Grangemouth sits on Britain’s deepest underground valley

The prehistoric valley has been mapped for the first time by the British Geological Survey (BGS), and is 162 metres deep and filled with clay.

The valleys mostly date from the last ice age, which ended around 11,500 years ago, and are ancient drainage networks from rivers and glaciers that over the years became partly or completely buried by more recent sediments.

Sometimes a part of the valley peeks above the surface, but usually they are completely hidden underground with no way for hydrologists, civil engineers, planners or construction companies to tell what lies beneath.

BGS first identified a hidden valley in the 1870s, under the river Mersey, and since then has been collecting data from thousands of boreholes across Britain.

Now the digital age has brought a new opportunity - to collect and collate all the buried valley data in one place and make it publicly available online.

Dr Tim Kearsey, the BGS geologist who has been leading the project said: “Britain’s buried valleys might be underground, but they could and have had a huge impact on what happens above the surface.

“We need to know where these buried valleys are for a number of reasons.

“They could be a target area for shallow geothermal energy, like in Cardiff.

“They could be unsuitable places for skyscrapers or bridges to be constructed. They cause problems for groundwater supplies, as they already do in South East England”.

He added: “We combined historical BGS survey activities with over 200,000 borehole records from our national borehole database to identify these previously hidden features across the UK.

“Now that we know where they are, the next stage of the work is to find out what’s in all of them, and whether they could be useful for providing geothermal energy or as a groundwater source for the whisky or manufacturing sectors.”

The Buried Valleys dataset is online at https://www.bgs.ac.uk/products/onshore/BuriedValleys.html