Tuesday 29 May 2012

Earthquake on the Isle of Islay.

On Monday 28 May 2012, at 3.07 pm, British Summertime (2.07 GMT), the British Geological Survey recorded an Earthquake in Loch Indaal on the Isle of Islay, about 2.5 km southwest of the island's administrative capital, Bowman. The quake was recorded as measuring 1.6 on the Richter Scale and occurring at a depth of 10 km. Such a small quake at thus depth is highly unlikely to have caused any damage or injuries, and may not even have been felt by anyone.

The location of the 28 May quake. BGS.

As a rule of thumb, the further north and west you travel in Great Britain the more Earthquakes you will encounter (though quakes large enough to cause significant damage are very rare), making the west coast of Scotland one of the most earthquake-prone areas of the country. The largest quake ever recorded in Scotland, on 28 November 1880 is thought to have been centered in Argyll, about 70 km northwest of the 28 May 2012 quake. This is thought to have measured 5.2 on the Richter Scale and to have occurred at a depth of 25 km (there were no seismometers in 1880, so these are estimates).

Most earthquakes in Scotland are attributed to glacial rebound; till about 10 000 years ago the northernmost parts of Britain were buried beneath hundreds of meters of ice, pushing the lithosphere down into the underlying mantle. Now this ice is gone the rocks are rebounding, albeit very slowly, and this can lead to Earthquakes.

This is slightly over-simplistic, as the rocks of Scotland are subject to stresses from a number of sources, and the origin of quakes is generally complex, without a single obvious cause. Eurasia, including Scotland, is being pushed to the east by the expansion of the Atlantic Ocean, and to the North by the impact of Africa from the south. There are also lesser centers of expansion beneath the North Sea, the Rhine Valley and the Bay of Biscay, all of which have some influence on rock movements beneath the UK.

Follow Sciency Thoughts on Facebook.