Q: What is the likelihood of volcanic activity occurring in Britain over the next 10,000 years?
From Mr James Scott (February 2011)
Reply by Prof Martin Culshaw
The simple answer is almost none but it rather depends upon what we mean by volcanic activity!
The generally understood view of what constitutes volcanic activity is the eruption of volcanoes. However, another way of looking at it is as the 'relatively rapid' transfer of energy, particularly heat, from within the earth to the surface. This transfer manifests itself as volcanic eruptions and the ejection of molten lava, ash and gases, sometimes rather violently. However, heat is also transferred to the surface by much gentler degassing in fumaroles or by heating of groundwater to produce thermal springs (usually termed geothermal activity). These springs are warm/hot because the groundwater has come from considerable depths where temperatures are much higher than at the surface – in Britain temperatures increase at the average rate of about 260C per kilometre (though, in places, it can be as high as 350C). Such springs are to be found in a number of places in Britain, for example Matlock Bath in Derbyshire, Bath in Somerset, Droitwich in Worcestershire and Harrogate in Yorkshire.
The reason why there are no volcanoes in Britain is that such activity usually occurs at the edge of the tectonic plates that make up the surface of the earth. Britain lies on the Eurasian plate, some 1-2000 kilometres away from the plate boundary. Volcanic eruptions relate to two separate processes going on at the margins of tectonic plates:
- First, where the plate material is generated by up-welling of molten rock, for example along the mid-Atlantic ridge, which includes Iceland.
- Second, where two plates collide and one plate is pushed under the other, for example along the west coast of Sumatra and the southern coast of Java, in Indonesia.
As Britain lies a long way from the plate boundaries, we have no volcanic activity.
Plates move very slowly (a few centimetres per year) and so it will take millions of years before Britain will be 'at' a plate boundary. Consequently, we shall not need to worry about volcanoes for quite a long time to come!
Of course, Britain has experienced several phases of volcanic activity in the geological past, when parts of the country were at plate boundaries and the remains of some of these volcanoes are to be found in Snowdonia, the Lake District, Edinburgh and the Inner Hebrides, but that's another story!
If you want to read more about this, go to the website of the British Geological Survey (
www.bgs.ac.uk) and that will lead you to pages with further information and to other relevant websites.