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July 24, 2007

Did the earth move for you?

The recent report of a severe earthquake in East Africa got me thinking about the huge forces at work in the surface of the planet we infest, sorry, inhabit. What is remarkable - and says a lot about the parochialism of the BBC and other "news" agencies - is that this 7.4 on the Richter Scale, barely registered at all on the Western Media, yet it killed four people and injured dozens more. Even more interestingly it occured in an area which is, not unnaturally, a very sensitive zone for earthquakes and one which, perhaps, should be more closely examined.

Earthquakes are something most of us would prefer to avoid, yet almost everyone will, at some time, feel at least a tremor in the earth. Personally I have felt three in my lifetime, all of them rather remote from where I actually was in relation to the quake zone, but still an unsettling experience. Certainly for those near the epicentre in each case it was much more alarming, damaging or injurious to life and limb than where I was during the quake itself. Frankly, that was close enough for me anyway.

My interest in matters geological wasn't, until fairly recently, much more than a passing acquaintance with some of the better known aspects such as plate tectonics and the whole issue of why volcanoes occur along fairly defined zones. But, more recently, I have been subscribing to a range of Geographic Society magazines and have learned a great deal more about this subject. One of the more interesting aspects being that geographically "inactive" areas, tend to have very poor soil, lack significant mountains and therefore usually also tend to be very arid. Mountains are upthrusts as a result of one techtonic plate overriding another, so it should be no surprise then to find that the Himalayas, the Andes, The Rockies, Caucases, the Urals and almost all "young" mountain ranges sit on the "upper" plate along these fault lines. Volcanoes tend to sit along the fault lines and, no surprises here, earthquakes are usually centred on them as well.

So why my sudden interest in the East African earthquake? Well, it's been quite a while since that area had one this big. Secondly, "rift" valleys tend to be in the same sort of geological timebomb scale as the so called "super" volcanoes. They occur when the crust ruptures suddenly due to stresses transmitted from the tectonic plate movements - and they can be utterly devastating. That is why geophysicists are watching an area running from the Bering Strait down the coast of Mongolia and into Northern China quite keenly. It is where they predict the next "rift" will take place, and if it is anything like their models predict - well, good by all mammilian species and most others as well. There are some who argue that the formation of the Great Rift Valley in Africa (and which extends from Ethiopia all the way South to the Drakensberg/Maluti Mountains in South Africa was reasponsible for one of the great extinctions in prehistory. This rift valley is also slowly tearing apart and will eventually see Africa tear into two landmasses - though probably not in anything like our lifetimes.

OK, so this was an event in a remote part of Africa, not on the tourist trail and it didn't kill any tourists from Britain or anywhere in the "civilised" world. So our media ignored it. Yet, if you stop and think about the overall picture, each quake in a sensitive zone like this does have an impact somewhere else in the world. Pressure released in the crust in one zone means a sudden increase of pressure somewhere else. Perhaps we should pay a bit more attention to what is going on under our feet. After all, the next time the earth moves - it might be exactly where we might all feel it.

Posted by The Gray Monk at July 24, 2007 04:02 PM

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