University of Leicester eBulletin

Mapping the Earth's Crust

October 2002
No 223


Geologists from the University of Leicester and the University of Cambridge have produced the first maps of the structure of the deep crust beneath the UK, which will lead to a better understanding of the geological evolution of the British Isles.

While earthquakes that affect Scotland are seen as the result of the retreat of ice sheets about 8,000 years ago, geologists do not yet understand the cause of many of the earthquakes occurring in England and Wales, which tend to occur at deeper levels in the Earth’s crust.

Dr Richard England of the University of Leicester Department of Geology said: “It is hoped that the new study by Leicester and Cambridge scientists will lead to an understanding of the cause of these earthquakes, and therefore to the ability to predict where they will occur. This would be a useful advance in hazard prediction, since the present record of earthquake locations appears almost random and is difficult to relate directly to known faults at the near surface of the earth.”

map showing thickness of the lower crust beneath the UK
Above map shows the thickness of the lower crust beneath the UK through which seismic waves travel at a velocity greater than 7 km/s. Because these rocks are less dense than the underlying mantle they caused the surface to be uplifted, producing a source of sediment which was washed into the North Sea and West of the UK and Ireland where it formed the sedimentary rocks which are now reservoirs for oil and gas.

The maps have been drawn from deep seismic surveys using technology developed with the oil industry over the past 20 years. While research is still at an early stage, and data need to be refined and predictions tested against other observational evidence, key findings so far indicate that erosion and formation of the Earth’s landscape are – long term – controlled by the evolution of the deep crust as well as surface processes.

As well as providing a new way of understanding the geological evolution of the British Isles, the research is assisting the petroleum industry in discovering natural resources more effectively and safely.

The Earth’s crust floats on the underlying asthenospheric mantle, rather like an iceberg on the sea. The density of the crust determines the height of the land above sea level.   Long term changes in the density of the crust can contribute to rising and falling relative sea levels.

Scientists studying the surface geology of the UK have known for some time that the northern and western regions of the UK rose by as much as 500 metres about 60 million years ago, when Europe separated from Greenland to form the Atlantic Ocean.

Until now, what was not well understood was the exact cause of this surface uplift. The new maps produced by the Leicester and Cambridge geologists indicate that it was caused by magma trapped in the lower crust. This solidified to form a high density igneous rock, but some rose to the surface to feed volcanoes, the extinct remains of which are now the islands of Skye, Rum and Mull in the Inner Hebrides.

NOTE TO EDITORS:   Further information is available from Dr Richard England, University of Leicester Department of Geology, telephone +44 (0)116 252 3795, facsimile +44 (0)116 252 3918, email

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