The earth moves for UK scientists

November 28, 2003

The ground beneath your feet may seem solid enough, but a new map created by a team of geophysicists reveals how parts of the British Isles "bounce" by up to 10cm twice a day.

Preliminary results from a national survey show the impact of the tides in moving the countryside up and down.

When the tide is in, the weight of the water pushing down on the continental shelf has a greater effect than when the tide is out. The result is a flexing in the earth's crust and a regular rise and fall of the whole country.

But research carried out by scientists at Newcastle University, with colleagues from the Ordnance Survey and the Proudman Oceanographic Laboratory, shows how much this "bounce" varies between parts of Britain.

Peter Clarke, lecturer in geomatics, said: "Britain isn't 'fixed' at all - the land is bouncing up and down by varying amounts for each tide."

Devon, Cornwall, the western tip of Pembrokeshire and the Western Isles have the most "bounce", with variations of up to 10cm. The highest value measured so far was at a site at Cambourne. At the Ordnance Survey headquarters in Southampton, the movement can be as little as 3cm.

Proximity to continental Europe restricts the movement of eastern Britain.

The rhythmic bounce repeats roughly every 12 hours, but is complex in detail.

The team used measurements between ground stations and global positioning system satellites to extract the data to determine bounce in different parts of the country.

Preliminary analysis of 1,000 days of data from points about 150km apart will be presented at the American Geophysical Union meeting in December.

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