Thursday 30 August 2012

Small Earthquake on Islay, Argyle and Bute.

On Monday 27 August, slightly before 2.00 pm British Summertime (slightly before 1.00 pm GMT), the British Geological Survey recorded a small Earthquake 8 km beneath the Rhinns of Islay Peninsula, to the west of Loch Indaal on the Island of Islay in the Southern Hebrides, measuring 1.6 on the Richter Scale. Such a small tremor os highly unlikely to have caused any damage or casualties, and quite often will pass completely unnoticed, although on this occasion some people on the island reportedly did feel the quake.

Map showing the location of the 27 August Earthquake. BGS.

The UK is not close to any tectonic plate margins, so major Earthquakes are an unusual occurrence, but small quakes are not infrequent, and become more common as one travels north and west in the country, making the west coast of Scotland Britain's most Earthquake-prone area (which is possibly why people there are more likely to notice small tremors, and realize what they are).

The precise cause of quakes in the UK is seldom possible to determine, as the country is subject to tectonic stresses from a number of different sources, and most quakes are probably a result of a combination of these. The strongest source of stress in Scotland is probably glacial rebound; much of the north of the UK was covered by thick ice until about 10 000 years ago, pushing the rocks of the lithosphere down into the underlying mantle. Now this ice has gone and the rocks are slowly rebounding, causing the occasional small Earthquake in the process. The country is also being pushed to the east by the expansion of the Atlantic Ocean (along with the rest of Eurasia) and to the north by the impact of Africa into Europe from the south. There are also lesser spreading centers beneath the North Sea, Rhine Valley and Bay of Biscay, all of which exert tectonic pressure on the UK to some extent.

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