Monday 29 October 2012

Small Earthquake on the Isle of Mull.

On Saturday 27 October 2012, slightly after 6.05 pm British Summertime (slightly after 5.05 pm, GMT) the British Geological Survey recorded a Magnitude 1.1 Earthquake at a depth of 4 km on the Isle of Mull, to thenorth of Loch Scridain. This is a small quake which is highly unlikely to have caused an damage or casualties, and may not have been felt at all - or if it was felt may not have been recognised as a quake.

Map showing the location of the 27 October 2012 quake. Google Maps.

As a rough rule of thumb Earthquakes become more common in the UK as you travel north and west, making the west coast of Scotland the most quake-prone part of the country. The precise cause of Earthquakes in Scotland is not always easy to to determine, as the country is not obviously influenced by any single overiding tectonic feature, but rather by a number of smaller sources of stress, with most quakes being the result of a combination of more than one of these.

Scotland, along with the rest of Eurasia, is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. There are also lesser areas of spreading beneath the North Sea, the Rhine Valley and the Bay of Biscay, all of which have an impact on Scottish geology. Finaly there is glacial rebound; until about 10 000 years ago much of the north of the UK was covered by a thick layer of ice, which pushed the rocks of the lithosphere down into the underlying mantle. This ice is now gone, and the rocks are slowly sprining back into position, causing the occasional Earthquake in the process.

Witness reports of Earthquakes can help geologists to understand these events, and the rock formations that cause them. If you felt this quake, or if you were in the area and did not (which is also useful information) then you can report it to the British Geological Survey here.

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