Wednesday, 11 January 2017

Sinking Feeling

To supplement the post on Global Warming and the rising sea-levels that will precede the next ice-age, this is another problem that will become ever more frequent.....

A lot is being said about rising sea-levels but there is little mention of it on a subterranean basis. So far we have been relatively lucky, in that it is rare more than one or two people die in these events. I'm talking about sink-holes of course. This phenomenon is on the increase and pretty soon there will be multiple deaths. Sink-holes can range in size (so far) from 1-600 metres. Imagine a sink-hole 600 metres in diameter in the middle of a busy town or city. Couldn't happen?

Guatemala City sinkhole developed after a tropical storm

There are a variety of causes for sink-holes but they all have water as a common denominator. Most often it is a result of the dissolution of soluble rock which causes a cavity below the surface. Many rocks are susceptible to dissolution but reliable reports are hard to come by. For example, I read one report from March 2013 which stated 20% of the USA was susceptible to sink-holes, but by July 2013 the figure was stated as 40%.
Below is a map of potential sink-hole areas in the UK

Oddly enough it isn't just excess water that can cause sink-holes, a lack of it can have the same affect. In some countries drought, or ground-water abstraction, can alter the water table. Building works can alter water tables causing either a build up, or a run off. It's not all doom and gloom though, some of these sink-holes in remote places are quite spectacular.

No doubt there will be more tragedies associated with sink-holes in the future, but I still think statistically the odds are against us popping our clogs in this manner. I certainly won't be losing any sleep, at least they wouldn't have to bury me.

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