of Afrikaans twins, the Viljoen brothers. I think they had a hard time being believed at first!

Keith said...

The fifteen hundred klicks isn't a typo!